Initial Installation; Adding The Refrigerant After Running The System For Many Years; Air Purging With Vacuum Pump; Procedure - Century B-VMH36SD-1 Service Manual

6.4 Initial Installation

Air and moisture in the refrigerant system have
undesirable effects as below:
 Pressure in the system rises.
 Operating current rises.
 Cooling or heating efficiency drops.
 Moisture in the refrigerant circuit may
freeze and block capillary tubing.
 Water may lead to corrosion of parts
in the refrigerant system.
Therefore, the indoor unit and the pipes
between indoor and outdoor units must be
leak tested and evacuated to remove gas and
moisture from the system.
Gas leak check (soap and water method):
Apply soap water or a liquid neutral detergent
on the indoor unit connections or outdoor unit
connections by a soft brush to check for
leakage of the connecting points of the piping.
If bubbles form, the pipes have leakage.

1. Air purging with vacuum pump

1) Completely tighten the flare nuts of the
indoor and outdoor units, confirm that both
the 2-way and 3-way valves are set to the
closed position.
2) Connect the low pressure charge hose to
the 3-way valve's gas service port.
3) Connect the high pressure hose to the
vacuum pump.
4) Fully open the handle of the low pressure
manifold valve.
Service Manual - VMH 9/12/18/24 SU & VMH30/36S D Series
5) Evacuate for 30 minutes and check that
micron gauge reads <500 microns. If not, it
should be pumped 20 minutes more. If the
pressure can't achieve <500 microns after
pumping 50 minutes, please check for
leakage points. Fully close the handle valve
of the low pressure manifold set and stop the
operation of the vacuum pump. Confirm that
the gauge needle does not move above 500
microns (approximately 5 minutes after
turning off the vacuum pump).
6) Turn the flare nut of the 3-way valves about
45° counterclockwise for 6 or 7seconds after
the gas coming out, then tighten the flare nut
again. Make sure the pressure display in the
pressure indicator is a little higher than the
atmosphere pressure. Then remove the
charge hose from the 3-way valve.
7) Fully open the 2-way valve and 3-way valve
and securely tighten the cap of the 3-way
valve.
6.5 Adding the refrigerant after running
the system for many years

Procedure

1) Connect the charge hose to the 3-way
service port, open the 2-way valve and the
3-way valve. Connect the charge hose to
the valve at the bottom of the cylinder. Turn
the cylinder bottom up to ensure liquid
charge.
2) Purge the air from the charge hose. Open
the valve at the bottom of the cylinder and
press the check valve on the charge set to
purge the air (be careful of the liquid
refrigerant).
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