SUBJECT: PRESSURE SETTINGS
ADJUSTMENT:
To increase the back pressure, remove the cap and turn the adjustment screw clockwise. To decrease the back
pressure, turn the adjustment screw counter clockwise.
Warning:
Freezing in the lowside will occur if the setting is too low.
If this should happen, allow the machine to remain idle for 24 hours, and if no damage has resulted, raise the lowside
pressure by adjusting the expansion valve to the correct pressure. A drop in the lowside pressure may also be the result
of a loss of refrigerant.
EXPANSION VALVE:
Warning:
Keep the adjustment cap on the valve when the machine is in operation. This
prevents moisture from accumulating in the diaphragm.
Never remove the valve or open any part of the system when the compound gauge
reads below zero (0) pounds pressure.
TOO LITTLE REFRIGERANT IN THE SYSTEM:
Should a compressor operate too long a period, or too often, it is generally due to the refrigerant supply being low, even
though the temperature is cold enough.
A good method of checking the amount of refrigerant is to open, the expansion valve a few turns more than normal. Place
a screw driver (metal end) on the refrigerant outlet of the expansion valve, and the handle against the ear, and listen. A
lack of refrigerant is indicated by a slight hissing sound. If the amount of refrigerant were normal, the result would be
barely noticeable.
When the refrigerant is a little low, the head pressure may be below normal with the machine running; when the supply is
very low, the pressure may drop considerably within 10 or 15 minutes after the compressor stops. The suction or back
pressure may be higher than normal, while the machine is idle and drop more quickly than it should when the compressor
starts, and may continue to be lower than normal with the apparatus in operation.
In any case of low refrigerant, first locate the cause which is almost certain to be a leak (see page for testing for leaks).
Do not attempt to add any refrigerant until you have found the leak and have repaired it.
