This section describes how to compute energy and power from pulse counts.
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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 the table in Calculating power in kW). 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.
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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 in Calculating energy in kWh). 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.
Calculating energy in kWh
To calculate energy in kilowatt-hours, you need the kilowatt-hours per pulse. When configuring scaling for smart sensors, type the value for kilowatt-hours per pulse in the Multiplier field and enter 0 in the Offset field. Type kWh for the Scaled Units and Energy for the Scaled Measurement Type.
To find the value for kilowatt-hours per pulse for a WattNode sensor, refer to WattNode Scaling Factors for Energy below. (These values are for the Standard Bidirectional Output model WattNode sensors only. You can find the scaling factors for other WattNode models in the WattNode manufacturer's manual included with each WattNode sensor.) To find the value 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 and energy meter.
| CT Size (amps) | Model #: 3Y-208/3D-240 | Model #: 3Y-400/3D-400 | Model #: 3Y-480/3D-480 | Model #: 3Y-600 |
|---|---|---|---|---|
| 5 | 0.000125 | 0.0002396 | 0.0002885 | 0.0003615 |
| 15 | 0.000375 | 0.0007188 | 0.0008656 | 0.0010844 |
| 20 | 0.0005 | 0.0009583 | 0.0011541 | 0.0014458 |
| 30 | 0.00075 | 0.0014375 | 0.0017313 | 0.0021688 |
| 50 | 0.00125 | 0.0023958 | 0.0028854 | 0.0036146 |
| 60 | 0.0015 | 0.002875 | 0.0034625 | 0.0043375 |
| 70 | 0.00175 | 0.0033542 | 0.0040396 | 0.0050604 |
| 100 | 0.0025 | 0.0047917 | 0.0057708 | 0.0072292 |
| 150 | 0.00375 | 0.0071875 | 0.0086563 | 0.010844 |
| 200 | 0.005 | 0.0095833 | 0.011542 | 0.014458 |
| 250 | 0.00625 | 0.011979 | 0.014427 | 0.018073 |
| 300 | 0.0075 | 0.014375 | 0.017313 | 0.021688 |
| 400 | 0.01 | 0.019167 | 0.023083 | 0.028917 |
| 600 | 0.015 | 0.02875 | 0.034625 | 0.043375 |
| 800 | 0.02 | 0.038333 | 0.046167 | 0.057833 |
| 1000 | 0.025 | 0.047917 | 0.057708 | 0.072292 |
| 1200 | 0.03 | 0.0575 | 0.06925 | 0.08675 |
| 1500 | 0.0375 | 0.071875 | 0.086563 | 0.10844 |
| 2000 | 0.05 | 0.095833 | 0.11542 | 0.14458 |
| 3000 | 0.075 | 0.14375 | 0.17313 | 0.21688 |
Calculating power in kW
Calculate power in kilowatts 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 in the table. For other manufacturers, refer to the documentation that comes with the sensor. The E50B2 Power & Energy Meter uses different scaling factors; see Scaling factors for the E50B2 power and energy meter.
Note: If you change the logging interval for a device with a sensor scaled for kWh, you must recalculate the scale factor.
| 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 |
