Unmet Hours

System 9 - Excessive unmet hours - eQUEST DOE 2.2

asked 2019-09-27 13:49:44 -0500

emseaman413
51 ●3

updated 2019-09-29 10:14:42 -0500

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

Hello,

I'm finishing up an LEEDv4 energy model (ASHRAE 90.1-2010) on eQUEST, but am running into an issue with excessive unmet (cooling) hours. The unmet hours are above 2000 for cooling; summary tab shows my three system 9's 'heating &ventilation' are primarily responsible. My primary system type is System 5 pkgd VAV w/ reheat, secondary systems are mostly System 3 PSZ. In the storage spaces and stairwells I've used System 9.

My question is, how does eQUEST know to exclude unmet cooling hours for 'heating & ventilation' systems where design cooling temperature does not need to be met?

Thanks!

Ethan

answered 2019-10-01 12:26:18 -0500

emseaman413
51 ●3

I answered my own question. I'm posting here for anyone who has a similar issue.

I had a heating and ventilation system selected, and was getting ~2000 unmet hours for cooling. Turns out I still had a cooling schedule specified on the zone level. The zone essentially was calling for cool air, and my system choice was not allowing it.

That's all; happy modeling!

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Comments

a question i would have is - were cooling thermostat schedules removed in the Baseline that are assigned to zones in the Proposed? The thermostat set point schedules should match between the models, hence the question.

If a zone in the Proposed has cooling, then the Baseline should either be on a System 5 or System 3.

If a zone in the Proposed does not have cooling, then it too should not have a cooling thermostat schedule.

Goal is to avoid a LEED review comment if possible

dradair ( 2019-10-03 10:39:28 -0500 )edit

Good question - the zones I have specified as 'system 9' in baseline are all where we have unit heaters in the proposed. Both models are still thermally similar.

What happened was this project was started and went on hold (for a long time) - the original model was in compliance with 90.1-2007, so everything was either a system 5 or 3. When the project came back we had to model to 90.1-2010 for LEEDv4. We had set up our system 9's, but forgot to turn of the (zone) cooling schedule in the baseline. This was causing the zone to to call for cold air while being assigned to a heat/vent system.