[Equest-users] DOAS in baseline

Thu Jan 27 11:30:47 PST 2011

Nick:

The problems I have experienced with using a dummy zone, without OA From Units, 
for the DOAS, as confirmed by different hourly reports I input are as follows:
1.    The dummy zone does not equal the size of the conditioned space served and 
heat loss/gain is not accurate.
2.    The return air temperature is not indicative of what is being returned to 
the DOAS when a ERV is used.
3.    The fan kW of a variable speed DOAS does not track correctly.
4.    The dummy zone occupancy level and schedule do not equal that of all the 
systems served.

When using an OA From System, if the system served is not running, eQuest 
assumes no outside air is being supplied.  The designer needs to specify OA 
isolation dampers on the systems served.

I recently modeled two projects with DOAS that was conditioning one zone 
(Corridors) and supplying ventilation air to the other systems.  This design 
results in more accurate modeling, a dummy zone is not needed, but the same 
problem of incorrect return air temperatures for an ERV, since only the heat 
loss or gain from the corridor is included.

DOAS is becoming more and more popular, due in large part to LEED 62.1 
requirements, and hopefully the eQuest developers will refine the program to 
accurately model this system

Paul Diglio

________________________________
From: Nick Caton <ncaton at smithboucher.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>; Susan F <modelsenergy at gmail.com>; 
equest-users at lists.onebuilding.org
Sent: Thu, January 27, 2011 10:55:07 AM
Subject: RE: [Equest-users] DOAS in baseline

Hi Paul!

1.       You could specify the DOAS as part of the systems it’s serving 
(breaking out the fan energies/ERV components/preconditioning and so forth), 
then the OA and scheduling specified at the zonal level carries through.
2.       If the DOAS has preconditioning/ERV elements maintaining specific 
temperature setpoints, then those could be specified at the systems being 
served.  This may not be technically feasible for every system type.

I’ve used both approaches in the past: OA-FROM-SYSTEM using dummy zone(s) and 
integrating DOAS/ERV into the proposed systems served.  I believe both are 
viable approaches, with the first benefiting from more nuanced control over 
system behavior (fans, specifically), and the latter being much easier/simpler 
to set up and troubleshoot.

~Nick

NICK CATON, E.I.T.
PROJECT ENGINEER
Smith & Boucher Engineers
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
www.smithboucher.com

From:Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Thursday, January 27, 2011 9:41 AM
To: Nick Caton; Susan F; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DOAS in baseline

Nick:

If you do not use the OA From System how will eQuest calculate the CFM required 
by varying occupancy?  In addition, since the DOAS system might not provide the 
supply air temperatures required eQuest will not correctly calculate the energy 
required to condition the OA.

Paul Diglio

________________________________

From:Nick Caton <ncaton at smithboucher.com>
To: Susan F <modelsenergy at gmail.com>; equest-users at lists.onebuilding.org
Sent: Thu, January 27, 2011 10:21:55 AM
Subject: Re: [Equest-users] DOAS in baseline
Hi Susan!

Whether or not a baseline model gets a separate system for a proposed design 
featuring a DOAS is dependent on a few things, including how you decided to 
approach modeling the DOAS in the proposed model.

-          A clarification first:  Type and quantity of baseline systems is 
determined first and foremost per Appendix G.3.1.1.  You generally have either 
one system per floor or one system per zone, depending on the system type.  You 
never start with “one system per proposed system” except by coincidence.
-          Ifyou use a dummy zone approach (not integrating the DOAS into the 
proposed systems), and you have one baseline system serving only the dummy zone 
per G.3.1.1 (or its exceptions), and you have specified the ventilation 
requirements at that dummy zone (not indirectly from the actual zones - using 
OA-FROM-SYSTEM for the proposed systems)… then you’ll end up with a distinct 
baseline system handling the ventilation requirements analogous to the proposed 
DOAS.  

-          In many/most cases (partially dependant on your preferred strategy 
for handling DOAS’s in your proposed models), you will not have a dedicated 
baseline system handling the ventilation air.  That’s okay.

~Nick

NICK CATON, E.I.T.
PROJECT ENGINEER
Smith & Boucher Engineers
25501 west valley parkway
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 Susan F
Sent: Thursday, January 27, 2011 6:11 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] DOAS in baseline

This is not exactly an eQUEST question but y'all have been so helpful in the 
past so I'm hoping you can help here too.  I'm looking for a little 
clarification.  It was my understanding if you had a DOAS system that heated and 
cooled the outside air before delivering it to the floor mechanical room to be 
combined with return air and further conditioned by the AHU in your Proposed 
building that this system would NOT be modeled separately in the Baseline.  I 
cannot find anything in 90.1 that would regulate the DOAS system and I'm not 
sure how you would model it.  (I understand the dummy zone concept for modeling 
DOAS but not sure that would apply to the Baseline.)

Should it be separate system in the Baseline and would it be VAV or constant 
volume?  And if it is a separate system what section of 90.1 would you reference 
for this?

Thanks in advance.
Nick:
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