240 volt circuit

[jmmyers]

Does anyone know for certain if a 240 volt appliance, such as a clothes dryer, will work with no neutral wire or ground wire connected to it (meaning just the two hot wires are connected)? Or a stove, or water heater etc....

I am not looking for guesses, just the facts please.

Joe Myers

 

[don_resqcapt19]

Re: 240 volt circuit

First, these devices all will require an equipment grounding conductor for safe operation. That being said, the water heater is 240 only and will function with only the two hot wires connected. The stove may function, but some stoves use 120 volts for the very low heating settings on the burners, and if there are clocks or oven controls, they often require 120 volts. Most control circuits and fan and drum motors in dryers are 120 volts. Again, these all require an equipment grounding conductor. Do not attempt to operate any equipment of these types without the grounding conductor.
Don

 

[jmmyers]

Re: 240 volt circuit

Don,

Thanks for the reply Don. The question is not of safey it is whether it will operate. As in the case of the clothes dryer, I always understood the motor being powered by 1 leg of the 240 volt and the heating element being powered by the other leg of the 240 volt. For the life in me I can not see how it could opertate giving there was no equipment grounding conductor or neutral to complete the circuit. Another inspector is telling me that it will opertate and I say it will not.

You don't have anything to worry about. I am not about to burn up my clothes dryer over this dis-agreement.

Joe Myers

 

[curt swartz]

Re: 240 volt circuit

Joe,

The heating elements in a clothes dryer are 240 volts and do not require the neutral for operation. The motor and controls are 120 volts and are connected to one of the hots and the neutral. So to answer your question the heating elements would work but the motor and controls would not.

You definitely do not want to try connecting a dryer without a neutral connection. Dryers come from the factory with the neutral connected to the frame. Supplying power to the dryer with out with out a neutral connection would energize the entire cabinet of the dryer causing serious injury or death to anyone that comes into contact with it.

Curt

 

[david luchini]

Re: 240 volt circuit

Curt,

Since 1996, the NEC hasn't allowed use of the neutral to ground the frames of dryers, ranges, etc. (250-140) Are dryer manufacturers still selling dryers that way so that electricians have to remove the jumper and install a new cord and plug in new installations? Just curious.

Dave

 

[curt swartz]

Re: 240 volt circuit

Dave

Yes, all of the dryers that I have seen still come with a jumper in place. I would guess that most sales are for replacement use in which case a 3-wire connection is still permitted. I have seen several installations where 4-wire cords have been installed without the jumper being removed. This creates a parallel neutral path on the equipment grounding system not only for the dryer load but for other loads in the building. I have often wondered if it would be better for the factory to install a 4-wire cord and supply and optional adaptor to allow use in a 3-wire receptacle.

Curt

 

[david luchini]

Re: 240 volt circuit

Curt,
Thanks for the information. I think that when designing dryer circuits, I should add a note to ensure that the jumper gets removed.

I think you've got a good idea about the factory four wire cord. Do you think that replacing a four wire plug with a three wire plug, and connecting the the ground and neutral conductors to the neutral prong of the plug (rather than using a jumper at the dryer frame) would meet the intention of 250-140? It seems to me, that would be easier than replacing the three wire cord and jumper.

Dave

 

[jmmyers]

Re: 240 volt circuit

Curt,

Good information! Thanks.

I was not about to try it, although Don and you confirmed what I was thinking. The elements would but the rest would not.

Are you familiar with stoves? Do the heating elements on the stove top work on 120 or 240? I thought it was 120. I vaguely remember someone telling me usually the right works off one of the 120 legs and the left works off the other leg. Is that correct?

The 4 wire configuration is only required for new cicuits correct?

I like the idea of new appliances being sold with the cords. It is much easier for everyone to just keep using the old circuit with the three wire. If they were to come with the four wire it would be more likely to get everyone in tune with the thinking the circuit needs to be updated, rather than we can make this one work just fine.

Joe Myers