I'm trying to understand the derating to be applied to equipment capacity when using an IAT different than 80F. I've seen it a couple different ways on this site.
Let's say there's a 3-ton unit rated at 36K Btuh with 27K sensible (at the ARI 80F IAT & 1200 cfm). If you design for an IAT of 75F, what is the total capacity and sensible capacity of the equipment at those conditions?
Using the derating formula, I would assume
So, do you derate the total capacity and figure sensible based on SHR (I assume SHR=.75 for this example) like:
Tot Capacity=36k-5k=31k & Sensible=31k*.75=23.25k
do you derate the sensible only like:
Sensible=27k-5k=22k and I'm not sure what the Total Capacity is in this case(I could argue for 31k btuh or 29.3 btuh).
I'm thinking the latter but not sure. I assume this is covered in Manual S - I have J and D but maybe need to spring for S to do all my own calcs before talking to some contractors.