HVAC Loads Based on eQuest

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Just wondering... Has anyone based their HVAC design on eQuest results?
Typically we us Trane Trace for load calcs and do our energy models in
eQuest. However, this questions was brought up in our office. I just
wanted to see what everyone thought of this matter.

Arturo Hernandez

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I did load calcs in both eQuest and Trace for a small addition on a
local government office building (5,000 SF) to try to answer this
question for myself. For that size there was no difference between the
two and since I was utilizing eQuest for the energy modeling for LEED
then I decided to drop the Trace version to keep myself focused on such
a small, quick project.

JEREMY R. POLING, PE, LEED AP

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That's the way are offices typically do it as well (i.e. Trace for loads, eQuest for energy).

I have found that when both programs use the same inputs for envelope, lighting, misc equipment, etc., the two programs produce results that are pretty close.

Regards,

James A. Hess, PE, CEM

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I guess the problem is when calculating loads you may want to be a
little more conservative with you internal loads and when you are doing
energy modeling you want to be more exact with your assumptions. In
addition, my understanding is that internal loads contribute to space
heating in eQuest load calcs. Which something that many engineers would
not feel comfortable with.

ARTURO HERNANDEZ

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Not sure if that is accurate. If you schedule your internal loads HDD to be zero in each hour, then the winter peak loads should not include these values/gains.

Timothy Howe, MS, LEED? AP

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If you're just designing offices, strip malls, churches, etc., then the
Trane program is much, much quicker, and any difference in accuracy is
smaller than the uncertainty embedded in your assumptions. (e.g., will
the customer add more equipment, leave the door open, keep the blinds
open, etc.)

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You are correct. Therefore one would just have to schedule that to be off all the time in HDD. So are there any other any concerns with using eQuest? Is the answer simply: It is easier to get the load calculations from Trane Trace?

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I think there is another question about how detailed your load calculation will be in breaking down the building compared to the resolution required for your energy model, but you might be able to navigate the differences successfully. And for some projects there may not be much difference.

Also whether the same person is doing both tasks, and their familiarity with both software packages. Arturo, if you were doing both then great, but what if you have to hand the load calc tasks off to someone at your office that doesn't use eQuest?

David

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So does this mean that the eQuest default is to use internal gains to size heating equipment thereby under-sizing it compared to what mechanical designers would typically do, but that you can over-ride this by setting the internal loads HDD to zero?

To James and others who have compared eQuest loads to Trace (HAP, etc):
To get good correlation, are you creating design day schedules to use in eQuest, much like the mechanical loads software uses design day conditions for sizing? I've always thought that the difference between eQuest loads and sizing software loads is due to the fact that eQuest uses typical hourly weather data which may not include the design day extremes, unless you create custom design day schedules?

Thanks,

Luka Matutinovic, B.A.Sc., LEED? AP

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Last thing I would like to bring up on this topic: Is solar heat gain
taken as a credit during your HDD and if so how could this be
"shut-off".

ARTURO HERNANDEZ

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When you build a project in eQuest using the wizard, the HDD schedules are
set to 0 for all internal loads.

When eQuest auto-sizes, it uses the weather file data and takes solar gain
into account for both heating and cooling, if you need any. You can create
custom heating and cooling design days that specify the hour at which the
high and low temperature is reached. For a heating design day, the hour low
could be specified to be at night, when there is no solar gain. Also, in
LS-B and LS-C reports, the solar gain is clearly called out, if there is any
solar gain during the heating design day, it cab be subtracted out of the
total load for the space.

Thanks,

Karen Walkerman

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