Cold Point CNC series Installation, Operation And Maintenance Manual - Page 9
Browse online or download pdf Installation, Operation And Maintenance Manual for Air Conditioner Cold Point CNC series. Cold Point CNC series 10 pages. Remote condensing unit
Print PageSUB-COOLING METHOD FOR EXPANSION
VALVE INDOOR UNITS:
An air conditioning system utilizing a thermostatic
expansion valve (TXV or TEV) for its metering device
will automatically maintain proper evaporator superheat
regardless of varying operating conditions. Therefore,
when charging a TXV system, the charge is adjusted to
assure that there is pure liquid refrigerant, void of any
flash gas, entering the expansion device. Verifying a
liquid 'seal' at the expansion valve can be accomplished
by measuring the sub-cooling, (sub-cooling is the
sensible heat removed from the liquid refrigerant as it
travels through the last passes of the condenser). As
with superheat, the proper level of sub-cooling is
important. If the sub-cool level is too low or
nonexistent, flash gas will form, causing restricted flow
through the TXV reducing system capacity. Higher
than normal sub-cooling is an indication that liquid
refrigerant is "backing up" in the condenser, reducing
its effective condensing area. If too high, due to an
overcharge, it can lead to high condensing pressure
problems.
PROCEED as FOLLOWS:
1. Operate unit a minimum of 10 minutes prior to
checking refrigerant charge.
2. Measure liquid service valve pressure by attaching an
accurate gage to the service port. Determine saturation
temperature from T/P chart.
3. Measure liquid line temperature by attaching an
accurate thermistor type or electronic thermometer to
liquid line near service valve.
4.Calculate sub-cooling (Saturation temp.-measured
temp.)
5.Sub-Cooling should be 15 deg. Add refrigerant if
sub-cooling is lower than 15deg. Recover refrigerant if
sub-cooling is higher than 15 deg..
6. Whenever charge is removed or added, the system
must be operated for a minimum 20 minutes to
stabilize before additional measurements can be made.
RECHARGE:
When it is necessary to completely recharge the system
refer to the unit nameplate for the starting charge.
Verify the final charge using the 'superheat' or 'sub-
cooling' method. Be sure proper refrigerant handling
and reclaiming methods are used. Technician
certification is required by law.
FINAL INSPECTION:
Do a final visual inspection of the entire installation and
complete any final details and clean up.
Review Unit Operation with the homeowner/user.
9