HP and DOAS

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I really need some help ASAP on this.

I have a geothermal HP system and am comparing it to an air-2-air HP
system, per ASHRAE 62.1. My cooling energy usage on the GSHP's are
significantly higher than the air-2-air HP and this despite higher EER
for the GSHP. Why is this? Is there some pumping being added into the
GSHP? It appears the pumps are separate on the Monthly Energy
Consumption report.

I am set up a DOAS and each HP receives its fresh air from the DOAS
system, yet the DOAS shows zero loads for cooling and heating in the
SS-A System Loads Summary report. This despite the warning I have in
the ATTN report that the System DOAS may have inadequate cooling
capacity. The summary report shows the full amount of CFM for the DOAS,
and also shows the capacity.

Thanks.

Caleb Bulow

mr_bulow's picture
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Joined: 2010-10-07
Reputation: 1

There are a bunch of issues that could potentially be causing your
results - we'd need the .inp and .pd2 files to be able to troubleshoot.

Off the bat, if your DOAS system shows zero loads, then it sounds like
you need to make sure there is a fan schedule for the DOAS system, the
actual fan CFM is specified, and the dummy zone has a heating/cooling
thermostat roughly matching the supply temps of the DOAS system.

James Hansen, PE, LEED AP

James Hansen's picture
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Joined: 2011-09-30
Reputation: 200

My dummy zone didn't have t-stat temps set, but that adjustment didn't
seem to affect anything.

I've attached my INP and PD2 files. The air-2-air HP system is the
Baseline files and the proposed system is the DE files. The DOAS is a
MAU with heating and cooling coils served by a W2W HP, as you can see.

Thanks,

Caleb B.

mr_bulow's picture
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Joined: 2010-10-07
Reputation: 1