Method of controlling heating and cooling sources

A method of controlling heating and cooling sources utilizes a computer or an electronic thermostat to control a plurality of heating or cooling resources for regulating indoor temperature within a narrow temperature range. The method maintains a temperature within the control range by activating a required number of heating or cooling sources and proportionally controlling one of the sources within the control range. An additional heat source is activated each time the indoor temperature falls below a preset "add heat" temperature, and a heat source is deactivated each time the indoor temperature passes a preset "delete Heat" temperature. Similarly, when the method is operating in the cooling mode, an additional cooling source is activated when the indoor temperature passes an "add cooling" temperature, and an additional cooling source is deactivated each time the indoor temperature passes a "delete cooling" temperature.

BACKGROUND OF THE INVENTION 
The invention relates to a temperature control system and, more 
particularly, to a temperature control system which is capable of 
controlling temperatures within a selected temperature band when a number 
of heating or cooling sources are used. 
A conventional multi-stage heating system initially draws all heating 
requirements from a single source by switching that source "on" while 
maintaining the other heating sources in the "off" position. In a 
two-stage heating system which utilizes a heat pump and an electrical 
resistance heater, the initial source of heat is usually the heat pump 
because it is more efficient than its companion electrical resistance 
heater. When the initial source or heat pump is no longer capable of 
supplying the heat demanded, the second source is activated to provide 
additional heating to the system. When the additional stage or heat source 
is no longer needed, that stage is turned off. A heating system with three 
or more stages operates in a similar manner. The heating sources are 
sequentially activated or deactivated depending upon the ambient 
conditions. 
A conventional multi-stage system uses a separate thermostat for each heat 
source or stage. Each thermostat is set at a different temperature range 
so that the staged heat sources turn on at successively lower 
temperatures. A typical mercury thermostat has a temperature sensing range 
of about 11/2.degree. F., and the thermostats are placed about 1.degree. 
apart. Accordingly, a two-stage unit would have a control range of 
4.degree., without considering drop. A three-stage unit would have a 
control range of about 61/2. These relatively wide temperature ranges can 
cause inefficient energy use and user discomfort. In addition, wide 
temperature variations may necessitate frequent manual resetting of the 
temperature control. 
Recent efforts to achieve increased energy efficiency have rekindled 
interest in the proportional control of heating and cooling systems. A 
multi-stage thermostat is used in proportional control systems and is a 
limiting factor in the number of stages employed. 
SUMMARY OF THE INVENTION 
The method of this invention overcomes the aforementioned limitations by 
allowing many stages to overlap each other in temperature range. The 
stages are time separated, in that only one stage is proportionally 
controlled at any one time. The other stages are locked "on" or "off" to 
supplement the proportionally controlled stage. The method uses only a 
single thermostat and therefore avoids the wide band of temperature ranges 
created by conventional multi-stage thermostat systems. 
The method initially draws all heating requirements from a predetermined 
single heat source by proportionally controlling the source in order to 
maintain a constant temperature. When the first heat source is no longer 
capable of supplying the heat demanded, the first heat source is switched 
to a continuous "on" mode, and a second heat source is proportionally 
controlled to the same set point to which the first source was controlled. 
This process of switching the proportionally controlled heat source to a 
full "on" mode and modulating the next additional heating source continues 
until no additional heating sources are available or until a sufficient 
amount of heat is being delivered to maintain the indoor temperature 
within a desire temperature range. As the outdoor temperature rises, the 
process reverses itself through each stage. 
In addition, the method can automatically switch from a heating mode to a 
cooling mode and vice versa. This is very useful in climates where 
relatively large temperature changes can occur over short periods of time. 
Finally, the method has a cost and reliability advantage in that 
relatively low-cost, off-the-shelf computer components are used.

GENERAL DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, a computer or microprocessor 15 receives input from an 
information gatherer 16 and provides output to an information communicator 
17 and a digital display device 18. The information gatherer 16 receives 
information or input signals from an indoor temperature sensor 19, an 
outdoor temperature sensor 20, and thermostat setting buttons 23. The 
information communicator 17 delivers information or output signals to an 
air handler 24, an outdoor fan 25, the first heat pump 21 (H1), the second 
heat pump 22 (H2), a reversing valve 26, an indoor blower 27, and a 
resistance heater 28 (H3). 
The various components illustrated in FIG. 1 are conventional and well 
known in the art, and a detailed description thereof is unnecessary. The 
invention does not relate to the details of the particular components 
illustrated but rather to the way in which these components are controlled 
to regulate the indoor temperature of a building. 
The computer or microprocessor 15 is programmed or wired so that the heat 
pumps and the resistance heater are activated as the indoor temperature 
passes through certain preset temperature settings. These temperature 
settings are fed into the computer by the thermostat setting buttons 23. 
