Tapping a 120V circuit from a 240V circuit

[pmurph991]

Originally Posted by jimmarako

Good question, I didn't think of that. When I re-wired my house I ran a neutral with all 240V circuits. I figured its already required for dryers and stoves that its only a matter of time before they all require it. Get ahead of the curve.

I asked my neighbor to check. If there is no neutral then Plan A falls apart. I'll expand the question a bit. If the breaker has the proper spaces for two wires could I run a new line from one side of the breaker?

Thanks
Jim M.

The reason a neutral is required for Dryers and electric ranges is they are 120/240V circuits that use the 120V for timer, clock, display etc. 240v WELL PUMPS DON'T NEED 120V.

But that being said it would work but would be a code violation. Would do it in my own home? Possibly would I recommend someone else do it? Definitely NOT!

[ScottBrownstein]

Originally Posted by weatherguru1

Scott, In our area, Western PA, inspectors will not allow double lugs. You can use double breakers, I.E.Mini breakers, as I said. My inspector works specifically for Atlantic Inland.

The NEC is there for a reason, Safety. Why it is not he same across the land is anyone's guess. For example, and there are many, NY State allows and demands Breaker Boxes be grounded to Natural Gas Lines. Try that in PA and there goes your License and or credibility. Go Figure.

Actually I think they ground gas lines to the panel ground for gas safety purposes. All of my installations had a conventional ground rod at the meter panel for the main ground.


...and then the power company guys come and hook up the lateral to your meter and break all the rules with no inspection...

Go figure.

[pmurph991]

Originally Posted by ScottBrownstein

Are you saying that a double tapped breaker is against code. A number of breakers (like Square D QO) are designed to be double tapped and, unless it is a recent change, why put a feature in a spec sheet that is counter to the NEC.

You are definitely correct that Square D "QO" breakers are designed with a pressure plate that is designed to accept 2 separate wires but most home inspectors and real estate people do NOT know the difference.

[cavie]

I enjoy showing the Home Inspectors they are not as smart as they think they are. I really mess with their head when I remove the 2 wires form an illegal double tapped breaker, use a wire nut to splice the two together with a short pigtail and put them back in the single breaker with a single wire because there was no room for adding a breaker. Very legal. SQ D QO are designed for 2 wires as stated above.

[pmurph991]

Originally Posted by cavie

I enjoy showing the Home Inspectors they are not as smart as they think they are. I really mess with their head when I remove the 2 wires form an illegal double tapped breaker, use a wire nut to splice the two together with a short pigtail and put them back in the single breaker with a single wire because there was no room for adding a breaker. Very legal. SQ D QO are designed for 2 wires as stated above.

I assume that you are an electrician as I am!

[cavie]

Originally Posted by pmurph991

I assume that you are an electrician as I am!

50 years Master. Retired. Still qualify 2 business.

[DouglasReid]

Originally Posted by cavie

I enjoy showing the Home Inspectors they are not as smart as they think they are. I really mess with their head when I remove the 2 wires form an illegal double tapped breaker, use a wire nut to splice the two together with a short pigtail and put them back in the single breaker with a single wire because there was no room for adding a breaker. Very legal. SQ D QO are designed for 2 wires as stated above.

Works great, IF they are the same amp circuit. IF you add a #12 wire to a #10 wire of 30 amp circuit that #12 would not be protected for its 20 amp rating. Not Good!

[cavie]

Originally Posted by DouglasReid

Works great, IF they are the same amp circuit. IF you add a #12 wire to a #10 wire of 30 amp circuit that #12 would not be protected for its 20 amp rating. Not Good!

And why would a Master Electrician such as myself, or anyone for that matter, want to do that.

[DouglasReid]

Originally Posted by cavie

And why would a Master Electrician such as myself, or anyone for that matter, want to do that.

I would not believe that you would!

I simply wanted to clarify what you were doing so others less knowledgeable would not make that mistake. If I recall the OP was wanting to add a 120 V 20 amp to a 240 V 30 amp circuit.

[cavie]

Originally Posted by DouglasReid

I would not believe that you would!

I simply wanted to clarify what you were doing so others less knowledgeable would not make that mistake. If I recall the OP was wanting to add a 120 V 20 amp to a 240 V 30 amp circuit.

Gottca! Just to clairify;. From the OP post #1

"I have not seen his setup yet, but if it is like mine then his well most likely runs off a 240V/20A feed".

[DouglasReid]

Originally Posted by cavie

Gottca! Just to clairify;. From the OP post #1

"I have not seen his setup yet, but if it is like mine then his well most likely runs off a 240V/20A feed".

See, there it goes again, the aging grey matter failing me in my time of need.

But even so the clarification may save some hapless soul.

[jimmarako]

Thanks all for the great replies. Finally got a chance to go over and give my neighbor a hand. As I expected, his well is run with a 240V/20A service, but only three wires. So that kinda killed any tinkering with it.

I also misunderstood him. He thought we could use the overhead light as a place to tap the new outlet from (not the well pump). Of course the light was the last on in the run, so there was no live power. The nearest (i.e. easiest) tap point was 25' away using the outlet for an old fridge that was down there. Simple enough, just more wire than I wanted to use. But everything works so now he just needs his other friend to come over and hack up his plumbing system.

