Unique solution to an expensive situation.

[Strife]

Ok, customer needs a dedicated receptacle in a particular location.
I got a panel within 10 feet of location, problem is there's no neutral.
Panel is fed with 150A breaker, 3 #1/0 and a #4 black used as a ground.
Panel feeds 2 ovens at three phase, 40 some amps each. Plenty available, but no neutral.
The conduit feeding the panel is EMT
Any other options would cost in the thousands of dollars as the next panel is some 200 feet away and the location is like an island in the middle of the store.

My solution: Changed the tape from green to white on both ends of the #4, moved the #4 from the ground bar to the neutral bar and run 10' of EMT.

I haven't double checked the derating allowed on the neutral, but other than this (or even this) can anyone find faults in this solution?

 

[augie47]

If you confirm your EMT is continuous and presents an adequate equipment ground your plan seems o.k.
If for any reason you elect not to follow that path, a 240(208) to 120 transformer at the panel could also solve your problem.

 

[mcclary's electrical]

Ok, customer needs a dedicated receptacle in a particular location.
I got a panel within 10 feet of location, problem is there's no neutral.
Panel is fed with 150A breaker, 3 #1/0 and a #4 black used as a ground.
Panel feeds 2 ovens at three phase, 40 some amps each. Plenty available, but no neutral.
The conduit feeding the panel is EMT
Any other options would cost in the thousands of dollars as the next panel is some 200 feet away and the location is like an island in the middle of the store.

My solution: Changed the tape from green to white on both ends of the #4, moved the #4 from the ground bar to the neutral bar and run 10' of EMT.

I haven't double checked the derating allowed on the neutral, but other than this (or even this) can anyone find faults in this solution?

It sounds like that would cover it to me. Assuming the EMT feeder is continuous to be used as EGC.

 

[brian john]

Transformer sized for the load, with a CB sized for the primary of the transformer 2 or 6 circuit panel.

Someone put the EGC in there for a reason. Specs?, Equipment manufacture requirement? People seldom waste copper for no reason.

 

[Strife]

Well in South Florida everyone installs a redundant ground wire, regardless.
And if it was in the specs, believe me, the store doesn't care about that at this point, they care more about spending 2-3K vs 300-400.
BTW store was built when copper was REALLY cheap, so no one cared back then.

Transformer sized for the load, with a CB sized for the primary of the transformer 2 or 6 circuit panel.

Someone put the EGC in there for a reason. Specs?, Equipment manufacture requirement? People seldom waste copper for no reason.

 

[augie47]

Is the entire run of EMT visible ?

 

[chicar]

I would change the ground to neutral. Test the emt for a grounding path. Make it a done deal.

 

[Strife]

Yeah forgot to mention this:
I already disconnected the ground, put a clamp on the EMT and tested it with a megohmeter. I got less than one ohm between the ground wire and the EMT.

I would change the ground to neutral. Test the emt for a grounding path. Make it a done deal.

 

[roger]

Yeah forgot to mention this:
I already disconnected the ground, put a clamp on the EMT and tested it with a megohmeter. I got less than one ohm between the ground wire and the EMT.

Then you have a real problem with trying use the insulated conductor as a neutral.

If you still have less than one ohm of continuity between the insulated conductor and the emt after you lifted it from the buss you can not do what you want to do.


Roger

 

[Dave58er]

Was the ground isolated at both ends when you checked the resistance?

 

[Jim W in Tampa]

If the wire is connected at one end i sure hope it read close to ZERO.
I do not condone your method.
You just bit off liability should that emt ever fail. Not something i would risk.
Also consider that depending on if building is steel or not the reading might be from building steel and not emt. Might be legal but not good idea.
Rather see a 208 to 120 transformer

I would accept a new grounding wire on outside of emt

 

[growler]

Is the entire run of EMT visible ?

Good question.

Even better: did this job get a permit and an inspection?

If the local AHJ ( inspector ) is OK with it then it's good enough for me.