The thermostat setting buttons 23 include buttons for indicating the 
various temperature triggers which will be described hereinafter and 10 
buttons for digits 1 through 0 for setting the desired numerical value of 
the temperature at each temperature trigger. The numerical valves are 
displayed by the digital display 18. 
FIG. 2 illustrates how the method reacts to temperature changes and 
controls heat sources in the heating mode. The graph is depicted in terms 
of house or indoor temperature versus time. 
In the embodiment illustrated, an indoor set temperature of 75.degree. F. 
is fed into the computer by the push buttons 23. The computer is 
programmed to set 74.degree. F. as the "Add Heat Trigger" temperature and 
76.degree. F. as the "Delete Heat Trigger" temperature. The computer also 
sets 73.5.degree. and 76.5.degree. as the Full Heat and No Heat 
temperatures, respectively. The 2.degree. range between 74.degree. and 
76.degree. is the proportional control range, and the upper and lower 
limits of this range vary with the indoor set temperature. For example, 
for an indoor set temperature of 70.degree., the Add Heat trigger 
temperature will be 69.degree. and the Delete Heat Trigger temperature 
will be 71.degree.. The Full Heat and No Heat temperatures will be 
68.5.degree. and 71.5.degree., respectively. 
When the heating system is initially activated at Time 0, the indoor 
temperature is 68.degree.. Since the temperature is below 73.5.degree., 
the "Full Heat" mode of the system turns on all heating sources, H1, H2, 
and H3. The heating sources remain on as the indoor temperatures passes 
73.5.degree.. When the temperature reaches 74.degree. (Time 1), which is 
also set as the "Heat Off" temperature as the temperature rises, all 
heating sources are shut off. The indoor temperature continues to rise for 
a period of time and overshoots 74.degree. before the temperature begins 
to decline. As the temperature passes back down through 74.degree., which 
is the "Add Heat Trigger" temperature (Time 2), a first heating source, 
H1, is transferred from the "off" mode to the proportional controller 
mode. In the proportional control mode, the computer is programmed to 
modulate a heating source between the 74.degree. and 76.degree. range (the 
thermostat being set at 75.degree.). Since the indoor temperature is now 
below 74.degree., H1 is turned on by the proportional controller. 
If H1 is not sufficient to keep the house warm, the temperature continues 
to fall until it once again passes below 73.5.degree. (Time 3), and the 
Full Heat demand activates all of the heating sources. All of the heating 
sources remain on until the 74.degree. level is again reached (Time 4), at 
which time all the heating sources except H1 (which is still on 
proportional control) are turned off. The temperature again overshoots 
74.degree. before it begins to fall. When the temperature does fall past 
the 74.degree. "Add Heat Trigger" at Time 5, two things occur. H1, which 
was on proportional control, is switched by the computer to the locked on 
or continuous "on" mode. Also, the second heating source, H2, is 
transferred by the computer from the "off" mode to the proportional 
control mode. H2 is turned fully on by the proportional controller because 
the indoor temperature is below 74.degree.. If we assume that heat 
resources H1 and H2 combined are more than adequate to maintain a 
temperature of 75.degree., the indoor temperature will rise until the 
74.degree. level is reached at Time 6. As the temperature further 
increases, the proportional controller feature of the computer modulates 
the heating output of H2, while H1 remains in the locked-on mode. The 
combined heating sources stabilize the indoor temperature in the 
74.degree.-76.degree. control range. All other unneeded heating sources 
remain off. 
When the outdoor temperature changes, the system reacts accordingly. If at 
Time 7 (FIG. 3) the outdoor temperature were to rise, the proportional 
controller would continue to modulate the output of H2. This monitoring 
would continue until the indoor temperature rose above the "Delete Heat 
Trigger" at 76.degree. (Time 8), at which time the computer would transfer 
H2 to an off mode and would transfer H1 from the locked-on mode to the 
proportional control mode. If the temperature continued to increase and 
passed the 76.5.degree. "No Heat" temperature, H1 would also be shut off. 
The proportional controller would begin to modulate H1 to maintain the 
temperature between 74.degree. and 76.degree.. If the outdoor temperature 
continued to rise, the indoor temperature would again rise past the 
76.degree. Delete Heat trigger, and the computer would transfer H1 from 
the proportional control mode to the "off" mode. 
Referring again to Time 7, in FIG. 3, if the outdoor temperature were to 
decrease, the proportional controller would continue modulating H2 until 
the indoor temperature dropped below the 74.degree. "Add Heat Trigger." H2 
would then be transferred by the computer from the proportional controller 
to the locked-on mode, and a third heating source, H3, would be 
transferred to the proportional controller. Since the temperature is below 
74.degree., the proportional controller would turn H3 fully on until the 
indoor temperature rose above 74.degree.. Thereafter the proportional 
controller would begin modulating the output of H3. 
