mystery heating load

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Hello,

I've created a model using eQuest 3.65 (DOE 2.2) build 7173 that is of a 20
storey multi-residential building located in Toronto, Ontario (Canada).
There is a basement with a elevator lobby that is an interior space (no
exterior walls).

My model keeps telling me I have underheated hours for this lobby. I'm
trying to figure out why there is a heating load and I'm stumped. I have
removed what I believe to be all potential sources of heat loss. I've
deleted the underground floor (which was R-100 anyway), I've deleted the
interior walls (just to be thorough), there is no infiltration, and I've
set the ventilation to zero. In my mind, there is no source of heat loss.
I've even added a significant (10 W/ft2) equipment load and yet there are
still underheated hours (I've even reduced my Tstat setpoint to 60F).

I've run an hourly report to help figure out the loads for both the space
("Sum of all weighted loads except infil and latent") and zone ("Load
Calc'd SPACE Sensible load at const temp (Btu/hr)"). These reports all
indicate a positive load (i.e. net heat gain) from my lights, plug loads
and occupants. However through this process I'm also questioning these
reports as the lighting, people and equipment load being reported don't
exactly align with my modeled schedules for these loads....but I've put a
pin in that.

Regardless, I have no idea how to figure out what may be resulting in net
heat loss for this zone. To be thorough, I checked the elevator lobby on
the ground level and the same thing is happening. Has anybody seen this
before...any ideas what might be causing heat loss for a zone with no
ventilation and no walls and no infiltration? It does seem to be seasonal
(i.e no underheated hours in the summer) so it has some connection to
weather file but does not correlate exactly.

If you do take the time to read this, a big thank you. If you provide the
answer, you'll for sure be on Santa's "nice" list.

Chris

Chris Hadlock's picture
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I've had a few responses requesting the modeling files so I've attached the
INP and PD2 file (weather file is CWEC\Toronto.bin). The zone in question
is "L0 Elev Lobby S" and I've already removed all exterior surfaces from
this space (i.e. there are no Child Components). I've assigned this zone to
it's own system (it's the last system on the air-side tab) called "Test
System". I've already created the hourly reports where you'll see all of
the underheated hours (which only occur in the winter). The LS-B report
shows no (zero) htg load. I realize the system is not really providing any
heating to this zone the way it's setup.

Thanks,
Chris

Chris Hadlock's picture
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That last sentence is the issue ? the system is providing some amount of air including return and OA to the space, without a heating coil, meanwhile the thermostat may be expecting 70F all of the time.

The issue could be resolved by ?upgrading? the unit to heat, removing/reducing the OA quantity, or by relaxing or removing the thermostat schedules depending on what your goals are for the project.

David

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Associate

Direct: (847) 316-9224 | Mobile: (773) 490-5038

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Bruce Easterbrook's picture
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Hi David,

Thank you for your feedback. The zone is only getting 1 cfm of supply air
from the system and 0 ventilation, so I don't think that is what is
providing the heating load. And if I do add heat capacity (say an electric
baseboard), I need to add a significant amount (like 13,000 Btu/hr) in
order to maintain heating setpoint (which is only set to 60F). I don't get
why a zone without ventilation, without infiltration, without any walls
needs such a large heating capacity? I can't explain it.

Chris

On Thu, Dec 20, 2018 at 2:33 PM David Eldridge via Equest-users <

Chris Hadlock's picture
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Thanks to all who responded...the problem has now been solved. My faith in
eQuest remains.

Chris

On Thu, Dec 20, 2018 at 2:33 PM David Eldridge via Equest-users <

Chris Hadlock's picture
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This might be true in the real world, but not in eQUEST (nor any other
simulation program that I know) because it would require CFD modeling of
the spaces.

Joe

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I see this was answered as I?m typing, but here?s my logic path if it?s helpful:

1. LS-B confirms you?ve effectively killed all sources of heat load that wouldn?t be introduced by the HVAC (i.e. ventilation loads).
2. You have no exhaust in the zone.
3. It therefore has to be a load introduced from the system (ventilation or active cooling or similar).

I observe electric heating and empty inputs / defaults for the OA and active cooling inputs for the associated PSZ system. If I push cooling capacity and min OA fraction to zero, I get no unmet heating hours.

Philosophical food for thought (future reference): Hindsight 20-20, you may have made an issue like this harder to solve by doing something ?extreme? like eliminating all interior surfaces, in kind removing all means of heat transfer? if the space has no way to get rid of built up heat it might cause a system to do something weird like desperately economize in sub freezing temps to deal with ever-building heat loads, creating a new artificial problem out of the earlier shotgun remedy efforts. If you should find no remedy in this sort of ?turning the dials,? I?ve found it is usually a good practice to undo / step back those efforts before trying other solutions.

Here?s that LS-B for reference:

[cid:image001.png at 01D49874.A131F0E0]

~Nick

[cid:image002.png at 01D49874.A131F0E0]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

D 913.564.6361
M 785.410.3317
F 913.564.6380
E nicholas.caton at schneider-electric.com

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

[cid:image003.png at 01D49874.A131F0E0]

Nicholas.Caton at schneider-electric.com's picture
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And the cause for the mystery load is ??? Don't just leave us hanging!

Joe

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right...although I had deleted all child components for my zone in
question, there were interior walls (defined in adjacent zones) that were
exchanging heat transfer with my zone. The adjacent zone just happened to
be an unconditioned parking garage that was very cold...foolish that I
missed it.

On Thu, Dec 20, 2018 at 4:00 PM Joe Huang via Equest-users <

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OH!? I'm so glad I asked, because from the thread I got the impression
that the mystery load was due to outside air introduced by the HVAC
system!?? So, your experience should be a warning to all eQUEST users
that the LS-B, LS-D, etc. reports give only the heat flows from outdoor
or indoor sources, and not heat flows from HVAC operations or the true
interzone heat transfer from adjacent spaces.? The former is quite
understandable since the HVAC simulation has not taken place yet, but
latter needs a little bit of explanation.? In DOE-2 (underlying engine
to eQUEST), the "Loads" loads are calculated based on the input
temperatures for each space.? Since most runs are done using the same
space temperatures, the LS-X reports would show no interzone heat
transfer.? The subsequent System simulation solves for the true zone
temperature, so that when zone temperatures are different between
adjacent zones, there would be interzone heat transfer. Unfortunately,
this interzone heat transfer does not appear in any summary reports,
although the hourly values can be obtained through the HOURLY-REPORT
generator.

Joe

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