[Bldg-sim] Appendix G Fan Power

[David S Eldridge]

Only you could say whether these factors were significant in your own project.

It could be possible that if you allocated all of the power to the supply fan, which might be variable flow with a VFD for example, and operate at part-load conditions much of the time, the energy consumption might be different than if an exhaust fan was included that runs continuously at fixed load with some allocation of the power usage.

Also the program may have some variances in heat gain to the airflows from the motor heat.

I’ll second Ellen Franconi’s suggestion of apportioning by design document sizing when there are equivalent pieces of equipment in both models.

David



From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James Hess
Sent: Thursday, July 02, 2009 9:28 AM
To: Bldg-Sim
Subject: Re: [Bldg-sim] Appendix G Fan Power

We got a review comment on a recent LEED project asking us to break down the baseline HVAC power into components even though there is no direction, or requirement, from 90.1-2004 to do so.

Can someone please help me understand why this would be necessary?

LEED guidelines say we have to model per Appendix G, but Appendix G doesn't say we have to do this.

I do not think it is necessary to do this as the baseline total fan energy consumption numbers would still be the same.

The equation in Appendix G is meant to give a total allowance (for each system) for supply, return, and exhaust fans. It doesn't matter if we break the allowance down into components or not as the total fan energy consumption remains the same. Therefore, there is no value in doing this.

If we did break the fan energy numbers into components, how would we do that given that there is no direction from ASHRAE or LEED on how to do this?

Thoughts?

Regards,

James A. Hess, PE, CEM
Energy Engineer
TME, Inc.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20090702/67c23323/attachment-0002.htm>