Are CTs “Standardized”?

[John Polasek]

The Emporia Vue 2 I purchased replaced a 28 circuit Sitesage unit after its voltage meter failed.  The SItesage device came standard with 20 amp CTs for the individual circuits and 200 amp ones for the mains;  I had to buy 50s for the hot water heater and AC separately.  The 20 amp rings (which match the circuit breakers in the panel) were much smaller than the 50s that come standard with the Emporia;  I’d like to add a second Vue 2 because with the 16 circuits I am monitoring, I still have a 5oo to 1000 balance, but I don’t think I can cram another 16 50 amp CTs into the breaker panel… but I still have the Sitesage boxed up somewhere in the attic and was wondering whether I could grab THOSE old 20 amp CTs and use them on everything except the big loads.  Would anyone know if they are compatible?

[djwakelee]

CTs are not standardized.  Besides physical and electrical connector differences, each has a given Amps to Volts conversion ratio.  So you’d first need to understand what the CTs specs are between the different devices.  If they aren’t the same current to voltage conversion factor, Emporia will let you scale readings in the software, but this isn’t always ideal.  Also, to get accurate readings, CT’s need to be coupled to an electrical circuit which is properly matched to the transformer (so called burden or loading).  If not matched, you may have inaccuracies for large or small current measurements.

[tlsvict]

I know it has been a while, but I thought I would expand on this a little for the benefit of others that might be thinking the same thing .. I’ve seen various things on the forums that suggest that Emporia is using current to voltage CTs [e.g. wire in series wanting to connect 2 CTs to a single input] — you should also be aware that there are current to current CTs on the market — some of which are protected with TVS to keep from getting dangerous voltages when unplugged and some which don’t.  Regardless of if the current to current CT has a TVS protector or not, plugging a current to current CT into your emporia could end up damaging it — would such damage be limited to just the single CT input, multiple CT inputs, or the entire emporia unit is an unknown .. the only thing we can be relatively sure of is that emporia would not be under any obligation to replace/repair a unit damaged in such a fashion.

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