Self contained heating and cooling system with emergency heating

A self contained heating and cooling system is disclosed comprising a heat pump unit having a heat exchanger for heating and cooling air in a space, an auxiliary heating unit for heating air in the space, a support housing for the heat pump and auxiliary heating units, a cycling thermostat for governing operation of the heat pump and auxiliary heating units to enable establishment of a predetermined space air temperature, and a changeover thermostat. The changeover thermostat includes switch having first and second conditions wherein operation of the auxiliary heating means is enabled and disabled, respectively, a control switch operator for operating the control switch to its first condition in response to sensed atmospheric air temperatures below a predetermined temperature and a second control switch operator comprising a mechanism supported by the housing at a location accessible to a system user and manually actuable to effect operation of the control switch to its first condition regardless of sensed atmospheric air temperature levels.

BACKGROUND OF THE INVENTION 
The present invention relates to self-contained heating and cooling systems 
and more particularly to self-contained systems employing heat pump 
airconditioning units for accomplishing heating and cooling as well as an 
auxiliary heating unit. 
So-called window, through the wall, and/or packaged terminal heat pump 
airconditioning systems are all self-contained systems in that they are 
constructed in a single package-like housing. These systems are generally 
assembled in production quantities by the manufacturer and shipped to 
installation sites. This enables the systems to be completely installed 
simply by emplacing them at an installation site and making connections to 
an appropriate electrical power supply. Accordingly the systems include 
all the necessary system operating controls, a refrigerant compressor, a 
refrigerant reversing valve and indoor and outdoor heat exchangers by 
which heat is transferred to and from the refrigerant in the system. 
Typically these kinds of systems are not designed for heating by operation 
of the heat pump when outdoor air temperatures are near or below freezing 
because effective removal of the frozen moisture which accumulates on the 
outdoor refrigerant heat exchanger is a problem in many installations. 
Even in installations where removal of frozen moisture from outdoor heat 
exchangers is not a problem, heat pumps operate at less than maximum 
effectiveness when outdoor tempertures are below freezing. For these 
reasons many self-contained systems are provided with an auxiliary heating 
unit operated exclusively to heat the indoor air when outdoor air 
temperatures are close to and below freezing. 
In order to appropriately schedule operation of the heat pump and auxiliary 
heating units the systems have been provided with a changeover thermostat 
which senses outdoor air temperature to prevent operation of the heat pump 
compressor and enable operation of the auxiliary heating until when sensed 
outdoor temperatures are below a predetermined level, e.g. 40 F..degree.. 
By the same token the changeover thermostats prevent the auxiliary heating 
units from operating when outdoor air temperatures exceed the 
predetermined level. In the event the heat pump unit malfunctions (for 
example the compressor has failed in some manner), if the changeover 
thermostat prevents the auxiliary heating unit from being operated, the 
system is incapable of heating the indoor air when outside air 
temperatures are above the predetermined level but nevertheless cold 
enough that heating is required. (e.g. 45 F..degree.). 
In order to enable the systems to operate on a temporary, emergency basis 
when heating is required but cannot be provided by the heat pump unit, 
proposals have been made for providing an emergency heat switch which 
functions to shunt the changeover thermostat switch and enable operation 
of the auxiliary heating unit. This proposed solution to the requirement 
for an "emergency heat" capability is costly and adds to the complexity of 
the systems. 
SUMMARY OF THE INVENTION 
The present invention provides a new and improved self-contained heat pump 
air conditioning system wherein a temperature responsive switch unit 
senses outdoor, or atmospheric, air temperatures below a predetermined 
level to enable operation of an auxiliary heating unit, with the 
temperature responsive switch unit including an override mechanism having 
a manually operated member for actuating the switch unit to enable 
operation of the auxiliary heating unit at sensed outdoor air temperatures 
above the predetermined temperature level. 
In a preferred embodiment of the invention a self-contained heating and 
cooling system is provided having a heat pump unit, an auxiliary heating 
unit and a support housing for the units. A cycling thermostat controls 
operation of the heat pump unit or the auxiliary heating unit to govern 
the temperature of air in the space being heated or cooled by the system. 
A temperature responsive switching unit functioning as a changeover 
thermostat senses outdoor air temperature to condition a control switch 
for enabling operation of the auxiliary heating unit at outdoor air 
temperatures below a predetermined level and preventing operation of the 
auxiliary heating unit above the predetermined temperature. The changeover 
thermostat includes a control switch operator mechanism supported 
accessibly to a system user for actuation to effect operation of the 
control switch to its condition enabling operation of the auxiliary 
heating unit regardless of the sensed outdoor air temperature. 
