Hi all,

My name is Hisham and I am from Malaysia. It's great to be a member of a very active and helpful forum in HVAC. I am not a HVAC engineer per se, but I am a utility engineer which means I cover a wide range of equipment such as steam boilers, UPV's, WWTP, STP, air compressors, CIP, gensets, AHU's, and chillers. I handle big projects as well.

I have several ammonia chillers. Each chiller has a COP of 5.35, of course this is based on full load.

The temperatures (return and supply) are 11 deg.C/5 deg. C. The rated capacity is 1500 kWR with a drive power of 450 kW (COP was based on 1500 kWR and 280 kW power). In actual operation, the load (for the screw compressor) indicated on the panel was 495 A at 1554 kWR, and since the maximum rated amp is 790 A (no VSD), the motor was run at 63% and the chiller was run at 100% based on load.

I have three questions, hope if you can help:

1. I have another NEW ammonia chiller (1500 kWR, 450 kW with VSD) which is not yet run, and we intend to put a new load of 560 kWR from a new plant. There is a centrifugal R134a chiller (old) which is run at 478 kWR. Is it going to be a cost saving if I combine these two loads (478 kWR + 560 kWR = 1038 kWR) and put in the new ammonia chiller (1500 kWR)? How do you calculate the saving?

2. 5.35 is the COP at 100% load, how to know the COP (or Integrated part load efficiency) at 75% and 50% load?

3. I have a cooling tower with a capacity of 800 ton/h. It supplies condensing water to the chillers at 28 deg. C and the return temperature is 32 deg. C. If I were to increase the supply temperature from 28 deg. C to 32 deg.C (for cost saving purpose), will the chillers do extra work resulting in more power requirement by the chillers?

Thanks for your kind attentions.

I have no intensive training in English language, and I'd apologize if my questions are difficult to comprehend or contain a lot of grammatical errors.

Best regards