Other heating sources could also be added to the system if desired. Each 
heating source would be consecutively turned over to the proportional 
controller as the previous heating source was handed to the locked-on mode 
by successive temperature fallings through the Add Heat Trigger of 
74.degree.. 
The Delete Heat Trigger of 76.degree. has the opposite effect of the Add 
Heat Trigger. Successive temperature risings past the Delete Heat Trigger 
will cause the heat source which is being modulated by the proportional 
controller to be transferred to the off mode, and the next heat source 
would be transferred from the locked-on mode to the proportional 
controller. 
If at any time the temperature were to dramatically rise past the 
76.5.degree. "No Heat" trigger, all heating sources would be turned off. 
The computer or microprocessor 15 can be programmed by conventional 
programming methods so that the various temperature triggers can be 
inputted to the computer for controlling the heat sources. The 
proportional control mode is controlled by the computer by programming the 
computer so that it turns the proportionally controlled heat source on and 
off to maintain the indoor temperature within the proportional control 
range of 74.degree. to 76.degree.. 
Cooling can be controlled by the computer in an analoguous manner. In the 
cooling mode, the first and second heat pumps are operated as first and 
second cooling sources C1 and C2. Referring to FIG. 4, a desired indoor 
temperature of 75.degree. in the cooling mode is inputted to computer by 
the thermostat buttons 23, and the computer program sets 76.degree. and 
74.degree. as the "Add Cool Trigger" and "Delete Cool Trigger" 
temperatures, respectively, The program also sets 76.5.degree. as the Full 
Cooling temperature and 73.5.degree. as the No Cool temperature. The 
various temperature levels function as follows: 
______________________________________ 
76.5.degree. 
Full Cooling. 
76.degree. Add Cool Trigger (Moves one cooling 
resource to the proportional 
controller. If a cooling resource 
is locked-on proportional control, that 
resource is transferred to the on 
mode.) 
74.degree. Delete Cooling Trigger (Moves one 
cooling source away from the pro- 
portional controller to the off 
mode. The next cooling source is 
transferred from the locked-on mode to 
the proportional controller.) 
73.5.degree. 
No Cooling. 
______________________________________ 
Once again, the 74.degree.-76.degree. range is the proportional control 
zone. If the house temperature is above 76.5.degree., the Full Cooling 
trigger turns all cooling resources on (Time 0 in FIG. 4). The temperature 
falls to 76.degree., all cooling resources are turned off (Time 1). The 
temperature overshoots 76.degree. on the way down, and when the 
temperature rises past the Add Cool Trigger at 76.degree. (Time 2), the 
first cooling resource C1 is handed to the proportional controller and 
turned fully on because the temperature is above 76.degree.. If C1 is not 
sufficient to keep the house cool, all cooling resources will be turned on 
when the temperature rises above 76.5.degree. (Time 3) and will stay on 
until the temperature again falls to 76.degree. (Time 4). As the 
temperature again rises past the Add Cooling Trigger at 77.degree., (Time 
5), C1 is transferred to the locked-on mode, and C2 is handed to the 
proportional controller. 
The 74.degree. level acts as a Delete Cool trigger in the same manner that 
76.degree. acted as a Delete Heat Trigger. Successive temperature fallings 
past 74.degree. will transfer cooling resources from the locked-on mode to 
the proportional controller and then to the off mode. The 73.5.degree. 
level acts as a No Cool trigger, turning all cooling sources off. 
FIGS. 5-8 illustrate three heat resources and three cooling resources, 
which could all be provided by three heat pumps. The arrow represents the 
proportional selector feature of the invention and points to the resource 
currently on proportional control. If the arrow points to 0 (as in FIG. 5) 
or to one of the heat resources, the computer program locks cooling out. 
Successive temperature fallings past the Add Heat Trigger at 74.degree. 
will increment the arrow to the left. Referring to FIG. 5, if the 
temperature is below 73.5.degree., Fall Heat demand will turn on all heat 
resources. The first temperature falling past 74.degree. after overshoot 
(Time 2 in FIG. 2) will move the arrow one position to the left to H1 
(FIG. 6). H1 is now operated by the proportional controller. 
The next temperature falling past 74.degree. (Time 5 in FIG. 2) moves the 
arrow one more position to the left to H2 (FIG. 7). H2 is now operated by 
the proportional controller and H1 is turned over to the full or locked-on 
mode. 
