Calculating Power in kW
Power in kilowatts is calculated by multiplying the pulse count by the multiplier. To calculate the multiplier, use the following equation:
(3600 ÷ Logging Interval in seconds) ÷ pulses per kWh = multiplier
When configuring scaling for smart sensors, type the result of that equation in the Multiplier field and enter 0 in the Offset field. Type kWh for the Scaled Units and Power for the Scaled Measurement Type.
To determine the value for the pulses per kWh, refer to the WattNode Scaling Factors for Power below. For other manufacturers, refer to the documentation that came with the sensor. The E50B2 Power & Energy Meter uses different scaling factors; see Scaling Factors for the E50B2 Power & Energy Meter for details.
Note: If you change the logging interval for a device with a sensor scaled for kWh, you will need to recalculate the scale factor.
WattNode Sensor Scaling Factors for Power
| Pulses per kilowatt hour | ||||
| CT Size (amps) | Model #: 3Y-208/3D-240 |
Model #: 3Y-400/3D-400 |
Model #: 3Y-480/3D-480 |
Model #: 3Y-600 |
| 5 | 8000.00 | 4173.91 | 3465.70 |
2766.57 |
| 15 | 2666.67 | 1391.3 | 1155.24 |
922.19 |
| 20 | 2000.00 | 1043.48 | 866.450 |
691.643 |
| 30 | 1333.33 | 695.652 | 577.617 |
461.095 |
| 50 | 800.000 | 417.391 | 346.570 |
276.657 |
| 60 | 666.667 | 347.826 | 288.809 |
230.548 |
| 70 | 571.429 | 298.137 | 247.550 |
197.612 |
| 100 | 400.000 | 208.696 | 173.285 |
138.329 |
| 150 | 266.667 | 139.13 | 115.523 |
92.219 |
| 200 | 200.000 | 104.348 | 86.643 |
69.164 |
| 250 | 160.000 | 83.478 | 69.314 |
55.331 |
| 300 | 133.333 | 69.565 | 57.762 |
46.11 |
| 400 | 100.000 | 52.174 | 43.321 |
34.582 |
| 600 | 66.667 | 34.783 | 28.881 |
23.055 |
| 800 | 50.000 | 26.087 | 21.661 |
17.291 |
| 1000 | 40.000 | 20.87 | 17.329 |
13.833 |
| 1200 | 33.333 | 17.391 | 14.440 |
11.527 |
| 1500 | 26.667 | 13.913 | 11.552 |
9.2219 |
| 2000 | 20.000 | 10.435 | 8.6643 |
6.9164 |
| 3000 | 13.333 | 6.9565 | 5.7762 |
4.611 |
Calculating Power Examples
Example 1: WattNode Transducer Model WNB-3Y-208-P with 50 Amp CT
The logging interval is set to 1 minute, or 60 seconds and the pulses per kWh for this transducer is 800 (see table above). Therefore the multiplier equation is (3600 ÷ 60) ÷ 800 = 0.075. The offset is 0, the scaled units name is KW, and the scaled measurement type is power. With this information entered, the sensor on the Sensor Configuration page looks like this:
Example 2: WattNode Transducer Model WNB-3D-240-P with 100 Amp CT
The logging interval is set to 15 minutes, or 900 seconds and the pulses per kWh for this transducer is 400 (see table above). Therefore the multiplier equation is (3600 ÷ 900) ÷ 400 = 0.01. The offset is 0, the scaled units name is KW, and the scaled measurement type is power. With this information entered, the sensor on the Sensor Configuration page looks like this:
