Parasitic Power on Enphase system?

A

am1954

Member
Location
NY
Occupation
contractor
We have an Enphase job where we have multiple strings running from the roof to subcombiners down below. Each subcombiner has 5 circuits. All 5 circuits run to the subcombiner in a shared conduit. It's Enphase 3phase, so 15 phase conductors, 5 neutrals and a ground per conduit.

With 1 breaker turned off, and the 4 other breakers turned on, we still see a small amount of current on the micro inverter side of the breaker that is turned off (0.5 amps +/-). As I continue to turn the remaining breakers off, the amperage will drop lower and lower. Once all breakers in the subcombiner are turned off, the amperage will finally say 0 amps.

Enphase says this is probably parasitic power coming off the remaining conductors in the shared conduit. I've never seen this before. Normally we kill one circuit and it automatically goes to zero, even if it shares a conduit with other strings on the roof.

Does Enphase's assessment seem correct? Wasn't sure if something weird was going on.,,
 
I'm not sure 'parasitic power' is the appropriate term here. It seems like your meter is measuring an induced field from the other conductors, but it is probably not real current in the one you've turned off. Roughly how many amps total are flowing in the other conductors? Are you using the same amp meter as in the past? Does it matter which circuit is turned off or are the results the same for any of them?
 
Jaggedben, there was probably +/- 8amps flowing through the remaining circuits. I was using the same amp meter that I normally use, but I guess it might be interesting to try with a different amp meter? The pattern was consistent across multiple subcombiners, and I'm pretty sure that it didn't matter which circuit I turned off first (although I could double check that).
 
With the circuit open there is no path for current to flow unless you have a fault in the conductor. You might get induced voltage on the conductors with the CB open from the other conductors in the conduit but any current flow you read on an open conductor is a phantom.
 
Try physically isolating the conductor in which you are measuring current flow from the other conductors and see if you get the same result. I would guess that the adjacent circuits are inducing a reading in your meter when there is actually no current on the open circuit.
 
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