ok, I know electronics, but am NOT an electrician. But I don't quite
get why we don't need a nuetral? Where's the return path?
240v comes in and in the main service panel I know the nuetral and
ground are bonded.... never have understood that one. then each leg of
the 240v is one side of the bus bar array in the service panel.
So what am I missing? I'm asking in all seriousness. I "added" a 220
outlet for my wife one day so she could have an electric stove and I
popped the breaker immeaditly when I fired it up because of the nuetral
being tied to ground. So I shrugged said I don't get why its doing
that, read the directions with the receptacle and removed the nuetral.
All was well. I look at my dryer cord and its got 3 wires. I know the
top angled two are "hot" 120vac each and the other is the ground.
I realize that we can take a +12vdc and a -12vdc circuit and using only
2 wires get +24vdc across them and then have to have a chassis ground.
Man its been a long time since I studied electronics!

Troy

Doug Miller wrote:
In article . com, wrote:


By which you mean, I hope, that the ground and neutral busses in the subpanel
are not bonded to each other. It's *supposed* to be that way. The *only* place
where they are ever bonded together is in the service entrance panel.



No. The neutral isn't used at all in a pure 240V circuit (and can be omitted
altogether), and the ground isn't used except in the case of a ground fault in
the equipment (i.e. in normal operation, the ground isn't used either). So
nothing involving either the ground or the neutral would have any effect on
the problem you're seeing.



In *most* panels, any place that you can put a double-pole breaker will give
you 240V. Your panel may be an exception, as at least a couple of us have
noted, and the easiest way to tell where you can and can't is to look at the
label on the inside of the panel cover -- that will show the possible
configurations. Another way to tell is to probe between the lug screws on
adjacent breakers (with the breakers on) to see where you measure 240V and
where you get only 120V. Yet another way is to pull the breakers, and look at
the configuration of the bus bars.

But before you do any of that, the *first* thing you should do, in my opinion,
is to measure the voltage between the two main breakers (or lugs) in the
subpanel, and see whether you get 240V or 0V. I think you'll see 0V, because
- assuming that you've described everything accurately - the simplest
explanation for the problem you're seeing is that the subpanel is not wired
correctly at the main. Specifically, I think that if you look in the main
panel at the wires feeding the subpanel, you'll find that when the subpanel
was installed, the black and red wires feeding it were connected to two
separate single-pole breakers (instead of to one double-pole breaker), and
those two breakers are on the same leg of the service.


That's fine -- just wasn't necessary for *this* application. But planning for
the future is always good. :-)