United States Patent |
4,442,972 |
Sahay
, et al.
|
April 17, 1984
|
Electrically controlled programmable digital thermostat and method for
regulating the operation of multistage heating and cooling systems
Abstract
An electronically controlled programmable wall thermostat provides better
control of comfort temperature and permits improved energy-saving
temperature setback at selected intervals of the day or night in
multistage heating and cooling systems and is particularly useful in
achieving improved energy savings for systems having heat pump means in
the main temperature conditioning stage of the system. The thermostat
includes clock means, temperature sensing means, means for displaying
desired parameters of time and temperature, data entry and storage means
for programming the thermostat to maintain desired temperatures during
selected time intervals, and a processing means with a memory
incorporating a permanently stored program instruction sequence which
responds to signals from the temperature sensing means for controlling the
heating and cooling systems in accordance with the time-temperature
sequence programmed into the thermostat by the user. A novel method of
temperature control is described in which the temperature sensing and
processing means cooperate in a unique way to regulate operation of the
main or heat pump stages of the heating and cooling systems relative to a
programmed set temperature and to regulate operation of the auxiliary
stages of the systems only with respect to the actual rate of change of
temperature being effected by any operation of the system. In that way,
the thermostat provides improved control of the comfort temperature under
varying weather conditions and in different types of housing conditions
and achieves timely and more energy-efficient recovery from setback
temperatures at an optimum temperature restoring rate to result in more
selective use of the heat pump means in the main stages of the systems.
Inventors: |
Sahay; Bharat B. (Johnson City, TN), Jones; James J. (Elizabethton, TN) |
Assignee: |
Texas Instruments Incorporated
(Dallas,
TX)
|
Family ID:
|
23164853
|
Appl. No.:
|
06/301,783 |
Filed:
|
September 14, 1981 |
Current U.S. Class: | 236/1EA; 165/238; 165/261; 236/46R |
Current CPC Class: |
F23N 5/203 (20130101); G05D 23/1917 (20130101); G05D 23/1904 (20130101) |
Current International Class: |
F23N 5/20 (20060101); G05D 23/19 (20060101); F23N 005/20 () |
Field of Search: |
;165/12,29 ;236/46R,1R,1EA,1ER ;62/231
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Wayner; William E.
Attorney, Agent or Firm: Haug; John A.
McAndrews; James P.
Sharp; Melvin
Claims
We claim:
1.
Thermostat means for regulating a temperature conditioning system
having independently operable main and auxiliary temperature
conditioning means comprising means for sensing the
temperature in a zone whose temperature is to be conditioned, means for
scheduling temperatures to be provided in the zone during respective
periods of time in a selected time sequence, and control means
responsive both to the temperature sensing and
scheduling means for operating the main temperature conditioning means
when required in any of said time periods either to maintain a scheduled
temperature in a period or to initiate conditioning of the zone
temperature to provide the zone temperature
scheduled to be provided in a next scheduled time period, said control
means being responsive to the temperature sensing and scheduling means
for comparing the zone temperature being provided in a time period with a
temperature scheduled to be provided
in that period, for comparing the zone temperature in any of said time
periods with the temperature scheduled to be provided in the zone in the
next scheduled time period in said time sequence to determine a time
period when any operation of the main
temperature conditioning means is required to be initiated for
conditioning the zone temperature at a predetermined and desired rate of
change of zone temperature to provide said next scheduled zone
temperature at the start of said next time period, and
to operate the main temperature conditioning means when required to
maintain said scheduled zone temperature or at said determined time to
initiate conditioning of the zone temperature to provide said next
scheduled temperature, said control means being
further responsive to the temperature sensing means for determining the
actual rate of change of temperature then effected in the zone by the
temperature conditioning means of the system during any operating
thereof and for operating the auxiliary
temperature conditioning means to aid the main temperature conditioning
means in conditioning zone temperature only when said actual rate of
change of zone temperature is less than said predetermined and desired
rate of change of zone temperature.
2. An electronic thermostat for regulating independently operable main and auxiliary temperature conditioning means comprising:
(a) switch means actuable for selectively operating the main and auxiliary temperature conditioning means;
(b) means for sensing the temperature in a zone whose
temperature is to be conditioned and for providing a signal indicative
thereof;
(c) means for generating time signals;
(d) means for storing data selectively entered therein;
(e) data entry means for entering data into the storage means
representative of selected temperatures scheduled to be provided in the
zone during selected periods of time in a selected time sequence; and
(f) logic circuitry coupled to the data storage means and
responsive to the temperature sensing and time signal generating means
for actuating the switch means to operate the main temperature
conditioning means when required in any of said time
periods to initiate conditioning of the zone temperature to provide the
zone temperature scheduled to be provided in that time period, said
logic circuitry being adopted to compare the zone temperature in each of
said time periods with the temperature to
be provided in the zone in the next scheduled time period in said time
sequence to determine a time prior to the start of said next scheduled
time period when any operation of the main temperature conditioning
means is required to be initiated for
conditioning the zone temperature at a predetermined and desired rate of
change in zone temperature to provide said next scheduled zone
temperature at the start of said next time period and to actuate the
switch means to operate the main temperature
conditioning means at said determined time to initiate conditioning of
the zone temperature to provide said next scheduled temperature, said
logic circuitry being further responsive to the temperature sensing
means to determine the actual rate of change
of zone temperature then effected by the temperature conditioning means
during any operation thereof and to actuate the switch means to operate
the auxiliary temperature conditioning means to aid the main temperature
conditioning means in conditioning
zone temperature only when said actual rate of change of zone
temperature is less than said predetermined and desired rate of change
of zone temperature.
3. A programmable electronic digital thermostat for regulating
independently operable main auxiliary temperature conditioning means
comprising;
(a) switch means actuable for selectively operating the main and auxiliary temperature conditioning means;
(b) means for sensing the temperature in a zone whose
temperature is to be conditioned and for providing a digital signal
indicative of said temperature;
(c) means for generating time signals;
(d) first memory means for storing digital coded information
into the first memory means representative of selected temperature
scheduled to be provided in the zone during selected periods of time in a
selected time sequence; and
(f) digital processor means having digital coded information
constituting an instruction sequence permanently stored therein, said
processor means being coupled to the first memory means and being
adopted to respond to said time and temperature
signals in accordance with said instruction sequence for actuating the
switch means to operate the main temperature conditioning means when
required in any of said time periods to initiate conditioning of the
zone temperature to provide the zone
temperature scheduled to be provided in that time period, said processor
means having a predetermined and desired rate of change of zone
temperature established as a constant and being adopted to determine the
actual rate of change of zone temperature
being effected by the temperature conditioning means during any
operation thereof and to actuate the switch means to operate the
auxiliary temperature conditioning means to aid the main temperature
conditioning means in conditioning zone temperature at
said selected constant selected rate to provide said scheduled
temperature when said actual rate of change of zone temperature is less
than said selected constant rate of change of zone temperature, said
digital processor means comparing zone temperature
in each of said time periods with the temperature to be provided in the
zone in the next scheduled time period in said time sequence in
accordance with said permanently stored instruction sequence to
determine a time prior to the start of said next
scheduled time period when any operation of the main temperature
conditioning means is required to be initiated for conditioning the zone
temperature at said predetermined and desired rate of change of zone
temperature to provide said next scheduled zone
temperature at the start of said next time period and to actuate said
switch means to operate the main temperature conditioning means at said
determined time.