The reason a neutral is required for Dryers and electric ranges is they are 120/240V circuits that use the 120V for timer, clock, display etc. 240v WELL PUMPS DON'T NEED 120V.

Yes, this is what I had read back when I was re-wiring my house. Since I had already bought a bunch of 12/3 for other reasons I figured might as well use it for the well pump. Same as my water heater. Already bought a bunch of 10/3 for the dryer, so the water heater has a neutral. Part of me also did this for future proofing. Who know one day some fancy water heaters may need 4 wires. Maybe some of those new 200% efficient water heaters already use 240 & 120.

But that being said it would work but would be a code violation. Would do it in my own home? Possibly would I recommend someone else do it? Definitely NOT!

So again I realize this is an RV site and not the Mike Holt forums, but seems that a few electricians have joined the party. Several people mention that its a code violation to pull 120V off a 4 wire 240 circuit. Yet dryers and electric ranges are doing this (granted, internally). Even worst they originally were using the ground as a neutral conductor before the codes changed. So does any one know of the actual sections that would prohibit this? I'd like to read up on it. There have been many things I've seen over the years, like double taping breakers, or putting two pieces of romex through a clamp that are perfectly legal, yet every one jumps in with how illegal and dangerous it is.

As a side note, I know this is legal. Or at least it was years ago when the inspector told me this was the typical way to do things. You can use a two pole breaker and run a single 12/3 wire from it to a junction box somewhere. Then at that box you can split into 2 separate 120V circuits. I guess people do this to save time/money pulling two runs of wires. While not what I originally asked its similar in nature.

Thanks again.
Jim M.

[Oldhserst]

If you are not sure and have to ask this many questions....hire an electrician. Electricity is not something that is very forgiving if mistakes are made. Not being judgmental but as an electrician I’ve been called out to many hazardous home wiring projects that were a fatal accident waiting to happen. Best of luck to you....

[Pococj]

Always enjoy reading through these types of threads. As a USN Chief Electrician's Mate, my world was significantly different from industrial and household electrical systems. Shipboard systems have no neutral; both legs of a single phase system, and all 3 of a 3-phase system, are hot. This is done for reliability. In both single and 3-phase systems a ground on any one phase has essentially no effect on a system. Also, on a 3-phase system, battle damage can take out a phase and leave any motors still running for quite awhile, giving more time for repairs to be made. So, for household circuits, these threads "learn me" new things, LOL!

Which brings me to my question - Since a household neutral and a household ground both tie to ground at some point, why is it considered unsafe to use a ground wire as a neutral?

Tied in with that, you wouldn't believe what I've run across in old houses here in small town East Texas (no codes, no inspectors required nor wanted, LOL).

[TimVWulp]

Pococj
brings me to my question - Since a household neutral and a household ground both tie to ground at some point, why is it considered unsafe to use a ground wire as a neutral?

The Neutral wire purpose is to give the 110 volt power a path after it has gone though the device it is powering. It provides a safe path to the neutral bar in the breaker panel and then to the neutral wire from the power grid and ground.

The ground wire is a safety wire to ground. It make sure that the parts or components of a piece of equipment that uses electricity that you may touch dose not have any voltage higher then ground voltage so you don't get electrocuted.

Taking this thread back to RV power supply you need to take very good care of your power cable/extension cords plug ends to keep them clean and corrosion free to provide good connections.

Hope I did not make to much mud Tim

[ScottBrownstein]

You could definitely do that...but the pump (current load) is a 240 volt device and wouldn't run on 120.

[Pococj]

Originally Posted by TimVWulp

Pococj
brings me to my question - Since a household neutral and a household ground both tie to ground at some point, why is it considered unsafe to use a ground wire as a neutral?

The Neutral wire purpose is to give the 110 volt power a path after it has gone though the device it is powering. It provides a safe path to the neutral bar in the breaker panel and then to the neutral wire from the power grid and ground.

The ground wire is a safety wire to ground. It make sure that the parts or components of a piece of equipment that uses electricity that you may touch dose not have any voltage higher then ground voltage so you don't get electrocuted.

Not quite what I was asking. I know the purpose of the neutral and ground wires, but am looking for an explanation as to why using a ground as a neutral is considered dangerous as they are at the same potential with respect to each other and to earth ground.

Thinking about this some since yesterday, I can see a couple situations where the typical ground lead, not having insulation around the actual conductor, might present a problem if it goes to ground at some point prior to the ground bus in a panel, or if it loses connection at the panel ground bus.

In the first case, I can imagine a problem if the unwanted connection is tenuous, coming and going due to vibration, other movement.

In the second instance, if it loses connection at the panel's ground bus the potential on that bare ground becomes 120v due to the now open circuit. Not having any insulation on the conductor could be a hazard if it is accessible to prying fingers. And seeing a ground disconnected in a panel, too many wouldn't consider the possibility it might be hot and grab it to stick it back under a terminal. Ouch!

This is what happens when someone is retired and in between projects at the wife's massage therapy office!

[cavie]

Pococj. you have very correctly answered your own question.