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503.3.1 economizer requirement for all systems in buildings >300 mBtu/h
January 27, 2017
9:28 am
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fgrable@iccsafe.org
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April 6, 2015
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Section C404.3 of the 2015 IECC completely changed or was new. Perhaps that is where the answer lies?  Go view the code using the publicACCESS tab on the ICCsafe.org webpage.

January 26, 2017
12:04 pm
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nathanj@lenityarchitecture.com
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January 26, 2017
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I am dealing with the same issue. Does anybody have a clear understanding of Table 503.3.1(1), note "a", specifically if it applies to the aggregate amount of PTACs in hotel rooms? If I go off of how the COMcheck software it looks like I could only have about 40, 1-ton, PTACs before I hit the cap of 480,000 BTU/h. 

February 19, 2014
1:00 pm
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jerry campbell
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February 19, 2014
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I am working on a hotel design. The newest version of COMCheck is requiring an economizer on all the small systems because the total installed cooling capacity for the building exceeds 300 mBtu/h. We have about 900 mBtu/h of PTACs in the guest rooms and only about 200 mBtu/h of other common area cooling, mostly 1.5 ton DX split systems. Previous versions of COMcheck did not flag similar designs for economizers, so something has changed in the programming.

I don't believe the current version is right. Hotel rooms are small residential loads and should be considered separately from the rest of the commercial load. Hotel PTACs do not benefit from economizers becase the guests aren't using the air conditioner when OA temps are below 55 degrees. Why should that force every other small system in the building to require an economizer? It says I even need an economizer for the 9,000 Btu mini-split in the elevator equipment room. Does that really make sense?