4. A temperature conditioning system comprising main
temperature conditioning means operable for conditioning the temperature
in a zone, auxiliary temperature conditioning means operable to aid the
main temperature conditioning means for
conditioning the zone temperature, means for sensing temperature in the
zone, means for scheduling temperatures to be provided in the zone
during respective periods of time in a selected time sequence, and
control means responsive to the temperature
sensing and scheduling means for operating the main temperature
conditioning means when required in any of said time periods to initiate
conditioning of the zone temperature to provide the zone temperature
scheduled to be provided in that time period,
said control means being responsive to the temperature sensing and
scheduling means for comparing the zone temperature in any of said time
periods with the temperature scheduled to be provided in the zone in the
next scheduled time period in said time
sequence to determine a time prior to the start of said next scheduled
time period when any operation of the main temperature conditioning
means is required to be initiated for conditioning the zone temperature
at a predetermined and desired rate of
change of zone temperature to provide said next scheduled zone
temperature at the start of said next time period and to operate the
main temperature conditioning means at said determined time to initiate
conditioning of the zone temperature to provide
said next scheduled temperature, said control means being further
responsive to the temperature sensing means for determining the actual
rate of change of temperature then effected in the zone by the
temperature conditioning means of the system during
any operation thereof and for operating the auxiliary temperature
conditioning means to aid the main temperature conditioning means in
conditioning zone temperature only when said actual rate of change of
zone temperature is less than said predetermined
and desired rate of change of zone temperature.
5. A temperature conditioning system comprising main
temperature conditioning means operable for conditioning the temperature
in a zone, auxiliary temperature conditioning means operable to aid the
main temperature conditioning means for
conditioning the zone temperature, and a programmable electronic digital
thermostat comprising;
(a) switch means actuable for selectively operating the main and auxiliary temperature conditioning means;
(b) means for sensing the temperature in a zone whose
temperature is to be conditioned and for providing a ditial signal
indicative of said temperature;
(c) means for generating time signals;
(d) first memory means for storing digital coded information selectively entered therein;
(e) data entry means for entering digital coded information into
the first memory means representative of selected temperatures
scheduled to be provided in the zone during selected periods of time in a
selected time sequence; and
(f) digital processor means having digital coded information
constituting an instruction sequence permanently stored therein, said
processor means being coupled to the first memory means and being
adopted to respond to said time and temperature
signals in accordance with said instruction sequence for actuating the
switch means to operate the main temperature conditioning means when
required in any of said time periods to initiate conditioning of the
zone temperature to provide the zone
temperature scheduled to be provided in that time period, predetermined
and desired rate of change of zone temperature established as a constant
and being adopted to determine the actual rate of change of zone
temperature being effected by the
temperature conditioning means during any operation thereof and to
actuate the switch means to operate the auxiliary temperature
conditioning means to aid the main temperature conditioning means in
conditioning zone temperature at said predetermined and
desired constant rate to provide said scheduled temperature when said
actual rate of change of zone temperature is less than said
predetermined and desired rate of change of zone temperature, said
digital processor means comparing zone temperature in
each of said time periods with the temperature to be provided in the
zone in the next scheduled time period in said time sequence in
accordance with said permanently stored instruction sequence to
determine a time prior to the start of said next
scheduled time period when any operation of the main temperature
conditioning means is required to be initiated for conditioning the zone
temperature at said predetermined and desired rate of change of zone
temperature to provide said next scheduled zone
temperature at the start of said next time period and to actuate said
switch means to operate the main temperature conditioning means at said
determined time.
6. A temperature conditioning system as set forth in claim 5
wherein said main temperature conditioning means comprises heat pump
means having relatively higher energy efficiency than said auxiliary
temperature conditioning means.
7. A temperature conditioning system as set forth in claim 6
wherein said auxiliary temperature conditioning means comprises
electrical resistance heater means.
8. A method for regulating operation of a temperature
conditioning system having independently operable main and auxiliary
temperature conditioning means comprising the steps of scheduling
temperatures to be maintained in a zone during
respective periods of time in a selected time sequence, continously
sensing the zone temperature, comparing zone temperature sensed in each
time period to the temperature scheduled to be provided in that period
and operating the main temperature
conditioning means when required to initiate conditioning of zone
temperature to provide said scheduled temperature comparing the zone
temperature sensed in each of said time periods with the temperature
scheduled to be provided in the zone in the next
scheduled time period in said time sequence and determining a time prior
to the start of said next scheduled time period when any operation of
the main temperature conditioning means is required to be initiated for
conditioning the zone temperature at a
predetermined and desired rate of change of zone temperature to provide
said next scheduled temperature at the start of said next time period,
initiating operation of the main temperature conditioning means at any
such determined time to initiate
conditioning of the zone temperature to provide said next scheduled
temperature, and determining the actual rate of change of zone
temperature being effected by the temperature conditioning means during
any operation thereof and operating the auxiliary
temperature conditioning means to aid the main temperature conditioning
means in conditioning zone temperature when said actual rate of change
of zone temperature is less than said predetermined and desired rate of
change of zone temperature.
Description
BACKGROUND OF THE INVENTION
The field of this invention is that of electronic thermostats
for multistage heating or cooling systems and the invention relates more
particularly to programmable thermostats for multistage heating and
cooling systems which use heat pumps in the
main stages of the systems and to methods for regulating operation of
such multistage systems.
Electronic programmable digital thermostats are being used
extensively and with great success to achieve substantial energy savings
by providing automatic shutdown or temperature setback of conventional
temperature conditioning systems during
sleeping hours or when a living space is unoccupied. Many of such
systems use multiple heating or cooling stages to obtain greater
operating efficiencies. Some systems incorporate heat pumps to achieve
other energy savings by taking advantage of the
greater energy efficiency of heat pumps relative to conventional
furnaces. Heat pump systems are usually of the multistage type in that
they have less efficient auxiliary stages such as electrical resistance
heaters which supplement the heating capacity
of the heat pump means during colder weather. Frequently however,
multistage systems present some comfort temperature control problems,
and multistage systems using heat pump means or the like in the main
system stages often fail to achieve satisfactory
economies when used in temperature setback operation.
For example, under some climatic conditions, the temperature
provided by a typical multistage temperature conditioning system using a
conventional thermostat is permitted to fluctuate around a temperature
which is offset by as much as 2.degree.
F. From the intended control temperature set by the user. That occurs
because, in such conventional thermostats, the temperature set by the
user serves as the threshold temperature of the main heating or cooling
stage of the system while the threshold
temperatures of the other, auxiliary heating or cooling stages vary by
up to about 2.degree. F. from the main stage threshold temperature.
The auxiliary thresholds are selected and arranged so that, under most
normal weather or housing conditions, the
comfort temperature is regulated around the control temperature the user
has selected. However, when climatic conditions are relatively severe
so that the main heating or cooling stage of the system does not in
itself have sufficient capacity to bring
room temperature to the control temperature set by the user, the
threshold temperature of a second or subsequent stage of the system can
become the effective control temperature of the system. In that
situation, the temperature provided by the system
fluctuates around that alternate "control" temperature which is offset
by as much as 2.degree. F. from the desired control temperature,
thereby resulting in considerable user discomfort.
Similarly, when a temperature set back has been provided during
the night, the amount of heating or cooling and the period of system
operation required for recovery from the setback temperature in the
morning can vary widely with changes in
climatic conditions. This is particularly true where the thermal
characteristics of the building are relatively poor or where the heating
or cooling capacity of the system is relatively limited with respect to
the size of the comfort controlled zone.
As a result, where conventional thermostats control operation of the
various stages of the system by reference to independent threshold
temperatures for the various system stages, they frequently do not
restore the desired comfort temperature at the
scheduled time and either cause discomfort by tardy temperature
restoration or lose potential energy savings by premature temperature
restoration.
