Switch branches/tags
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
65 lines (38 sloc) 3.81 KB
layout title description date sidebar comments sharing footer published
Use In North America
Using emonPi in USA
2015-03-08 21:36

The emonPi / emonTx hardware units are designed for use on single-phase systems. However, the they can be used on a North American Split-Phase system with the following considerations:

1. Ensure clip-on CT sensor will fit your conductors

Typical residential Service Entrance Wires are AWG 2/0 Copper or AWG 4/0 Aluminum. The opening in the standard clip-on CT sensor sold in the OpenEnergyMonitor shop is 13mm, and hence can accommodate a maximum wire size of AWG 1/0. Therefore, we recommend you measure the diameter of your feeders before purchasing a CT sensor.

View in Shop →

If the standard CT sensor does not fit your conductors there are two options:

  1. Use an Optical Pulse Sensor instead of CT sensor to interface directly with a utility meter. This will give an accurate reading of energy consumed (KWh) but will not provide a real-time power reading (W).

  2. Use an alternative larger CT sensor: It's possible to obtain larger CT sensors. However, using an alternative CT will usually require re-calibration and possibly, hardware modification (burden resistor may need replacement). See Learn > EmonTx in North America for more info. 'Learn' CT sections. Please search / post on the community forums for further assistance.

Installing clip-on CT sensors on USA electrical systems should only by undertaken by a professional electrician. In a typical residential installation, even if the main breaker is swiched off, the load center Service Entrance Wires and busbars are always live.

2. Use USA AC-AC Adapter

Use the USA AC-AC voltage sensor adapter sold via the OpenEnergyMonitor Shop. The system has been calibrated to work with this adapter. Using any other adapter will usually require re-calibration.

View in Shop →

3. Software Calibration

a.) emonPi: Set EmonHub USA Calibration

In the [[RFM2Pi]] interfacer section of emonhub.conf set:


emonhub.conf can be edited directly in local Emoncms as described in Setup > Logging Remotely.

See [[RFM2Pi]] section of emonHub configuration guide for advanced emonhub config info.

b.) emonTx: Enable USA calibration using on-board DIP switch

4. Sum power values

If monitoring a split-phase system the power values from each leg can be summed in Emoncms to calculate the total power.

The emonPi by default reports power1_plus_power2, this input will need to be logged to a feed. See Setup > Logging Locally.

If using emonTx then the power values from multiple CT inputs can be summed in Emoncms using + feed Input Processor.

See Learn > EmonTx in North America for further technical info about the USA system.