6
Service Valves
The service valves in the outdoor unit come from the factory
frontseated. 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 valve cannot be field repaired, therefore, only a
complete valve or valve stem seal and service port caps are
available for replacement.
Defrost Controls
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 tops outdoor fan, energizes reversing valve
solenoid to return system to cooling cycle (outdoor unit as
condenser, indoor unit as evaporator), and activates accessory
electric heater.
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.
Reversing Valve
In heat pumps, changeover between heating and cooling modes is
accomplished with a valve that reverses flow of refrigerant in the
system. The reversing valve solenoid can be checked with the
power off using an ohmmeter. Check for continuity and shorting to
ground. With 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 8 and 9 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. Remove all charge from system.
3. Remove valve using a tubing cutter.
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.
LEGEND
TP —
Test Point
A07433
Fig. 8
---
Reversing Valve
(Cooling Mode or Defrost Mode, Solenoid Energized)
LEGEND
TP —
Test Point
A07434
Fig. 9
---
Reversing Valve
(Heating Mode, Solenoid De--energized)
Refrigerant Charging
!
WARNING
PERSONAL
INJURY
AND/OR
EQUIPMENT
DAMAGE HAZARD
Failure to follow this warning could result in personal injury
and/or equipment damage.
Wear safety glasses and gloves when handling refrigerant.
Do not overcharge system -- this can cause compressor
flooding.
!
WARNING
PERSONAL
INJURY
AND/OR
EQUIPMENT
DAMAGE HAZARD
Failure to follow this warning could result in personal injury
and/or equipment damage.
Service valves must be fully backseated to close service
port. There is no Schrader valve at the service port, and
failure to backseat the valve could result in loss of system
charge or personal injury.
NOTE
:
Do not vent or de--pressurize unit refrigerant to
atmosphere. Remove and recover refrigerant following accepted
practices.
All units are shipped with the refrigerant charge listed on the
nameplate.
Refer to Product Data and consider the following when working
with Puron (R--410A) refrigerant:
S
Puron refrigerant cylinders are rose colored.
538B
