Question:
With the GFCI open,
there can *not* be any voltage drop on the neutral from the hot tub to the
GFCI. Is this 3.5V the stray voltage you're worrying about?
Answer:
A "dangerous neutral" can be caused by a floating, (open), neutral on a
120V/240V split circuit. If the other side of the circuit has a heavy
load, the voltage on the floating neutral can be close to the 120V "hot"
wire on the other side. I've seen this happen from a neutral coming
loose from a wire nut in an "up-stream" outlet box.
Considering the proper voltage drop that would be available even on the
Considering the proper voltage drop that would be available even on the
'sub-panel feeding a hot tub scenario', just how much voltage do you think a
neutral will have to ground? The hot tub properly bonded and grounded, and
its occupant somehow contacting a neutral that goes to a sub panel, while
the sub panel supplies some other 'heavy' 120V load?? 100 ft of #10AWG
carrying 30A would have a voltage 'rise' of about 3.5 volts. Mind you,
that's 100ft between the main service panel and the sub panel and a full 30A
load on. Of course, if the sub-panel is supplying a 30A load *and* a hot
tub, then the conductors are larger than #10AWG, resulting in even less
voltage 'rise' when the GFCI to the hot-tub is open. With the GFCI open,
there can *not* be any voltage drop on the neutral from the hot tub to the
GFCI.
