[Equest-users] Reply： The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007
David Eldridge
DEldridge at grummanbutkus.com
Sun May 24 08:25:43 PDT 2015
The referenced 90.1 method of testing for boiler efficiency should be the guide. The value is not presented as an "IPLV" type of weighted efficiency.
The reviewer might have a question if your baseline boiler is cycling a lot, did the Appendix G sizing instructions provide an oversized boiler?
DSE Mobile
On May 24, 2015, at 8:53 AM, Nicholas Caton <ncaton at catonenergy.com<mailto:ncaton at catonenergy.com>> wrote:
I received some similar review language very recently suggesting 80% efficiency is expected at all/most part load conditions for the baseline boiler¡. Similar context in that case with the boiler rarely operating near full load.
My comment has other issues that would cloud the topic at-hand, but here is truncated version:
¡°¡Furthermore, the average boiler efficiencies in the Baseline PS-C output reports, calculated by dividing the boiler energy consumption by the annual boiler heating energy generated was¡ [approximately 5% lower than the nominal efficiency input & documented]. Revise the baseline boiler efficiency to 80% and revise the boiler curve for the Baseline case as necessary to have an average efficiency that is near 80%. Provide updated PS-C reports for the Baseline confirming that the average baseline efficiency is near 80%.¡±
This is the first time I have run into commentary checking up on PS-C¡¯s output at all, and I¡¯m using the same library curves as always for typical baseline boilers.
I believe the PS-C discrepancy is explained both by the non-flat library curve and by the boiler¡¯s default start-up loads, in combination.
Here is the default library curve ¨C it is (roughly, but not quite) linear:
<image001.png>
[cid:image002.png at 01D095EE.52E0BE80]
[For those unfamiliar, the Y-axis is a unitless multiplier]
If I¡¯m not mistaken, this curve serves double-duty: it simultaneously applies the hourly PLR to the full capacity (as either input or auto-sized) and also accounts for increased HIR (lower efficiency) as the PLR drops. My understanding in equation form:
Energy Consumed (for the hour) = (Boiler full capacity as input/autosized) * (Boiler nominal HIR input @ full load) * HIRf(PLR)
If all of that is true, a perfectly ¡°flat efficiency¡± curve, returning your nominal input HIR at all efficiencies, would therefore be Z = X. That¡¯s plotted above for reference with a light/thin line.
Even with such a ¡°flat efficiency¡± curve applied to a test-case, PS-C¡¯s outputs still suggest an annual equivalent HIR higher than the nominal input. Zeroing out the startup/standby inputs as well is required to get PS-C to report your nominal HIR = annual fuel / annual load:
<image005.png>
I think the correct response (which perhaps I¡¯ve mostly composed above) is to demonstrate the causes (library curve shape, startup/standby defaults), and to assert these are all appropriately applied to the baseline boiler, though none of this is regulated by 90.1 to the best of my knowledge so it might be relatively shaky territory.
I would wager 90% of all eQuest baseline boilers submitted to GBCI to date probably don¡¯t mess with the library curves or standby/startup inputs, but that¡¯s pure speculation on my part.
Has anybody ever tried to explain/justify the default boiler curve and default startup/standby inputs? Do we know where those defaults come from?
~Nick
NICK CATON, P.E.
Owner
Caton Energy Consulting
1150 N. 192nd St., #4-202
Shoreline, WA 98133
office: 785.410.3317
www.catonenergy.com
From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of ???
Sent: Sunday, May 24, 2015 5:34 AM
To: Julien Marrec
Cc: equest-users at lists.onebuilding<mailto:equest-users at lists.onebuilding>
Subject: [Equest-users] Reply£º The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007
Hi,Julien
I understand his meaning is keep a constant efficiency and I know the flat efficiency in equest is a curve that is y=x, but I can't confirm if a constant efficiency is Ashrae 90.1-2007's original intent.
------------------
Yongqing Zhao
Changsha Green Building & Energy Saving Technology CO.,LTD
NO.438,Shaoshan Road,Changsha,Hunan,China
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com<mailto:Email%3Azhaoyongqing1987 at 126.com>
503271081 at qq.com<mailto:503271081 at qq.com>
------------------ ÔʼÓʼþ ------------------
·¢¼þÈË: "Julien Marrec";<julien.marrec at gmail.com<mailto:julien.marrec at gmail.com>>;
·¢ËÍʱ¼ä: 2015Äê5ÔÂ24ÈÕ(ÐÇÆÚÌì) ÍíÉÏ8:19
ÊÕ¼þÈË: "ÕÔÓÀÇà"<503271081 at qq.com<mailto:503271081 at qq.com>>;
³ËÍ: "equest-users at lists.onebuilding<mailto:equest-users at lists.onebuilding>"<equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>;
Ö÷Ìâ: Re: [Equest-users] The problem of minimum equipment efficiency requirement of Ashrae 90.1-2007
Hey,
He's saying that you need to make sure that the curve boiler-fPLR gives you a constant efficiency. As far as I remember, the default atmospheric curve from equest is like this.
Don't be confused by "flat". A flat efficiency curve is when you plot efficiency=f(PLR). In equest, it should be a curve that is y=x
Look at the curve you used.
Best,
Julien
Envoy¨¦ de mon iPhone
Le 24 mai 2015 ¨¤ 11:27, "ÕÔÓÀÇà" <503271081 at qq.com<mailto:503271081 at qq.com>> a ¨¦crit :
I get the energy model comments from LEED reviewer as following:
The narrative response indicates that the Baseline boiler has been modeled utilizing operating performance curves and a boiler HIR of 1.25. However, since the boiler operation HIR is based on the performance curves, the HIR is less than 1.25 in the part-load condition, which is inappropriate. Revise the Baseline boilers to include a flat efficiency of 80% for all part-loads. Provide eQuest input files or screen shots verifying the boiler efficiency has been modeled as required.
<545E22AD at FA528147.9F996155<mailto:545E22AD at FA528147.9F996155>>
However, I can not understand it very much. The minimum equipment efficiency requirement(80 % Et) of Ashrae 90.1-2007 should be base on full load condition.Why the LEED reviewer raise such a question?Any insight is appreciate!!
Thanks
------------------
Yongqing Zhao
Changsha Green Building & Energy Saving Technology CO.,LTD
NO.438,Shaoshan Road,Changsha,Hunan,China
Telephone:13574805636
Email:zhaoyongqing1987 at 126.com<http://126.com>
503271081 at qq.com<mailto:503271081 at qq.com>
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