Product data

NOTE: If pressure switch needs to be replaced, there is a Schrader valve located under the switch so that system will not
need to be evacuated.
CRANKCASE HEATER (If Unit is so Equipped)
Heater prevents refrigerant migration and compressor oil dilution during shutdown when compressor is not operating. If
crankcase heater is de-energized for more than 6 hours, both compressor service valves must be closed. Crankcase heater is
powered by high-voltage power of unit. It is connected across the line side of the contactor and operates
continually. Use extreme caution when trouble-shooting this device with unit power on.
To troubleshoot:
1. Apply voltmeter across crankcase heater leads to see if heater voltage is on. Do not touch heater. Carefully feel
area around crankcase heater; if warm, crankcase heater is probably functioning.
2. With power off and heater leads disconnected, check across leads with ohmmeter. Do not look for a specific
resistance reading. Check for resistance or an open circuit, and change heater if an open circuit is detected.
SERVICE VALVES
The service valves in the outdoor unit come from the factory front seated. This means the refrigerant charge is isolated from
the line-set connection ports. To prevent damage to the valve, use a wet cloth or other accepted heat sink material on the
valve before brazing. The service valves must be back seated (turned counter-clockwise until seated) before the service port
caps can be removed and the hoses of gage manifold connected. In this position, refrigerant has access from and through
outdoor and indoor unit. The service valve cannot be field repaired; therefore, only a complete valve or valve stem seal and
service port caps are available for replacement.
DEFROST CONTROL
The control, which consists of defrost control board and defrost thermostat, interrupts the normal system heating operation to
defrost the outdoor coil, if the coil saturated suction temperature indicates freezing temperatures. Defrost control board can
be field set to check need for defrost (every 30, 50, or 90 minutes of operating time) by connecting the jumper labeled W1
(on the circuit board) to the spade terminal for the defrost time desired. The board is factory set for 90 minutes. The defrost
period is field selectable, depending upon geographic areas and defrost demands. Control board has additional feature that
allows unit to restart in defrost cycle if room thermostat is satisfied during defrost. Defrost control simultaneously stops
outdoor fan, energizes reversing valve solenoid to return system to cooling cycle (out-door unit as condenser, indoor unit as
evaporator), and activates accessory electric heater (if so equipped). The defrost timer limits defrosting period to 10 minutes.
Normally, the frost is removed and the defrost thermostat contacts open to terminate defrosting before 10 minutes have
elapsed. When defrosting is terminated, the outdoor fan motor is energized and reversing valve solenoid is de-energized,
returning unit to heating cycle.
NOTE: If a Heat Pump unit is matched with a High Wall Unit the demand defrost will override the timed defrost. See fan
coil unit installation instructions for details.
REVERSING VALVE
In heat pumps, changeover between heating and cooling modes is accomplished with a valve that reverses flow of refrigerant
in system. The reversing valve solenoid can be checked with power off using an ohmmeter. Check for continuity and shorting
to ground. With the control circuit (24 v) power on, check for correct voltage at solenoid coil, and for burned or overheated
solenoid. With unit operating, other items can be checked, such as frost or condensate on refrigerant lines. Using a remote
measuring device, check inlet and outlet line temperatures. Do not touch lines. If reversing valve is operating normally, inlet
and outlet temperatures on appropriate lines should be similar. Any temperature difference would be due to heat loss or gain
across valve body. Temperatures are best checked with a remote reading electronic-type thermometer with multiple probes.
Figures 9 and 10 show test points on reversing valve for recording temperatures. Insulate points for more accurate reading.
If valve is defective:
1. Shut off all power to unit.
2. Recover all charge from system.
3. Un-sweat valve.
4. Install new valve (wrap valve with a wet rag to prevent overheating while brazing).
5. After valve is brazed in, check for leaks.
6. Evacuate and charge system. Operate system in both modes several times to be sure valve functions properly. (MORE)