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Heat Controller, Inc. VMH SERIES Service Manual
16
6.3 Pressure Test & Evacuation
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.
● Refrigerant lines and indoor coil should be evacuated using the recommended deep vacuum
method of 500 microns. The alternate triple evacuation method may be used if the procedure
outlined is followed.
1. System Evacuation and Charging
1) Completely tighten the flare nuts of the indoor and outdoor units, connect manifold gauge low side
hose to low side service valve.
2) Connect the manifold gauge charge hose to the vacuum pump.
3) Fully open the low side of manifold gauge.
4) Start vacuum pump.
5) Evacuate using either deep vacuum or triple evacuation method.
6) After evacuation is complete, fully close the low side of manifold gauge and shut off vacuum pump.
7) The factory charge contained in the outdoor unit is good for up to 16.5 ft. of line length. For line set
lengths over 16.5 ft., adjust charge according to chart in section 6.2.
8) Disconnect charge hose from low side service valve.
9) Fully open both high and low side service valves and securely tighten caps.
(Indoor unit)
(Liquid side)
(Gas side)
Vacuum
pump
Vacuum
pump
Lo
Hi
HI Side
Two-way valve
Close
Manifold valve
500 Microns
Low Side
Charge hose
Charge hose
(Outdoor unit)
Close
Three-way valve