[Bldg-sim] FW: Excess winter cooling load in eQuest

[Keith Swartz]

Xavier,

I would check the minimum airflows for the VAV zones. 30% of maximum air flow is generally a code minimum (unless there is a critical space that needs a high fraction of ventilation, such as a conference room, or the cfm/sf is near 0.4). If your percentage is abnormally high, then the system will have a lot of reheat. Unfortunately the eQUEST wizard limits assigning different minimum airflow percentages to only two types of zones - core and perimeter - so it's harder to deal with a critical space that affects the ventilation fraction.

Sincerely,

Keith Swartz, PE, LEED® AP
Energy Engineer / Senior Project Manager
Energy Center of Wisconsin
455 Science Drive, Suite 200
Madison, WI 53711

Phone: 608-238-8276 ext. 123, Fax: 608-238-0523
www.ecw.org  The Energy Center of Wisconsin is a nonprofit organization that seeks solutions to energy challenges.

-----Original Message-----
From: Xavier García Casals [mailto:xavier.garcia at aiguasol.coop] 
Sent: Thursday, June 26, 2008 8:56 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Excess winter cooling load in eQuest

Hello all,
I am finding an excess in winter cooling load when using DX coils for 
cooling and HW coils for heating with a Packaged VAV with HW reheat. The 
SS-C report shows a number of coincident cooling&heating load hours 
almos equal to the unexpected cooling loads. This that could be normal 
when the system serves many different zones, keeps on happening when I 
asign one system per zone. I need to change the heating source to 
Furnace  (for example Split System Single Zone DX with furnace) for 
getting rid of those winter cooling loads. Is there a way to manqage it 
with the Packaged VAV with HW reheat system?

On the other hand, from within the Wizards, the 'zone groups' assigned 
within each shell seem not to be available in the system assignement to 
thermal zones, and therefore, the system per area assignement overides 
the zone groups and their system assignements. Is it like this?

Regards,