The conventional thermostats also tend to lose potential energy
savings in setback operation of multistage temperature conditioning
systems by the excessive or unnecessary use of the usually less
efficient auxiliary stages of the system. This is
particularly true in the case of heat pump systems in which very high
efficiency heat pumps in the main temperature conditioning system stages
are typically combined with substantially less efficient electrical
resistance heaters in the auxiliary heating
stages. For example, when a conventional programmable thermostat is
used with a multistage heat pump system, the recovery from a setback
temperature is often scheduled to occur in the morning at the coldest
part of the day when a heat pump tends to
operate at its lowest level of efficiency. In that circumstance, sone
conventional thermostats call for immediate use of both the heat pump
and the auxiliary heating means to provide quick recovery of the comfort
temperature after reaching the scheduled
end of the night time temperature setback period. That is, because
there is a substantial difference between the setback temperature and
the desired comfort temperature to be restored at the end of the setback
period, both main and auxiliary heaters are
used in restoring the comfort temperature and a large part of the
temperature restoration tends to be effected by the less efficient
auxiliary heating means. Such use of the less efficient auxiliary
heating stages can result in loss of some or all of
the energy savings which had been accumulated during the overnight
setback period even though longer use of the more efficient heat pump
means alone might have resulted in suitably prompt comfort temperature
restoration in the morning in a more
energy-efficient manner. Other known thermostats attempt to regulate
operation of the various heating or cooling stages of multistage systems
by reference to estimated heating capacities of the system components.
One known system initiates system
operation after temperature setback a set time before the end of the
setback period whether there is a large or small difference between the
setback and desired recovery temperature.
With the present emphasis on energy conservation, it is
desirable to provide improved thermostats and control methods for use
with a multistage heating and cooling system to obtain improved control
of comfort temperatures while taking advantage
of the potential energy savings resulting from the use of heat pump
means and from the temperature setback type of system operation.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a novel
and improved thermostat for regulating operation of a heating or cooling
system; to provide such a thermostat which is particularly adopted for
regulating operation of multistage
temperature conditioning systems; to provide such a thermostat which is
particularly adopted for regulating operation of heating or cooling
systems incorporating heat pump means; to provide such a thermostat
which is particularly adopted for use in
energy-saving seetback temperature type of operation; to provide a novel
and improved thermostat which provides improved temperature control and
more energy efficient operation for a multistage temperature
conditioning system using heat pump means where
the system is adopted for the temperature setback type of operation; to
provide novel and improved methods for regulating operation of
multistage temperature conditioning systems; and to provide novel and
improved temperature conditioning systems
incorporating improved and advantageous thermostat means for controlling
the systems in a more energy efficient manner.
Briefly described, the novel and improved thermostat of this
invention comprises an electronic programmable wall thermostat and
preferably comprises a digital thermostat similar to that described in
U.S. patent application Ser. No. 970,019,
filed Dec. 18, 1978, entitled "Electronically Controlled Programmable
Digital Thermostat" and in U.S. patent application Ser. No. 183,703
filed Aug. 26, 1980, entitled "Electronically Controlled Programmable
Digital Thermostat Having Variable
Threshold Hysteresis With Time", which applications are copending with,
and commonly assigned to the assignee of, the present application. The
thermostat is adopted to be electrically coupled to an AC power supply
and to the fan and multiple heating and
cooling stages of a multistage temperature conditioning system,
preferably one which incorporates heat pump means in a main stage of the
system. The thermostat is adopted to control the system using a novel
method to provide desired comfort temperature
or energy-saving setback temperatures in a living space or the like
during respective intervals of the day or night in an improved manner.
In a preferred embodiment of the invention, the thermostat
comprises a programmable digital processor having a read only memory
(ROM) containing a permanently stored, fixed instruction set and having a
random access memory (RAM) which stores
coded instructions entered into the processor by the user. The user
instructions program the system to provide selected temperatures in a
temperature conditioned zone during respective periods of the day and
night in a selected time sequence. The
thermostat includes a plurality of mode switches for selecting a desired
type of system operation; keyboard data entry means for entering coded
user instructions; temperature sensing means to provide an analog
temperature-indicating signal corresponding
to an ambient temperature sensed in a heated or cooled space or zone;
and an analog-to-digital converter which transforms the analog
temperature-indicating signal to produce a corresponding digital signal
and to provide that digital signal to the digital
processor. The processor responds to the digital signal and to the
coded instructions stored in the RAM to selectively gate controllable
switch means such as triac means to activate and/or deactivate the fan
and the heating and cooling stages of the
system in dependence upon the state of the plurality of mode switches,
thereby to control the temperature of the living space or zone as
dictated by the instruction set permanently stored in the ROM and by the
user instructions entered into the RAM. The
thermostat is programmable to automatically maintain desired ambient
temperatures in the zone during selected time periods and is
programmable for automatic shutdown or temperature setback during
periods when the heated or cooled space is unoccupied or
when activity in the space is reduced during sleeping hours. The
thermostat is also operable in a manual mode to continuously maintain a
setback or comfort temperature if desired. The thermostat includes a 60
Hz. oscillator for timekeeping functions,
has a display for desired parameters of time and temperature, and has
characters for indicating operating modes and days of the week and the
like.
In the preferred embodiment of this invention, the instruction
set stored in the ROM as fixed, permanently stored firmware provides a
routine which periodically compares the ambient temperature sensed by
the thermostat with the control
temperature the thermostat is programmed to maintain. In accordance
with the method of this invention, the routine actuates the main heating
or cooling stages of the system when there is a selected difference
between those temperatures. Preferably,
that routine incorporates hysteresis which is variable with time in
regulating main stage operation to avoid unnecessary system cycling as
has been previously described in the latter of the two patent
applications noted above. In accordance with this
invention, the routine also repeatedly updates the signal provided by
the temperature sensing means; utilizes that signal to periodically
determine the rate of change of the sensed ambient temperature being
effected in the temperature conditioned zone by
any operation of the main temperature conditioning means or the like;
and operates the auxiliary heating or cooling stages of the system by
reference to that detected rate of ambient temperature change so that
the auxiliary stages operate only when they
are actually shown to be necessary to supplement the main system stages
for restoring set temperatures at a temperature which is selected as an
optimum or desired temperature restoring rate. That is, the auxiliary
stages are actuated only when the main
stage is operating and only when the actual rate of temperature change
being effected by the main stage is less than a selected or desired rate
of change of zone temperature. Any such operation of the auxiliary
stage is terminated if the rate of change
of zone temperature becomes greater than the desired optimum temperature
restoring rate and any operation of both of the main and auxiliary
temperature conditioning stages is terminated when zone temperature is
restored to main stage threshold
temperature as set by the user. In that way, the thermostat controls
temperature to consistently maintain the control temperature set by the
user even during sharp or severe changes in climatic conditions; the
period of recovery for a setback
temperature is proportioned to permit maximum use of the more energy
efficient main stage temperature conditioning means; improved energy
savings are achieved by operating the less efficient auxiliary
temperature conditioning means of the system only
when there is a positive showing that they are actually required to
supplement the rate of heating being provided by the more
energy-efficient main system stages; and the desired set temperatures
are promptly but not prematurely restored as necessary
even where the thermal characteristics of the building or the heating or
cooling capacities of the system may tend to require substantially
different degrees of heating or cooling under different climatic
conditions.