The arrow is moved to the right by successive temperature risings past 
76.degree.. Three of these events, caused by the outdoor temperature 
warming up to, e.g., 85.degree., would move the arrow to C1 (FIG. 8). In 
this position C1 would be operated by the proportional controller, C2 and 
C3 would be off, and all of the heat resources would be off. 
A computer-controller system has the advantage of variability, since many 
combinations of temperature control levels can be inputted to the computer 
by the thermostat setting buttons 23. For example, the computer can be set 
for the following temperature limits: 
______________________________________ 
Cooling Discomfort (economy operation) 
85.degree. 
Cooling Comfort (normal operation) 
78.degree. 
Heating Comfort (normal operation) 
72.degree. 
Heating Discomfort (economy operation) 
65.degree. 
______________________________________ 
The Cooling Comfort level is the temperature which is selected for 
initiating cooling during waking hours, and the Heating Comfort level is 
the temperature which is selected for initiating heating during waking 
hours. The range between 72.degree. and 78.degree. is a "dead band" range, 
and no heating or cooling occurs within this range. 
The Cooling Discomfort level is the temperature which is selected for 
initiating cooling during sleeping hours or during the periods when the 
dwelling is unoccupied. This is the temperature which is selected by the 
occupant at which he will become uncomfortable even during sleeping. The 
Heating Discomfort level is the temperature which is selected to initiate 
heating during sleeping hours or when the dwelling is unoccupied. This is 
the temperature at which the occupant will become uncomfortable even 
during sleeping. The system is set for economy operation during the hours 
at which the system is controlled by the Heating and Cooling Discomfort 
levels. In other words, the dead band range during these periods is 
widened to the 20.degree. range between 65.degree. and 85.degree.. 
The temperatures and times for the various levels can be inputted to the 
computer by the thermostat setting buttons 23. 
The dead band range is particularly advantageous when the system is set for 
automatic changeover from heating to cooling. The variations in the 
outdoor temperature throughout the day might be sufficient to vary the 
indoor temperature from, e.g., 65.degree. to 80.degree.. The system is 
shut off while the indoor temperature is within the dead band range from 
72.degree. to 78.degree., thereby saving energy. 
The dead band range can be varied as desired by inputting the information 
to the computer by the setting buttons 23. The dead band can be reduced to 
zero if desired, for example in a restaurant, so that the indoor 
temperature will remain substantially constant. 
DESCRIPTION OF ELECTRONIC THERMOSTAT 
The preferred embodiment of the invention uses a computer or microprocessor 
which is programmed to control the heating and cooling resources in the 
manner previously described. However, the heating and cooling resources 
can also be controlled by an electronic circuit. In this embodiment two 
cooling resources and three heating resources are used: 
______________________________________ 
C2 24,000 BTU air conditioner 
C1 12,000 BTU air conditioner 
H1 12,000 BTU heat pump 
H2 24,000 BTU heat pump 
H3 15,000 BTU electrical resistance heater 
______________________________________ 
C1 and H1 can be provided by one heat pump HP1 (see FIG. 11), and C2 and H2 
can be provided by a second heat pump HP2 (FIG. 11). Three capacities can 
be generated from C1 and C2 (or from H1 and H2): 
Capacity 1--12,000 BTU (C1) 
Capacity 2--24,000 BTU (C2) 
Capacity 3--36,000 BTU (C1 and C2) 
Still another capacity can be obtained by alternately switching C1 and C2 
to the proportional controller. When C2 is on, C1 is off, and vice-versa. 
This produces an intermediate capacity between the two resources (18,000 
average BTU). 
The position of the proportional controller (represented by the arrow in 
FIGS. 5-8) is controlled by a three digit binary number, which provides 
eight positions or stages represented in the truth table of FIG. 9. The 
truth table uses the following designations: 
______________________________________ 
ON The resource is in the on mode. 
CYC The resource is being cycled by 
the proportional controller. 
##STR1## Two resources are being inter- changed by the 
proportional 
controller. For example, when 
C2 is on, C1 is off, and vice- 
versa. 
______________________________________ 
FIG. 10 illustrates the analog and digital circuitry used to implement the 
multi-stage operation. A three digit binary number is produced by the 
circuit 32 and fed into the digital logic represented in FIG. 11. 
Referring now to FIG. 10, a variable resistor 33 is preset for the desired 
temperature level of 75.degree.. A thermistor 34 measures the actual room 
temperature. The signals produced by the variable resistor 33 and the 
thermistor 34 are reduced by resistors 35, 36, 37, and 38 and individually 
fed into scaling amplifier 39 to produce an output signal which is 
characteristic of the actual room temperature and which is characteristic 
of the actual room temperature and which has voltage in the range of 0-10 
volts. The output signal from the scaling amplifier 39 is delivered to 
comparators 40-44. 
