240v to 120v

[theoldwizard1]

This is more theoretical than actual.

Say you have a location with 3 wire 240v, no neutral, but you need 120v load at that location. Replacing the 3 wire with 4 wire is not practical.

In the "old days", I would just connect the 120V load to one hot and use the ground for neutral.

If I put in a 240/120v transformer, I now have a hot and a neutral, but can I use the ground from the 240v side of the transformer ? This ground is not bonded to the 120V neutral. Can I bond it at the transformer ?

 

[Stuff]

yes you can do that as it is the way that it is done at the pole but with a much higher voltage coming in.

Cheaper way would be to change the wires at the breaker to feed hot, neutral, and ground. Change the breaker to 15 or 20 amp and wire-nut pigtails to put a regular receptacle on the end.

 

[theoldwizard1]

I am trying to figure out how to replace the 2 conductor plus ground with 3 conductor plus ground.

 

[Rock knocker]

Can I bond it at the transformer ?

I think you could only bond if there was a panel and over current protection at the place of bonding on the secondary side of the transformer

 

[AP514]

You could pull a Neutral from a near-by 110 plug ? and run the wire over from there ?

 

[CoopVA]

Why do you need a 4 wire 120v? Do you need 2 120v circuits at that location? If you need 2 circuits then it would be more cost effective to just run new wire.

If you only need one 120v circuit at the location...

Assuming you have a 120v breaker in the panel, disconnect the two hots from your 240 breaker. Leave the ground wire for that circuit as is... Take one of the 240 hots to the 120v breaker. Take the other wire and wrap it in white electrical tape at both ends and take it to the neutral bar.




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[nick2010tundra]

Actually Stuff at the pole you have 2 hots and one neutral, and our neutral is bonded to ground. The voltage is the same at the pole on the secondary side of our transformer, just the amperage is way higher.

 

[Rock knocker]

You could pull a Neutral from a near-by 110 plug ? and run the wire over from there ?

You could double the load on the borrowed neutral, best to leave it where it is.

 

[Stuff]

I am trying to figure out how to replace the 2 conductor plus ground with 3 conductor plus ground.

Sounds like it is no longer theoretical. Why do you need 3 conductor? What are you loads?

 

[JoeFin]

Hey Guys -

Once you pass through a transformer - any transformer, you now have a "Separately Derived System".

Yes you have to re-establish ground (the code allows small current limited transformers to use the existing ground supplied)

You then need to "Bond the Current Carrying Grounded Conductor" - (Nuetral) to the ground

So whats the problem