Heatcraft Refrigeration Products 25000102 Symptom Cause Remedy Low, High Suction, Low Suction

Parallel Compressor Systems

Symptom		Cause		Remedy
Low	1.	Insufficient refrigerant in system	1.	Check for leaks. Repair and add charge
Discharge	2.	Faulty condenser temp. regulation	2.	Check condenser control operation
Pressure	3.	Compressor suction or discharge valve inefficiencies	3.	Clean or replace leaky valve plates
	4.	Low suction pressure	4.	See corrective steps for low suction pressure
	5.	Head pressure control valve set wrong	5.	Adjust valve or install a head pressure control valve
		or no head pressure control valve
High Suction	1.	Excessive load	1.	Reduce load or add additional equipment
Pressure	2.	Expansion valve overfeeding	2.	Check remote bulb. Regulate superheat
Low Suction	1.	Lack of refrigerant	1.	Check for leaks. Repair and add charge
Pressure	2.	Evaporator dirty or iced	2.	Defrost or clean coil
	3.	Clogged liquid line filter drier	3.	Replace cartridge(s)
	4.	Clogged suction line or compressor	4.	Clean strainer or replace filters
		suction strainer
	5.	Expansion valve malfunctioning	5.	Check and reset for proper superheat
	6.	Condensing temperature too low	6.	Check means for regulating
				condensing temperature
	7.	Improper TXV	7.	Check for proper sizing
Little or No	1.	Clogged suction oil strainer	1.	Clean
Oil Pressure	2.	Excessive liquid in crankcase	2.	Check crankcase heater. Reset TXV for
				higher superheat. Check liquid line solenoid
				valve for proper operation.
	3.	Low oil pressure safety switch defective	3.	Replace
	4.	Worn oil pump	4.	Replace
	5.	Oil pump reversing gear stuck in	5.	Reverse direction of compressor rotation
		the wrong position
	6.	Low oil level	6.	Determine where the oil is or add oil
	7.	Worn bearings	7.	Replace compressor
	8.	Loose fitting on oil lines	8.	Check and tighten fittings
	9.	Pump house gasket leaks	9.	Replace gasket
Compressor	1.	Lack of refrigerant	1.	Check for leaks. Repair and add charge
Loses Oil	2.	Excessive compression ring blowby	2.	Replace compressor
	3.	Refrigerant floods back	3.	Maintain proper superheat at compressor
	4.	Improper piping or traps	4.	Correct piping
Compressor	1.	Operating beyond design limits	1.	Add facilities so that conditions are within
Thermal				allowable limits
Protector	2.	Discharge valve partially shut	2.	Open valve
Switch Open	3.	Blown valve plate gasket	3.	Replace gasket
	4.	Dirty condenser coil	4.	Clean coil
	5.	Overcharged system	5.	Reduce charge

Parallel Compressor Systems Installation & Operations Manual, October 2004 35