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CS-v4 EAp2:Minimum energy performance

Heating coil as a preheat in DOAS with VRV

Dear Everyone

I am quite confused because I got a review comment recently where Reviewer suggests to exclude preheat coils from Baseline System 7. 

It is a project located in Poland. Building is equipped with AHU as Direct Outside Air system which treats only 100% fresh air supply. It is equipped with heating coil to provide 20 C. Then for indoor comfort treatment VRV is used. 

For our first LEED project we were recommended to set preheat in such situation. Reviewer said that heating coil in DOAS is a kind of preheat, but it can not be set to 20C ( the same manner) because it is higher than supply air temperature, so we set it to be lower than SAT. 

That method we used for maybe 20 projects and now we were asked to switch off preheat. 

 

My question is if we should set preheat or not in such situations, so simply, if heating coil CAV AHU which is DOAS should be treated as preheat coil or not. 

 

Best Regards

 

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Wed, 03/25/2020 - 17:30

I think there is considerable confusion about the application of this requirement since ASHRAE 90.1 does not provide a definition for preheat. My interpretation has been that a DOAS would not be considered preheat, so in this example the Baseline would not include preheat as the reviewer has requested. However, I admit I don't have a strong basis for my interpretation and could also see an argument for this being considered preheat. In either case the Baseline system type would not change, because the fuel source of the DOAS would be factored into Baseline heating source classification from Table G3.1.1A regardless of whether or not it was considered preheat. 

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