[Equest-users] erv static vs kw/cfm

[Joe Fleming]

If you back out the math using the simplified fan power equation of hp =
(CFM x SP) / (6356 x effic.), then the numbers you have provided for kw/cfm
are one magnitude off.   They give a static pressure of roughly 7.3" instead
of 0.73". 
Try using 0.00006 kw/cfm make-up and 0.00012 kw/cfm exhaust.


Joe Fleming, PE, LEED AP BD+C, BEMP

-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick J.
O'Leary, Jr.
Sent: Monday, February 27, 2012 5:49 PM
To: equest-users
Subject: [Equest-users] erv static vs kw/cfm

has anyone ever noticed a difference in simulation results when using a
sensible wheel and kw/cfm power input versus a sensible wheel and static
pressure thru the heat exchanger input?

for example, i have an existing building of about 60,000 sf and i have a
test & balance report for it.

if i simulate the building and use a site measured static through the erv
heat exchanger section (sensible wheel, typically about 0.73" wg) the
building has a cost difference of $7,037 dollars less than if i simulate the
same building using the site measured kw/cfm input (typically about 0.0006
kw/cfm oa supply fan, 0.0012 exhasut air fan).

i have previously found this is not limited to a field measurement
situation.  any project i've simulated where there's been an erv in the
design performs more cost effectively using the manufacturer's catalog data
for static input instead of the manufacturer's catalog data for kw/cfm (or
kw).

if kw/cfm and static are both entered equest still uses the kw/cfm for the
calculations - at least that is how i'm reading the help function.  
if kw/cfm (or kw) are not entered then either the default static (1" wg) or
user entered static are used.
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