[Equest-users] Modeled Interior Floors as Exterior Roofs

Sun Jul 17 20:09:30 PDT 2016

Whew!

You're making me think on a Sunday PM...which may not have accurate results...but here goes.

First, although this is painful, you can always "test" what you are doing by running w/ and w/o the plenums and see what shows up. To do this you'll be looking in the LOADS printout for the peak load by space, where it shows the magnitude of the different components, i.e., roof, opaque walls, etc. Unfortunately, this requires a whole-lot of reconfiguring of plenum walls, zone adjacencies, etc.

Once you have your system configured both wasys you can trace this through the system peak load, keeping in mind any duct losses that you put into the system and/or thermostat settings (probably best to use SYSTEM = SUM), depending on how you configured your ductwork. You will also be able to see the peak loads for the roof versus =0 for the roof when you have a plenum between the drop ceiling and the roof above. Of course, all this depends on whether or not you've switched on return = plenum. If you haven't then you shouldn't see any difference if you're using return = direct, or something else.

Second, I suspect even if you do see something, and you're still worried, you need to pay attention to the magnitude of the peak cooling and/or heating contribution by the component relative to the other components. For example, windows of any size usually overwhelm other loads.

Third, in regards to your perimeter zones, the loads from any plenum will mostly have an impact on the top floor and not the in-between floors if the zone temperatures are the same between floors. Especially, if you are using multipliers, which further complicates things.

That should give you something to chew on for now...and I can't really shouldn't go much further without looking further at your design in detail.

Jeff

PS: I'll be teaching a DOE-2 class in the fall if you interested in taking it at a distance via an ON-LINE link.

Jeff S. Haberl, Ph.D., P.E.inactive, FASHRAE,FIBPSA

Department of Architecture

Texas A&M University

College Station, TX 77845-3581

Office: 979-845-6507, Lab: 979-845-6065

Fax 979-862-2457

jhaberl at tamu.edu,www.esl.tamu.edu<mailto:jhaberl at tamu.edu,www.esl.tamu.edu>

________________________________
From: Darryl Kasun <darryl.kasun at gmail.com>
Sent: Wednesday, July 13, 2016 4:38 PM
To: Haberl, Jeff
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Modeled Interior Floors as Exterior Roofs

Hi Jeff,

I think I'm on the same page as you now.  Let me give a little information about this project just so I can assure myself I'm modeling this correctly.

I have the design drawings/specs for a hospital which using as the inputs for the eQUEST model.  The majority of spaces are heated/cooled/ventilated by central AHUs with VAVs c/w reheat coils along the perimeter.  If I model the zones without plenums, do I not run the risk of seeing unmet loads in the perimeter zones as the reheat coils may not be large enough for say the peak heating load for that zone?.

On Wed, Jul 13, 2016 at 2:24 PM, Haberl, Jeff <jhaberl at tamu.edu<mailto:jhaberl at tamu.edu>> wrote:
Hello Darryl:

Yes, the heating/cooling loads should be showing up in the SYSTEMS reports. However, it will be in a “lump” that does not allow you to separate out the individual components. You can switch it on/off by using the direct return option, but then this chops out those surfaces from participating in the simulation, depending on how you’ve linked up the plenums to the spaces in the next-to commands (or how the DOE2.2 robot does it).

You can see the loads in the plenums, but it will not show up in the UNMET loads because there is no thermostat in the plenum…hence no UNMET loads.

Jeff

PS: That’s off the top of my head…the eQUEST manual might shed more light on this.

8=!  8=)  :=)  8=)  ;=)  8=)  8=(  8=)  8=()  8=)  8=|  8=)  :=')  8=) 8=?
Jeff S. Haberl, Ph.D.,P.E.inactive,FASHRAE,FIBPSA,......jhaberl at tamu.edu<mailto:........jhaberl at tamu.edu>
Professor........................................................................Office Ph: 979-845-6507<tel:979-845-6507>
Department of Architecture............................................Lab Ph:979-845-6065<tel:979-845-6065>
Energy Systems Laboratory...........................................FAX: 979-862-2457<tel:979-862-2457>
Texas A&M University...................................................77843-3581
College Station, Texas, USA, 77843..............................URL:www.esl.tamu.edu<http://www.esl.tamu.edu>
8=/  8=)  :=)  8=)  ;=)  8=)  8=()  8=)  :=)  8=)  8=!  8=)  8=? 8=) 8=0

