Findings: Bubbles in sight glass after filter
Cause: Pressure drops across filter too high.
Action: Compare filter size with system capacity. Replace filter drier.
Cause: Filter under-sized.
Action: Replace filter drier
Cause: Insufficient refrigerant charge.
Action: Charge necessary refrigerant.
Cause: Filter clogged.
Action: Replace filter drier
Cause: Insufficient sub-cooling.
Action: Check reason for insufficient subcooling. Do not charge refrigerant only because of insufficient sub- cooling.
Findings: Moisture indicator discolored
Cause: Moisture in system. (Yellow)
Action: Check system for leakage. Repair if necessary. Check system for acid. Replace filter drier, several times if necessary. In severe cases it can be necessary to change refrigerant and oil.
Cause: Impurities, i.e. small particles in system. (Yellow)
Action: Replace filter drier. Please remember to seal the old filter after removal.
Cause: Too much moisture in system. (Brown or black)
Action: Clean out system if necessary. Replace SGI/SGN sight glass and filter drier.
Findings: Filter outlet side colder than inlet side (can be iced up)
Cause: Pressure drops across filter too high.
Action: Compare filter size with system capacity. Replace filter drier.
Findings: Vapor bubbles in sight glass ahead of thermostatic expansion valve
Cause: Condensing pressure too low.
Action: Set condensing pressure to higher value on KVR or fan speed controller. If there are still bubbles in the sight glass, add refrigerant.
Cause: Receiver stop valve too small or not fully open.
Action: Replace valve or fully open it.
Cause: Hydrostatic pressure drop in liquid line too high (height difference between thermo- static expansion valve and receiver too large).
Action: Install heat exchanger between liquid and suction lines ahead of rise in liquid line.
Cause: Badly or incorrectly set condensing pressure regulation causing liquid collection in condenser.
Action: Replace or reset KVR regulator at correct value.
Cause: Condenser pressure regulation by start/stop of condenser fan can cause vapour in liquid line for some time after fan start.
Action: If necessary, replace regulation with condensing pressure regulation via valves (KVD + KVR) or with fan motor speed regulation e.g RGE or XGE.
Cause: Insufficient liquid in system.
Action: Few bubbles are present, otherwise there is a risk of the system becoming overcharged.
Cause: Liquid line too long in relation to diameter.
Action: Replace liquid line pipes with a suitable/correct diameter.
Cause: Liquid line diameter too small.
Action: Replace liquid line pipes with a suitable/correct diameter.
Cause: Sharp bends, etc. in liquid line.
Action: Replace sharp bends and components causing too large a pressure drop.
Cause: Partial blockage of filter drier.
Action: Check for impurities, clean out if necessary, replace filter drier.
Cause: Solenoid valve defect.
Action: Change to a smaller size of solenoid valve in case unstable operation of solenoid valve occurs (frequent opening and closing = operation below minimum pressure drop of a servo valve).
Cause: Insufficient liquid subcooling because of heat penetration of liquid line, possibly from high temperature around liquid line.
Action: Reduce ambient temperature or install heat exchanger between liquid and suction lines or insulate liquid line, possibly together with suction line.
Cause: Vapor bubbles in sight glass ahead of thermostatic expansion valve.
Action: Swap over cooling water inlet and outlet. (Water and refrigerant flow must be opposite).
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