I’ve been re-reading the CT Basics and I am getting the feeling that I’ve been doing it all wrong.
The total wattage on my Main_1 and Main_2 have never quite added up and I believe that I have been using the incorrect CT’s for both sub-panels as well as incorrectly grouping multiple CT’s.
I live in the US and have a 150 Amp main panel in the basement with a 100 Amp subpanel adjacent to it and a 60 Amp sub-panel in the garage.
The 100 Amp sub-panel is being fed by a Square D by Schneider Electric QO2100CP QO 100-Amp Two-Pole Circuit Breaker
The 60 Amp sub-panel is being fed by a Square D by Schneider Electric QO260CP QO 60 Amp Two-Pole Circuit Breaker
According to CT basics, each sub-panel is a 120/240V circuit, and the two legs must be measured individually. The wires are too thick to pass both through one individual CT in a U shape, so I put one CT on each wire, BUT - and here is where I believe I went wrong - I used 50A CT’s on each wire had one wire K -->L and the other L <–K. See below for how I have the CT’s hooked up. (my phone broke today so I had to resort to drawing on paper):
Since the breaker is the source and the sub-panel is the loan, I assume I need to make sure both wires are K -->L where L is pointing towards the sub-panel?
The next question I have is regarding the sizing of the CT’s. In the CT Basics, I read: Two individual CTs can also be combined with a common headphone splitter and fed into a single IotaWatt input. When combining this way, both CTs must be the same model with an individual capacity sufficient to measure the combined capacity of the two circuit breakers. (emphasis mine)
Does this mean that each CT individually must be greater than the circuit breaker size, or that both CT’s combined must be greater than the circuit breaker.
So, for the 60 amp sub-panel circuit breaker, each CT is rated for 50A. Do I need to go up to a 100A CT, or do I go by the combined CT rating (50A *2 = 100A) and therefore I am sized correctly on the 60 amp sub-panel circuit breaker?
Same question for the 100 amp sub-panel circuit breaker. Are the two 50A CT’s enough or am I essentially undersized by 50%?
Finally, and last question: when combining multiple wires, can I wrap a single CT around multiple wires (see below):
Or do I have to use exactly one CT per wire then combine via a 3.5mm Y-splitter (see below):
If I do have to use 3 separate CT’s to combine, say, 3 20Amp circuit breakers, do I need to move up to a 100Amp CT? Or will one 50 Amp CT be sufficient?
Appreciate any help!