[Equest-users] Using PSZ as DOAS?

Thu Apr 21 07:08:15 PDT 2016

Thanks for the input Nathan.  Since I do have an ERV, I am trying to deal
with that more complicated issue.  I actually ended up using a Powered
Induction Unit as suggested by Elizabeth and that seems to be working well.

On Thu, Apr 21, 2016 at 10:04 AM, Nathan Miller <nathanm at rushingco.com>
wrote:

> I’m just getting back from a vacation, so sorry for the delayed response
> on this, but there is a way to force a PSZ system to have discharge air
> temp control. I’m ignoring the ERV portion of your system right now because
> that complicates matters.
>
>
>
> We use this methodology frequently to model corridor/DOAS systems for
> multifamily projects. Note that this is only accounting for the energy use
> of the ventilation air. I’m assuming you will model separate systems for
> the dwelling units to meet the space conditioning demands (basically it
> looks like you are supplying neutral vent air, which won’t have much impact
> on how much load shows up on the in-unit VRF).
>
>
>
> 1)      Create a new space (call it “DOAS Dummy space” or something).
> Make the size minimal- 1’x1’x1’ works well. Make sure there are no internal
> loads or walls/roofs/floors assigned to it.
>
> 2)      Create a new zone (call it “DOAS Dummy zone” or something).
> Assign the dummy space to the zone. Give the zone Heating/Cooling t-stat
> schedules that are equivalent to the discharge air temp range you want to
> control to. In your example you’d have a 24/7 heating schedule at 73 deg F
> and 24/7 cooling schedule at 75 deg.
>
> 3)      Give this dummy zone control of your PSZ unit. Because there are
> no loads in the space, the PSZ unit should discharge air between 73-75 Deg
> to keep that 1 cubic foot space at the desired temp range. You can confirm
> this by looking at hourly reports.
>
> 4)      If you have multiple conditioned zones assigned to the unit, they
> will “come along for the ride” meaning they will get the same supply air
> temp, with no consideration for their space temps. You may have to assign a
> realistic “relaxed” t-stat schedule to those space to avoid lots of unmet
> load hours.
>
> 5)      Depending on how the vent air is being distributed in the
> dwelling units, you might have to play around with how the fan power is
> assigned. For example- do the in unit fans have to run 24/7 to distribute
> the vent air, or do they only cycle to meet the loads in the space?
>
>
>
> Having an ERV can significantly complicate this modeling method depending
> on where the return air is coming from (and the expected temperature of
> that return air)  for the heat-recovery.
>
>
>
>
>
> *Nathan Miller, PE, LEED AP BD+C** – **Mechanical Engineer/Senior Energy
> Analyst*
>
> *RUSHING* | *D* 206-788-4577 | *O* 206-285-7100
>
> *www.rushingco.com <http://www.rushingco.com/>*
>
>
>
> *From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
> Behalf Of *Michael Campbell via Equest-users
> *Sent:* Monday, April 18, 2016 4:07 PM
> *To:* Elizabeth Gillmor <elizabeth at energetics-eng.com>
> *Cc:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Using PSZ as DOAS?
>
>
>
> Thank you Elizabeth!
>
>
>
> On Mon, Apr 18, 2016 at 3:30 PM, Elizabeth Gillmor <
> elizabeth at energetics-eng.com> wrote:
>
> Hi Michael,
>
> I have always used a Powered Induction Unit system type for DOAS systems.
>  (Or standard Induction Unit system if CHW instead of DX.)  This should
> give you the control and heat source capability that you need.
>
>
>
> Good luck!
>
> Elizabeth
>
>
> *Elizabeth Gillmor  **PE, BEMP, LC, LEED AP*
>
>
>
> *e n e r g e t i c s  **consulting engineers, llc*
>
> energetics-eng.com | 303.619.0091
>
>
>
> On Mon, Apr 18, 2016 at 12:52 PM, Michael Campbell via Equest-users <
> equest-users at lists.onebuilding.org> wrote:
>
> I also have a follow up question.  Is there any system type that I can use
> which will allow me to select heat pump as the heating source and also be
> controlled by the supply air temperature?  It appears that constant temp
> control would be available for PMZS but I cannot use heat pump heat with
> this type of system.
>
>
>
> On Mon, Apr 18, 2016 at 9:37 AM, Michael Campbell <mcamp1206 at gmail.com>
> wrote:
>
> Hello,
>
> I'm trying to use a PSZ system as a DOAS.  The system I'm trying to model
> uses and ERV tied to a heat pump to supply fresh air to common areas and
> dwelling units.  There are then separate VRF systems for space
> conditioning.  The DOAS is designed to supply a constant temperature
> outside air (73F when heating, 75F when cooling).  How can I make the PSZ
> system in equest supply a constant temperature supply air?
>
> Thank you
>
>
>
>
>
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