Hitachi Chiller Problem

Do you have any information on the suction and discharge pressures of the compressor, or the appearance of liquid/bubbles/vapor in the sight glass? Is the unit actually running?

One guess might be that there is a leak in the system, with loss of refrigerant charge.

Insufficient cooling? The inlet and outlet temperatures are the same indicating no cooling is being done. This unit rated at 5-15 degree C. outlet temperature. Without a complete list of the operating conditions there is no good solution to be offered for your problem. The inlet temperature would indicate that there is no load for the unit to cool. Without a higher inlet temperature the unit controls may well not even be calling for the compressor to start. I would start by checking the sequence of operation for this unit for the application it is being used on.

Some of the causes are:

No cooling load on the system

Shortage of refrigerant

Defective compressor valves

Air or condensate in system

Wrong expansion valve super heat setting

Dirty or defective expansion valve

Restriction in refrigerant circuit.

Dry coils.

How much should be chilled water inlet temperature and outlet temperature?

Please check suction and discharge pressure of compressor. If compressor is running you will find difference in it. If these pressures are normal, evaporator must be evaporating some liquid refrigerant and giving cooling effect. From your incomplete narration of problem I suspect either of the following:

1. You do not have cooling load & compressor is automatically switched off. Suction and discharge pressure of compressor shall be same in this case. Compressor kW or Amps will be Zero.

2. Motor & compressor got disconnected and only motor is moving. Suction and discharge pressure of compressor shall be same in this case also. Compressor kW or Amps will be Zero.

3. Your system lost refrigerant considerably due to leak somewhere. Check operating parameters and evaporator liquid level to confirm.

4. Lube oil got mixed-up with refrigerant in abnormal proportion (some mixing-up may be allowed). Higher lube oil consumtion in previous weeks can be checked. Being lighter compared to refrigerant oil will float on top of refrigerant level in evaporator and reduce evaporation which is required for cooling. This in combination of sl. no. 3 above is desasterous.

I want to correct sl no. 2 of my preceding post.

Instead of "Compressor kW or Amps will be Zero" please read

"Compressor kW or Amps will be abnormally low- required for motor no load run."

If the water flow through the cooler barrel is 2, 3, or 4 pass, consider the possibility that water is slipping pass a separator plate in an end bell and bypassing the heat exchanger