In one preferred embodiment of the invention, the routine
provided as fixed, permanently stored firmware in the ROM periodically
determines the difference between the temperature in the living space
during a setback period and the temperature to
be provided in that zone at the end of the setback period. That
temperature difference is then utilized in determining the start up time
for the main stage which would be necessary for restoring the desired
comfort temperature at the end of a setback
period. That is, the routine continuously determines the difference
between the actual zone temperature during the setback period and the
next scheduled zone temperature; determines the time prior to the start
of the next scheduled time period when any
operation of the main temperature conditioning means is required to be
initiated for restoring the desired comfort temperature at the end of
the setback period assuming a selected optimum rate of change in zone
temperature during operation of the main
temperature conditioning means; and initiates operation of the main
system stage at said determined restart time to initiate restoration of
the desired comfort temperature. Operation of the auxiliary temperature
conditioning stages of the system are
then regulated by reference to the actual rate of change of zone
temperature effected by the main temperature conditioning means as above
described, thereby to aid the main conditioning means as may be
required in restoring the desired comfort
temperature at the desired rate. In that way, further improved
temperature control and further improved energy efficiencies are
obtained particularly where the high efficiency heat pump type of
heating or cooling means are incorporated in the main
stages of the heating or cooling system.
In the preferred embodiment of this invention, the processor
means comprises a single-chip digital processor of the type
conventionally used for calculator type applications having an internal
ROM permanently dedicated to storage of the
above-noted instruction set. However, it will be understood that
various components of the thermostats are also adopted to be implemented
with independent discrete logic circuitry and the like in any
conventional manner within the scope of this
invention.
DESCRIPTION OF THE DRAWINGS
Other objects, advantages and details of the novel method, of
the novel and improved electronic programmable digital thermostat, and
of the novel and improved temperature conditioning system of this
invention appear in the following detailed
description of preferred embodiments of the invention, the detailed
description referring to the drawings in which:
FIG. 1 is a block diagram of the thermostat of this invention
incorporated in the temperature conditioning system of this invention;
FIG. 2 is a block diagram of digital processor means used in the thermostat of FIG. 1;
FIG. 3 is a perspective view of the thermostat of this invention;
FIG. 4 is a graph illustrating a desired time-temperature sequence programmed into the thermostat by a user;
FIG. 5 is a circuit diagram illustrating electrical connection
of the electronic components of the thermostat of this invention in the
temperature conditioning system of this invention;
FIGS. 6a and 6b are graphs illustrating operation of conventional thermostat means; typical operating conditions;
FIGS. 7a and 7b are graphs illustrating operation of the thermostat of FIG. 1 under similar operating conditions; and
FIG. 8 is a flow chart illustrating a routine used in implementing the control concepts of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, 10 in FIG. 1 indicates the novel and
improved electronically controlled programmable digital thermostat of
this invention which is shown to be used in a temperature conditioning
system 12 to control the temperature in a
living space or zone 14. The thermostat includes a digital processor
means 16, clock means 18, temperature sensing means 20 for sensing the
temperature in the zone 14, scaling amplifier means 21,
analog-to-digital converter means 22 responsive to an
amplified signal from the temperature sensing means 20 for providing a
digital signal 23 to the processor 16 corresponding to the temperature
in the zone 14 when interrogated by the processor as indicated at 24 in
FIG. 1, data entry means 26 for
programming the thermostat 10 to maintain selected temperatures in the
zone during selected periods of time in a selected time sequence, means
28 for displaying desired parameters of time and temperature programmed
into the thermostat, a plurality of
manually operable mode switches indicated diagrammatically at 30 in FIG.
1, and switch or relay driver means 32 such as triac means or the like.
As indicated diagrammatically in FIG. 1, the thermostat 10 has a power
supply 34 connected to a power source
35 for the temperature conditioning system 12 and is preferably arranged
to selectively operate a main heating or temperature conditioning means
such as heat pump 36 through a relay 38 and to operate an auxiliary
heating or temperature conditioning means
such as an electrical resistance heater 40 through a relay 42.
Preferably, the relay driver means are also connected to fan means 44
through a relay 46 and, where the temperature conditioning system 12 is
also adopted to provide cooling, the driver
means 32 are connected to cooling means 48 through a relay 50.
Preferably, for example, where the temperature conditioning system
utilizes conventional reversible heat pump means to serve both main
stage heating and cooling functions, the relay 50 is
arranged to operate the reversing valve of the heat pump which is used
in converting the heat pump from heating to cooling functions in
conventional manner as will be understood.
In the preferred embodiment of this invention, the digital
processor means 16 preferably comprises a microprocessor such as that
shown in U.S. Pat. No. 3,991,305 the disclosure of which is hereby
incorporated herein by this reference.
Preferably for example, the processor 16 comprises a single chip
semiconductor digital processor corresponding to the processor made and
sold by Texas Instruments Incorporated as a standard product under the
designation TMS1670 for general availability
to the industry. As is diagrammatically illustrated in FIG. 2, that
processor includes a ROM 52 which in accordance with this invention is
adopted to permanently store a full instruction set of digital coded
instructions as hereinafter described for
controlling operation of the thermostat 10 in a novel and advantageous
manner; includes a RAM 54 for storing digital coded information (such as
that entered into the processor by the thermostat user to designate
desired time-temperature parameters) while
such information is being processed in the thermostat; and includes an
arithmetic logic unit 56 for performing arithmetic and logic operations
as hereinafter described.
The clock means 18 comprises any conventional 60 Hz. oscillator
means or the like adopted to supply a continuous series of timing
pulses to the processor 16 and, in the preferred embodiment, is
preferably incorporated in an interface device such
as that sold by Texas Instruments Incorporated under the designation
SN7205.
In the preferred embodiment of this invention, the temperature
sensing means 20 preferably comprises a sensistor having an electrical
resistance which varies substantially linearly with temperature over the
selected range of temperatures likely
to be encountered in the living space or temperature conditioning zone
14. Preferably for example, the temperature sensing means comprises a
sensistor of the spreading resistance type such as that manufactured and
sold by Texas Instruments Incorporated
under the designation TSP102 which is adopted to provide an electrical
output varying substantially linearly with temperature from about
32.degree. F. to 122.degree. F.
In the preferred embodiment of this invention, a scaling
amplifier or the like 21 of conventional type applies the sensor output
in appropriately amplified form to the analog-to-digital converter 22
which is arranged in any conventional manner to
be responsive to the electrical output provided by the temperature
sensing means 20 during temperature variations in the zone 14 to provide
digital coded information at 23 to the processor 16 corresponding to
the temperature sensed in the zone 14 as the
sensor is repeatedly interrogated by the processor through the
converter. Preferably for example, the A/D converter 22 comprises the
low cost, high reliability unit made and sold by Texas Instruments
Incorporated under the designation SN78565 which is
generally available to the industry and the scaling amplifier 21 is
incorporated in the interface device SN7205 previously noted above.
In the preferred embodiment of this invention, the thermostat 10
is incorporated in a housing 58 and the data entry means 26 and display
means 28 as well as the plurality of mode switches 30 are provided on a
control panel 60 of the housing as is
illustrated particularly in FIG. 3. If desired, a cover 61 is hinged to
the housing 58 to permit covering of the panel when not in use.
Preferably for example, the mode switches indicated generally at
30 in FIG. 1 include three manually operable switches 62, 64 and 66
each having three operational positions as is illustrated in FIG. 3.
The first manually operable switch 62 is
moveable from HEAT position, where it limits the operation of the
temperature conditioning system 12 to a heating function only; to COOL,
where it limits operation of the system to a cooling function only; or
to AUTO, where it permits the system to
provide either heating or cooling as may be required. The second
manually operable switch 64 is moveable between a first ON position
where it regulates the system fan 44 to operate independently of the
remainder of the system 12; and an AUTO position,
where the fan 44 is operated only when the heating means 36 or 40 or the
cooling means 50 of the system are operating as is hereinafter
described; or EMER HEAT position where the fan is operated only with the
heating means 40 to override control of the
thermostat 10 where special circumstances may require. The third
manually operable switch 64 is moveable from an OFF position wherein
operation of the system 12 is not enabled; to an ON position wherein the
system 12 is operated under regulation by the
thermostat 10; and to a SET position wherein entry of data into the
thermostat 10 by use of the data entry means 26 and display means 28 is
permitted. The mode switches preferably comprise 1-3 pole multiple
throw slide switches of any conventional type.