Comparators 40-43 are arranged to provide a flash encoding method of 
analog-to-digital conversion. This method consists of a series of 
comparators whose outputs are either 1 or 0, depending on the analog input 
signal from the scaling amplifier 39. A reference voltage for each 
comparator is supplied by voltage reference 45 and a number of suitable 
resistor dividers 46-53. Each reference voltage is representative of a 
particular temperature. The reference voltage for cool override comparator 
40 is 8 volts, which corresponds to the 78.degree. temperature level. 
Similarly, the reference voltages for down comparator 41, up comparator 
42, and heat override comparator 43 correspond to 77.degree., 73.degree., 
and 72.degree., respectively. The 73.degree. and 77.degree. levels are the 
"Add Heat" and "Delete Heat" trigger levels, and the 72.degree. and 
78.degree. levels are the "Full On" and "Full Off" trigger levels. 
The output analog signal from scaling amplifier 39 is divided by resistors 
54-57 prior to being fed into comparators 40-43. The analog signal is then 
compared with each specific reference voltage fed into comparators 40-43. 
If the analog signal exceeds the reference voltage, a logic 0 output is 
generated. If the analog signal falls below the reference voltage, a logic 
1 output is generated. 
Up comparator 42 and down comparator 41 generate an operations code for 
implementing the various stages of the system. Output from down comparator 
41 is fed directly into a conventional up-down counter 58. The output from 
up comparator 42 is inverted by inverter 59 before it is delivered to the 
up-down counter 58. A three-bit binary output is generated from the 
up-down counter 58. This binary number is then delivered to the circuitry 
illustrated in FIG. 11. The binary number generated by the up-down counter 
58 represents a particular stage and is shown by the truth table of FIG. 
9. 
The heat override comparator 43 normally registers a logic 0 output when 
the house temperature is above 72.degree. (a 3 volt signal) and a logic 1 
output when the house temperature is below 72.degree.. However, when a 
logic 1 output is already registered, the house temperature must rise to 
74.degree. (a 5 volt output signal from scaling amplifier 39) before the 
output from the heat override comparator 43 will flop back to a logic 0. 
This hysteresis effect on the heat override comparator 43 is produced by 
resistor 40. 
The cool override comparator 40 operates in a similar manner. A logic 0 
output is generated when the house temperature is above 78.degree. (an 8 
volt signal), and a logic 1 output is generated when the house temperature 
is below 78.degree.. A hysteresis effect on the cool override comparator 
40 is produced by resistor 61. When a logic 0 output is already registered 
as the output from the cool override comparator 40, the house temperature 
must fall to 76.degree. (a 6 volt signal) before the output from the cool 
override comparator 40 will flop to a logic 1. 
The output signal from the scaling amplifier 39 is also compared with a 
varying voltage signal from a ramp generator 62 at proportional control 
comparator 44. The signals from the scaling amplifier 39 and the ramp 
generator 62 are reduced for comparison purposes by resistors 63 and 64, 
respectively. Ramp generator 62 generates a sawtoothed signal having a 
twenty minute cyclic period. A 5 volt signal generated at the beginning of 
the cycle gradually increases over the twenty minute period to a 6 volt 
signal. The signal drops back down to the 5 volt level at the end of 
twenty minutes and the cycle is repeated. The 5-6 volt range corresponds 
to the 74.degree.-76.degree. temperature range. 
The comparator 44 activates the particular heating source which is on 
proportional control. When the output signal from scaling amplifier 39 is 
below the varying voltage signal from the ramp generator 62, the 
comparator 44 registers a logic 1 output. Conversely, the comparator 44 
registers a logic 0 output when the output signal from the scaling 
amplifier 39 is greater than the varying voltage signal from the ramp 
generator 62. As a result, the digital output of the comparator 44 changes 
at some point during each twenty minute cycle when the house temperature 
is in the 74.degree.-76.degree. range. Whenever the house temperature is 
outside the 74.degree.-76.degree. range, a constant logic is maintained. 
Referring to both FIGS. 10 and 11, the three-bit digital output from the 
up-down counter 58 is selectively fed to AND gates 65-73. In addition, the 
pulse output from comparator 44 is delivered to AND gates 66, 67, 68, 70, 
71, and 73. Selected inputs to the AND gates are provided with inverters 
for inverting the digital pulses from the up-down counter 58 and the 
comparator 44. These inverters are represented by the circles to the left 
of the AND gates. 
The HI output from up-down counter 58 also delivered to OR gate 74 along 
with the output from heat override comparator 43. The resulting output 
from gate 73 controls the heat reversing valves 75 of the heat pumps HP1 
and HP2. 
