Heat Controller DMH24DB-1 - Manual (Page 31)

Service Manual 31
Air Purging and Evacuation
Air and moisture remaining in the refrigerant system have undesirable effects as indicated below.
1. Pressure in the system rises.
2. Operating current rises.
3. Cooling(or heating) efficiency drops.
4. Moisture in the refrigerant circuit may freeze and block capillary tubing.
5. Water may lead to corrosion of parts in the refrigeration system.
Therefore, the indoor/outdoor unit and connecting tube must be checked for leak tight, and vacuumed to remove incondensi-
ble gas and moisture in the system.
Preparation
• Check that each tube(both liquid and gas side tubes) between
the indoor and outdoor units have been properly connected and
all wiring for the test run has been completed. Remove the ser-
vice valve caps from both the gas and the liquid side on the out-
door unit. Check that both the liquid and the gas side service
valves on the outdoor unit are kept closed at this stage.
Leakage test
• Connect the manifold valve(with pressure gauges) and dry nitro-
gen gas cylinder to this service port with charge hoses.
CAUTION: Be sure to use a manifold
valve for leak testing.
The high side manifold valve must always
be kept closed.
• Pressurize the system to no more than 150 P.S.I.G. with dry
nitrogen gas and close the cylinder valve when the gauge
reading reached 150 P.S.I.G. Next, test for leaks with liquid
soap.
CAUTION: To avoid nitrogen entering the
refrigerant system in a liquid state, the top
of the cylinder must be higher than its bottom
when you pressurize the system. Usually, the
cylinder is used in a vertical standing position.
: Leakage test shoud be done for each indoor
unit connection set, separately.
1. Do a leakage test of all joints of the tubing(both indoor and
outdoor) and both gas and liquid side service valves.
Bubbles indicate a leak. Be sure to wipe off the soap with a
clean cloth.
2. After the system is found to be free of leaks, relieve the
nitrogen pressure by loosening the charge hose connector
at the nitrogen cylinder. When the system pressure is
reduced to normal, disconnect the hose from the cylinder.
NOTICE
Checking method
Charge hose
Nitrogen gas
cylinder(in vertical
standing position)
Indoor unit
Outdoor unit
Lo Hi
Manifold valve
Pressure
gauge
Air Purging and Evacuation