 

[Volta]

How long / difficult is the existing feeder run?

If you confirm your EMT is continuous and presents an adequate equipment ground your plan seems o.k.
If for any reason you elect not to follow that path, a 240(208) to 120 transformer at the panel could also solve your problem.

Transformer sized for the load, with a CB sized for the primary of the transformer 2 or 6 circuit panel.

Someone put the EGC in there for a reason. Specs?, Equipment manufacture requirement? People seldom waste copper for no reason.

Might be hard to get to the GES if "the location is like an island in the middle of the store".

If the wire is connected at one end i sure hope it read close to ZERO.
I do not condone your method.
You just bit off liability should that emt ever fail. Not something i would risk.
Also consider that depending on if building is steel or not the reading might be from building steel and not emt. Might be legal but not good idea.
Rather see a 208 to 120 transformer

Agreed, but still may have trouble adding a GEC.

I would accept a new grounding wire on outside of emt

Good thought, if possible.

If the GEC run is reasonable the you could derive a neutral from a transformer as suggested, or if the wires are THHN you could technically fit up to a #1 THHN, if the existing is THW you could replace the #4 with two #6 wires [smallest allowed 215.2(A)(1)], assuming the feeding OCP is greater than 130 amps [250.122(B)].

I say you could 'cause it won't be easy, maybe not possible without withdrawing all four wires to put five back.

 

[iwire]

If the wire is connected at one end i sure hope it read close to ZERO.
I do not condone your method.
You just bit off liability should that emt ever fail. Not something i would risk.
Also consider that depending on if building is steel or not the reading might be from building steel and not emt. Might be legal but not good idea.
Rather see a 208 to 120 transformer

I would accept a new grounding wire on outside of emt

Do you just make this stuff up as you go?

Is beer involved? :grin:

 

[iwire]

How long / difficult is the existing feeder run?




Might be hard to get to the GES if "the location is like an island in the middle of the store".


Agreed, but still may have trouble adding a GEC.

Good thought, if possible.

If the GEC run is reasonable the you could derive a neutral from a transformer as suggested, or if the wires are THHN you could technically fit up to a #1 THHN, if the existing is THW you could replace the #4 with two #6 wires [smallest allowed 215.2(A)(1)], assuming the feeding OCP is greater than 130 amps [250.122(B)].

I say you could 'cause it won't be easy, maybe not possible without withdrawing all four wires to put five back.

EMT is an acceptable EGC, if I could verify it is continuous I would use it as the EGC and not make a mountain out of a mole hill.

 

[Volta]

EMT is an acceptable EGC, if I could verify it is continuous I would use it as the EGC and not make a mountain out of a mole hill.

Sure, once we know why the OP "got less than one ohm between the ground wire and the EMT" and fix it.

 

[brian john]

Well in South Florida everyone installs a redundant ground wire, regardless.
And if it was in the specs, believe me, the store doesn't care about that at this point, they care more about spending 2-3K vs 300-400.
BTW store was built when copper was REALLY cheap, so no one cared back then.

I have been in the trade 40 years and everyone has ALWAYS cared about the price of copper.

 

[brian john]

I would change the ground to neutral. Test the emt for a grounding path. Make it a done deal.

How are you testing for this?

It seems the OP has done all the testing necessary to prove his idea is not feasible. Unless he checks for JBs and possible grounding in these boxes.

 

[iwire]

Sure, once we know why the OP "got less than one ohm between the ground wire and the EMT" and fix it.

I think you are putting the cart before the horse.

If I was looking to verify a continuous steel raceway my first step would be to lift the EGC at the load end only and test for continuity, at that point I would be hoping for a low resistance reading. If it had a high reading that would be bad.

If I got past that first step I would than lift the EGC at the supply end to check there is at this point no continuity.

Obviously if at this point I still had a low resistance reading I would have to look for the reason.

 

[iwire]

It seems the OP has done all the testing necessary to prove his idea is not feasible.

Really?

I see he posted one test result.