4800 watt construction heater wiring

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On Oct 17, 12:58 am, snipped-for-privacy@shaw.ca wrote:

The crew has given you good suggestions. Please keep us informed when you discover what the problem was. It helps us with other questions.
thanks,
r
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Sounds like you are measuring from each leg to ground. Measure the voltage across the red and black wire. It should be 240 volts. If it is 0 or 120, check back at the breaker panel. Something is miswired. -S
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Thanks for all your help!
When I get home tonight I'll check the voltage accross for 240v. I didn't do that. At the main panel I connected the black and red to the 2 pole breaker, ground to ground bus, and white to the neutral bus (not used). I'm thinking I'll find that I don't have 220v. The sub-panel is not bonded. Could that have anything to do with it? How will I know where in the panel I can add 220v breakers and where I can't?
I used the 10/3 so that I can change the configuration should my needs change in the future.
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Actually the sub-panel is a Stab-Lock.
Thanks
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snipped-for-privacy@shaw.ca 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. :-)
--
Regards,
Doug Miller (alphageek at milmac dot com)
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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:

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Voltage is a potential difference. The difference between the two current carrying conductors measures 240v. The difference between a current carrying conductor and the grounded (aka neutral) conductor is 120v. This being AC, rather than DC, the concept of a "return path" doesn't really apply, per se. Note that the grounded conductor is derived from a center-tap on the distribution transformer.
scott
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OK! now this makes sense.. I can center-tapping transformers sometimes in multiple places as a youngster to get different voltages for power supply's and ham radio circuits.
Troy
Scott Lurndal wrote:

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Troy said:

You don't need a neutral to utilize the 220, in fact doing so negates it from _being_ 220v. This is 180 degree out of phase AC, not DC. All you need is a voltage potential and somewhere for it to travel, for current to flow. This is provided by the two 120v out-of-phase legs of your typical residential service. Hopefully you do not become part of the conduction path, and is the primary reason that most woodworking equipment requires a ground. It is not designed to be a current carrying conductor.
Great confusion exists among novices as concerns Grounds and Neutrals, especially when it involves outbuildings. Protection against electrocution and lightning are two of the main reasons that the current grounding guidelines/codes exist.
The ground on most 220vac equipment is for safety grounding only. It is a ground, not a neutral, although they do eventually connect together in your main panel, but never in an in-house subpanel.
Older stoves and cloths dryers sometimes used a common ground/neutral to provide 120v for lamps and timer motors, but the new code and all new appliances require a 4 conductor plug and wiring. Two hots, a neutral, and a ground. It's a safety thing...
Get a copy of the NEC if you want to read up on how to wire things safely, and to code. Otherwise, please, call an electrician. Mistakes can be deadly and cause great property loss.
FWIW
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DGG said:

More precisely, should have read:
...all new 220v appliances that need the use of 120vac for lamps/motors/etc. require a 4 conductor plug and wiring...
FWIW
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its been forever since I read any of the electrical code stuff and OBVIOUSLY don't use it very often hardly. I'll be sure to ask any questions before I mess with anything other then 120. At least I know what I'm doing with that.
Troy
DGG wrote:

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There isn't a "return path" per se in a 240V circuit. In a 120V circuit, the hot is at a potential of 120V with respect to ground and neutral. In a 240V circuit, the potential between the two hots is 240V; each is at a potential of 120V with respect to ground and neutral.

That's to ensure that the neutral is at true earth ground potential.

That's not why you popped the breaker. Not having seen what you did, I can't say why you *did* pop the breaker, but I can say with certainty that tying neutral to ground didn't trip the breaker, in and of itself. Unless it was a GFCI breaker.

Means you had it connected to a hot lead somewhere...

Yep, it's basically the same concept.

Residential electrical supply isn't quite the same animal. There are a number of books available at any decent library or bookstore, or at most home centers, if you want to learn more.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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It's AC, think about it. If you "know electronics" it should become obvious.

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Forgot to mention. The main panel is a Siemens EQ Load center and the sub is also a Siemens.
Thanks
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