Chiller Operation

Hvactech58

I have just taken a look at the air handler for the second floor of a school I am attending and I noticed that the loop temperature from the chiller to the chilled water coil is 61 degrees. Now I'm not too sure but I think the temperature should be approximately 45 to 50 degrees at this point in the system. What do you think?

Eugene Silberstein 3

Chilled water temperatures

Under design conditions, the chilled water should be supplied to the remote cooling coils at a temperature of about 45 degrees. Since there is tupically a 7 degree aproach temperature between the evaporator saturation temperature and the supply water temperature, you are looking at an evaporator saturation temperature of 38 degrees. The water should be LEAVING the coil at 55 degrees.

If you are reading a supply water temperature of 61 degrees, there are a number of issues that should be checked. These include a refrigerant undercharge, fouled water loop piping, improper cooling tower operation, underfeeding metering device, and non-condensables in the system.

In order to isolate the problem, you would need to take a complete set of system readings including high side pressure, low side pressure, condenser outlet temperature, water temperature split across the cooling tower, wet bulb temperature of the outside air, approach temperature of the chiller barrel. In addition, you would need to check the saturation temperature of the refrigerant in the circuit with the system off for at least 30 minutes to compare it to the outdoor ambient to confirm/eliminate the presence of non-condensables.