Chillers

[Michael R. Boyett]

I've read the discussions regarding the pro's and con's of using the temperature split (supply -vs- return temps) on freon based a/c systems. Earlier this week I inspected a fairly expensive hi-rise condo unit that used a chiller for the a/c system. The building purchased btu's from the city, ran city chilled water thru a heat exchanger for the entire building and then circulated the resulting secondary chilled water thru-out the building for each unit's individual a/c. For lack of a better method I used the temp split as an indicator of the proper performance of that system. My question is, can I use the 14° to 21° split that I normally use for a freon based split system as a guide for a chiller system? If not, then what split temp or other method should I have used to judge the performance of the system?

[Thomas Duchesneau]

Depending on how well the CHW lines are insulated, and how far the unit is away from the chiller, usually one would get about 40/45*F into the coil, and 55/60*F out. These would be the readings with the apt. at 70-75*F.
The only problems likely are dirty air filters, coil, or defective water modulating valve.
Discounting problems with the primary water chiller, of course...

[Michael R. Boyett]

Thanks Thomas. This was a 5 year old upscale condo ($440,000 for 820 sf), the unit was on the 9th floor of the 12-14 story building. I was getting a 12° temp differential and the building maintenace supervisor told me even before I checked the differential to expect 10° to 12°. Sounds like you agree with those numbers. I did not call anything out as in need of repair or service.

[Bruce D. Pinel]

You may also want to make sure they are not using any reheat devices, (electric coils) to raise the discharge air if they are doing dehumidification.

[Michael R. Boyett]

Interesting...I hadn't considered that possibility. I may call the building super and ask him if they do dehumidify the air. Thanks!

[Bruce D. Pinel]

There may be 2 stats or a single, dual element device in the room for sensing both T&H. Real easy to do if they have an Energy Management System, (EMS). If no EMS, they may not be doing it.