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25VNA0 Pumpdown & Evacuation
If this system requires either a Pump Down or Evacuation for any
reason, the procedures below must be followed:
Pump Down
Because these systems have an inverter controlled compressor and
suction pressure transducer, conventional procedure cannot be used
to "pump down" and isolate the refrigerant into the outdoor unit.
The wall control has provisions to assist in performing this
function.
1. Connect gages to 25VNA0 liquid and vapor service ports to
monitor operating pressures during and at completion of the
procedure.
2. In the advanced menu of the UI, go to Checkout > Heat
Pump> Pumpdown
3. Select mode to pump down in (COOL or HEAT), COOL
mode allows refrigerant to be isolated in outdoor unit.
HEAT mode allows the refrigerant to be isolated in indoor
coil and lineset. Set desired time period. Default time peri-
od for the procedure is 120 minutes.
4. Select START on wall control to begin the pumpdown
process. Unit will begin running in selected mode after a
brief delay.
5. Close the liquid service valve.
6. The unit will run in selected mode with the low pressure
protection set to indicate pumpdown is complete when the
suction pressure drops below 0 psig. Compressor protec-
tions are still active to prevent damage to the compressor or
inverter (high pressure, high current, high torque, scroll
temperature, etc.) .
7. Once system indicates pumpdown complete or failure to
complete shutdown, close vapor service valve.
8. If pumpdown does not complete due to compressor safety
shutdown, a recovery system will be required to remove fi-
nal quantity of refrigerant from indoor coil and line set.
9. Remove power from indoor and heat pump unit prior to ser-
vicing unit.
NOTE: A small quantity of charge remains in the OD unit that
must be manually recovered if isolating refrigerant to indoor coil
and lineset via HEAT mode PUMP DOWN.
Evacuation and Recovery of Refrigerant from within
25VNA0
CAUTION
!
ENVIRONMENTAL HAZARD
Failure to follow this caution may result in environmental
damage.
Federal regulations require that you do not vent refrigerant to
the atmosphere. Recover during system repair or final unit
disposal.
Because this system has an EXV for the heating expansion device,
additional steps must be taken to open the EXV if the heat pump
unit must be evacuated for service reasons. If the EXV is not open
when pulling a vacuum or recovering refrigerant from the heat
pump unit, extended evacuation time may be required and/or
inadequate vacuum obtained.
provisions to open the EXV for refrigerant recovery and/or
evacuation.
1. Connect gages to 25VNA0 liquid and vapor or suction cap-
illary service ports to monitor operating pressures during
and at completion of the procedure. Attach recovery system
or vacuum pump to gage set as needed for the service pro-
cedure. The service valves must be open to evacuate the
unit through the line set service ports. The suction capillary
The UI (User Interface) has
service port is a direct connection to the suction port of the
compressor.
2. In the advanced menu of the wall control, go to Checkout >
Heat Pump> > Evacuation.
3. Set desired time period. Default time period for the proce-
dure is 120 minutes.
4. Select START on UI to open the valve.
5. Begin evacuation or refrigerant recovery as required for the
procedure after UI indicates the EXV is open. Power may
be removed from heat pump after the UI indicates "READY
TO EVACUATE."
6. Remove power from indoor and heat pump unit prior to ser-
vicing unit. The EXV will retain the open position.
NOTE: See service training materials for troubleshooting the EXV
using EXV CHECK mode.
FIELD
SIDE
SEAT
BAR STOCK FRONT SEATING VALVE
Fig. 30 – Suction Service Valve (Front Seating)
NOTE: All outdoor unit coils will hold only factory- -supplied
amount of refrigerant. Excess refrigerant, such as in long- -line
applications, may cause unit to relieve pressure through internal
pressure- -relief valve (indicated by sudden rise of suction pressure)
before suction pressure reaches 5 psig (35kPa). If this occurs, shut
unit off immediately, front seat suction valve, and recover
remaining pressure.
Reversing Valve (25VNA0)
In heat pumps, changeover between heating and cooling modes is
accomplished with a valve that reverses flow of refrigerant in
system. This reversing valve device is easy to troubleshoot and
replace. The reversing valve solenoid can be checked with power
off with an ohmmeter. Check for continuity and shorting to
ground. With control circuit (24v) power on, check for correct
voltage at solenoid coil. Check for overheated solenoid.
With unit operating, other items can be checked, such as frost or
condensate water on refrigerant lines.
The sound made by a reversing valve as it begins or ends defrost is
a "whooshing" sound, as the valve reverses and pressures in system
equalize. An experienced service technician detects this sound and
uses it as a valuable troubleshooting tool.
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 close to each other. Any 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.
Route thermocouple leads to inside of coil area through service
valve mounting plate area underneath coil. Fig. 31 and Fig. 32
show test points (TP) on reversing valve for recording
temperatures. Insulate points for more accurate reading.
If valve is defective:
1. Shut off all power to unit and remove charge from system.
2. Remove solenoid coil from valve body. Remove valve by
cutting it from system with tubing cutter. Repair person
44
STEM
SERVICE PORT
W/SCHRADER CORE
A91447
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