[Equest-users] DOAS with dehumidification

Mon May 23 14:21:39 PDT 2016

Awesome – less work then!

With a little more verification/tinkering, you could make sure the dummy-DOAS’s reheat is leveraging a source type (heat pump) & efficiency to match whatever the secondary systems would be doing.

~Nick

------------------------------------------------------------------------------------------------------------------------------

Nick Caton, P.E.

  Senior Energy Engineer
  Energy and Sustainability Services
  North America Operations
  Schneider Electric

D  913.564.6361 
M  785.410.3317 
E  nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com> 
F  913.564.6380

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

From: Michael Campbell [mailto:mcamp1206 at gmail.com] 
Sent: Monday, May 23, 2016 2:00 PM
To: Nicholas Caton
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DOAS with dehumidification

Thanks for the reply Nick.  The air will be conditioned by a secondary system.  The system is designed so the DOAS/ERV supplied "neutral" air (~75F) to apartments and the space loads are met by split system heat pumps in the apartments.  So, if the system is dehumidifying, it is possible that the DOAS could supply air at ~60F, and the assumption is that the heat pumps in the apartments will be able to handle that additional load. 

On Mon, May 23, 2016 at 2:04 PM, <Nicholas.Caton at schneider-electric.com> wrote:

Mike,

Ref: Volume 2: Dictionary > HVAC Components > SYSTEM > Airside Control > Humidity Control > MAX-HUMIDITY

To my understanding, no explicit mode of doe2 dehumidification DOESN’T assume some form of reheat to deliver the specified/derived supply air temperature.  In turn, I’m not certain whether it’s going to be easy to (a) force “sub-cooling” without the use of a custom COOL-SET-SCH schedule (that’s where I’d suggest you go next with this), deriving the anticipated additional coil operations from the weather data and/or the model you’ve already built, and (b) transfer that “sub-cooled” air reheating load to the other systems in your model.

Fair question before you dive further:  is the associated reheating going to occur somewhere in the building anyway (i.e. by other systems), and as such would it be a major stretch to simply permit your dummy-zone DOAS perform that reheating?  If that’s a reasonable analysis, you might not need to do anything else.

Of course, presence of ERV just layers on the fun.  Frankly when ERV gets involved, that’s one of my primary drivers for shifting away from a dummy zone approach and approximating the DOAS system (and its ERV components) into the other conditioning systems to more directly capture what’s coming off the exhaust/relief stream.

~Nick

------------------------------------------------------------------------------------------------------------------------------

Nick Caton, P.E.

  Senior Energy Engineer
  Energy and Sustainability Services
  North America Operations
  Schneider Electric

D  913.564.6361 
M  785.410.3317 
E  nicholas.caton at schneider-electric.com <mailto:nicholas.caton at schneider-electric.com> 
F  913.564.6380

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael Campbell via Equest-users
Sent: Wednesday, May 18, 2016 7:37 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] DOAS with dehumidification

Hello,

I am trying to model a DOAS that supplies conditioned outside air to dwelling units.  It also has an ERV.  I have created a dummy zone with no loads and made the setpoints for the dummy zones my desired heating and cooling supply air temperatures (73F for heating and 75F for cooling).  However, the DOAS also has dehumidification in which it will operate in cooling mode to dehumidify at >60% RH.  There is no reheat coil, so when the system is dehumidifying, the supply air temperature should drop below the setpoint.  

Here is the issue I'm having.... when I look at my hourly reports, I can see that the air leaving the cooling coil will drop down to about 60F at times when the system is dehumidifying.  However, the dummy space is still showing a space temperature of ~74F.  How is this possible?  Does anyone have any ideas?

Thank you,

Mike C

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