Emerson DH Manuel D’Utilisation

Compressor continually 

cycles

Faulty low pressure switch

Repair or replace.

Dirt or restriction in tubing to 

pressure stat

Check and clean tubing.

Defective liquid line solenoid 

valve

Check valve and solenoid operator; replace if necessary.

Plugged filter-dryer

Replace filter

Compressor motor 

protectors tripping or 

cycling

High discharge pressure

Check for loss of condenser water or blocked condenser fan 

or coil.

Defective overload relay

Replace.

High suction temperature

Reduce suction temperature by expansion valve adjustment 

or provide desuperheating.

Loose power or control circuit 

wiring connection

Check all power and control circuit connections.

Defective motor

Check for motor ground or short. Replace compressor, if 

either condition is found.

Compressor cycles on 

locked rotor

Low line voltage

Check line voltage and determine location of voltage drop.

Seized compressor (remove 

bearing head assembly and 

attempt to rotate crankshaft)

Replace compressor.

Compressor motor defective

Check for motor winding short or ground.

Single phasing

Check voltage across all 3 legs at contactor. Correct source 

problem.

Liquid refrigerant condensing in 

cylinder

Check and replace valve plates.

Motor burnout

Check control panel for welded 

contactor contacts or welded 

overload contacts

Replace defective components.

No dehumidification

Control not calling for 

dehumidification

Check monitor status.

Compressor contactor not pulling in

See Compressor Section.

Compressor won't run; fuse blown 

or CB tripped

See Compressor Section. Check fuses or CBs and 

contacts. Check line voltage

Suddenly stops 

pumping

Clogged strainer or impeller

Clean out debris.

Suddenly slow pumping

Clogged impeller, diffuser, or line

Clean out debris and use strainer.

Excessive leakage 

around the pump shaft 

while operating

Worn seal or packing

Replace seal or packing.

Performance poor

Worn impeller or seal

Replace with new impeller or seal.

Suction lift too high

Relocate pump closer to supply.

Motor not up to speed; low voltage

Larger lead wires may be required Check for proper 

line voltage (±10%).

Worn bearings

Replace pump

Noisy operation

Worn motor bearings

Replace pump

Low discharge head

Throttle discharge-improve suction conditions.

Debris lodged in impeller

Remove cover and clean out.

Cavitating pumps

Adjust system pressures.