# [Equest-users] Baseline PTAC Fan Energy for a Proposed Merv13 + Return Duct System

Kathryn Kerns kathryn.kerns at bceengineers.com
Mon Feb 25 15:56:53 PST 2013

```Everyone, I have been modeling some dormitories with a proposed HVAC
system involving a DOA with a full exhaust air HX and MERV 13 filters.
The puzzle is what to do about the baseline PTAC fan power energy? If I
use 0.3 w/cfm as Appendix G suggests, my PTAC baseline system does not
account for a fully ducted return\exhaust or MERV 13 filters. The
commercial fan power equation for systems 3-8 accounts for this, but I
am not supposed to use that formula for System 1 and 2.

Another puzzle is if I develop an cooling EIR value for my baseline PTAC
using the 365 w/kCFM conversion rule and equate that with 0.3 w/cfm,
what happened to the other 65 w/kCFM?

Maybe ARI 310/380 doesn't use 365 w/cfm fan power?  I read it and didn't
find any statement regarding fan power requirements, but I assume it
works the same as ARI 210/240?

I am wondering if a compromise of

PTAC fan power = CFMs *0.000365 + A
where A= PD*CFMs /4131 and PD = 1.4

might be a reasonable solution?

PTAC fan power = 0.00063 kw/cfm

Does anyone else have experience with this puzzle?

Kathryn Kerns

Systems Specialist

BCE Engineers, Inc.

| Ph: 253.922.0446 | Fx: 253.922.0896 |

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