Self-contained heating and cooling systems constructed according to the 
invention are thus effective to provide for heating the indoor air by the 
auxiliary heating unit on an emergency basis in case the heat pump unit is 
ineffective when outdoor temperatures are such that auxiliary heating 
would otherwise be prevented. This is accomplished without requiring any 
additional switching assemblies, associated wiring and components. 
Other features and advantages of the invention will become apparent from 
the following description of a preferred embodiment made with reference to 
the accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT 
A self-contained room heating and cooling system 10 constructed according 
to the present invention is illustrated schematically by FIG. 1 of the 
drawings. The system 10 includes a heat pump unit, generally indicated by 
the reference character 12, an auxiliary heating unit 14, a system support 
housing 16, a room temperature responsive thermostat 18, and a temperature 
responsive switching unit 20, both the latter being supported adjacent an 
operator accessible control panel 22 situated on the housing 16. The 
thermostat 18 and switching unit 20 coact in controlling energization of 
the heat pump unit and the auxiliary heating unit when the system 10 is 
operated to heat the room air. 
The heat pump unit 12 is a so-called condenser-evaporator type including a 
refrigerant compressor 30, an indoor heat exchanger 32, an outdoor heat 
exchanger 34 and a refrigerant flow reversing valve 36. The illustrated 
compressor is formed by a suitable positive displacement pump 30a which is 
driven by an electric motor 30b. The motor 30b is operated from a 220 volt 
alternating current power supply across power lines L1, L2 via a contactor 
assembly 38 which completes and interrupts a motor energizing circuit 
across the power lines. 
When the heat pump unit 12 is operated to cool the indoor air, refrigerant 
is directed from the compressor discharge through a discharge pipe 40, the 
reversing valve 36, a pipe 42, the outdoor heat exchanger 34 (which 
functions as a refrigerant condenser) and to the indoor heat exchanger 32 
via a pipe 44 and a refrigerant expansion valve 46. The indoor heat 
exchanger 32 functions as a refrigerant evaporator and absorbs heat from 
the air in the space being cooled. Refrigerant from the indoor heat 
exchanger returns to the compressor intake through a pipe 48, the 
reversing valve 36, and a compressor intake pipe 50. 
When the heat pump unit 12 is operated to heat the space, the reversing 
valve 36 is actuated to reverse the direction of refrigerant flow so that 
refrigerant discharged from the compressor 38 via the pipe 40 is routed 
through the pipe 48 to the indoor heat exchanger 32 which, functioning as 
a refrigerant condenser, transfers heat from the refrigerant to the air in 
the space. The refrigerant then flows to the outdoor heat exchanger 34 via 
the pipe 44 and expansion valve 46. The outdoor heat exchanger 34 
functions as the refrigerant evaporator with the refrigerant passing 
through it absorbing heat from the outdoor air. Refrigerant flows from the 
heat exchanger 34 to the compressor intake pipe 50 through the pipe 42 and 
the reversing valve 36. The various components of the heat pump unit can 
be of any conventional or suitable construction and therefore are 
illustrated schematically and not described here in further detail. 
When outdoor air temperatures are approximately at or below freezing it is 
often difficult to remove frozen water from the vicinity of the outdoor 
heat exchanger. In many installations defrosting the outdoor heat 
exchanger results in the water removed from the heat exchanger refreezing 
in the vicinity of the exchanger and eventually building up sufficiently 
to block air flow across the heat exchanger and possibly creating other 
hazardous conditions. 
Accordingly the illustrated system 10 is constructed and arranged so that 
when outdoor air temperatures are below a predetermined level, e.g. 40 
F..degree., the auxiliary heating unit 14 is operated to heat the air in 
the space and the heat pump unit 12 is deactivated. The auxiliary heating 
unit 14 can be of any suitable or conventional construction but in the 
illustrated and preferred embodiment of the invention the unit 14 is 
formed by an electric resistance heater which is connected across the 
power lines L1, L2 via a contactor assembly 52. 
In the illustrated embodiment of the system 10 a blower 54 is supported by 
the housing 16 for circulating indoor air across the indoor heat exchanger 
32 and the auxiliary heating unit 14 while a blower 56 is provided for 
directing outdoor, or atmospheric, air across the outdoor heat exchanger 
34. The blowers 54, 56 are schematically illustrated and may be of any 
suitable or conventional construction. 
