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Joseph Meehan wrote:
wrote:
This is perhaps a safety question. Most of the disconnects to 220v
appliances are two hots plus ground (I have an air conditioning
compressor, a well pump, and an accessory heater wired this way) with
no neutral wire. The neutral isn't "necessary" as each hot is 180
degrees out of phase negating the need for a separate neutral.

But doesn't this mean if there is a short the appliance case AND the
separate disconnect box (if metal) are BOTH electrified since their
grounds are connected and there is rarely if ever a separate
ground-to-earth at the appliance?

Unless there is a failure of the ground wire the short to the appliance
case be a short to ground and the breaker will kill the circuit and both
legs will be cut if it was properly connected to begin with.

Exactly what I was thinking. How people can be saying that the
appliance and the disconnect case will both be hot at 240V is beyond
me.

If so is this why 220v household clothes dryers are now four wire (hot
hot neutral ground) or is there something in the dryers that needs
120v and thus needs the neutral for the 120v circuit?

They are providing for a neutral for 120V needs, like a timer.

If the disconnect were to a subpanel that is a different issue since
the subpanel would require a distinct neutral (old school was to combo
neutral and ground at the downstream panel but I think code frowns on
that now).

--
Joseph Meehan

Dia duit