6
428 01 9702 01
Specifications subject to change without notice.
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 7 and 8 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. 7
-
Reversing Valve
(Cooling Mode or Defrost Mode, Solenoid Energized)
LEGEND
TP —
Test Point
A07434
Fig. 8
-
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 back
−
seated to close service
port. There is no Schrader valve at the service port, and
failure to back
−
seat 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 Specification Sheet and consider the following when
working with R
−
410A refrigerant:
S
R
−
410A refrigerant cylinders are rose colored.
S
Recovery cylinder service pressure rating must be 400
psig, DOT (Department of Transportation) 4BA400 or
DOT BW400.
S
R
−
410A systems should be charged with liquid refrigerant.
Use a commercial type metering device in the manifold
hose when charging into suction line with compressor op-
erating.
S
Manifold sets should be 700 psig high side and 180 psig
low side with 550 psig low
−
side retard.
S
Use hoses with 700 psig service pressure rating.
S
R
−
410A refrigerant, as with other HFCs, is only compat-
ible with POE oils.
S
Vacuum pumps will not remove moisture from oil.
S
Polyol Ester oils absorb moisture rapidly. Do not expose oil
to atmosphere.
S
Polyol Ester oils may cause damage to certain plastics and
roofing materials.
S
Wrap all filter driers and service valves with wet cloth when
brazing.
S
factory approved, liquid
−
line filter drier is required on ev-
ery unit.
S
Do not use a TXV (thermostatic expansion valve) designed
for use with R
−
22 refrigerant. Refer to separate indoor unit
installation instructions for more details.
S
If using a suction line drier, do not leave in place for more
than 72 hours.