Service Valves And Pumpdown - Carrier Infinity 25VNA0 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. 29)
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.
24VNA0 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 24Vvna0 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 > Cooling
> Pumpdown
3. Select desired time period. Default time period for the pro-
cedure 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 air conditioner unit prior to
servicing unit.
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.
FIELD
SIDE
SEAT
BAR STOCK FRONT SEATING VALVE
Fig. 29 – 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.
43
STEM
SERVICE PORT
W/SCHRADER CORE
A91447