[Equest-users] Exhaust Fans

[Keith Swartz]

Simge,

One idea is to take the exhaust air flow from two separate spaces-take as much as you can out of the space that actually has the exhaust, and take the rest of the exhaust air from a space that the air is probably being transferred from. Enter the fan energy for each exhaust fan so that the total matches what you need. Splitting (or lumping) equipment like this works fine as long as the part-load performance is proportional. If the part-load performance curve is non-linear, then there is some error from splitting/lumping.

eQUEST does not handle air transfers from one room to another as well as some other programs. If the transfer air is at room temperature, then you might not need to model transferring the air. For example, in motels air is often supplied to the corridors and is transferred under the doors at room temperature and exhausted out of the restrooms. You could simplify the model by taking the restroom exhaust from the corridors instead of the restrooms. This approximation breaks down if the transfer air is not at room temperature and the temperature difference is needed to handle a load in the room. Keep in mind that we are trying to model the energy use of the building, not model every detail of the building.

Sincerely,
Keith Swartz, PE, BEMP, LEED AP
Senior Energy Engineer | Energy Center of Wisconsin | Madison.Chicago.Minneapolis
608.210.7123 | www.ecw.org<http://www.ecw.org/>

From: Simge Andolsun [mailto:simgeandolsun at gmail.com]
Sent: Tuesday, November 12, 2013 9:53 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Exhaust Fans

Dear eQuest users,

I am trying to model a lab building in compliance with ASHRAE 90.1 to compare it with an as built model that represents the real case as described in Appendix G. The actual building (the as built model) has a few zones which have exhaust air flow rate higher than supply air flow rate as per the building schedules. I unfortunately do not have any information regarding the operation schedule of the exhaust fans. When I model the exhaust air flow rates of these zones to be always lower than the zone supply air flow rate, then the actual building is not represented closely enough. When I increase the zone supply air flow rate such that it is always equal to the actual exhaust air flow rate, then the zone air flow rate is assumed to be higher than it actually is increasing the overall energy consumption of the building. eQuest does not allow for the exhaust air flow rate of a zone to be higher than the supply air flow rate which would result in high unmet hours in the zone. In order to make a reasonable comparison between the baseline and the as built models as per Appendix G, how do you think I should represent the exhaust fans in these two models? and why? Would you also explain the settings I should use in eQuest to model the case you are suggesting? I would appreciate it very much.

Thank you very much,
Best Regards,
S.Andolsun, PhD
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20131113/b8c9df2b/attachment-0002.htm>