In a preferred embodiment of this invention, the display means
28 comprise a four digit vacuum fluorescent (VF) display 68 for
time-of-day parameters and a two digit VF display 69 for temperature
parameters. Those displays are preferably
arranged either to operate continuously together; to display only the
time of day continuously; to display only the existing temperature
continuously; or to be blank as the DISPLAY key 70 is mannually
activated by pressing four times to move the display
through said four display statuses in sequence. In the preferred
embodiment, the display means 28 also include similar displays 71 for
days of the week, include indicator lights 72 for DUAL, SINGLE and
CONSTANT types of operating schedules as described
below, include indicator lights 73 for stages 1-4 in those operating
schedules as described below, include indicator lights 74 for COMFORT,
VACANT and SLEEP temperatures to be provided in those scheduled stages
as described below, and preferably include
other indicator lights 75 to indicate when the heating or cooling means
36 or 40 is running and when a back up battery used in the thermostat
requires replacement.
In the preferred embodiment of the invention, the data entry
means 26 includes a plurality of switches 76, 77, 78, 80, 82, 84 and 86
which cooperate with the display means 28 and with the mode switches 30
for programming the thermostat 10. In
that regard, the thermostat is preferably adopted to provide three
different temperatures (COMFORT, VACANT or SLEEP) in each of the two
operating modes (Heating and Cooling) of the system 12 and to provide
three alternate time-temperature sequences
comprising a DUAL temperature setback schedule wherein zone temperature
is changed from SLEEP to COMFORT, to VACANT, to COMFORT and back to
SLEEP during respective sequential periods of the day, a SINGLE
temperature setback schedule wherein zone
temperature is changed from SLEEP to COMFORT and back to SLEEP during
respective sequential periods of the day, and a CONSTANT temperature
schedule wherein the same COMFORT temperature is maintained throughout
the day. The thermostat is preferably
adopted to provide such schedules in any selected sequence for seven
days and to continuously repeat that selected seven day sequence until
one or more of the time or temperature settings is changed by the user
or until such scheduled operation of the
system is overriden by operation of the mode switches 30 or by one of
the specific overriding switches 88, 90 or 92.
In its preferred embodiment, the thermostat is programmed or
reprogrammed for control of heating by positioning the mannually
operable switch 62 at HEAT and by positioning the manual switch 66 at
SET to enable the data entry means 26 for entering
selected time and temperature parameters for the heating mode of the
system in the form of digital coded information into the RAM 54 in the
processor 16.
Pressing of the CLOCK TIME key 76 then permits the time display
68 to be changed to the actual time of day by pressing either one of the
slew switches 77 or 78. Each pressing of the CLOCK DAY key 80 then
changes the day of the week display 71 by
one day to permit the actual day of the week to be set on the display at
71 for correlating the thermostat with real time.
Pressing of the TEMP key 82 then activates one of the indicator
lights 74 at COMFORT for example and pressing of one of the slew keys 77
or 78 changes the temperature display 69 to a desired COMFORT
temperature such as 72.degree. F. Pressing of
the CLOCK TIME key 76 then completes that programming step and sets the
thermostat to provide a temperature of 72.degree. F. whenever a COMFORT
temperature is scheduled. Subsequent pressings of the TEMP key 82 move
the indicator light 74 from COMFORT
to VACANT to SLEEP and back to COMFORT in sequence permitting a VACANT
temperature such as 55.degree. F. and a SLEEP temperature such as
62.degree. F. to be programmed into the thermostat in similar manner
for regulating operation of the system 12 in
the heating mode.
Pressing of the SCHEDULE key 84 then activates an indicator
light 72 and an indicator light 73, at DUAL and at "1" respectively for
example, and pressing of one of the slew keys 77 or 78 changes the time
display 68 to display a desired time such
as 7:00 A.M. as the time when the user intends to rise from bed in the
morning for example. Pressing of the TEMP key 82 as necessary to light
the indicator light 74 at COMFORT and pressing of the CLOCK TIME key 76
then completes that programming step
and sets the thermostat to provide the COMFORT temperature of 72.degree.
F. at 7:00 A.M. during the "1" schedule period when the system is
operated on the DUAL temperature setback schedule described above.
Subsequent pressings of the SCHEDULE key 84
moves the indicator lights 72 and 73 from DUAL and "1" to DUAL and "2",
to DUAL and "3" etc. to pass through the four periods of the DUAL
schedule to the two periods of the SINGLE setback schedule and to the
CONSTANT temperature schedule and permits "go
to work" times and temperatures, "come back from work" times and
temperatures, "bedtime" times and temperatures to be programmed into the
thermostat for both DUAL and SINGLE schedules. A typical schedule for
DUAL temperature setback operation is
illustrated in FIG. 4 and shows that the thermostat is adopted to
setback the temperature in zone 14 to the SLEEP temperature of
62.degree. F. during the nightime, to recover to the COMFORT
temperature of 72.degree. F. at 7:00 A.M. when a user
prepares for work, sets back the zone temperature to the VACANT
temperature of 55.degree. F. while the user is absent from his home
during the workday, restores the COMFORT temperature at 5:00 P.M. at
the end of the workday, and then again sets back
the zone temperature to SLEEP temperature at 11:00 P.M.
In the preferred embodiment of this invention, the thermostat 10
is programmed to provide any of the desired temperature setback
schedules on any of seven days in sequence and to continuously repeat
that seven day sequence. That is, each
presssing of the SELECT DAY key 86 changes the day of the week display
71 by one day for setting the display at a selected day. Pressing the
SCHEDULE key 84 the required number of times to designate the DUAL
temperature schedule, for example, followed
by pressing of the CLOCK TIME key 76 completes that programming step and
sets the thermostat to provide the DUAL schedule on the selected day.
Subsequent pressing of the SELECT DAY key permits other schedules to be
set for the respective days of the
week in a similar manner. Typically, for example, the thermostat is
programmed to provide the DUAL schedule on work days and the SINGLE
schedule on weekend days although any desired combinations may be set.
As will be understood, the thermostat is also
adopted to be programmed in the same way while the manual switch 62 is
set at COOL to additionally program the thermostat to provide
corresponding COMFORT, VACANT and SLEEP temperatures in similar setback
schedules for cooling operation of the system 12
for the seven days of the week. After completing the progamming,
movement of the mode switch 66 to ON position then initiates operation
of the thermostat to regulate the system 12 for heating or cooling as
determined by the setting of the mode switch
62.
In a preferred embodiment of the invention, the 2HR CONSTANT
overriding switch means 88 is adopted to be pressed for providing the
selected COMFORT temperature for a two hour period following pressing of
the key regardless of the temperature
scheduled to be provided by the thermostat during that period.
Similarly, the thermostat is preferably provided with another CONSTANT
switch means 90 which is pressed to override the programmed
time-temperature sequence of the thermostat to provide the
COMFORT temperature continuously until the key is repressed to permit
the thermostat 10 to resume its scheduled time-temperature sequence.
Similarly, the thermostat is also preferably provided with VACANT
overriding switch means 92 which, when pressed,
overrides the program time-temperature sequence to provide the selected,
VACANT low temperature during a period when the living space or zone 14
is to be vacant. Repressing of the switch 92 permits the thermostat to
resume its scheduled time-temperature
sequence control of the system 12. The thermostat permits resumption of
the desired time-temperature sequence in correct correlation to the
actual time of day after the end of the overriding control of the system
12 by the switches 88, 90 and 92 as will
be understood.