The digital output from AND gates 65 and 66 along with the digital pulse 
from the cool override comparator 40 are fed to OR gate 76. The digital 
output from AND gates 67 and 68 along with the digital output from the 
comparator 40 are delivered to OR gate 77. In a similar fashion, the 
output from AND gates 69 and 70 and the output from the heat override 
comparator 43 are delivered to OR gate 78, and the output from AND gates 
71 and 72 and the comparator 43 are delivered to OR gate 79. 
The outputs from AND gate 73 and the comparator 43 are delivered to OR gate 
80, which controls the electrical resistance heater H3. The outputs from 
OR gates 77 and 78 are fed to OR gate 81, which controls the compressor of 
heat pump HP1. Similarly, the outputs from OR gates 76 and 79 are 
delivered to OR gate 62 which controls the compressor of heat pump HP2. 
Operation of Electronic Thermostat 
The operation of the electronic thermostat and the cycling of the resources 
will be explained with reference to FIG. 12, which is a graph of time v. 
temperature similar to FIG. 2. 
The up-down counter 58 is preset with an output of 011 when the system is 
initially activated at Time 0 (see FIG. 12). The output terminal 58a of 
the up-down counter which is designated HI in FIG. 10 is 0, the output 
terminal 58b is 1 and the output terminal 58c, which is designated LO, is 
also 1. The thermistor 34 (FIG. 10) measures the room temperature of 
68.degree., and this measurement is fed into scaling amplifier 39 along 
with the desired preset temperature of 75.degree. from the variable 
resistor 33. The scaling amplifier 39 converts this input into an output 
signal having a voltage between 0 and 10 volts, and the output voltage is 
representative of the actual temperature. The voltage signal is 
subsequently reduced by resistors 54-57 and 59 before it is fed into 
comparators 40-44. At comparators 40-43, this voltage signal is compared 
with a particular reference voltage which is supplied from the voltage 
reference source 45. Since the voltage signal from the scaling amplifier 
39 does not exceed any of the reference voltages, the outputs of 
comparators 40-43 all register a logic 1. The voltage signal supplied to 
comparator 44 is compared with the varying 5 to 6 volt signal from ramp 
generator 63. Since the signal from scaling amplifier 39 is below 5 volts, 
the output from comparator 44 is also a logic 1. 
The logic 1 output from the down comparator 41 is fed into the up-down 
counter 58. The logic output from the up comparator 44 is delivered to the 
inverter 59 and changed to a logic 0 before delivery to the up-down 
counter 58. Neither the logic 1 input from the down comparator 41 nor the 
logic 0 output from inverter 59 change the output of the up-down counter 
58. In order for the up-down counter 58 to count down, a logic--input from 
the down comparator 41 must be followed by a logic 1. The three-bit 
digital code from the up-down counter 58 increases by one when a logic 1 
from the inverter 59 is followed by a logic 0 input from the inverter 59. 
The logic 1 output from the cool override comparator 40 is delivered to 
the inverter 83, thereby flopping the digital pulse to a logic 0. This 
logic 0 output is delivered to OR gates 76 and 77. 
The logic 0 output of the HI terminal of the up-down counter 58 and the 
logic 1 output from heat override comparator 43 are delivered to OR gate 
74, thereby producing a logic 1 output which causes the reversing valves 
75 of the heat pumps HP1 and HP2 to be positioned in the heating mode. The 
heat pumps HP1 and HP2 will therefore be operated as heat resources H1 and 
H2, respectively. The logic 1 output from heat override comparator 43 is 
delivered to OR gates 74, 78, 79, and 80. Simultaneously, the 011 output 
from the up-down counter 58 is selectively delivered to AND gates 65-73 
while a logic 1 is delivered from the comparator 44 to AND gates 66, 67, 
68, 70, 71, and 73. Some of the logic is inverted before entry into the 
AND gates, as noted above. This combination of inputs results in all AND 
gates 65-73 generating logic 0 outputs which are then fed to OR gates 
76-80. 
The logic 0 outputs from AND gates 65 and 66 combine with the inverted 
logic 0 output from the cool override comparator 40 to generate a logic 0 
output at OR gate 76. Similarly, logic 0 outputs from AND gates 67 and 68 
combine with the inverted logic 0 from the comparator 40 to register a 
logic 0 output or OR gate 77. On the other hand, the logic 0 outputs from 
AND gates 69 and 70, AND gates 71 and 72, and AND gate 73 combine with the 
logic 1 output from heat override comparator to generate logic 1 outputs 
at OR gates 78, 79, and 80. The logic 1 output from OR gate 80 activates 
the electric heater H3. The logic 1 output from OR gate 78 and the logic 0 
output from OR gate 77 enter OR gate 81 to register a logic 1 output, and 
the logic 1 from OR gate 79 and the logic 0 from OR gate 76 enter OR gate 
83 to generate a logic 1 output. The logic 1 outputs from OR gates 81 and 
82 activate H1 and H2 respectively. Thus a "Full on Demand" level has been 
reached. 
