[Bldg-sim] Large Unmet Heating/Cooling in Baseline

[Rob Bialobrzeski]

I am modeling a school gymnasium building that has two gyms and a two story
office/locker room wing.  The office/locker room wing has several zones that
have very different loads, but are designed to all be served by the same
packaged, constant volume, 100% outside air ERV.  In the design case model,
heating is supplied to these zones primarily by HW baseboards, while cooling
loads are satisfied by the supply air.

Appendix G dictates that the baseline HVAC system be Type 3, PSZ-AC with
constant volume DX cooling and furnace heating (no reheat).  When modeling
this system type, I am getting a large amount of unmet heating and cooling
hours (as many as 1,500 hours for a given zone) in the office/locker room
zones.  My guess is that this is happening because the baseline HVAC system
has no heat source at the zone level (where the proposed case has
baseboards), and many of the slave zones have very different heating/cooling
loads than the control zone.  I am not sure how I can adjust the model to
eliminate these unmet hours while still being consistent with Appendix G.
The only method that has worked for me so far is to drastically increase the
system supply flow, but this creates large fan savings that may not be
reasonable.  Is it appropriate to add zone reheat even though it is not
called for in Appendix G? 

 

Hopefully I've presented my problem clearly enough.  Any help would be much
appreciated!

 

Thanks,

 

Rob Bialobrzeski

 

DMI

35 Walnut Street

Wellesley, MA 02481

Phone: 781-431-1100 x17

Fax: 781-431-1109

 

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