[BLDG-SIM] Appendix G Baseline HVAC system and modeling packaged VAV with gas heat

[Andrew Craig]

I have two questions that have come up recently...

 

1.	If the a proposed building pursuing LEED is going to use a
Packaged VAV system with a gas furnace in the unit and electric reheat
in the boxes, would the baseline building (according to ASHRAE Appendix
G) fall under the Fossil/Electric Hybrid category or the Electric
category since that is the predominant heating source?
2.	Secondly, what is the best way to model this type of system in
eQUEST?  I have experimented with first defining a packaged VAV unit in
the wizard with hot water coils as the heating source.  Then in the
detailed edit mode, I changed the system "Heat Source" to furnace and
"Zone Heat Source" to electric and deleted the boiler and hot water
loop.  When I simulated this model, no natural gas usage showed up in
the BEPS report under Space Heating, however, there was a tiny amount
(~2% of total heating energy) that appeared in the Pumps & Aux category.
Can anyone explain what's happening and/or suggest the best way to model
this kind of system?  As a side note, from projects we have monitored
here in Oregon, we would expect to see about 30% of the total heating
energy use go to natural gas for this type of system, primarily from
morning warm-up.

 

Thanks for your input.

 

Regards,

 

Andrew Craig, EIT, LEED(r) AP | Mechanical Designer

INTERFACE ENGINEERING 
708 SW Third Avenue | Suite 400 | Portland, OR 97204 

direct: 503.382.2696
office: 503.382.2266
fax: 503.382.2262
email: Andrew_C at ieice.com
web: www.ieice.com 

Consultants of Choice to the Built Environment for over 35 years
Kirkland, WA | Portland, OR | Sacramento, CA | Salem, OR | SanFrancisco,
CA

 



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