The support housing 16 is illustrated schematically and includes the usual 
supporting framework of structural members to which the various components 
of the system 10 are attached as well as mounting elements for securing 
the system to the building in which it is installed and a sheet metal and 
plastic outer cabinet for covering the equipment. An insulative barrier 
16a is schematically illustrated separating the outdoor heat exchanger 34 
and blower 56 from the remaining components of the system. The housing 16 
projects through a conforming opening in the wall of the building of which 
it is installed and the building wall is schematically illustrated in FIG. 
1 as aligned with the insulative barrier 16a. 
The room thermostat 18 can be of any suitable or conventional construction 
and for the purpose of description is a mechanical thermostat which 
enables and prevents operation of the heat pump unit 12 and the auxiliary 
heating unit 14 in response to sensed indoor air temperature. The 
thermostat 18 is illustrated schematically as having a single pole single 
throw switch 60 (see FIG. 3) which is actuated by a bellows type power 
element 62 via a suitable lever system (not illustrated). Movement of the 
lever system by the bellows 62 is resisted by a spring (not shown) whose 
force is adjustable by rotating a control knob 64 (see FIG. 1). Rotation 
of the knob 64 therefore sets the sensed temperature at which the switch 
60 opens and closes. The bellows 62 is associated with a closed capillary 
tube 66 which extends to bulb section in the intake of the indoor air 
blower 54 so that the temperature of the indoor air returning to the 
intake of the blower 54 primarily governs operation of the switch 60. 
The thermostat 18 has been illustrated schematically and described in 
relation to controlling the refrigerant compressor and auxiliary heating 
unit. In practice the thermostat 18 contains additional switching 
components which are effective to govern operation of the refrigerant 
reversing valve and operation of the compressor for cooling. Thermostats 
of this nature are known and commercially available and therefore further 
description of the thermostat 18 here is omitted. One such commercially 
available thermostat is produced by Ranco, Inc. and known as type C17. 
The temperature responsive switch unit 20 functions as a changeover 
thermostat for controlling whether heating of the inside air is 
accomplished by the auxiliary heating unit 14 or the heat pump unit 12 in 
response to sensed outdoor air temperature as well as for enabling 
emergency operation of the auxiliary heating unit 14 in the event the 
indoor air cannot be heated by the heat pump unit 12. A preferred 
construction of the switching unit 20 is schematically illustrated by FIG. 
2 of the drawings. 
As shown by FIG. 2 the unit 20 comprises a control switch 70, a first 
control switch operator 72 and a second control switch operator 74 all 
supported by a sheet metal control body 76 attached to the support housing 
16 adjacent the operator accessible control panel 22. The control switch 
70 is schematically illustrated as a snap acting single pole double throw 
switch having fixed contacts 80, 82 a movable contact 84 and a snap acting 
electrically conductive spring blade 86 which supports the moving contact 
84. The switch is supported within a molded plastic electrically 
insulative housing 88 from which terminals 90, 92, 94 extend for 
connection to the respective switch contacts 80, 82, 84. The blade 86 is 
operated by a motion transmitting plunger 96, preferably constructed from 
a plastic electrically insulative material which is movably secured to the 
switch housing 88. 
The first control switch operator 72 is constructed to operate the control 
switch between its operative conditions in response to sensed outdoor air 
temperatures and includes a lever system 100 for engaging the control 
switch plunger 96 and a thermally responsive actuator for the lever 
system. The actuator is formed by a bellows 102 and an associated 
capillary tube 104 which are hermetically assembled to each other and 
closed after being filled with a vaporizable fluid. 
Changes in temperature of the fluid filling the capillary tube 104 cause 
expansion or contraction of the bellows 102 in a manner which is well 
known. The bellows 102 is fixedly secured to the sheet metal housing 76 
and the capillary tube 104 extends from the bellows through the insulative 
barrier 16a to bulb located at the intake of the outdoor air blower 56 so 
that the bellows 102 expands and contracts in response to changes in 
outside air temperature at the intake of the blower 56. The bellows 102 
carries a rigid operating member 106 by which motion of the bellows is 
transmitted to the lever system 100. 