From: Darryl Kasun [mailto:darryl.kasun at gmail.com<mailto:darryl.kasun at gmail.com>]
Sent: Wednesday, July 13, 2016 4:18 PM
To: Haberl, Jeff <jhaberl at tamu.edu<mailto:jhaberl at tamu.edu>>
Subject: Re: [Equest-users] Modeled Interior Floors as Exterior Roofs

Hi Jeff,

Thanks for the reply.  A couple of comments:

- The hospital does have plenums and the heat gains/losses thru the plenum exterior surfaces would affect the return air to whatever system is serving that space.  Will the system not see this load?  I suspect it does and thus other than not being able to see the peak load, is there any other downside to having plenums?
- If I want the plenum loads to show up in the peak loads report by not creating plenums, I suspect I will see unmet loads in these plenum-less and thus larger zones as the designed equipment capacities will not be able to meet loads.

Thanks again
Darryl Kasun

On Wed, Jul 13, 2016 at 2:04 PM, Haberl, Jeff <jhaberl at tamu.edu<mailto:jhaberl at tamu.edu>> wrote:
Hello Darryl:

It may be worse than you think.

>From the looks of the image it also appears that you have plenums in the building, which further complicates the simulation, and for reasons that are not always obvious. For example, in DOE-2 if you declare the return air path as having a plenum and then assign the walls, roof, floor, etc. to that plenum as the zone, then the heat gain/loss from that surface is assigned to the air that is returning from the zone on its way back to the HVAC system and therefore, it will not show up in the peak load in LOADS because it is a heat gain to the return air and not the zone. You can prove this to yourself using the SAMP1 file that comes with DOE-2.

For example, in the SAMP1.INP file that comes with DOE-2, RUN 3A, there is a single story 5 zone model with a plenum. What you will notice when you run this model is there is no roof load in LOADS because the single story building has a plenum and the roof load has been assigned to the plenum as the zone. The load from the roof does show up when you assign a SYSTEM where it then appears as heat gain/loss from the return air.

To “see” the load from the roof you have to remove the plenum and re-proportion the roof to the zone area. Then the roof shows up in the component loads in the LOADS peak load report.

I suspect that deep inside the bowels of the model you showed below this is going on.

Jeff

8=!  8=)  :=)  8=)  ;=)  8=)  8=(  8=)  8=()  8=)  8=|  8=)  :=')  8=) 8=?
Jeff S. Haberl, Ph.D.,P.E.inactive,FASHRAE,FIBPSA,......jhaberl at tamu.edu<mailto:........jhaberl at tamu.edu>
Professor........................................................................Office Ph: 979-845-6507<tel:979-845-6507>
Department of Architecture............................................Lab Ph:979-845-6065<tel:979-845-6065>
Energy Systems Laboratory...........................................FAX: 979-862-2457<tel:979-862-2457>
Texas A&M University...................................................77843-3581
College Station, Texas, USA, 77843..............................URL:www.esl.tamu.edu<http://www.esl.tamu.edu>
8=/  8=)  :=)  8=)  ;=)  8=)  8=()  8=)  :=)  8=)  8=!  8=)  8=? 8=) 8=0

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Darryl Kasun via Equest-users
Sent: Wednesday, July 13, 2016 2:42 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Modeled Interior Floors as Exterior Roofs

Hey everyone,

The hospital I am working has different footprints for each level (see snapshot below).  While going thru the bldg. envelope in detailed mode, I noticed that the surfaces separating interior floors are modeled as exterior roofs.  Now it’s been a while since I’ve modeled using eQUEST but I’m sure these surfaces should be modeled as interior floors.

[cid:image001.png at 01D1DD22.FA3467A0]

So a couple questions:

1)      What did I miss in the DD Wizard?  One shell was made for each elevation, and for the each above grade floor, below is the input entered for the floor info.  Is this where I made my mistake?  Or do I need to model the shells with and without roofs separately?

[cid:image002.png at 01D1DD22.FA3467A0]

2)      Is there a fast way to change what’s needed without deleting each “interior roof” and replacing it with an interior floor or going back into the DD wizard?  Pretty sure not but here’s hoping!

Thanks everyone.  Hope your mid-week is going well!!

Darryl Kasun

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