[Equest-users] Condensing boiler curve issues

[Lapierre, Patrick]

Hi Adam,

eQUEST's default curve performs just as you say it should.
Be careful that when you calculate your corrected efficiency, you must take the PLR into account.
The correct formula is :

Corrected Efficiency = Nominal Efficiency * PLR / f(PLR)

You calculate the f(PLR) with the eQUEST curve.
See below the quick graph I charted out :












[cid:image002.png at 01D0F555.125D3CF0]


























































































CondBlr-HIR-fPLR&HWR























a

b

c

d

e

f























-0.09439243

0.90319633

0.01547839

0.00159793

-0.00000645

0.00111453



























































Nominal Efficiency

90%































































PLR

Water T

f(PLR)

Corrected Efficiency



























1

80

1.00000

90%



























1

90

1.01616

89%



























1

100

1.03103

87%



























1

110

1.04461

86%



























1

120

1.05690

85%



























0.9

80

0.89782

90%



























0.9

90

0.91287

89%



























0.9

100

0.92662

87%



























0.9

110

0.93909

86%



























0.9

120

0.95026

85%



























0.8

80

0.79596

90%



























0.8

90

0.80989

89%



























0.8

100

0.82253

88%



























0.8

110

0.83388

86%



























0.8

120

0.84394

85%



























0.7

80

0.69440

91%



























0.7

90

0.70721

89%



























0.7

100

0.71874

88%



























0.7

110

0.72898

86%



























0.7

120

0.73792

85%


















































































[cid:image003.jpg at 01D0F554.9B7098D0]

Patrick Lapierre_ing.
plapierre at bpa.ca


De : Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] De la part de Adam Barker
Envoyé : 22 septembre 2015 16:03
À : 'equest-users' <equest-users at lists.onebuilding.org>
Objet : [Equest-users] Condensing boiler curve issues

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>

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