[Equest-users] Condensing boiler curve issues

Wed Sep 30 05:39:14 PDT 2015

Adam,

I will like to say something about curve and the part load factor values
and also on hot water return temperature.
The curves in the condensing part load based curve is dependent on two
things the part load factor and hot water return temperature and the
resulting is HIR.
You can have a look at the data points in the default condensing curve.

[image: Inline image 1]
As mostly the design supply water temperature is nearly 130 °F for
condensing boiler and the hot water default delta T is 40 ° F.
So the supply design temperature is 120°F as per eQUEST if there is 80 °F
return water temperature.
Also i found as after few simulations that the HIR below 1.00 i.e. Z is not
the possible condition for simulation for HIR input in eQUEST at full load.
The best condition for the default curves to operate as per condensing
boiler curve to have operate is the return water temperature is 80 °F.At
lower temperature the efficiency are the best for part load and full load
which can be seen from the data points.

As from your snapshot of PS-C command the boilers are operating at full
load for more number of hours  for the return water temperature  80 °F.and
at 160 °F the boilers are operating more at part loads.
Going to 160 °F return water temperature the boiler have lower efficiency
at all loads which can be seen from curve data points.

But as per your snapshot the number of hours being operated for part load
is much higher at 120°F and there is less energy consumption and at part
load there is less fuel input required.
It is the default curve nature that is resulting in better performance at
higher return temperature as at that time the boiler are more being
operated at part loads and at part load the energy consumption is less.Hope
this will make your words coherent with mine.

Thanks,
Sharad.Kumar
Green Horizon Consulting LLP
Gurgaon
India.

On Wed, Sep 30, 2015 at 1:31 AM, <equest-users-request at lists.onebuilding.org
> wrote:

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>    1. Re: Condensing boiler curve issues (Porter, Frederick         NOR)
>
>
>
> *From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
> Behalf Of *Adam Barker
> *Sent:* Friday, September 25, 2015 2:39 PM
> *To:* Brian Fountain
> *Cc:* 'equest-users'
> *Subject:* [External] Re: [Equest-users] Condensing boiler curve issues
>
>
>
> 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:
>
>
>
> At 100 F return water temp:
>
>
>
> At 120F return water temp (which is probably closest to reality, but I
> don’t trust the results):
>
>
>
>
>
> Am I getting to the fringes of this curve’s limits so its starting to go
> out of whack?
>
>
>
> Regards,
>
>
>
> Adam
>
>
>
> *From:* Brian Fountain [mailto:bfountain at greensim.com
> <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).
>
> Brian
>
> 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> <abarker at pemi.com>
>
>
>
>
>
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