In article ,
Cydrome Leader wrote:

But still, if you're in the US, have 20 volts on neutral relative to
ground, you probably have a bad neutral, which is also a big deal. This
problem could even exist outside your home, over at the distribution
transformer or wiring from there to your meter.

If your neutral "drifts" by 20 volts from ground, where it should be
bonded at the service entrance, and you have split phase 240 (120+120)
service you've got half the house with 100 volts at the oulets and other
side with 140 volts. That's not good for any devices or appliances you
have.

Yup. In 20 years we've had that problem occur twice at our house,
with the usual weird symptoms (e.g. lights getting *brighter* when you
turn on something else). In both cases it was due to a squirrel
chewing through the neutral wire, in the drop between the pole-pig
transformer and our service panel.

In both cases, reporting a "low voltage / high voltage" situation to
the power company resulted in a rapid response... the last time
it happened there was a truck rolling up outside our door within about
20 minutes. PG&E considers this a problem which requires a rather
urgent repair, due to the potential for equipment damage, fires, and
so forth.

If the neutral isn't actually open, then a persistent 20-volt
neutral-to-good-ground differential would indicate a really huge
current draw on the circuit... probably well more than the wiring is
rated for. The National Electric Code seems to allow for only a 5%
voltage drop for a fully-loaded circuit.