[Equest-users] Modeling common areas in multi-family

Tue Feb 21 07:02:01 PST 2017

Something else comes to mind – check that the zonal exhaust you specified for the trash rooms & similar has the source (paraphrasing) “from air handler,” and not “infiltration.”  This will ensure the makeup air associated with the exhaust quantities you’re specifying is coming through their parent system(s).

Shauns advice to check interior + exterior surfaces holds true.

After these checks, if you are still seeing sub-freezing temperatures in any spaces, I’d consider this a warning sign from your model quite worthy of a back-of-envelope check:  is the specified exhaust air CFM sufficient to keep the space above the freezing mark at all hours, assuming perfect mixing?

·         Consider adjusting the exhaust CFM downwards if you can’t find specification of door grille free area in coordination with the fan’s SP specification.

·         Consider also pushing the transfer air temperature downwards if the closet/space is relatively remote from the corridor thermostat and/or is near any windows / exterior exposures in the corridor (account for imperfect mixing in the corridor).

·         If after this check you are even remotely close to freezing temperatures (like 45 or less after accounting for heat transfer), flag the design team to pay mind to the situation your energy model is painting.  A trash room is unlikely to have great circulation between bins and exterior walls (your model and back-of-envelope calcs to this point likely assume perfect mixing for the space volume), so the potential for sub-freezing conditions within the envelope and incident to piping systems is real.

All told however, your approach is sound from a “get the energy draws right” modeling perspective.

~Nick

[cid:image001.png at 01D28C1E.C08365F0]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Regional Energy Engineering Manager
  Energy and Sustainability Services
  Schneider Electric

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Shaun Martin via Equest-users
Sent: Monday, February 20, 2017 4:22 PM
To: 'Michael Campbell' <mcamp1206 at gmail.com>
Cc: 'equest-users' <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Modeling common areas in multi-family

Hi Michael,

I frequently find that rooms like this will have exterior components, like roofs or floors, placed there by the wizard.  Also check your interior walls.  Inter-zone heat transfer through interior walls is all you have to maintain temperature, as there is no air flow.

Shaun

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Michael Campbell via Equest-users
Sent: Monday, February 20, 2017 11:48 AM
To: equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] Modeling common areas in multi-family

Hello eQUEST Users,
I have a question regarding modeling common areas in a multifamily building.
I have 4-story residential building.
Floors 2-4 have corridors which are provided with outside air supply.
There are trash rooms, storage rooms, mechanical rooms off these corridors.
These trash rooms, storage rooms, mechanical rooms do not have their own heating/cooling systems, they are conditioned indirectly by the Corridor HVAC system.
Trash rooms and mechanical rooms have exhaust systems so i have modeled this per the design.

So in eQUEST I have modeled these spaces together as a single PSZ system using the Corridor space as the control zone.
I have modeled the Corridor with its specified outside air CFM supply per the drawings and I have modeled the trash rooms and mechanical rooms with their specified exhaust air CFM per the drawings, with exhaust air being made up via the air handler.
I have thermostat schedules set for the Corridor spaces (heat to 68F and cool to 78F), but have not used thermostat schedules for the trash rooms, mechanical rooms, storage spaces.  The reason I excluded thermostat schedules is because this is a single zone system and these spaces are essentially "along for the ride".
The issue I am having is that when I review my SS-F reports I am seeing temperature below 30F at times in the trash rooms.  I would expect that the temperatures would not be exactly the same as my Corridor since they are not being directly controlled but I am surprised to see such low temperatures as 30F and am sure the spaces will not reach these temperatures in real world conditions.  I am looking for some guidance on how to best model this scenario.  Any help would be appreciated.
Thank you,

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