Re: Reminder: Never connect a generator to home wiring without transfer switch

[Owen DeLong via NANOG <nanog () nanog org>]

> On Aug 31, 2021, at 09:23 , Sabri Berisha <sabri () cluecentral net> wrote:
>
> ----- On Aug 31, 2021, at 2:11 AM, Forrest Christian (List Account) lists () packetflux com wrote:
>
> Hi,
>
> > I just wish the electrical code would permit or require certain low cost things
> > which make temporary generator connections more likely to be safe.
>
> > For example, code requires most furnaces to be hardwired. But a furnace is one
> > of the first things you want on a generator in an extended winter power outage.
> > If instead of hardwired, the code required plug and socket connections at each
> > 120v furnace then Joe homeowner would be more likely to run an extension cord
> > from his generator to his furnace instead of trying to rig up his generator
> > with a suicide cord.
>
> Now I'm wondering which jurisdiction you're talking about. I live in California
> in a home which was finalized in 2019. As I'm the first owner, I was there when
> the inspector went up into the attic and checked my HVAC. My HVAC has a plug in
> power cord running into a regular household socket (all in the attic). The 
> inspector didn't say a word about it and issued the occupancy permit.
>
> My electrically powered oven is hardwired, but I guess that's because it requires
> two 50amp breakers?

It only sort of looks like two 50amp breakers… In reality, it’s a “ganged” breaker that is
50A on both sides of a 220V circuit so that if either side of the circuit exceeds 50A,
it will trip both breakers and shut down both sides.

A 220V circuit in the US (or 215/230/240, varies widely from utility to utility and for
other reasons) is both hot sides. The three wires coming into your house from the
utility are the two hots from opposite ends of the secondary winding in the utility
stepdown transformer along with a center-tapped “neutral”. The neutral is (or 
at least should be) tied to earth ground at exactly one place in your home (usually
inside the main breaker panel). The two “hot” sides each provide a 110V(approximately)
AC source relative to the reference (0V Neutral and Ground), but they provide that
at a phase difference of 180º. This means that the potential between the two
hot lines is (nominally) 220VAC.

Owen