ClimaCool UCR 30, 50 and 70 tons Manual - Manual (Page 27)

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Charging of Systems with Sporlan Head Pressure
Control in Ambient ABOVE 70°F
(After normal evacuation procedures)
Before Starting System:
1. Connect refrigerant cylinder to a charging or gauge port
on the receiver outlet valve.
2. Open the receiver valve approximately one-half way
(so receiver and liquid line are connected to charging or
gauge port).
3. Charge liquid refrigerant into the high side of the
system. Weighing the charge is recommended with the
initial charge consisting of approximately 2.5 pounds
per system ton.
4. Remove the refrigerant drum and connect it to the
suction side of the compressor.
5. Charge refrigerant vapor into the low side until the
pressure is above atmospheric pressure. Do not admit
liquid refrigerant into the low side.
6. Start the system.
7. Observe sight glass (at receiver outlet) to see if system
is properly charged for normal refrigeration cycle.
CAUTION: Bubbles in the sight glass can be caused by
fl ashing due to pressure drop from pipe or accessory
losses, etc.
8. If the sight glass shows bubbles, more refrigerant
should be added, while allowing suffi
cient time for the
refrigerant to stabilize and clear the sight glass.
9. The extra refrigerant charge for head pressure
control should be weighed in now by admitting liquid
refrigerant to the high side.
Charging of Systems with Sporlan Head Pressure
Control in Ambient BELOW 70°F
(After normal evacuation procedures)
NOTE: When charging in ambient below 70°F the procedure
is very critical. Be sure to adhere to the following steps
without fail. Failure to do so will result in overcharging the
system.
1. Follow instructions 1 through 7 above.
2. If the LAC valve setting is correct for the system being
charged, it is quite likely that some refrigerant will be
backed up into the condenser and the sight glass will
indicate bubbles in the liquid line.
3. Add more refrigerant, while allowing suffi cient time for
the refrigerant to stabilize and clear the sight glass.
4. At this point the system is correctly charged for
this type of head pressure control at the ambient
temperature that exists while the charging procedure is
taking place.
5. If the system is designed to operate at ambient below
the ambient that exists during charging, additional
charge will have to be added now.
6. To calculate the additional charge required, follow the
examples outlined under “Refrigerant Charge” except
remember that the “head pressure control charge” is
partially charged already. Refer to Tables 2 and 3.
The diff erence in percentages between the minimum design
ambient temperature and the ambient temperature at
the time the system is charged gives the percent of extra
charge still needed in the system. E.g., if this system was
charged at an ambient of 50°F, we have approximately 40%
of the extra charge in the system. This holds true as long as
the compressor is not allowed to unload during charging.
Therefore, the additional charge required is 95 minus 40 or
55% of the total extra charge calculated previously. This is
.55 x 119 or 65 pounds.
Service Procedures
There are several possible causes for system malfunction
with “refrigerant side” head pressure control and these may
be diffi
cult to isolate from each other. As with any form of
system trouble-shooting, it is necessary to know the existing
operating temperatures and pressures before system
problems can be determined. Once the actual malfunction
is established, it is easier to pinpoint the cause and then
take suitable corrective action. The following chart lists the
most common malfunctions, the possible causes, and the
remedies. Since the LAC valves are hermetic, they cannot be
disassembled for inspection and/or replacement of parts,
they must be replaced if they become inoperative.