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Accessory Description and Usage
1. Compressor Start Assist-Capacitor/Relay Type
Start capacitor and start relay gives “hard” boost to compressor motor at each start-up.
SUGGESTED USE: Installations where interconnecting tube length exceeds 50 ft (15.24m).
Installations where outdoor design temperature exceeds 105
°
F (40.6
°
C).
Replacement installations with hard shutoff expansion valve or liquid line solenoid on indoor coil.
Units installed with low-ambient controller.
2. Evaporator Freeze Thermostat
A SPST temperature actuated switch which stops unit operation when evaporator reaches freeze-up conditions.
SUGGESTED USE: All units where low-ambient controller has been added.
3. Filter Drier—Bi-flow
A device for removing contaminants from refrigerant circulating in an air conditioner or heat pump system; bi-flow for heat pumps.
SUGGESTED USE: All field-connected split-system units.
4. High-Pressure Switch
Auto reset SPST switch activated by refrigerant pressure on high side of refrigerant circuit. Cycles compressor off if refrigerant pressure rises to about 425 psig.
Provides additional protection against compressor damage due to loss of outdoor airflow.
SUGGESTED USE: Installations exposed to very “dirty” outdoor air.
Installations where condenser inlet air temperature exceeds 125
°
F (51.7
°
C).
5. Interface Control (Optimizer II)
An electric control for controlling a heat pump and gas or oil furnace system for maximum energy savings. It allows heat pump to operate down to a predeter-
mined economic balance point temperature, then switches to allow furnace operation only below that temperature. Requires outdoor thermostat to be adjusted
for economic balance point temperature.
SUGGESTED USE: All heat pump and gas- or oil-fired furnace combination systems.
6. Isolation Relay
A SPDT relay which switches the low-ambient controller out of the outdoor fan motor circuit when the heat pump switches to heating mode.
SUGGESTED USE: All heat pumps where low-ambient controller has been added.
7. Liquid Solenoid Valve (LSV)
An electrically operated shutoff valve to be installed at the outdoor unit and which stops and starts refrigerant liquid flow in response to compressor operation.
Maintains a column of refrigerant liquid ready for action at next compressor operation cycle.
Note: Compressor start assist–capacitor/relay type (Item 1) must be used on single-phase reciprocating compressors.
SUGGESTED USE: In certain long-line applications. (Refer to Long-Line Application Guideline.)
8. Outdoor Thermostat
A SPDT temperature actuated switch which turns on supplemental electric heaters when outdoor air temperature drops below set point.
SUGGESTED USE: Heat pump installations with multiple-stage supplemental heaters
9. Secondary Outdoor Thermostat
A SPDT temperature actuated switch which turns on a third stage of supplemental electric heaters when outdoor air temperature drops below the second-stage
set point.
SUGGESTED USE: Heat pump installations where 3-stage operation of supplemental heaters is desired.
10. Sound Blanket
Wraparound sound attenuation cover for the compressor. Reduces the sound level by about 2 dBA.
SUGGESTED USE: Unit installed closer than 15 ft (4.55m) to quiet areas—bedrooms, etc.
Unit installed between 2 houses less than 10 ft (3.04m) apart.
11. Thermostatic Expansion Valve (TXV)
A modulating flow-control valve which meters refrigerant liquid flow rate into the evaporator in response to the superheat of the refrigerant gas leaving the
evaporator. Kit includes valve, adapter tubes, and external equalizer tube. Both hard shutoff and RPB valves are available.
SUGGESTED USE: For improved system performance in cooling mode.
12. Time-Delay Relay
A SPST delay relay which briefly continues operation of the indoor blower motor to provide additional cooling after the compressor cycles off.
SUGGESTED USE: For improved efficiency ratings for certain combinations of indoor and outdoor units. (Refer to ARI Unitary Directory.)
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