[Equest-users] Baseline PTAC Fan Energy for a Proposed Merv13 + Return Duct System - Goodness Me I had No Idea

[Cam Fitzgerald]

Kathryn,

 

If you do submit you model for a LEED project you will not be permitted to
make any pressure drop adjustments to the Baseline residential system fan
power calculations. The formula for system types 1 and 2 in Section G3.1.2.9
is: Pfan = CFMs*0.3. Note that there is NO "A" factor in the formula. If the
project intends to pursue LEED certification, you may wish to consider an
inquiry to GBCI before you overestimate the projected savings (and those
ever-important points) and find yourself trying to justify your initial
modeling approach to the powers that be.

 

Just come friendly advice J

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Kathryn
Kerns
Sent: Wednesday, February 27, 2013 6:24 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Baseline PTAC Fan Energy for a Proposed Merv13 +
Return Duct System - Goodness Me I had No Idea

 

Well everyone, it seems I have hit a nerve with my original inquiry and
thank you all for your responses. After reading over the responses I think I
am going to run both the baseline and proposed fans continuously (it seems
the most conservative case) and use 0.0003 kw/cfm for the baseline fan
energy but add an A value equal to 1.4 to cover the proposed system Merv 13
filters and return ductwork.

I think I will also modify the EIR cooling equation to use 300 w/cfm fan
power instead of 365 w/cfm power. 

 

So baseline PTAC fan power = CFMs *0.0003 + (1.4* CFMs/4131) which works out
to be 0.00057 kw /cfm for a small 0.83 efficient motor

 

and baseline PTAC Cooling EIR will have a 0.10 constant instead of a
0.012167

 

If I ever have to submit this to LEED I will probably regret it, but it
seems to be the most logical approach. Of course logic and LEED don't
necessarily go together. 

 

Oh well, thanks again for the feedback.

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Kathryn
Kerns
Sent: Monday, February 25, 2013 5:57 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Baseline PTAC Fan Energy for a Proposed Merv13 +
Return Duct System

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 | 

 

 

 

Kathryn Kerns

Systems Specialist

BCE Engineers, Inc.

| Ph: 253.922.0446 | Fx: 253.922.0896 | 

 

 

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