[Equest-users] Non-existing cooling Fan power for proposed case

[Nick Caton]

It's my sense that the nitty-gritty decisions for such cases remain reliant on some subjective interpretation on the modeler's part.  I've added my personal take on your queries [bracketed and in red] below.

The most solid advice I can offer on the matter is to be clear in your documentation.  At the end of the day, whatever course you take may be disagreeable to your reviewer (even if inconsequential to the results) - so being clear on your interpretation and application of these rules is cheap insurance to save yourself time/effort later, should you have to make a revision and/or explain your approach to others/yourself.

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Patsos
Sent: Thursday, March 13, 2014 8:01 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Non-existing cooling Fan power for proposed case

Hi all,

I have an issue modelling spaces not designed with cooling equipment in LEED. The spaces are considered conditioned (occupied) but only heated in reality. The only cooling that is considered can come from natural ventilation or in some spaces from ERV ventilators.

Since the spaces do not fall in the 'heated storage' category of ASHRAE addenda 'DN', I think its proper to model a system to be the same as baseline, in my case Packaged VAV. [Agreed.]

So, what happens with fan power in the proposed case? What W/cfm should be modelled since this is a hypothetical system (same as baseline - PVAVS)?  [I would allow the proposed system to autosize airflow, just as the baseline model will (they may appropriately be rather different depending upon varying envelope loads and such).  Proposed fan power (W/CFM) and cooling efficiency (EIR) would be set to match whatever is calculated for the corresponding baseline system.  As a point of consistency for documentation, I like to present my "fake proposed" systems' calculations alongside my baseline systems' calculations, with some footnotes to clarify where I'm simply referencing the corresponding baseline system.]

Furthermore, this can be more complex if considering spaces with ERV ventilators (no cooling), for which I have the W/cfm. [Agreed!] Should I include the hypothetical system's fan power for cooling as well? [In this scenario, I would use the actual W/CFM (and designed airflow) for the proposed model, and the baseline-calculated Pfan (and autosized airflow) for the baseline model.  Again for the proposed cooling efficiency, match the EIR you come up with for the corresponding baseline system.]

Thank you in advance.

Best regards
Nick Patsos
Mechanical Engineer
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