# [Equest-users] Condensing Boiler Curves

Xavier Garcia Casals xgcasals at telefonica.net
Mon Oct 19 23:54:29 PDT 2009

```Hi Dana,
I've also checked the condenser boiler curve in eQuest.
FIrst of all you have to take into account that the ratio of efficiency
at part load to nominal efficiency is not 1/HIR_curve, but
1/(HIR_curve*PLR).
This will bring the curves closer to what you expect.
Besides, you have to input the return water temperature in ºF (Y-value).

However, the part load efficiencies that come out from this curve are
well below the ones of condensing boilers used in europe. In fact, as
RWT increases, the curve produces even worst part load efficiencies than
the ones of low temperture boilers.

En/na Dana Troy ha escrit:
> Has anyone done any verification of the eQUEST 3.63 condensing boiler
> curves?
>
> The performance curve specifies the HIR being dependent on the part load
> and the return water temperature with a formula as such:
>
> Z = a + bX + cX^2 + dY + eY^2 +fXY
>
> where:
>
> X = PLR
> Y = RWT
> a = -0.09439243
> b = 0.90319633
> c = 0.01547839
> d = 0.00159793
> e = -0.00000645
> f = 0.00111453
>
> Since the default curve for a standard boiler seems to be a multiplier
> on the EFFICIENCY, which is 1 / HIR, and not the HIR itself, I am
> assuming that this curve also modifies the efficiency.
>
> Pulling this formula and coefficient into Excel produces some graphs
> that do not resemble at all what a condensing boiler efficiency graph
> looks like at all.
>
> For example, the AERCO Benchmark 3.0 looks like the first picture in the
> attachment, while the eQUEST default looks like the second picture in
> the attachment.
>
> Am I looking at the eQUEST curve wrong in some way? Is it not using the
> formula as it says it does in the help file?
>
> Thanks,
> Dana
>
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--

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*Xavier García Casals*

Tel: (+34) 91 843 19 85

Móvil: 660 22 94 45

xgcasals at telefonica.net <mailto:xgcasals at telefonica.net>

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