[Bldg-sim] ASHRAE systems exception B interpretation

[Veronica Ochoa]

Hi,

I'm modelling a data center with 50 thermal zones for LEED EAp2/c1 purposes. The baseline system determined based on area and building type is system 8. However when doing the load deviation average to determine suitability for System 4 (under exception B), all but 6 zones are greater than the 31 W/m2 of the averaged cooling load per system/floor. This means that I will have 6 zones (2.5% of total area) as system 8 and 44 zones as system 4. Do I need to follow the exception that says that each zone served by System 4 should be modelled as one zone per system?? I find this a bit too much... I was wondering if you can simplify this by grouping similar spacetypes by setpoints or floors and reduce the number of systems.

Also, in the preliminary submission 100% of the zones were submitted as system 4, but this was noted by the USGBC reviewer as an error (as it was based on the average of the entire building not per system). As it has been now corrected and only 2.5% of the zones will be system 8, we are estimating the difference will be negligible. Would a narrative explaining this suffice? Has anyone been in this situation and how did you approach it?

Many thanks in advance for your help,

Veronica Ochoa


Consultant

hurleypalmerflatt

building sustainability


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