Danfoss VLT Series Programming Manual page 170

Parameter Description
3.21.5 23-8* Payback Counter
The frequency converter includes a feature which can give a rough calculation on payback in cases where the frequency
converter has been installed in an existing plant to ensure energy saving 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.
P
The difference between the Reference Power at fixed speed and the Actual Power yielded with speed control represent the
actual saving.
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 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 23-84 Cost Savings.
Cost Savings =
{
t
(
Rated Motor Power ∗ Power Reference Factor
∑
t =0
Actual Power Consumption
−
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 23-80 Power
Reference Factor to 0.
Parameter overview:
Parameter for settings
Rated Motor Power
Power Reference Factor in %
Energy Cost per kWh
Investment
23-80 Power Reference Factor
Range: Function:
100 % [0 - 100 Set the percentage of the rated motor size
*
%] (set in 1-20 Motor Power [kW] or 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.
®
VLT HVAC Drive Programming Guide
Rated power for the
motor size used
(P 1-20/21)
Reference power
(at xed speed)
(P 23-80)
Actual power yielded
with variable
speed control
(read P 16-10/11)
)
}
Energy Cost
×
1-20 Motor Power [kW]
23-80 Power Reference Factor
23-81 Energy Cost
23-82 Investment
®
MG.11.CC.02 - VLT is a registered Danfoss trademark
Parameters for readout
Energy Savings
Actual Power
Cost Savings
23-81 Energy Cost
Range: Function:
1.00 [0.00 - Set the actual cost for a kWh in local
*
999999.99 ] currency. If the energy cost is changed
later on it will impact the calculation
for the entire period.
23-83 Energy Savings
16-10 Power [kW], 16-11 Power
[hp]
23-84 Cost Savings
169
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