Safely getting 110 volts from a 3 wire 220 volt conductor

[Bird76Mojo]

I'll try to keep this short.

Have a hot water heater already wired with 3 conductor cable. Two hots and a ground.

I already have 110v heat tape installed and insulated. I need to power it.

Any advice on using step-down transformers in this case? It is regularly done on large industrial equipment to power Windows PC's and 110v lighting. The transformer creates the neutral?


Thoughts? Experience in this area? Anyone?

 

[Curious Hound]

Not advised. And here is why.

1. You're adding load to the original circuit, which was (hopefully) sized properly for the load of the water heater only.

2. Yes, adding a transformer would get you the 120volts. But, you would need to add more than the transformer. Fuses or circuit breaker for the 120volt load side, suitable enclosure, and what about switching to turn it on and off? The original wiring and breaker would need to be upsized to account for the new load. In the industrial systems you mention, everything is properly sized and engineered to do that from the beginning, including all necessary controls and safeties.

3. Somebody is likely to recommend using the ground as a neutral and deriving 120 volts that way. This is bad. It is against code and unsafe. You would be running current on the uninsulated ground conductor. Plus, you would no longer have a dedicated safety ground. Do NOT do it.

I would strongly recommend running a new circuit for your heat tape. Or, add it into an existing 120volt circuit that has little or no load on it, such as a guest bedroom receptacle circuit.

 

[rubydist]

You get 120V by using one of the hot wires and the neutral. Whether that is a good idea on that circuit or not depends on the existing loading and how much you are going to add with the heat tape as Eric described above.

 

[Curious Hound]

You get 120V by using one of the hot wires and the neutral. Whether that is a good idea on that circuit or not depends on the existing loading and how much you are going to add with the heat tape as Eric described above.

He already said his cable doesn't have a neutral.

 

[lil_Blue_Ford]

Not advised. And here is why.

1. You're adding load to the original circuit, which was (hopefully) sized properly for the load of the water heater only.

2. Yes, adding a transformer would get you the 120volts. But, you would need to add more than the transformer. Fuses or circuit breaker for the 120volt load side, suitable enclosure, and what about switching to turn it on and off? The original wiring and breaker would need to be upsized to account for the new load. In the industrial systems you mention, everything is properly sized and engineered to do that from the beginning, including all necessary controls and safeties.

3. Somebody is likely to recommend using the ground as a neutral and deriving 120 volts that way. This is bad. It is against code and unsafe. You would be running current on the uninsulated ground conductor. Plus, you would no longer have a dedicated safety ground. Do NOT do it.

I would strongly recommend running a new circuit for your heat tape. Or, add it into an existing 120volt circuit that has little or no load on it, such as a guest bedroom receptacle circuit.

This.

Why people have such a casual disregard for the dangers of electricity and why it should be done correctly is beyond me. You can die or burn things to the ground by doing it wrong. Don’t do it wrong, if it’s beyond your abilities, find someone who does the work.