120/240V 3PH 4WIRE (DELTA)

[JSK]

I have an industrial lead melter that requires 208V-1PH which I can take from the disconnects center high phase leg to ground.
Question: what happens to the equipment ground should it stay connected or does it have to be disconnected?

 

[ptonsparky]

I have an industrial lead melter that requires 208V-1PH which I can take from the disconnects center high phase leg to ground.
Question: what happens to the equipment ground should it stay connected or does it have to be disconnected?

No, you do not use the high leg to ground for 208 volt loads.
Others can give you the technical reasons, but in short, No.

Leave the EG alone. It is never purposely used as a current carrying conductor.

 

[winnie]

You _never_ use the ground as a current carrying conductor.

If you are talking about the neutral conductor at the main disconnect which is bonded to ground, that is a valid current carrying conductor.

Using the 208V high leg to ground is problematic. The issues have to do with poor effective power factor on the supply transformers and bad voltage regulation because of the higher effective transformer impedance. If you have a small load on a large service it might work just fine.

Likely the correct solution for installing this load is a buck/boost transformer stepping 240V down to 208V.

-Jon

 

[ptonsparky]

I came across a little strong.
Welcome to the Forum. Use the search function and you will find numerous threads about Deltas.

 

[JSK]

Guys,

Ungrounded equipment incase there's a short is where I was confused... not sure what would happen and wouldn't want to touch the unit.
The load is small (12A 208V on a 100A 3PH disconnect and it's only for testing not permanent) but still dont know what would happen if there is a heating element failure short to ground.

Thanks again

 

[winnie]

What do you mean 'ungrounded'?

A piece of equipment without an EGC connected to it?

An ungrounded service (not legal for a high leg delta)?

Something else?

-Jon

 

[4-20mA]

I think he is saying he gets 208 from the high leg to ground and is asking if he can use that 208 to run the equipment... I donno...

The answer is still, no.

 

[Little Bill]

Guys,

Ungrounded equipment incase there's a short is where I was confused... not sure what would happen and wouldn't want to touch the unit.
The load is small (12A 208V on a 100A 3PH disconnect and it's only for testing not permanent) but still dont know what would happen if there is a heating element failure short to ground.

Thanks again

If the case is not grounded/bonded, then a short to ground would energize the case and no tripping of the breaker. Bad idea all around.

 

[JSK]

Hello All,

That answers my question., I will need to get a step down transformer.

Thanks!

 

[Ponchik]

As little Bill said: "it will energize the case"

 

[ptonsparky]

Hello All,

That answers my question., I will need to get a step down transformer.

Thanks!

Buck Boost would be cheaper and better.

 

[Stevenfyeager]

Can I ask a stupid question ? The thread is talking about using '208 hot to ground.' Is that the same as 'hot to neutral ?' Is the OP going to use a neutral wire ? My post yesterday (which I will stop) was similar. My customer wants to use each 3 rd 208 v space for lighting. (his is a sub panel having the neutral and ground separated) So are you all saying using the 208 v single pole is bad in any case ? Thank you.

 

[ptonsparky]

Can I ask a stupid question ? The thread is talking about using '208 hot to ground.' Is that the same as 'hot to neutral ?' Is the OP going to use a neutral wire ? My post yesterday (which I will stop) was similar. My customer wants to use each 3 rd 208 v space for lighting. (his is a sub panel having the neutral and ground separated) So are you all saying using the 208 v single pole is bad in any case ? Thank you.

Yes, it's not designed/intended for hi leg to neutral loads.

 

[Stevenfyeager]

Yes, it's not designed/intended for hi leg to neutral loads.

Thank you

 

[jim dungar]

My customer wants to use each 3 rd 208 v space for lighting. (his is a sub panel having the neutral and ground separated) So are you all saying using the 208 v single pole is bad in any case ? Thank you.

You would need to buy a 480/277V panel if you wanted to use single pole breakers for the 208V loads. It is rarely worth the hassle and potential confusion for future additions.

 

[Little Bill]

Even if you use the high leg to ground to achieve (close) 208V, you couldn't use a standard slash rated breaker such as 120/240V. It would have to be a full 240V, which would be hard to find and expensive.

 

[ptonsparky]

Can I ask a stupid question ? The thread is talking about using '208 hot to ground.' Is that the same as 'hot to neutral ?' Is the OP going to use a neutral wire ? My post yesterday (which I will stop) was similar. My customer wants to use each 3 rd 208 v space for lighting. (his is a sub panel having the neutral and ground separated) So are you all saying using the 208 v single pole is bad in any case ? Thank you.

and it's not 'stupid'!!!

Ask! You are not the only one learning in the Education forum. Or any other for that matter.

 

[tortuga]

The load is small (12A 208V

I'll add you're heater *might* work fine on 240, I have converted several pieces of equipment to run on 240. Lots of heating elements in that class are marked 208/240. The element will run hotter but if its thermostatically controlled your temps will be the same.

 

[JSK]

I'll add you're heater *might* work fine on 240, I have converted several pieces of equipment to run on 240. Lots of heating elements in that class are marked 208/240. The element will run hotter but if its thermostatically controlled your temps will be the same.

Thanks for the that information, The heating element I'm working with is straight 208V.
I know some heating elements are 208/240 rated or straight 240V.

Thanks

 

[JSK]

Can I ask a stupid question ? The thread is talking about using '208 hot to ground.' Is that the same as 'hot to neutral ?' Is the OP going to use a neutral wire ? My post yesterday (which I will stop) was similar. My customer wants to use each 3 rd 208 v space for lighting. (his is a sub panel having the neutral and ground separated) So are you all saying using the 208 v single pole is bad in any case ? Thank you.

Can I ask a stupid question ? The thread is talking about using '208 hot to ground.' Is that the same as 'hot to neutral ?' Is the OP going to use a neutral wire ? My post yesterday (which I will stop) was similar. My customer wants to use each 3 rd 208 v space for lighting. (his is a sub panel having the neutral and ground separated) So are you all saying using the 208 v single pole is bad in any case ? Thank you.

See Jon's answer from yesterday's #3. it might answer your question.