H1, H2, and H3 will remain activated to increase the house temperature 
until the voltage signal from the scaling amplifier 39 reaches the 5 volt 
level, which corresponds to 74.degree. (see FIGS. 10 and 12). As the house 
temperature passes through the 72.degree., the outputs from comparators 
40-44 remain the same. The hysteresis effect created by resistor 60 on the 
heat override comparator 43 prohibits the comparator's output from 
flopping to a logic 0. 
At Time 11 in FIG. 12, the house temperature passes above the 73.degree. 
level, causing the signal from the scaling amplifier 39 to exceed the 4 
volt reference voltage at the up comparator 44. The up comparator 44 
responds by registering a logic output 0, which is then inverted to a 
logic 1 by the inverter 59 and fed into the up-down counter 58. The 
three-bit code generated by the up-down counter 58 is not altered by this 
logic input. However, the counter 58 is now triggered to increase the 
three-bit binary output by one when the up comparator 44 next changes. 
When the house temperature reaches 74.degree. (Time 12), the scaling 
amplifier 39 transmits a 5 volt signal. This signal now exceeds the 
hysteresis level maintained on the heat override comparator 43, thereby 
causing the output comparator 43 to change to a logic 0. This logic 0 
output is then delivered to OR gates 74, 78, 79, and 80. The outputs from 
these gates change to a logic 0 because the other inputs are also a logic 
0. The logic 0 output from OR gate 74 switches the reversing valves 75 
away from the heating mode. At the same time, all three heating sources 
are deactivated. The logic 0 from OR gate 80 turns off H3. The logic 0 
outputs from OR gates 78 and 79 are delivered to OR gates 81 and 82, 
respectively, to produce logic 0 outputs which turn off H1 and H2. 
The house temperature begins to decline with all heating sources 
deactivated. At Time 13, the house temperature passes below the 73.degree. 
level, thereby reducing the signal from scaling amplifier 39 below 4 
volts. Accordingly, the output from the up comparator 42 now registers a 
logic 1 which is then inverted to a logic 0 by the inverter 59 before 
being fed into the up-down counter 58. The change in input from a logic 1 
to a logic 0 causes the counter 58 to count up by one and generate a 100 
output (see FIG. 9). 
The logic 1 output from HI terminal 58a causes OR gate 74 to register a 
logic 1 output and switch the reversing valves 75 back to the heating 
mode. In addition, the new three-digit code from the up-down counter 58 
and the output from the proportional control comparator 44 are selectively 
delivered to AND gates 65-73. The proportional control comparator 44 
registers a logic 1 output because the signal from scaling amplifier 39 
remains below the 5-6 volt varying signal from generator 62. Only the 
output from AND gate 69 is altered to a logic 1 output. The other AND 
gates maintain a logic 0 output. The logic 1 output from AND gate 69 
causes OR gate 78 and subsequently OR gate 81 to also register a logic 1 
output, thereby activating H1. However, the heating capacity of H1 is not 
enough to maintain the desired 75.degree. level, and the house temperature 
continues to decline. 
At Time 14, the house temperature falls below the 72.degree. level, and the 
signal from the scaling amplifier 39 consequently falls below 3 volts. The 
heat override comparator 43 registers a logic 1 output, thereby delivering 
logic 1 inputs to OR gates 78, 79, 80, and 83 and activating H2 and H3. H1 
continues to remain turned on. The house temperature again begins to rise. 
When the house temperature passes the 73.degree. level (Time 15), the up 
comparator 42 registers a logic 0 which is inverted to a logic 1 by the 
inverter 59 and fed into the up-down counter 58. The logic 1 input does 
not changes the three-digit output from the counter 58 but prepares the 
counter to change the next time that the output from the up comparator 
changes. The house temperature continues to increase, and the 74.degree. 
level is again reached (Time 16) causing the output from the heat override 
comparator 43 to change to a logic 0. This change affects only the outputs 
at OR gates 79, 80, and 82, which all flop to a logic 0. As a result, H2 
and H3 are deactivated, while H1 remains on, and the temperature begins to 
decline. 
At Time 17, the house temperature again passes through the 73.degree. 
level, and the scaling amplifier 38 transmits a signal which does not 
exceed the 4 volt level. Consequently, the up comparator 42 registers a 
logic 1 which is inverted to a logic 0 by the inverter 59 and delivered to 
the up-down counter 58. The change in logic input from 1 to 0 increases 
the three-digit output from the counter 58 to 101. In the meantime, the 
proportional control comparator 44 contineus to register a logic 1 output. 
