Johnson Pump SPX Flow CombiLine Series Instruction Manual page 19

CombiLine-CombiBlocHorti
CL-CBH/EN (1901) 7.6
• 'House of Efficiency'
The decision scheme 'House of Efficiency' takes into account design and application
purposes as well as the pump minimum efficiency dependence on flow. The minimum
acceptable efficiency is therefore different for each pump type. The pass-or-fail scheme
is based on two criteria A and B.
Criterion A is the pass-or-fail minimum efficiency requirement at the best efficiency point
(BEP) of the pump:
 
η , ≥ η
n Q
Pump s BEP BOTTOM
Where
Q
BEP
×
-------------------
n = n
s N
H
0.75
BEP
Criterion B is the pass-or-fail minimum efficiency requirement at part load (PL) and at
overload (OL) of the pump:
η ≥ x η ⋅
,
BOTTOM PL OL – BOTTOM
Therefore a method is devised what is called a "house of efficiency" scheme that also
requires pumps to pass efficiency thresholds at 75% and 110% of rated flow. The
advantage of this is that pumps will be penalised for poor efficiency away from rated
efficiency, hence it will take account of real life pump duties.
It should be stated that while the scheme may appear complicated at first sight, in
practice it has been easy for the manufacturers to apply the scheme to their pumps.
Figure 1: House of Efficiency
Head
H
BEP
η
Pump Eff.
Curve
η
BEP
η = 0.98 η
OL BEP
η = 0.94 η
PL BEP
0
BEP
Q Q
PL BEP
General
System
Curve
Q
OL
Flow
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