In Square D's marketing copy for their plug on neutral load centers, they have a photo for demonstrating "cleaner wiring" in which the hot and neutral wires are twisted inside the panel before reaching the breaker. I agree it looks neater, but it got me thinking and I know just enough about electricity to be confused. I assume the practical answer is that a slow (~1 turn per inch) human-made twist in the last couple feet of a cable that runs 30-40 feet will have no real impact, but I'm curious.
In low-voltage DC data wires, twist is used to reduce emitted EMI and reject received EMI. In a typical home I doubt contractors care about the noise on the voltage line, but as someone with a lot of sensitive electronics it interests me. But I've also seen it suggested that the increased capacitance between the twisted wires could increase current drain, which in turn could cause nuisance trips of AFCI breakers.
And I pretty much only understand electricity at all in DC. I don't know or understand what impacts AC may have on this.
So what kind of impacts, if any, could we expect to see from twisting a previously parallel load/neutral pair, carrying 120V AC?
Best Answer
There is no electrical reason for the twist; it merely serves to keep the two wires physically associated with each other once the Romex jacket is removed. It both "looks neater" and is easier to do subsequent work on.
There is no increased capacitance (the distance between the wires doesn't change), except for the fact that the twisted wires need to be slightly longer than the untwisted wires.
Also, even if there were some increase in reactive current, this would have no effect on an AFCI (which is looking for high-frequency noise) or GFCI (which is looking for a current imbalance between the two wires).
Note that excess capacitance between hot and ground (not neutral) can pass enough current to trip a GFCI. I've seen some kinds of plug-in power line filters do this.