As shown in FIG. 9, H1 and H2 are both subject to proportional control 
when a 101 code is generated by the counter 58. However, only one source 
is capable of cycling at any one time. The new three-digit code changes 
the output from AND gate 69 back to a logic 0 while the output from AND 
gate 70 now registers a logic 1. These changes do not alter the output for 
any other gates, and H1 continues to be the only activated heat source. 
Thus, the house temperature continues to fall. The proportional control 
comparator 44 does not effectively cycle between H1 and H2 because the 
house temperature is below the 74.degree.-76.degree. range. Therefore, the 
output from the comparator 44 remains a logic 1. 
As the house temperature further declines, it passes below the 72.degree. 
level (Time 18). Once again, the output from heat override comparator 
flops to a logic 1 thereby activating H2 and H3 to run with the already 
activated H1. The output from the up comparator 44 is again reset to a 
logic 0 when the house temperature passes the 73.degree. level (Time 19). 
H2 and H3 are again shut off as the house temperature reaches the 
74.degree. level (Time 20). When the temperature again falls through the 
73.degree. level (Time 21), the up comparator 42 will again register a 
logic 1 output which is inverted to a logic 0 by the inverter 59 and fed 
into the counter 58 to increase the three-digit output to 110. 
Consequently, AND gates 69 and 72 register a logic 1 output while the 
remaining AND gates register a logic 0 output. As a result, OR gates 78, 
79, 81, and 82 register logic 1 outputs, thereby activating both H1 and 
H2. The house temperature again rises above the 73.degree. level (Time 
22), and the up comparator 42 registers a logic 0 output which is inverted 
to a logic 1 and fed into the up-down counter 58 without any affect on the 
heating sources. The temperature continues to rise past the 74.degree. 
level (Time 23), whereupon proportional control comparator 44 becomes an 
active varying controller to cycle H2 and level off the house temperature 
at around 74.5.degree.. 
When the house temperature is below the varying 5-6 volt signal generated 
by ramp generator, the comparator 44 registers a logic 1 output. When the 
house temperature is above the varying signal, comparator 44 registers a 
logic 0 output. The logic output from the comparator 44 determines whether 
or not H2 is activated. Once the house temperature levels off, H2 is 
turned on for approximately 25% of each twenty minute cycle it takes the 
signal from ramp generator 62 to increase from 5 to 6 volts. H2 is turned 
off for the remaining 75% of the cycle. The on-off time percentages will 
vary accordingly to maintain a level as long as the outdoor temperature 
does not push the house temperature above or below the 
74.degree.-76.degree. range. If this does occur, an appropriate stage will 
be selected to maintain a house temperature within the 
74.degree.-76.degree. range. 
It will be understood from the foregoing that if H1 and H2 are not 
sufficient to maintain the desired temperature, the three-digit output 
from the up-down counter 58 will increase to 111 the next time that the 
temperature falls below 73.degree.. This will increase the output from the 
up-down counter to 111 and turn H1, H2, and H3 on (see FIG. 9). When the 
temperature rises above 74.degree., H3 will be cycled by the proportional 
control comparator 44. 
As the outside temperature rises, the house temperature will increase until 
the temperature passes through the Full Off Demand level at 78.degree. and 
all heating resources will be turned off. The input from the down 
comparator 41 to the up-down counter 58 is changed as the temperature 
rises past 77.degree. and the three-digit output from the counter will 
decrease by one. This will change the operation of the system in 
accordance with the truth table of FIG. 9. Successive temperature rises 
through 77.degree. will ultimately change the output of the HI terminal 
58a of the counter to 0 and reverse the reversing valves 75. If the house 
temperature continues to rise the logic circuit will begin activating the 
cooling resources in accordance with the truth table. It is believed that 
the operation of the logic circuit is self-evident from the drawing and 
the foregoing detailed description of the heating system. 
The set temperature of 75.degree. has been used for illustration purposes 
only. The set temperature can be varied by the variable resistor 33 in 
FIG. 10. The output from the scaling amplifier 39 is a function of the 
difference between the set temperature and the actual temperature. A 
reduction in the set temperature of 5.degree. from 75.degree. to 
70.degree. will correspondingly lower the various temperature triggers by 
5.degree., and the temperature will ultimately be controlled within the 
69.degree.-71.degree. range. 
While in the foregoing specification detailed descriptions of specific 
embodiments of my invention have been set forth for the purpose of 
illustration, it will be understood that many variations in the details 
given herein may be made by those skilled in the art without departing 
from the spirit and scope of the invention.