In the preferred embodiment of this invention, the power supply
34 is adopted to be connected to a step down transformer 35 which is
connected to a conventional 115 VAC line indicated at 94 for providing
24 VAC to the power supply 34 and to the
relays 38, 42, 46 and 50 for operating the thermostat 10 and components
of the system 12. Preferably for example, the power supply 34 is
adopted to supply 24 VAC to the mode switches 30 and drive means 32 as
indicated at 34.1 in FIG. 1, to supply +9 VDC
to operate the processor 16 as indicated at 34.2, and to supply -16 VDC
to operate the display means 28 as indicated at 34.3. The power supply
is preferably incorporated in the interface device SN75205 previously
noted.
In the preferred embodiment of this invention, the driver means
32 comprises any conventional triac for other switch means adopted to be
selectively operated by the processor 16, such means typically
comprising triac means sold under the
designation TIC216A by Texas Instruments Incorporated which are
connected in conventional manner to driver means incorporated in the
interface device SN75205 noted above.
Interconnection of the noted sensor, A/D converter, keyboard,
display, interface device, mode switches and processor means and the
like as described above is effected in conventional manner to form the
thermostat 10 and the system 12 in
accordance with this invention as is diagrammatically illustrated in
FIG. 5. In that regard, the digital processor 16 controls the operation
of the system 12 by receiving input signals via input terminals K.sub.1
K.sub.2 K.sub.4 and K.sub.8 and by
transmitting output signals via output terminals R.sub.0 -R.sub.15 and
0.sub.0 -0.sub.7. The processor has a 60 Hz. clocking signal applied
to the processor input terminal K.sub.9 from the oscillator 18
incorporated in the interface divice SN75205
noted above which is referenced at 95 in FIG. 5. The processor also
receives a DC input of approximately 9 volts at the processor input
terminal V.sub.ss from the power supply in the interface device. The
display 28 and the keyboard data entry means 26
are selectively controlled and scanned from the output terminals R and O
of the processor terminal 16. That is, the output terminals R.sub.0
-R.sub.7 selectively scan the six time-temperature digits of the display
28 in sequence and output terminals
O.sub.0 -O.sub.7 activate selected segments A-G of each digit in
accordance with the scanned sequence. Output terminals R.sub.7, R.sub.8
and R.sub.9 scan the keyboard switches of the data entry means 26 and
input signals indicative of the positions of
those switches are received via processor input terminals K.sub.1,
K.sub.2, K.sub.4 and K.sub.8. Similarly, output terminals R.sub.8 and
R.sub.9 control and scan the day-of-the-week indications of display 28
and processor terminals O.sub.4, O.sub.6 and
O.sub.7 control operation of the display indicators 72-75. Processor
terminals R.sub.3 -R.sub.0 scan the mode switches 62, 64, and 66 and
input terminals K.sub.1, K.sub.2, K.sub.4 and K.sub.8 receive signals
indicative of the position of the switches.
Terminals R12, R13 of the processor provide control signals for
operating relays 97 and 98 as described below. Output terminals O.sub.0
and R.sub.11 of the processor scan the A/D converter 2 which is enabled
via output terminal O.sub.0. The A/D
converter is not continuously activated to avoid heat build-up problems
in the sensor 20.
In the preferred embodiment of this invention, the A/D converter
includes a resistance bridge (not shown) and a comparator (not shown)
which compares the voltages on each side of the bridge and transmits a
comparator output signal 23 to the input
terminal K.sub.1 of the processor when the bridge becomes balanced. The
bridge includes the temperature sensor 20 and a resistance ladder
having resistors whose resistance values are binary coded. These
resistors are selectively switched on by the
digital processor 16 in a sequence corresponding to binary coded
1.degree. F. step increments in the ambient temperature in the zone 14
until the bridge is balanced, whereupon comparator output 23 changes
state (i.e. changes from a logic "1" to "0" or
vice versa), thereby informing digital processor 16 that the ambient
temperature as measured by the temperature sensor 20 has been reached.
The digital processor compares that ambient temperature and real time
with coded time and temperature
instructions stored in the RAM 54 and controls the heating and cooling
system 12 to maintain the desired ambient temperature in accordance with
the stored instructions.
The processor 16 controls the actuation of the triac means 32 to
regulate the system 12 as shown in FIG. 5. That is, the processor
activates the relays 97, 98 in accordance with setting of the mode
switches 62, 64 and 66 and applies a gating
signal via the output terminal R14 and the interface device 95 to turn
on the triac means, thereby to drive AC current to the heating, fan
and/or cooling relays 38, 42, 46 and 50 via terminals 99 of the
thermostat in dependence on the state of the mode
switches.
If the fan switch 64 is in the AUTO position as shown in FIG. 5
for example, the fan is automatically activated in synchronism with the
heating or cooling means of the system 12. That is, for example, if
switch 66 is in ON position as shown and
relay 98 is positioned as shown for HEAT while switch 62 is in AUTO
position as shown in FIG. 5, the triac means 32 when triggered by the
processor 16 drives AC current through the fan relay 46, operates the
control relay 50 to position the change over
valve of the heat pump for heating, and drives AC current through the
heat pump. If the fan switch is set in the ON position, AC current by
passes the triac means 32 and drives the fan relay regardless of whether
the heating or cooling means of the
system 12 are activated. If the fan switch is set in EMER HEAT
position, the processor changes the position of relay 97 and activates
the auxiliary heating means 40 and the fan 44, also bypassing the triac
means 32. If the mode switch 66 is positioned
in SET position, the heating and cooling means of the system 12 are not
operated but the thermostat 10 is adopted for user programming. If
switch 66 is positioned in OFF position, the system 12 is deactivated
and programming is not enabled. If the mode
switch 62 is set in HEAT position, the system 12 is operable only in the
heating mode and if it is set in COOL position, only cooling operation
of the system is possible.
As microprocessor-based controls are well known and commercially
available and are adopted to be readily assembled by those of ordinary
skill in the control art interconnection of the above-described
components of the thermostat 10 and of the
multistage temperature conditioning system 12 are not further described
herein and it will be understood that the interconnections schematically
illustrated in FIG. 5 are complemented in any conventional manner
within the scope of this invention. Of
course, other circuit components are also adopted to be incorporated in
the circuit arrangement shown in FIG. 5 in accordance with conventional
practice as will be understood. In that regard, it will also be
appreciated that although system 12 is shown
to incorporate only one main stage heating component 36, one cooling
stage 48, and one auxiliary heating stage 40, the system is adopted to
incorporate more than one main system stage for either heating and/or
cooling, more than one auxiliary heating
stage, and one or more auxiliary cooling stages within the scope of this
invention. Further, although the thermostat 10 is primarily described
with reference to regulation of the system 12 having one main and one
auxiliary heating stage and one cooling
means, the thermostat is also adopted to be modified in conventional
manner to regulate operation of systems having other main and auxiliary
heating and/or cooling stages within the scope of this invention.
Preferably, the thermostat includes a battery power supply which
functions as a backup power supply for the processor in the event of
failure of the main system power supply. This permits the processor to
retain any user supplied information
programmed therein and to continue keeping real time.
In this regard, it will be understood that when a conventional
electronically controlled digital thermostat is used to control a
multistage temperature conditioning system having an energy-efficient
heat pump in the main heating stage and having
a less energy-efficient electrical resistance heater in an auxiliary
heating stage as above described, and when the thermostat is adopted to
provide energy-saving temperature setback during the nightime for
example, the threshold temperature of the main
heating stage typically corresponds to the desired setback temperature,
T.sub.setback in FIG. 6a, and the threshold temperature of the auxiliary
stage is frequently set 2.degree. F. lower than the main threshold.
