[Equest-users] Condensing boiler curve issues

Adam Barker ABarker at pemi.com
Fri Sep 25 13:38:52 PDT 2015

Sure Brian, thanks, and thanks to the others that responded.

I believe what's happening has to do with the part load, which as you say seems to have a big influence, as well as how the boilers are staged (or aren't staged).  My boilers are at very low part loads most of the time.  As mentioned if I increase that return water temperature, not touching anything else, my fuel use goes down.  Looking at PS-C, it is going up at higher part loads, but getting better, i.e. going down, at very low part loads - where my boilers are spending most of their time operating, hence the net decrease in energy consumption.

PS-C results for my lead boiler (does most of the work)
At 80F return water temp:
[cid:image002.png at 01D0F7B0.907CD7F0]

At 100 F return water temp:
[cid:image001.png at 01D0F7AF.531113F0]

At 120F return water temp (which is probably closest to reality, but I don't trust the results):
[cid:image003.png at 01D0F7B0.907CD7F0]

Am I getting to the fringes of this curve's limits so its starting to go out of whack?



From: Brian Fountain [mailto:bfountain at greensim.com]
Sent: Thursday, September 24, 2015 9:54 AM
To: Adam Barker
Subject: Re: [Equest-users] Condensing boiler curve issues

Hi Adam,

That is not what I have seen with the curve.  Note that there is a rated return water temperature field in the boiler at which the boiler achieves the rated HIR (thermal efficiency).  I have seen the curve be strongly dependent on loading -- i.e. much more efficient when the boiler has a low part load.

I did see an overlay of the default eQUEST condensing boiler curve and a Lochinvar Benchmark curve and they corresponded reasonably well.

I'd be interested in taking a peek at your file if you are able to share (perhaps a generic version of it).

On 22/09/2015 4:02 PM, Adam Barker wrote:

Has anyone come across issues with the default condensing boiler curve in eQuest?  This curve is a function of part load and return water temperature, and based on how condensing boilers work you would anticipate the part load efficiency to get worse as return water temperature increased (assuming part load is the same).

I am seeing the opposite in eQuest, where the default 80F RWT is giving me a poor seasonal efficiency, and a temperature like 160 RWT (in the non-condensing spectrum) is giving me a very high seasonal efficiency.

Any insight into why this might be happening?

Adam Barker, MBSc, C.E.T., LEED AP BD+C

Energy Project Manager

Provident Energy Management Inc.

T: 416-736-0630 x 1874 | abarker at pemi.com<mailto:abarker at pemi.com><mailto:abarker at pemi.com><mailto:abarker at pemi.com>


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