Wiring for a 30 amp RV

[royt]

Hi
I am trying to get 30 amp. service for my RV. I have a 220 welder receptacle that has two 40 amp. breakers tied together. What I would like to do is take one side which I would assume would give me 40 amps. I presently have two # 8 line feeds with a neutral. Can I disconnect one line feed and have the top prong with the ground and neutral tied together? In other words one of the bottom prongs would be hot with the other disconnected. The top prong will have the neutral and ground tied together. Will this work? Thanks for any advice.
Roy

[Wgoodrich]

A RV trailer requires a separated black hot, white neutral, and green ground. The neutral and grounding conductor must not touch or be the same wire in any manner.

You welder does not use a neutral wire. Most likely you have a black, white being both hot and a bare in a cable serving that welder with both the black and white wires connected to that 40 amp double pole breaker.

If this is true then if you want to give up the welder then you can convert two insulated and one bare wire into a 120 volt RV branch circuit by moving wires in the panel and changing the receptacle.

If you desire is to use the welder and the RV using the same branch circuit you can not do that is you only have two insulated wires and a bare wire in that branch circuit. The welder needs two insulated hot wires and a bare or green insulated grounding wire in that cable serving that welder being 220 volts. The RV needs one insulated black hot wire and one insulated white neutral wire and one insulated green equipment grounding wire serving that RV being 120 volts. SEE NEC 551 calling for a green insulated equipment grounding conductor to serve power to an RV. A bare equipment grounding conductor is not allowed to servce an RV.

Sorry back to the drawing board it sounds like.

Let us know how you come out.

Good Luck

Wg

[Anonymous]

WGoodrich
Thanks for the information. I am learning a lot from this site. Actually in the panel my welder has two #8 insulated red wires side by side and a white insulated wire going off to what I thought was a neutral. Just goes to show you how much I know about electric wiring. Why doesn't the welder require a neutral? I hope that I am not being a nuisance.
Thanks again
Roy

[Wgoodrich]

Concerning a/c current [electrical flow] you have two hot conductors that are out of sinc with each other. A/C currrent reverses its direction of flow approximately every 60 th of a second. This reversing of the flow of current every 60 th of a second is what makes it alternating current A/C. While you have two hot conductors that read 240 volts between the two wires you also will have one wire in the 60 times a second alternating cycle point of being a positive flow conductor. Then at the same 60 times a second alternating cycle point the second hot wire is flowing the opposite direction calling it a negative flow. The first hot wire is pushing electrons out and the second hot wire is pulling the electrons back. This is why you are reading 240 volts between these two hot conductors that are out of sinc with each other. The moving of electrons in opposite directions is what causes the electricity to do work.

When we only use one hot wire then we need a grounded leg [aka neutral] connected to the center tap of the transformer. The transformer is center tapped halfway between the two hot conductors that would measure 240 volt between. Now with using only one hot wire and the grouneded leg completing the path back to the center tap of the transformer we are able to make that 120 volt with a single hot wire and grounded leg perform work with only half the voltage but half the voltage will make that one hot wire work twice as hard to do the same work causing the amperage to encrease relative to the voltage.

When we have a tool or appliance we have a possibility to use the 240 volts between the two hot wires perform work but if we add a TRUE NEUTRAL [carries the unbalanced load between to hot wires out of sinc with each other back to the transformer] we then have the ability to also make 120 volts create work using only one of the two hot wires.

Example of a 240 volt appliance using both the to hot wires together to perform work, at the same time within that same appliance performing 120 volts of work would be an oven. An oven uses the two hot wires 240 volts to heat the heating elements then within that same oven we use only say the first hot wire 120 volts to light the light bulb and at the same time we use the second hot wire 120 volts to run the clock. In this oven we are using both 120 volts from either hot wire of unequal amperage and 240 volts to run the heavy work of heating the elements.

While the clock pulls a little amperage the light pulls a little more amperage both from only one hot wire each of opposite sinc. The two hot wires will obsorb within the hot wires an equal amount of the need for the return path back to the transformer by entering the current flow back into the transformer through the ends of hte transformer windings during the 60 cycle per second change of flow between the two hot wires. Yet we have a leftover amperage that is unequal between the two hot wires performing 120 volt work. The difference between the amperage the clock uses and what the light bulb uses both being 120 volt work is the answer as to what is left over that still needs to get back to the transformer. This unbalanced load is then carried back into the center tap of the transformer [able to take the flow of either direction of flow in that 60 cycle flucutation of A/C current] completing the path of electricity for that unequal amperage used in that certain 60th of a second instance.

This is why appliances such as ovens that use both 240 volt loads and 120 volt loads within the same appliance must be served with an insulated white wire called a true neutral.

You welder only uses 240 volt loads therefore has no unbalanced loads within that welder because there is no 120 volt work being done, only 240 volt work being done. No neutral conductor is needed in that welder because without any 120 volt loads on one hot conductor within that same tool being used of unequal amperage there is no unbalanced load that needs to get back to the transformer.

While using 240 volts with no 120 volt single hot loads each of the hot wires will act as the return path for the other hot wire out of sinc with each other therefor not needing a neutral wire to carry the unbalanced load.

An after thought should explain why I earlier referred to a grounded leg [aka neutral]. If we have an appliance that uses only 120 volts being one hot wire there is no second hot wire to obsorb any of the load therefore we need a return path that will take 100% of the current back to the transformer to complete the circuits electrical path. This means we now have a white wire that is not carrying the amperage of only an unbalanced load but is acting as a replacement of the second hot wire taking 100 % of the path back to the transformer only to the center tap of the windings same as a true neutral instead of a return path back into the transformer on one end of that tranformer during the 60 times a second cycling through the second hot wire that is not present in a single 120 volt circuit.

Hope you caught somewhat of a picture in your mind to answer your question as to why a neutral was not used in a welder that uses only 240 volt loads without any need of any 120 volt loads within that welder such as found in an appliance such as an oven or range.

Hope this helps a little anyway

Wg

[aphares]

Wg on the quote of the grounding conductor has to be insulated, I answered a very similar post on DIY, and did not pick up on it needed to be insulated. I how ever did pick up that if it was of Aluminum then it did have to be insulated, but that was in section VIII covering "Recreational Parks" And would that apply if this RV was setting in his drive way?
But either or if it was copper it did not have to be insulated.

[Wgoodrich]

Aphares, I stand corrected on the requirement of the equipment grounding conductor having to be isulated. Knowing your accuracy in your replies I went back and researched. My memory must have been mixing mobile homes with travel trailers. YOu are correct the equipment grounding conductor does not have to be insulated to serve as a part of a feeder to a travel trailer.

Good catch

Wg