[Equest-users] DOAS and system HP

[Bishop, Bill]

Jeff,
There are a number of workarounds for modeling DOAS units in eQUEST. The latest eQUEST beta version can run DOE-2.3 which has explicit options for modeling DOAS systems. A single DOAS can serve multiple other systems and be configured to supply the zones directly or to connect to the mixed air, as in your WSHP case. I don't have much experience with it but it looks promising.
For fan power, it sounds like you have sized the DOAS already, so the 20HP supply and 7.5HP return fan power (or better yet, the BHP for the fan selections) should be entered via some combination of inputs instead of letting the system(s) be autosized. If you specify HVAC-SUPPLY/RETURN for ERV-FANS, then any fan power entered in the Heat Recovery 2 tab inputs will be added to the fan power entered for the system SUPPLY-KW/FLOW or SUPPLY-STATIC. The fan power penalty for the ERV section appears in the ERV Energy Recovery Summary reports. I would also look at the SV-A and SS-H reports for the systems in question. You could multiply the fan hours reported in the SS-L report by the DOAS fan power to see if the reported energy makes sense.
Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Jeff Ross-Bain via Equest-users
Sent: Wednesday, October 04, 2017 11:54 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] DOAS and system HP

Dear eQuest Experts,

I have a nagging issue that I hope someone can clarify. It has to do with DOAS units and fan motor HP.

We have a DOAS unit that supplies all outside air (OA) to a battery of WSHP units. In preparing the model, I used the "dummy zone" approach, conditioned the air, and all of that air is then the source of OA to the WSHPs. By the way, in this system, a portion of the return air from the WSHPs enters the DOAS.

The question is how is the actual DOAS unit HP modeled? This unit is 20HP supply and 7.5HP return (exhaust). The dummy zone HP auto sized is much less than the actual. However, if I input actual (i.e. kW/cfm), the energy use soars.
Am I missing something? I wonder if the size of the dummy zone matters, or if some of the fan power is included in the WSHP and exhaust systems...

Thanks,

Jeff Ross-Bain, BEMP, LEED Fellow
President
404-220-8955
www.rbgb.com<http://www.rbgb.com/>

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