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WARNING: A clear sight glass can also indicate a completely EMPTY system. Anytime
the compressor is started, white foam should appear in the sight glass indicating that the
refrigerant is present. This foam may disappear quite quickly but, IF NO FOAM IS
EVIDENT and the system is not cooling, the system is empty. DO NOT OPERATE THE
SYSTEM in this empty condition. Operation in this mode will ruin the compressor. Turn
off the main breaker to the control panel to prevent operation until the system can be
properly leak tested and recharged.
Fast moving white foam with the compressor operating indicates an insufficient charge
level. Watch closely for a transition from foam to total liquid, (indicated by a clear sight
glass). This transition point can be missed if proper attention is not given. Also, IT IS
POSSIBLE for the sight glass to show large bubbles even when the charge is sufficient,
so it is important to differentiate between "foam" and "bubbles". The foam condition has
velocity and direction; the bubbles are large, temporary, and nearly stationary. Do not
try to chase away these larger bubbles with more refrigerant: overcharging will then
occur. Air in the system may give a false sight glass reading, which could lead to
overcharging. If in doubt, discharge a suspected overcharged system to continuous
foam and slowly add refrigerant to clear the glass. MONITOR THE SIGHT GLASS
CONTINUALLY since the glass will not indicate when the system is overcharged.
In a warm system, when the cabinet is above freezing (32.F) upon start-up, the sight
glass may take several minutes to clear. A cold cabinet may show a clear glass within
seconds of start-up.
TROUBLESHOOTING
The low side operating pressure of the system will not indicate the amount of
refrigerant in the system. The valve will not give proper operation or pressure if it is
undercharged. Check the valve scribe line. It should correlate to gauge pressure.
The system requires enough refrigerant to supply liquid to the valve. If the valve has a
steady hissing sound then the charge is ok. If the valve is sputtering then it is low. If
the valve is making a noticeable roar it is empty. If the low side pressure is properly set
the high side pressure will be 80 to 135 psi depending on the air temperature (50 to 95
degrees F.) at the unit. Almost immediately upon start up the valve body will begin to
frost.
Do not add refrigerant charge to a pre-charged system.
Maximum charge 12 oz. R-134a