Danfoss VLT HVAC Series, Programming Manual, Page: 250 / 338

3.21.5 23-8* Payback Counter
The adjustable frequency drive includes a feature which can give a rough calculation on payback in cases where the adjustable frequency drive has been
installed in an existing plant to ensure energy savings by changing from fixed to variable speed control. Reference for the savings is a set value to represent
the average power yielded before the upgrade with variable speed control.
The difference between the Reference Power at fixed speed and the Actual Power yielded with speed control represent the actual savings.
As value for the fixed speed case, the rated motor size (kW) is multiplied with a factor (set in %) representing the power produced at fixed speed. The
difference between this reference power and the actual power is accumulated and stored. The difference in energy can be read in par.23-83
Energy
Savings
.
The accumulated value for the difference in power consumption is multiplied with the energy cost in local currency and the investment is subtracted. This
calculation for Cost Savings can also be read in par.23-84
Cost Savings
.
Cost Savings
=
{
∑
t
=0
t
( Rated Motor Power
∗
Power Reference Factor )
− Actual Power Consumption × Energy Cost
}
− Investment Cost
Break even (payback) occurs when the value read in the parameter turns from negative to positive.
It is not possible to reset the Energy Savings counter, but the counter can be stopped any time by setting par.23-80
Power Reference Factor
to 0.
Parameter overview:
Parameter for settings Parameters for readout
Rated Motor Power par.1-20 Motor Power [kW] Energy Savings par.23-83 Energy Savings
Power Reference Factor in % par.23-80
Power Reference Factor
Actual Power par.16-10
Power [kW]
, par.
16-11
Power [hp]
Energy Cost per kWh par.23-81 Energy Cost Cost Savings par.23-84 Cost Savings
Investment par.23-82
Investment
23-80 Power Reference Factor
Range: Function:
100 %* [0 - 100 %] Set the percentage of the rated motor size (set in par.1-20
Motor Power [kW]
or par.1-21
Motor
Power [HP]
) which is supposed to represent the average power yielded at the time running with
fixed speed (before upgrade with variable speed control).
Must be set to a value different from zero to start counting.
3 Parameter Description VLT ® HVAC Drive Programming Guide
3-226
MG.11.C6.22 - VLT ® is a registered Danfoss trademark
3