Chillers

[Mike Boyett]

If this has been discussed before then I apologize but I could not find anything using the search feature.

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?

[Dom D'Agostino]

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?


As that split you posted is simply a "rough approximation", the simple answer to your question is, "No". Temperature spilts are but only one indicator of A/C performance.

[Jerry Peck]

the simple answer to your question is, "No". Temperature spilts are but only one indicator of A/C performance.

I'll make Dom's answer a little more complicate and accurate (I am sure Dom will not mind :) ), the "but one indicator of A/C performance" is like saying that it is raining out side, someplace, somewhere, and could be raining outside here, but might not be.

In other words, so many other things affect the TD that TD is of little use without all the other conditions being known.

Here are two examples:

1) The coil (or filter) is blocked. The TD will be artificially high, but could be 'within range'. The system, however, needs service.

2) The coil (or filter) may be brand-spanking-new clean with a open duct in the attic (or fan speed set too high). The TD will be artificially low, but could be 'within range'. The system, however, needs service.

I quit taking TDs years ago as they meant and indicated so little that they were of no indication of the systems operation.

I believe DavidR can (hopefully will) expand on this. He has before and he knows his stuff.

[Mike Boyett]

Like I said in my original post, I've read and understand all the pros/cons of temp splits or differentials. I get it....now, how would one judge the performance of a chiller based a/c like described?