Quick voltage output CT Question

Support
1

Does IoTaWatt support voltage output CT’s that output 333mv? If so, what would the Cal and Phase values look like? From the tables.txt for the YHDC 1 volt models:

{“model”:“SCT013-030”,“mfg”:“YHDC”,“type”:“V”,“cal”:30,“phase”:3.8},
{“model”:“SCT013-050”,“mfg”:“YHDC”,“type”:“V”,“cal”:49.8,“phase”:3.0}

Thanks

2

Not a quick question. Short answer is “sorta”.

The standard IoTaWatt unit that is sold accepts only mA inputs because it has a 20 Ohm burden resistor, which results in 1V presented to the ADC. The YHDC models that you reference in the tables output 1V. So if you were to remove the burden resistor in the IoTaWatt for that channel, you could configure one of those.

But you are asking about using a 333mV CT. Like the 1V YHDC CTs, with the burden removed it would be able to be read by the ADC, but would use only 1/3 of the ADC scale. Bottom line is that a CT outputting 333mV would have 1/3 the resolution.

If you decide to remove the burden resistor, go to Setup→Burden Resistors and set the burden value for that channel to zero. When you configure the channel set “Cal” to the CT rating x three. So if it is a 50Amp CT you would set Cal to 150. I would use a phase value of one.

3

Thanks for the quick reply. The reason I’m asking is because I need CT’s for my incoming mains(US split phase) supply. The CT aperture needs to be at least .6 inch and none of the YHDC CT’s seem to fit this need. I did find the Circuit IQ site and can order from them but the tariff issue and me being responsible for any additional charges has left me concerned (confused?). I did some searching and found the Accuenergy AcuCT Hinged series. However, these are all voltage 333mv outputs. After your explanation above, I think I’ll stay away from the 333mv CT’s. Do you have any suggestions? Also, I have a 200 amp service panel so I’m thinking the load on any one leg should never exceed 100 amps?? What are the recommendations for incoming power?

I followed your schematic and created my own unit. Works great so far. Awesome product!!
Again, thanks

4

Negative. A 200 Amp panel has 200A breakers on each leg and needs 200A CTs.

I agree.

Yes. There is a source for 50mA 200A AccuCTs in the USA. I have been corresponding with them lately and I believe they will be generally available soon. Will get back to you soon on that.