[Equest-users] FCU Fan Control Question

[Bishop, Bill]

Robert,
 
You could determine the difference in fan operation between undefined
and scheduled by creating a new hourly report block with variable type
"HVAC System", and selecting "Total system supply air flow rate". The
"undefined" fan is probably running more often, or all the time. If you
are modeling per Appendix G, you should be using the occupied/unoccupied
schedule that you created regardless.
 
The cooling fan schedule covers both cooling and heating. You would only
enter a heating fan schedule for the hot deck of a multizone or dual-fan
dual-duct system (per the DOE-2 help description).
 
Regards,
Bill
 
William Bishop, PE, BEMP, LEED(r) AP | Pathfinder Engineers & Architects
LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Sustainability - less is more.
________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Robert
Des Rosiers
Sent: Tuesday, June 29, 2010 1:14 PM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] FCU Fan Control Question
 
Does anyone have any thoughts regarding the question posted below?
 
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Robert
Des Rosiers
Sent: Monday, June 28, 2010 9:48 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] FCU Fan Control Question
 
All:
My building has individual 4-pipe FCU's attached to a central plant.  I
am seeking clarification as to how eQuest interprets an undefined 'fan
schedule' versus creating a fan schedule.
 
It is my understanding that, per the help topics, if a fan schedule is
left 'undefined' the "program assumes the fans are always available when
needed."  This seemed to be a viable option when designing a baseline
building.  Since I know the fan schedule I created one; on during
occupied hours, off during unoccupied with night-cycling enabled (per
ASHRAE section G).  This had a significant impact on steam consumption,
changing from 415 MBTU in the 'undefined option' versus 228 MBTU in the
'scheduled option'.  Since I am forcing the fans to be on in the
scheduled option one would think it would result in higher energy
consumption values.
 
Could someone clarify why adding a fan schedule would impact energy
consumption so significantly?  Could it be left as 'undefined' simply
allowing the fans to operate when they're needed?  Does this schedule,
listed as a 'cooling' fan schedule only operate cooling and if 'yes', is
the heating schedule defined under the 'Heating' --> 'Coil Cap/Control'
'Availability Sch' (which I have as 'undefined'?
 
Thank you all in advance for your assistance.
 
Robert Des Rosiers, LEED-AP
STUDIO MA
130 N Central Avenue, No.300 Phoenix, Arizona 85004
Telephone 602 251 3800
Fax 602 251 3100
 
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