3 Phase Generator Monitoring

I would like to monitor a generator that outputs 3 phase to a 200A panel. I only need to monitor the mains and I do not need to monitor individual circuits. Will a North American v4 IoTaWatt work for this application by enabling the derived 3 phase option or do I need to order the newer version with the additional reference voltage ports? I’d rather not use two AC reference transformers, finding a home to plug one into near the panel will already be a challenge.

Which CTs would you recommend for monitoring the 3 phase mains on a 200A panel?


To be clear, you want to monitor a three-phase panel with 200A mains that is connected to the grid and also has a generator backup, presumably with a transfer switch? Does this have anything to do with the panel we looked at last night?

There are no more V4 IoTaWatt - sold out.

This is unrelated to the 120/208v panel we have been discussing. This is for an off-grid generator.

I already have several of the v4 units. I was hoping to use one of them if possible, but I can order v5 if necessary.

Ok, so no grid power. The question whether to use direct or derived reference is subjective. It depends on how well balanced the voltages are and how accurate you need to be. My approach would be to use derived and switch to direct if that turns out to be unsatisfactory. You can upgrade to a V5 by simply swapping it in and moving the SDcard.

For CTs 200A should work, but if the generator is not capable of more than 100A and the cables no larger than 15mm diameter, go with the smaller. I don’t think you will see much difference in results, unless you are using very little power.

Do I need 3 CTs or will 2 work?

If the load is connected Delta (three-wire no neutral) you would use 2. If it’s connected Wye (four-wire) you would use 3.

I don’t know your application, but delta would be likely if there are transformers between the generator and load. If it’s Delta, and 120V/208V you would also need to use a 240V VT.