Manual

56
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REFRIGERANT CHARGING PROCEDURES — Normally
this information is supplied by the equipment manufacturer And
when it is available, it should be followed When it is not available
from the equipment manufacturer, the following suggestions are
recommended Once the amount of extra refrigerant charge is
calculated, care must be taken in charging the system to insure the
proper total amount of refrigerant getting into the system This is
especially true if the ambient temperature is below 70°F and the
liquid drain valve (ORI) is throttling the refrigerant ow from the
condenser A step by step procedure is given below for the two
possible situations that can exist And depending on the ambient
temperature at the time the system is charged, each should be
carefully followed to insure proper system operation in both summer
and winter In either case, a liquid seal must be established in the
receiver before the system can start to function correctly
NOTE: While charging any system with head pressure control, the
outdoor ambient temperature must be known And if the system has
compressor unloaders, it is important to know if they are functioning
during the charging procedure To keep this procedure as simple
as possible, it is recommended that the unloaders be locked out
(compressor fully loaded) during charging
Charging of Systems with Sporlan Head Pressure Control in
Ambients 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 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 suf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
Ambients BELOW 70°F (After normal evacuation procedures)
NOTE: When charging in ambients 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 ORI 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 suf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 ambients 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 difference 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 unloaders were not operating 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 Since good system performance during low ambient
operation depends on proper refrigerant charge, it is very important
that this phase of the installation procedure be done carefully Many
times, poor system performance will be due to too little or too much
charge And in many cases this will be the last item suspected
Head Pressure Control Valve Operation ORI/ORD