The lever system 100 includes a lever member 110 and a biasing assembly 111 
effective to resist movement of the lever member 110 by the bellows. The 
lever member 110 is movable about the axis of a pivot element 112 which 
extends between and is secured to the walls of the control housing 76. The 
member 110 includes an abutment element 114 which engages the bellows, a 
switch plunger engaging portion 116 engaging the plunger 96 and a 
projecting end section 120 remote from the pivot element 112 and the 
bellows. In the illustrated embodiment the switch plunger engaging portion 
116 is formed by an electrically insulative pad of plastic or similar 
material to further insure against the possibility of electrical 
conduction between the plunger 96 and the lever member 110 (the latter 
preferably being formed from a sheet metal stamping). 
The lever biasing assembly 111 is formed by a tension spring 122 connected 
to the lever member 110 via a force adjusting device formed by a screw 124 
and nut 126 which are mounted on the projecting end section 120. The 
opposite end of the spring a 122 is secured in a normally fixed position 
with respect to the lever member 110 during normal operation of the heat 
pump unit. The screw 124 is rotatably supported in the projecting end 
section 120 of the lever member while the nut 126 is carried on the screw 
threads and connected to the tension spring. An access hole 128 in the 
control housing 76 is aligned with the head of the screw 124 so that a 
screw driver can be inserted through the hole to turn the screw 124 and 
adjust the level of spring tension acting on the lever member 110. 
As outdoor air temperature increases, the bellows expands, rotating the 
lever body 110 clockwise (FIG. 2) about the axis of the pivot element 112. 
This motion tends to engage the switch contacts 80, 84. As the outside air 
temperature decreases the lever member 110 is urged to follow contraction 
of the bellows to move (counterclockwise as viewed in FIG. 2) by the 
spring 122 causing the switch contacts 82, 84 to engage each other. 
Operation of the switch contacts is determined by characteristics of the 
snap switch itself and the level of spring force acting on the member 110. 
These in turn determine the tempeature levels at which the switch unit 70 
operates. Accordingly, adjustment of the screw 124 enables the control 
unit 20 to be set so that the operation of the control switch 70 occurs at 
predetermined outdoor temperature levels. In the preferred and illustrated 
embodiment the contacts 80, 84 are disengaged at sensed outdoor 
temperatures below 40 F..degree. to prevent operation of the heat pump 
unit below such that temperature level. 
FIG. 3 schematically illustrates a portion of electrical control circuitry 
for governing operation of the system 10 when it is conditioned to heat 
the indoor air. The compressor motor 30b and the auxiliary heater 14 are 
connected across the power lines L1, L2 via their respective contactors 
38, 52. The contactors 38, 52 are schematically illustrated as having 
relay actuated contacts RC1, RC2, respectively, which are individually 
opened and closed to enable completion and interruption of energizing 
circuits for the compressor motor and auxiliary heater. The contacts RC1, 
RC2 are actuated to their closed positions by energization of relays R1, 
R2, respectively. The relay R1 forms part of the contactor assembly 38 
while the relay R2 forms part of the contactor assembly 52. The control 
switch contacts 80, 82 are electrically connected to the relays R1, R2, 
respectively, so that the contacts 80, 84 are engaged to enable the relay 
R1 to be energized while engagement of the contacts 82, 84 enables 
energization of the relay R2. 
The thermostat switch 60 is connected in series with the control switch 
contact 84 so that closure and opening of the thermostat switch contacts 
energizes and denergizes which ever of the relays R1, R2 is enabled by the 
control switch 20. Accordingly the indoor air is heated by the heat pump 
unit or by the auxiliary heating unit (depending on the condition of the 
control switch 70) in response to the room air temperature levels sensed 
by the thermostat 18. 
In the illustrated circuitry the switches 60, 70 and the relays are 
connected across the secondary winding of a low voltage transformer T via 
a full wave rectifier R. The transformer primary is connected between the 
line L1 and a common line so that 120 VAC is supplied to the primary 
winding. The secondary winding steps the voltage down to 24 volts. 
Conventional filter elements can be used in conjunction with the low 
voltage control circuit if it is desirable to provide filtered direct 
current to the relays. 
From the foregoing description it should be apparent that when sensed 
outdoor air temperatures exceed 40 F..degree. the control switch contacts 
80, 84 are closed to enable the heat pump unit 12 to heat the indoor air 
under control of the thermostat 18. When outdoor air temperatures are 
below 40 F..degree. the control switch contacts 82, 84 are closed to 
enable the auxiliary heating unit 14 to heat the indoor air under control 
of the thermostat 18, with operation of the compressor motor 30b being 
prevented. 