At the end of the setback period, the
main stage threshold is reset to a relatively higher comfort
temperature, T.sub.comfort, and the auxiliary stage threshold is also
increased to be 2.degree. F. less than the comfort temperature. The
thermostat compares the actual zone temperature to
the two noted threshold temperatures and activates one or both of the
heating stages if the zone temperature falls below the respective
threshold. In that arrangement, the zone temperature normally
fluctuates around the desired setback temperature
during the setback preriod as indicated at a in FIG. 6a and, at the end
of the setback, both of the main and auxiliary heating stages are
typically activated as indicated at b in FIG. 6a to begin to restore
zone temperature to a comfort level. When the
new auxiliary stage threshold is reached as a zone temperature is being
restored, the auxiliary heater is deactivated as indicated at c while
the main stage continues to operate until the comfort temperature level
is reached as shown at d. In that
system, the recovery from the setback temperature is largely
accomplished by the relatively less energy-efficient auxiliary heating
stage of the temperature conditioning system. That is, a substantial
part of the energy expended in restoring the comfort
temperature as indicated by the shading at e in FIG. 6b is attributable
to the less efficient auxiliary heater even though earlier and the
longer operation of the more energy efficient main heat pump stage of
the system might have restored the comfort
temperature at the desired time in a more energy efficient manner.
Substantial energy savings are therefore lost. In fact, in using
multistage heat pump systems under some climatic conditions, the energy
expended in restoring comfort temperatures after
a temperature setback period can use up a large part of the energy
savings which had been achieved by the temperature setback during the
entire nightime setback period.
The conventional thermostat control also tends to result in
other energy losses as well as in some difficulty in maintaining comfort
temperature at a desired level. For example, the period of time
indicated af f in FIG. 6a required for full
restoration of a comfort temperature after a setback period can vary
substantially with the conventional control system depending on existing
climatic conditions, on the thermal characteristics of the building in
which the temperature conditioned zone is
located, and the capacity of the temperature conditioning system
relative to the size and other heating requirements of the temperature
conditioned zone. Under poor conditions, the desired comfort
temperature may not be restored until long after the
time desired and can result at substantial discomfort to the system
user. On the other hand, where the temperature setback period is
scheduled to end at a selected time to permit the desired comfort level
to be restored an anticipated time thereafter,
the conventional control can result in premature restoration of the
comfort temperature level under mild weather conditions and that
premature restoration can result in loss of potential energy savings.
The conventional system also can result in poor control of the
comfort temperature under some weather and housing conditions. That is,
the conventional system normally permits the comfort temperature to
fluctuate around the threshold temperature
of the main stage heating means with some hysteresis provided by the
thermostat to limit cycling of the heating system as is indicated at g
in FIG. 6a. Where such fluctuations do not exceed the 2.degree. F.
threshold temperature differential between
the main and auxiliary stage thresholds, the comfort temperature is
maintained by activating the main heating stage of the system but the
auxiliary heating means may also be activated where larger temperature
fluctuations occur. However, where weather
conditions are more severe or where housing or capacity limitations of
the heating system are more critical, so that operation of both of the
heating stages are necessary to restore the desired comfort temperature
level, the zone temperature can
fluctuate around the relatively lower threshold temperature of the
auxiliary heating stages as is indicated by dotted lines h in FIG. 6a.
This again can result in substantial discomfort for the user of the
temperature conditioning system.
In accordance with this invention, the thermostat 10 provides
improved control of temperature in the zone 14 while achieving improved
energy savings by utilizing a new method for controlling the main and
auxiliary temperature conditioning stages
of the system 12. In accordance with this invention, the threshold
temperature of the main stage of the system 12 corresponds to the
temperature scheduled to be provided in the zone 14 during any selected
period of time. Accordingly, the main
temperature conditioning stage of the system is activated by the
thermostat 10 to initiate heating or cooling to provide that set
temperature at any time an actual zone temperature varies from the
scheduled set temperature to a selected extent. In that
regard, the thermostat preferably provides selected hysteresis as noted
below to limit cycling of the system 12 as will be understood. In
accordance with this invention however, the thermostat 10 continuously
senses the actual zone temperature while the
main temperature conditioning means of the system 12 is operating,
periodically determines the rate of change of zone temperature actually
being effected in the zone 14 by such operation of the system 12, and
actuates the auxiliary temperature
conditioning means of the system to aid the main temperature
conditioning means only when the rate of change of temperature actually
being effected in the zone 14 is below a selected or desired optimum
rate of temperature change. In that way, the
thermostat 18 consistently regulates zone temperature with respect to a
single threshold temperature and provides more, or less, auxiliary
temperature conditioning as may be required to maintain the zone
temperature with respect to that single threshold
temperature. The thermostat thus provides more consistent and reliable
control of comfort or setback temperatures as outdoor climatic
conditions may vary from mild to severe even where the building housing
the temperature conditioned zone may have very
poor insulation or other thermal properties and even where the
temperature conditioning capacity of the system 12 may be limited with
respect to the temperature conditioning requirements of the zone 14.
The optimum restoring rate is selected to be
typically within the capacity of the main stage temperature conditioning
means and also to assure maintenance of a comfort or setback
temperature at the desired level and to provide suitably prompt
restoration of a comfort temperature after a setback.
Typically, for example, the optimum rate for heating is selected to be
about 6.degree. F. per hour after an initial period of 10 to 30 minutes
during which the main stage conditioning means operates by itself. Of
course other rates are also possible
within the scope of this invention.
In addition, the thermostat 10 of this invention provides
improved energy saving during the setback temperature type of operation
of the system 12, particularly where that system incorporates heat pump
main stage temperature conditioning means.
In that regard, the thermostat 10 senses actual temperature in the zone
14 during any scheduled period of time and compares that actual
temperature to the temperature scheduled to be provided in the zone in
the next scheduled period of time. The
thermostat periodically determines whether any operation of the main
temperature conditioning stage of the system 12 is required for changing
zone temperature from the actual temperature to the next scheduled
temperature and determines when any operation
of the main stage means must be initiated to provide the next scheduled
temperature at the start of the next scheduled time period assuming that
the main temperature conditioning means is able to restore the desired
temperature at the desired rate of
change of zone temperature as previously noted. The thermostat 10 is
also adopted to initiate operation of the main stage of the system 12 at
that determined restart time to begin restoration of the zone
temperature to said next scheduled temperature at
the start of said next scheduled period of time. When any such
operation of the main temperature conditioning means is initiated, the
thermostat 10 periodically senses the rate of change of zone temperature
being effected by the operation of the main
system stage and, as has been described above, activates the auxiliary
temperature conditioning means where necessary to aid the main
temperature conditioning means in restoring zone temperature to the
desired level. The thermostat continues to monitor
zone temperature and, where both the main and auxiliary stages are
activated to restore the comfort temperature and where the rate of
change of zone temperature being effected by those conditioning means
exceed said selected rate of zone temperature, the
thermostat deactivates the auxiliary temperature conditioning stage. In
that way, the thermostat 10 provides for more timely restoration of the
desired comfort temperature after a temperature setback period and
tends to utilize the more energy efficient
heat pump temperature conditioning means to a much greater extent in
restoring the comfort temperature. This is particularly true where
weather conditions are relatively mild or where housing and system
capacity factors are favorable. That is, in many
of such favorable conditions, the comfort temperature is restored in an
improved manner completely by use of the heat pump main stage means of
the system 12.
For example, as is illustrated in FIG. 7, the thermostat 10
normally regulates operation of the system 12 during a setback
temperature period to maintain a setback temperature wherein the zone
temperature fluctuates around a scheduled setback
temperature T.sup.1.sub.setback with appropriate hysteresis as is
diagrammatically illustrated at a.sup.1 in FIG. 7a. Preferably, the
thermostat is arranged to provide variable hysteresis with time in
maintaining such a zone temperature as has been
previously described in the latter of the two patent applications
previously noted above. During that setback period, the temperature is
typically maintained by use of the main heat pump stage of the
temperature conditioning system 12 as is indicated at
a.sup.1 in FIG. 7b. However, if the rate of temperature restoration
being effected by the system is too low after any initiation of main
stage operation, the auxiliary heating stage of the system is activated
as has been previously described above.
