[Equest-users] Night Cycle Fan Control

[Porter, Fred AEC]

Gerard and others,
I would say that typical actual operation of most parallel box systems and the intent of System 8 in App G is a hybrid of the two eQ control strategies that can't be modeled in eQ. That would be Heating: Zone Fans Only; Cooling: Cycle AHU fans. Has this bothered anyone else ever? Do other programs allow the user to model this normal operation?

I suppose it's debatable whether this specifically adheres to the G3.1.2.x Fan System Operation, which states "Supply and return fans... shall be cycled to meet heating and cooling loads during unoccupied hours." A strict interpretation of that would lead to the use of "Cycle on any" for "System 8" baselines also. "Cycle on any" is also what the Comnet Guidelines say quite specifically to use for all baseline cases. So much for what I think.

As far as cooling, if the actual/proposed system stays off during unoccupied cooling as you imply by noting "The proposed design is Zone Fans only", what is the unoccupied zone cooling tstat schedule value for the baseline to cycle on? I suppose you could grab the values from some default schedule.

I think the T24 ACM rules make more sense for night cycle control in this case, that is baseline = proposed.  "Zone Fans Only" for both cases.

Clear as mud?
Fred
Fred Porter, BEMP, LEED(c) AP
Senior Energy Analyst
Architectural Energy Corporation
A Member of NORESCO Energy and Sustainability Services
2540 Frontier Ave, Suite 100, Boulder, CO  80301
Phone 303.459.7425 | fporter at archenergy.com<mailto:fporter at archenergy.com>
www.archenergy.com<http://www.archenergy.com>



From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Gerard Hazel
Sent: Wednesday, March 19, 2014 8:25 AM
To: equest-users at lists.onebuilding.org
Cc: Greg Sydlowski
Subject: [External] [Equest-users] Night Cycle Fan Control

Hi All,
We have an issue with a model that we were hoping to get some feedback on from the eQuest community.
For ASHRAE HVAC System #8, how would you approach the night cycle fan control?  ASHRAE 90.1 par. G3.1.2.4 doesn't really cover this for System 8 and leaves it open to have the baseline as "Cycle on Any."  However with PFP boxes, you could also argue it should be "Zone fans only" since they are part of System 8.  There is no clear direction one way or the other in ASHRAE that we can find.  Depending what you choose, it can be a major energy factor on the baseline.  What's the right answer?  The proposed design is Zone Fans only if that makes any difference.
Thanks in advance,
Gerry Hazel


Gerard Hazel
M&E Engineers, Inc.
908-526-5700 x14

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20140326/d09f0de8/attachment-0002.htm>