McQuay M4MC075D, Owner'S Manual

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109
outdoor unit
Shredder valve with
core in place
Shredder valve with core removed
Most split systems have a suitable connection on the outdoor unit
Shredder valves provide easy system access for pressure reading and addition of refrigerant. On small
systems, they provide a reasonable connection for evacuation also. However, Shredder valves and the
hoses connected to them can cause very severe pressure drops and can multiply evacuation time by a factor
of 4 or 5.
On the positive side, Shredder valves provide a restriction that slows the speed of liquid charging into the
suction side. When a pressure drop is desirable (charging liquid into suction), connect via a Shredder valve.
When a pressure drop is detrimental (evacuation), connect via an open fitting.
HOW MUCH REFRIGERANT?
The proper refrigerant charge should follow the volume as recommended by manufacturer and
recommendation should be followed by the installer. Refer to the table of Refrigerant Charge Level.
If the installer cannot find the correct charge but the system must be started, refrigerant should be carefully
added to the system until reasonable sub-cooling is measured in the liquid line and reasonable suction
superheat is measured at the compressor suction. Suction and discharge pressures must be monitored
carefully during the charging process.
CHARGE LIMITS
Copeland Scroll compressors have the different charge limits for different compressor models as shown in
table below. If the total charge exceeds these limits, the system should have a crankcase heater and/or
pump down cycle and/or accumulator to prevent liquid damage to the compressor. Some systems may
require accumulators to limit liquid floodback even though the charge is lower than the published limit.
Compressor Range Model lbs. kg.
Quest ZR46 to ZR81 10 4.5
Summit ZR84 to ZR144 16 7.3
Specter ZR90 to ZR19M 17 7.7
CHARGING PROCEDURES - SINGLE PHASE COMPRESSORS
Evacuate the system to 500 microns Hg. (67Pa). To reduce evacuation time, use short, large diameter hoses
and connect to unrestricted service ports on the system. Quality of vacuum cannot be determined by time – a
reliable vacuum gauge must be used. A battery powered model similar to the gauge shown below is practical
since it avoids the necessity of finding a correct power outlet.
Turn the refrigerant cylinder upside down, purge the charging hose and charge liquid through the liquid line
charging port until refrigerant no longer flows or until the correct charge has been weighed in. If additional
charge is required start the system and slowly bleed liquid into the suction side until the system is full.
Shredder core