[Bldg-sim] ASHRAE App G VAV Fan Curve

[Jim Dirkes]

Just saying....
I was thinking about upcoming professional events this morning...  All two of us at BPT are planning to attend the fall ASHRAE / IBPSA Energy Modeling conference and would love to find an opportunity to meet with all of the thoughtful energy modelers who have been sharing their insights on this thread.  It would be very nice to put faces with names and talk "shop"!
If you haven't already given some thought to attending the conference, please consider it!  I've attended the last two and found it well worth my time.

https://www.ashrae.org/membership--conferences/conferences/ashrae-ipbsa-usa


James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Wednesday, February 26, 2014 1:30 PM
To: Porter, Fred AEC; bldg-sim at lists. onebuilding. org (bldg-sim at lists.onebuilding.org)
Subject: Re: [Bldg-sim] ASHRAE App G VAV Fan Curve

Hi Fred,

I dove into this topic some time back specifically trying to understand the Appendix G curve in relation to reset strategies and the DOE2/eQuest default library curves.

Attached discussion (and attached discussions therein) recounts a lively discussion and some helpful visuals I produced to establish my observations, concluding the App. G curve is ultimately... not clear on the matter (and thus inappropriate for direct use in evaluating reset vfd control strategies).  You may find this an interesting read from the bottom up.

Hope that saves you a few steps!

~Nick

[cid:image001.jpg at 01CF33A7.251F3170]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Porter, Fred AEC
Sent: Wednesday, February 26, 2014 11:41 AM
To: bldg-sim at lists. onebuilding. org (bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>)
Subject: [Bldg-sim] ASHRAE App G VAV Fan Curve

All,
Does anyone know, particularly through having claims accepted by GBCI, whether the ASHRAE App G VAV fan curve is supposed to represent a fan system with or without static pressure reset. I always thought it was supposed to represent a system with sp reset, conforming to 6.5.3.2.3. However, most of the curve power values are even higher than curves representing VAV/VFD systems without sp reset. A confusing aspect is that compared to other VFD fan curves, the power values are high at high flows, but low at low flows, even going to zero at zero flow, though that is really meaningless.

As an aside, the 2013 Title 24 ACM now defines fan curves for central VAV systems with and without sp reset, taken from Taylor's VAV design guide. SP reset is the "baseline" or "standard."A

Thanks for any experience or thoughts on this.

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>


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