Service Valves And Pumpdown - Carrier 25VNA Service Manual

Service Valves and Pumpdown

WARNING
!
PERSONAL INJURY AND UNIT DAMAGE HAZARD
Failure to follow this warning could result in personal injury
or equipment damage.
Never attempt to make repairs to existing service valves. Unit
operates under high pressure. Damaged seats and o- -rings
should not be replaced. Replacement of entire service valve is
required. Service valve must be replaced by properly trained
service technician.
Service valves provide a means for holding original factory charge
in outdoor unit prior to hookup to indoor coil. They also contain
gauge ports for measuring system pressures and provide shutoff
convenience for certain types of repairs. (See Fig. 28)
The service valve is a front- -seating valve, which has a service port
that contains a Schrader fitting. The service port is always
pressurized after the valve is moved off the front- -seat position.
The service valves in the outdoor unit come from the factory
front- -seated. This means that the refrigerant charge is isolated from
the line- -set connection ports. The interconnecting tubing (line set)
can be brazed to the service valves using industry accepted
methods and materials. Consult local codes.
Before brazing the line set to the valve, the belled ends of the sweat
connections on the service valves must be cleaned so that no brass
plating remains on either the inside or outside of the bell joint. To
prevent damage to the valve and/or cap "O" ring, use a wet cloth
or other acceptable heat- -sinking material on the valve before
brazing. To prevent damage to the unit, use a metal barrier between
brazing area and unit.
After the brazing operation and the refrigerant tubing and
evaporator coil have been evacuated, the valve stem can be turned
counterclockwise until back- -seats, which releases refrigerant into
tubing and evaporator coil. The system can now be operated.
The service valve- -stem cap is tightened to 20 ± 2 ft/lb torque and
the service- -port caps to 9 ± 2 ft/lb torque. The seating surface of
the valve stem has a knife- -set edge against which the caps are
tightened to attain a metal- -to- -metal seal.
The service valve cannot be field repaired; therefore, only a
complete valve or valve stem and service- -port caps are available
for replacement.
If the service valve is to be replaced, a metal barrier must be
inserted between the valve and the unit to prevent damaging the
unit exterior from the heat of the brazing operations.
CAUTION
!
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Wear safety glasses, protective clothing, and gloves when
handling refrigerant.
Pumpdown & Evacuation
If this system requires either a Pump Down or Evacuation for any
reason, the procedures below must be followed:
Pump Down
Because this system has an inverter controlled, compressor, suction
pressure transducer and EXV, conventional procedure cannot be
used to "pump down" and isolate the refrigerant into the outdoor
unit. The UI (User Interface) has provisions to assist in performing
this function.
1. Connect gages to 25VNA liquid and vapor or suction capil-
lary 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 UI 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
25VNA
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 25VNA liquid and vapor or suction capil-
lary 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 proced-
ure. The service valves must be open to evacuate the unit
through the line set service ports. The suction capillary ser-
vice port is a direct connection to the suction port of the
compressor.
2. In the advanced menu of the UI, go to Checkout > Heat
Pump> > Evacuation.
3. Set desired time period. Default time period for the proced-
ure 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."
34
The UI (User Interface) has