I'm starting to realize that there is a fairly large range of approaches
when calculating the PTAC EER value for a baseline model. A simplified
approach I've always used is to get the baseline EER is to take the total
cooling capacity of all the apartments, and then divided that by the total
number of units. Then use this average value to calculate EER. I've used
this approach on a lot of LEED projects and never had a problem. I'm curious
if others are calculating in on a unit by unit basis. My approach does take
into account that top floor and corner units will probably need bigger and
less efficient units. But calculating it on a unit by unit basis could also
become very tedious, where a small change in the baseline model could
necessitate the re-calculation of every system's EIR. Also, this all assumes
one PTAC unit per apartment. But in a real world design you could easily
have one in the living room and a different unit in the bedroom.

I'm just curious what approach people use on this calculation.

Also, I've found the controls on the actual PTAC unit a little restrictive
so I've been using PSZ to model the PTAC systems at times and changing the
performance curves.

- Steve