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
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
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.
Any ideas what I am doing wrong?
Thanks in advance.
uh? just the red & black? Where's the nuetral connected? You gotta
have a return circuit.
if you've got 10/3 then you've to red, black, white, ground right?
Am I missing something here or just don't know what I'm talking about.
Chris Friesen wrote:
There are two 110 volt circuits in most CB boxes. Each is independent. They
also happen to be 180 degrees out of phase with one another. The upshot is
that while each is 120 volt with respect to ground, they are 220 volts with
respect to each other. The neutral is there for a variety of reasons but not
necessary for operation at 220vac. Ever wonder how your electric clothes
dryer works? The main coils are wired for 220 but the light bulb and other
parts like the timer use one side and the neutral.
With the groups help I was able to figure out what I was doing wrong.
As suggested I tested the main lugs in the subpanel I got 220v, but did
not get 220v when I tested the outlet accross both hots.
Turns out the the sub-panel installed only has two positions that will
give you 220v. I didn't connect the breaker to either one of these. I
removed the breaker, and re-connected it to the correct lugs and got
220v accross both hots. The heater now works! The inside of the panel
door has a diagram that shows which lugs are 120v and which are 220v.
Thanks for all your help!
No - the discussion was that for a 220V circuit, no neutral is needed.
However - when looking to also utilized 120V within a device that is hooked
up to a 220v circuit, then a neutral must be provided. The example given
was a clothes dryer. The dryer coils run on 220 and your clothes would dry
just fine with no neutral. However, the timer, any lights that may come on
when you open the door, etc. run on 110V. Therefore, you have to supply a
neutral so that those 110V devices can operate off of one leg of the 220V,
There is no neutral in a 240 volt circuit. Going from either leg of a 240
volt circuit to neutral gives you a 120 volt circuit.
Some appliances require both 120 and 240--they need a three-wire circuit
(two hots and a neutral) plus ground.
I've followed this thread and read some good questions and posts.
However, something of a trivial nature I guess, is the reference by some
to 110/220 VAC and others to 120/240 VAC. I grew up nearly always
hearing 110/220 until I worked several summers in college for an
electrical contractor. There, I found it was almost always really
120/240. Throughout my career, managing projects involving building
computer facilities and working around electricity, I've found the same
thing -- 120/240. I'm curious where the 110/220 terms/measurements came
from. Was that, at one time, the norm.
Actually, the 240 in 99% of US residential settings is single-phase,
using a center-tap to derive 120v. HV Distribution circuits are three
phase, with the phases 120 degrees apart. One of those phases feeds
the distribution transformer serving your residence, wherein there is
a center-tap which provides the neutral to the service entrance.
Could've used 10/2, since it's a pure 240V load, but that's just FYI, and
unrelated to the problem.
What do you get between the two hot legs? Here's my guess: measure that at
the outlet, and you'll see ZERO.
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.
Doug Miller (alphageek at milmac dot com)
Some panels will only accept 2 pole breakers in certain slots. I haven't
looked into why that is, but maybe because of this.
Look to see if your box has such a condition, and if you are doing it
I've encountered this as well. Look closely at the buss bar in the center
of the box and make sure that your 220v breaker is really connecting to
alternating buss lugs. Some boxes only have 220v capability on the first
few lugs of the buss bar and then everything below that point is 110v.
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