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Doug Miller

In article .com, wrote:
I can't figure out what I'm doing wrong. I'm currently trying to add
an oulet for 4800 watt construction heater in my shop. I've run 10/3

Could've used 10/2, since it's a pure 240V load, but that's just FYI, and
unrelated to the problem.

wire to the outlet, added a 2-pole 30amp breaker to the sub-panel, and
installed a 6-30 plug by connecting the black and red wires to the
blades on the plug, and the bare wire ground to the box 1st and then to
the ground on the outlet. The white wire is capped off and not being
used. When I plug in the heater it will not turn on. Breaker does not
trip.

I get 120v on each side of the plug with my voltmeter. I even was able
to test the voltage in the heater and there is 120v going to each input
inside the heater. I replaced the heater with a brand new one, and
also replace the outlet and get the same results.

What do you get between the two hot legs? Here's my guess: measure that at
the outlet, and you'll see ZERO.

Possible explanations:

1) You don't have the breaker for this circuit wired correctly. I doubt that's
the case, though, since you seem to have done everything else right.

2) I've heard of, but never actually seen, panels in which adjacent lugs are
on the *same* leg of the service, instead of on opposite legs (opposite legs
being on opposite sides). You may have such a panel. But I doubt it. If they
exist at all, I'm sure they're very rare.

3) You said you installed the new breaker in a subpanel. Have you verified
that there's actually 240V coming into the subpanel? I bet there's not. Put a
voltmeter across the two main breakers (or lugs) in the subpanel, and you'll
probably see 0V. I suspect that the subpanel is wired incorrectly at the main
panel, and nobody ever noticed before because nobody ever installed a 240V
circuit in the sub before.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.