Cooling demand is Super High

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Hi--does anyone have any suggestions on how to trouble shoot cooling energy
demand that is about 5 times too high?

I've looked through my schedules, fans/on/off, etc. My building has
packaged rooftops and I can't pinpoint the compressor energy demand versus
the fan energy demand.

I've searched the archives and haven't come across any solutions for my
model results. My energy consumption for elec & htg is aligned however,
just the demand is too high (extremely high...)

Thanks in advance for any insight you can share.

Pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 400

You can check to make sure your equipment sizing is reasonable.

Steve Jacobs's picture
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Reputation: 600

Report PS-E for your electric meter(s) will show cooling vs. fan and all other electric end uses for both consumption (kWh) and demand (kW).

Paul Riemer, PE, LEED AP BD+C
DUNHAM

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Thanks for all the responses, so quickly! I've checked my unit capacity
inputs--and thus tried an "auto-size" run. The capacities are correct, and
very low hours out of throttling range. Unfortunately the space cooling
demand (kW) did not move at all.

I've referenced my PS-E report and the highest demand is falling under the
"space cooling" end use which I think must be the DX compressor energy
demand driving this value?? Please correct me if I am wrong.

I will try adjusting the EIR values and see if that will move the kW values
down any...

Thanks so much! Any further thoughts are welcome. If anyone is curious
to see my model let me know and I am happy to share it for your
viewing/troubleshooting pleasure! :)

Pasha

Pasha Korber-Gonzalez's picture
Joined: 2011-09-30
Reputation: 400

"Space cooling" demand/consumption as an end-use category is relatively simple to track down. If I'm not mistaken, all kW/kWh figures for "space cooling" will tie back to cooling EIR inputs, and the associated scheduling/capacities, on the airside & waterside of things: DX compressors, heatpumps, and/or chillers.

If you're all packaged DX, that narrows the field nicely ;).

The statement "...XX times to high" suggests you have some target/expected value, which would logically be based (if anything) on system capacity... so that's a sensible place to start. Sounds like those inputs check out? Are there any inadvertent system and/or cooling multipliers in play (other than 1.0)?

Messing with the cooling EIR inputs should have a direct effect on the demand values you are observing. Checking the associated inputs is a natural step to follow.

If the maximum demand hour is very much dominated by the space cooling end-use, that makes me consider carefully reviewing the loads around that time of year, even if the annual unmet hours are within reason. These demand results may possibly be the result of some kind of irregular "spike" caused by a fractional load/occupancy schedule typo.

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.

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