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Accessory usage guideline
* For tubing line sets between 50 and 175 ft (15.24 and 53.34m), refer to Residential Split-System Long-Line Application Guideline.
† For buried line applications, refer to Residential Split System Buried Line Application Guideline.
‡ Only when low-pressure switch is used.
Accessory description and usage (Listed alphabetically)
1. Compressor Start Assist — Capacitor and Relay
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 on indoor coil.
Installations where Liquid-Line Solenoid Valve has been added.
Units installed with Low-Ambient Controller.
2. Compressor Start Assist — PTC
Solid-state electrical device which gives a “soft” boost to compressor motor at each start-up.
SUGGESTED USE: Installations with marginal power supply.
Replacement installations with rapid pressure balance (RPB) expansion valve on indoor coil.
3. Cycle Protector
Solid-state timing device which prevents compressor rapid recycling. Control provides an approximate 5-minute delay after power to the compressor
has been interrupted for any reason, including normal room thermostat cycling.
SUGGESTED USE: Installations in areas where power interruptions are frequent.
Where user is likely to “play” with room thermostat.
All commercial installations.
Installations where interconnecting tube length exceeds 50 ft (15.24m).
High-rise applications.
4. Evaporator Freeze Thermostat
An SPST temperature actuated switch which stops unit operation when evaporator reaches freeze-up conditions.
SUGGESTED USE: All units where Winter Start Control has been added.
All units where Low-Ambient Controller has been added.
5. Filter Drier—Bi-Flow
A device for removing contaminants from refrigerant circulating in a heat pump system: 2-direction flow.
SUGGESTED USE: All split-system heat pumps.
6. 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
426
±
7 psig and resets at 320
±
20 psig. Provides protection against compressor damage due to loss of outdoor airflow. To prevent rapid compressor
recycling, Cycle Protector can be used with this switch.
SUGGESTED USE: Installations exposed to very “dirty” outdoor air.
Installations where condenser inlet air temperature exceeds 125
°
F (51.7
°
C).
7. 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
predetermined 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.
8. Isolation Relay
An SPDT relay which switches the Low-Ambient Controller out of the outdoor fan motor circuit when heat pump switches to heating mode.
SUGGESTED USE: All heat pumps where Low-Ambient Controller has been added.
9. Liquid-Line 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 and Relay must also be used.
SUGGESTED USE: In certain long-line applications. Refer to Residential Split System Long-Line Application Guideline.
ACCESSORY
REQUIRED FOR
LOW-AMBIENT
APPLICATIONS
(Below 55
°
F/12.8
°
C)
REQUIRED FOR
LONG-LINE
APPLICATIONS*
(Over 50 Ft/15.24m)
REQUIRED FOR
BURIED LINE
APPLICATIONS†
(Over 3 Ft/0.914m)
Crankcase Heater
Ye s Ye s Ye s
Evaporator Freeze Thermostat
Ye s N o N o
Winter Start Control
Yes‡ No No
Accumulator
No No Yes
Compressor Start Assist
Capacitor and Relay
Yes Yes Yes
Low Ambient Controller
or
MotorMaster® Control
Ye s N o N o
Wind Baffle
See Low-Ambient Instructions No No
Support Feet
Recommended No No
Liquid-Line Solenoid Valve
or
Hard Shutoff TXV
No
See Long-Line
Application
Guideline
Ye s
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