windows on plenum walls

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Hi All,

I've always been able to do this before, but its not letting me do it today
on a model I am working on...

I'm am trying to place some windows on the plenum walls. In real life these
are actually a spandrel panel. I'm in the custom window placement and when
I place the window on the plenum wall it shows up in the custom window
screen, but when I go to check my 3D view, the window on the plenum wall is
not displayed.

Has anyone had this problem before? I've always been able to place windows
there before (I specifically remember being able to do it in the window
wizard for 3.63b version. I know I can verify thier existance when I move
to DDedit, but I'm just trying to be more efficient using my wizard tools
first.

thanks,
pkg

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

So, I figured out where my plenum windows were going...Because eQuest set up
a single plenum for my entire floor plan, as opposed to multilple plenum
spaces for each Zoned space that I have.

My new question that I haven't been able to figure out is this:

When (or how to determine when) eQuest will create a single plenum for the
entire floor plan, and when does it create a single plenum space for each
space zoned in my floor plan?

Sometimes I'll set up a model and it will do one approach and then sometimes
I'll set up a model and it will create a single space plenum??

Any hints anyone can give me are appreciated.

thanks,
Pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

I have found that this has to do with the system type you choose. If you
have a central system such as VAV reheat, which serves many zones, you'll
get one plenum. If you have PTACs, with one piece of equipment for each
zone, you'll have multiple plenums.

--
Karen

No Username provide's picture
Joined: 2011-09-30
Reputation: 200

When in the wizard you select or by default:

- System by floor : it results in a single plenum for entire floor

- System per zone: it results in multiple plenums per zone.

Gaurav Mehta, LEED? AP BD+C

Mehta, Gaurav's picture
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Joined: 2011-09-30
Reputation: 0

Ah-HA! Thank you Karen and Gaurav...I guess I didn't really pay attention
to the system assignments in the wizard as I usually abandon the wizard
after the custom windows anyway. I just like DDedit mode, better than
wizard mode.

Thanks again, as always this list is the BEST to turn to for support.

pkg

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 600

I'm not one to whine much, but I have run smack into this 'feature' enough times to issue a complaint "feature request" =).

Aside from losing custom window placements, many zones being lumped into one has caused me major headaches for other reasons... if you are in a proposed/baseline modeling situation, and don't pick up on the problem until you are well into detailed edits (it may not be as obvious if you don't see spandrel glass disappearing), it's simply a daunting task to create/assign all the associated surfaces and spaces to make the models sync - something I wouldn't wish on anyone.

Let it be on record that a very welcome feature in any future eQuest development would be an explicit option (radio button) to let the user decide whether individual plenums or cohesive 1-per-floor plenums are desired to be generated for the shell. This might logically show up in the wizard footprint/zone definition screen, immediately following the automatic/custom zone definition pull-down.

Does this seem feasible, or is there something fundamental to the way DOE2 operates that would get in the way?

NICK CATON, E.I.T.

Nick-Caton's picture
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Joined: 2011-09-30
Reputation: 805

My attitude, which comes from being older than dirt and using DOE2 in it's
infancy, is why have plenums at all? In fact, I am sure that at one point in
the dark ages it was suggested in the manuals that, since plenums are
generally the same temperature and space condition as the space below them,
that they need not be input. Of course there are instances when this "rule"
will need to be broken, as when you are specifying underfloor plenums and
maybe some other cases. But the 99% of the times when that's not the case,
it sure saves a lot of time, bother and space to not have plenums.

Carol

cmg750's picture
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Joined: 2010-10-05
Reputation: 0

I think that more than 1% of buildings will have times when the conditions in the plenums differ from the spaces below.

For example:
1) If you have recessed lights, some fraction of the heat gain from those lights will go straight to the plenum, rather than become a space load that needs to be cooled at the zone level. If you are economizer mode, this heat load could be directly exhausted, as opposed to needing to be cooled by the system or plant. If you are not in economizer mode, this heat load still contributes to the system load, but not to the zone load (i.e. less airflow required).
2) If you have a roof (as most buildings do), the condition in the plenum immediately below that roof is going to differ from the space below. In a high-rise bldg, this only impacts the top floor, but it surely has a non-negligible impact for low-rise buildings. With a plenum, the roof conduction load (whether it is a heat load when it is hot and sunny outside or the opposite when it is cold and dark) will go straight to the plenum air rather than become a space load. This could affect economizer performance, zone sizing, zone loads, system airflow, system loads, etc? in real life too, not just in the simulation world.

No doubt there are other impacts. Granted, ignoring the plenum won?t likely make or break an energy model, but I actually think it is very easy to make plenums in eQUEST (the program does it for you!) so why not just put them in?

Date: Thu, 2 Dec 2010 13:46:11 -0800

Hwakong Cheng's picture
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