During that setback period, the thermostat 10 senses the actual
temperature in the zone 14 and determines the time b.sup.1 when
operation of a main system stage must be initiated for assuring that the
main system stage is able to restore zone temperature
to the comfort level T.sup.1.sub.comfort at the start c.sup.1 of the
next scheduled time period assuming that the main stage is able to
change zone temperature at the rate indicated at d.sup.1 in FIG. 7a.
That is, the restart time for the main system
stage is determined assuming that the comfort temperature is to be
restored by operation of the main system stage alone as is indicated at
b.sup.1 in FIG. 7b. The thermostat 10 then continues to sense actual
zone temperature, and periodically, at
intervals of 10 minutes for example, determines the actual rate of
change of temperature being effected in the zone 14 by operation of the
main stage alone. If the actual rate of temperature change indicated by
the dotted line e.sup.1 in FIG. 7a is less
than the desired rate such as 6.degree. F. per hour as is indicated at
d.sup.1 in FIG. 7a, the thermostat 10 is adapted to activate the
auxiliary heating stage of the system 12 as indicated at f.sup.1 to
restore the zone temperature at a faster rate
g.sup.1. Similary, if the thermostat determines that after another 10
minute interval that the rate of change of temperature with operation of
both the main and auxiliary heating stages exceeds the desired rate
e.sup.1 as indicated at h.sup.1 in FIG.
7a, the thermostat deactivates the auxiliary heating means leaving the
heat pump operating alone. When the system 12 restores zone 14 to the
desired comfort temperature as indicated at c.sup.1, the thermostat
deactivates the main system stage and/or any
auxiliary stages of the system which may then be operating. In that
arrangement, the thermostat 10 provides for improved energy efficient
control of multistage temperature conditioning means.
In achieving these advantageous results with the thermostat 10,
the ROM 52 of the processor 16 or other comparable memory means
incorporated in the thermostat is provided with a full permanently
stored set of digital coded instructions for
controlling operation of the thermostat in the manner above-described.
As the functions of scanning and controlling operation of the Sensor 20,
A/D converter 22, data entry means 26, display means 28, mode switches
30 and processor 16 and the like to
permit programming and display, to schedule comfort or setback
temperatures in a desired time-temperature sequence, and to adjust the
threshold temperature of the main heating and/or cooling stage of the
system 12 are known and have been described for
example, in the two co-pending patent applications noted above, the
instruction codes or, basic routine for accomplishing those functions
are not set forth herein and it will be understood that they can be
implemented in any conventional manner within
the scope of this invention. Preferably, they generally correspond to
those described in the two patent applications noted above but other
conventional routines are also used within the scope of this invention.
In accordance with this invention, those
instruction codes for the basic routine are supplemented as set forth in
Table I below to provide supplementary routines for accomplishing
operation of the auxiliary heating or cooling stages of the system 12 in
the manner above-described and for
accomplishing anticipation and recovery of a comfort temperature from a
setback temperature in the manner which is also above-described. The
algorithm/source code corresponding to those instruction codes for the
supplementary routine are set forth in
Table II, and the flow charts of FIG. 8a and 8b diagrammatically
illustrate the control logic of the processor 16 in carrying out the
supplementary routine to implement the novel and advantageous
temperature conditioning control concepts of this
invention.
For example, where the system 12 includes a heat pump for main
stage heating and cooling and has a single stage of auxiliary heating,
the basic routine of the processor is adapted in any conventional manner
to periodically reference the
supplementary routine illustrated in FIG. 8 to update the need for
suxilliary heating and to anticipate recovery from setback temperature.
Typically for example, the supplementary routine is referenced at
intervals of 10 minutes. The supplementary
routine first determines whether the system is ON calling for
temperature conditioning and whether the system is to be operated in the
fast recovery (emergency heat), cooling or heating mode. If not in the
ON condition or if in the fast recovery or
cooling mode, a direct signal is provided as indicated at LHTOL to
immediately provide auxiliary heating (for fast recovery) or to signal
ommision of auxiliary heating (for OFF or cooling mode). However, if
the system is in the heating mode, the routine
first determines whether a desired, initial, 10 to 30 minute period of
operation of the main stage heating alone has been completed. If not, a
direct signal provided as indicated at LHTOL again omits auxiliary
heating. However, if the initial period is
over, the signal provided at LHTOL enables the auxiliary heating and
increases the threshold temperature of the auxiliary heating stage from
its original setting in 1.degree. F. increments at 10 minute intervals
(each time that the supplementary routine
is referenced), the original setting of the auxiliary heating
corresponding to the temperature at which the main heating stage last
changed state from OFF to ON. In that way, if zone temperature has
dropped below the main stage temperature while the
system 12 is scheduled to maintain a desired comfort temperature or
setback temperature so that the main stage has been activated to restore
the desired comfort or setback temperature, or if the main stage
threshold had been increased to initiate main
stage operation for recovery of zone temperature from a setback
temperature, the incremental increases of the auxiliary threshold
temperature corresponds to the desired temperature recovery rate of
6.degree. F. per hour. If the main stage heating is
not recovering zone temperature at the desired rate, the auxiliary
heating is activated as its threshold increases to exceed zone
temperature. Similarly, if a period of auxiliary heating increases zone
temperature at a rate faster than the auxiliary
threshold is incrementally increased so that zone temperature exceeds
the auxiliary threshold, auxiliary heating is discontinued.
When referenced, the supplementary routine further includes a
sub-routine which determines the temperature to be provided in the zone
in the next scheduled period of time provided in the thermostat proram,
compares that next temperature to the
actual zone temperature, determines the time prior to that next
scheduled time for restarting the main system stage to recover the
desired temperature at the start of that next period, and, if necessary,
initiates such restarting. That is, the routine
determines whether the system is to be operated in the CONSTANT mode
(and provides a direct signal at LHTOL if in that mode), whether the
actual temperature exceeds a next scheduled cooling temperature or
exceeds a next scheduled heating temperature, and
whether the heating/cooling reversing valve of the heat pump is
appropriately positioned. The routine for heating for example, then
determines the difference between the actual temperature and the next
scheduled temperature, truncates that difference to
a maximum such as (10.degree. F. for cooling and 20.degree. F. for
heating for example) to avoid excessive periods of recovery, converts
the difference to a desired recovery time assuming the desired rate of
temperature recovery, adds the recovery time
to the time of day to determine when restarting is to be initiated, and
preferably adds an offset period such as 10 to 30 minutes to assure
prompt restarting if the calculated restarting is imminent. The routine
also determines whether the actual time
exceeds the calculated restarting time for then setting the system to
begin appropriate temperature recovery.
It should be understood that various other routines are also
within the scope of this invention and that such routines are adapted to
be extended in known manner for regulating system 12 with other
combinations of heating and cooling stages
including systems having several heating stages and/or several cooling
stages.
It will be understood that, although the embodiments of the
invention as described above have been described principally with
respect to the provision of heating in the temperature conditioned zone,
the thermostat 10 is adapted to provide
comparable control of temperature conditioning systems in both heating
and cooling modes and to provide control of multistage systems
incorporating one or more auxiliary stages in addition to the main
system stage, It should also be understood that
although the preferred embodiments have been described as being
implemented by microprocessor means, this invention can also be
implemented with descrete logic circuitry within the scope of this
invention. ##SPC1## ##SPC2##
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