[Equest-users] Condensing Boiler Curves

Dana Troy DTroy at glumac.com
Mon Oct 19 16:34:35 PDT 2009

Has anyone done any verification of the eQUEST 3.63 condensing boiler

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


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? 

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