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Forum discussion

NC-2009 EAp2:Minimum Energy Performance

Decreasing Baseline Capacities for Unmet Load hours

F S

LEEDuser Basic Member

0 thumbs up

October 24, 2017

Hi All,

My question is basically about how much can you decrease the baseline capacities without going to far - that might call Red flags.

For example I have a baseline model that has 3 packaged VAV each having a total cooling capacity of about 650,000 Btuhs. My unmet hours on this project is around 96 hours. But I need to increase these unmet hours to meet the ASHRAE G3.1.2.2 requirement. I am asking because I only begin to see any increase in unmet hours when I drop the capacities to about 450,000 Btuh - which to me seems like a lot.

Any thoughts?

ASHRAE G3.1.2.2

“If unmet load hours in the proposed design exceed the unmet hour load hours in the baseline buildings by more than 50, simulated capacities in the baseline building shall be decreased incrementally and the building resimulated until the unmet load hours are within 50”

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Thu, 10/26/2017 - 19:12

Before I started messing with the baseline I would try to figure out why the proposed are so high. At 96 hours you seem to have a pretty good baseline. I assume you need to increase it because the proposed is higher and you want to get it within 50. Keep in mind that 90.1 has dropped the 50 hours in subsequent versions of the standard so the reviewers are not likely to be very picky about being over 50 hours depending on how far over.

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