According to the present invention the temperature responsive switching 
unit 20 is actuable to enable the heating unit 14 to heat the indoor air 
under control of the thermostat 18, on an emergency heating basis, 
irrespective of whether the sensed outdoor air temperature is greater than 
40 F..degree.. To this end, the second control switch operator 74 is 
effective to override operation of the first control switch operator 72. 
Hence in the event of a heat pump unit malfunction the auxiliary heating 
unit 14 can be operated at sensed outdoor temperatures above 40 
F..degree.. The second control switch operator 74 includes a lever member 
130 and a manual lever operator 131 (See FIGS. 2 and 4). The member 130 is 
pivotally movable about the axis of a pivot element 132 secured to the 
walls of the control housing 76 and defines first and second arms 134, 136 
which project away from the pivot axis. The first lever arm 134 has an end 
region 140 aligned and engageable with an abutment finger 142 formed on 
the projecting end section 120 of the lever member 110. The second lever 
arm 136 extends through a guide slot 144 in the control housing 76 for 
engagement with the lever actuator 131. 
The lever actuator 131 operates the lever member 130 between a first 
position, in which the lever member 110 may freely actuate the control 
switch in response to sensed temperature, and a second position in which 
the lever member 110 is locked in position and ineffective to actuate the 
control switch 70 to close the contacts 80, 84 regardless of sensed 
outdoor temperature levels. The actuator 131 is normally positioned as 
illustrated by FIG. 2 of the drawings with the lever member 130 in its 
first position. Accordingly the biasing spring 122 is attached to the 
lever arm 136 since that arm remains stationary in the illustrated and 
normal operating position. The spring 122 thus maintains the lever member 
130 biased to its first position. The actuator 131 includes an actuating 
shaft 150 rotatably secured to the control housing 76 by a journal 
construction schematically illustrated and indicated generally by the 
reference character 152, a cam 154 fixed to the shaft, and a shaft 
operating member 156 also fixed to the shaft. The cam 154 and shaft 
operating member 156 are both nonrotatably secured to the shaft, for 
example by the use of a "D" shaped shaft cross section and conforming 
openings in the cam 154 and shaft operating member 156. The preferred 
operating member 156 includes a shaft surrounding body 162 and an integral 
arm 164 extending radially from the shaft. The arm 164 (FIGS. 1, 4 and 5) 
projects through a slot-like opening 166 in the control panel 22. As 
illustrated by FIG. 5, the control panel 22 is provided with printed 
indicia indicating a "normal" position and an "emergency" heat position of 
the arm 164. 
The cam 154 has a lobe 170 for engaging the end of the lever arm 136 
projecting through the guide slot 144. The cam lobe section 170a provides 
a detent-like seat for the lever arm end under normal conditions of 
operation of the heat pump unit. If the heat pump unit should fail to 
operate and emergency heating is desired the arm 164 is moved to its 
"emergency heat" position (illustrated by broken lines in FIGS. 4 and 5) 
causing the cam lobe 170 to rotate and deflect the lever arm 136 thus 
pivoting the lever member 130 about the axis of the pivot element 132. The 
lever arm 134 engages the abutment finger 142 on the lever member 110 and 
forces the lever 110 against the bellows 102 away from the control switch 
unit 70. The control switch unit 70 therefore is actuated to engage the 
contacts 82 and 84 to enable energization of the auxiliary heating unit 14 
regardless of the sensed outdoor air temperature. Since the bellows 102 
and capillary tube 104 are filled in part by vaporized fluid the bellows 
can be compressed by the lever system without damage. 
In the "emergency heat" mode of operation the indoor air is heated by the 
auxiliary heating unit 14 and cycled by the thermostat 18 to maintain the 
indoor air temperature at desired temperature levels. Moreover, since the 
relay R1 is prevented from being energized operating current is not 
supplied to the compressor motor 30b thus avoiding possible additional 
damage to the heat pump unit. When the heat pump unit malfunction is 
corrected the lever 164 is moved back to its "normal heat" position so 
that the indoor air can again be heated by the heat pump unit or the 
auxiliary heating unit depending on the sensed outdoor air temperature. 
While a single embodiment of the present invention is illustrated and 
described herein in considerable detail the invention is not to be 
considered limited to the precise construction disclosed. Various 
adaptations, modifications and uses of the invention may occur to those 
skilled in the art to which the invention relates and the intention is to 
cover all such adaptations, modifications and uses which fall within the 
spirit or scope of the appended claims.