© 2009 Viking Preferred Service
16
Pressure and Temperature
(continued)
In evaluating this system, the best point to
determine if pressures are correct is at the end of
the production cycle. This is the point where there
is a thick slab formed on the evaporator and the
evaporator thermostat is near cut-out temperature.
Using Refrigeration Temperature/Pressure chart ,
convert temperature to a corresponding pressure.
If low side pressure is below pressure in
Refrigeration Temperature/Pressure chart , check
for the following:
1. A system leak.
2. Capillary tube is restricted.
3. Insufficient compressor (does not pump
properly)
If low side pressure is above pressure in
Refrigeration Temperature/Pressure chart , check
for the following:
1. Restricted air flow.
2. Dirty condenser coil.
3. Leaking or energized hot gas valve.
4. Overcharged system.
5. Low side leak.
Re-charging
RE-CHARGING OF THE UNIT SHOULD BE DONE
ONLY AFTER DIAGNOSING AND REPAIRING
THE SYSTEM Sealed System Introduction). Be sure
to flush the system with dirty nitrogen gas and
evacuate to 400 microns before re-charging.
THE METHOD FOR RE-CHARGING THE UNIT IS
BY WEIGHT USING VAPOR REFRIGERANT. Using
manifold gage set-up, hook up charge hoses to
the access valve on the compressor’s process tube.
If any access valve is attached to the high side
process tube, remove it and then seal the tube by
brazing before charging. Charge the unit to
5 oz. (0.313 lbs.) or 3.5 oz. (0.218 lbs.) of R-134a,
as specified on the serial plate.
After re-charging, check pressures. Refer to
Refrigeration Temperature/Pressure chart for
corresponding temperatures and pressures. If
pressures or temperatures are incorrect, check the
sealed system, recover the charge, repair, evacuate,
and then re-charge.
NOTE:
It is not uncommon to have some
condensation or a slight frost on the suction line.
This may occur towards the end of the production
cycle. Liquid refrigerant is not getting into the
compressor if the unit was charged properly.
It is important that the insulation remains on the
suction line and the capillary tube together after
any repair and that it is sealed at both ends. Repair
any rips or tears as needed with vinyl tape.
Service Diagnostics and Procedures
(Sealed System)
