Grounding secondary of a 30KVA single phase transformer 480 to 208

[texie]

what if the appliance had a circuit breaker that was only slash rated?

Or fuses as I mentioned back in post #5.

 

[roger]

what if the appliance had a circuit breaker that was only slash rated?

If it's part of the equipment it would not be a concern to an electrician providing power to it.

Roger

 

[roger]

Or fuses as I mentioned back in post #5.

If the equipment requires a specific type of system the manufacturer should specify the type circuit.

Roger

 

[LarryFine]

I'm curious.

What wire color would you choose to pull to the 208v Load?

One orange, one white.

 

[SSDriver]

If it's part of the equipment it would not be a concern to an electrician providing power to it.

Roger

I would think it would be a concern. I can supply 208 volts to a slash rated breaker with two wires at 120v each being compliant and safe within the specs of the breaker. I can also supply 208v on one leg and 0v on the the other, which would not be compliant and/or safe with a slash rated breaker. If I'm landing my wires on the breaker or fuse holder I feel I should follow code up to that point.

 

[jap]

One orange, one white.

I can say it would be very odd to see a white conductor pulled to a strictly 208v single phase load.


Jap>

 

[roger]

I would think it would be a concern. I can supply 208 volts to a slash rated breaker with two wires at 120v each being compliant and safe within the specs of the breaker. I can also supply 208v on one leg and 0v on the the other, which would not be compliant and/or safe with a slash rated breaker. If I'm landing my wires on the breaker or fuse holder I feel I should follow code up to that point.

Once again, what's inside of a listed (or not) piece of machinery is not my concern if there is not some information or warning to tell me to provide something specific as field wiring.

Roger

 

[winnie]

I am going to restate Roger's point: If the equipment requires 208V of a 208V wye system, then the instructions or dataplate should need to explicitly state that, in much the same way that a 'slash' rated breaker would explicitly state that on the label.

(If the breaker says 240V, then it is rated for a full 240V. If it is slash rated then it will say 240/120V.)

I agree with Roger in so far as how things are supposed to be. However a 208V as part of a 208/120V network is much more common than 208V L-GL (line - 'grounded line'), and there is a very real chance that the manufacturer goofed on this. Also the OP has not provided photos of the cooking appliance nameplate.

I would have no problem supplying 208V L-GL to an appliance if I could confirm that the appliance itself would not have a problem with it. Totally normal in data centers, for example, where 240V L-N is often used to feed servers with power supplies rated for such use.

-Jon

 

[SSDriver]

That's my whole point, without information from the manufacturer I wouldn't blindly state you could supply any 208v circuit and throw any issues back at the appliance maker. I would want to know what the appliance says. It can be a concern.

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[roger]

That's my whole point, without information from the manufacturer I wouldn't blindly state you could supply any 208v circuit and throw any issues back at the appliance maker. I would want to know what the appliance says. It can be a concern.

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And I see it the opposite, like the NEC, if it doesn't say I can't do something I can.

Roger

 

[LarryFine]

If there is no third line terminal (i.e., no "neutral" terminal), how can one line being grounded cause an issue?

 

[SSDriver]

And I see it the opposite, like the NEC, if it doesn't say I can't do something I can.

Roger

I agree I follow the NEC as well. I just re read the OP,s post and noticed where he says it requires 2 wires. After 2 days I forgot that he said 2 wires and I was just thinking it needed 208 V without any other information. I didn't remember reading the two wire statement. My bad.

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[Jamesco]

And I see it the opposite, like the NEC, if it doesn't say I can't do something I can.

Roger

But if you were hired to supply power to a piece of equipment wouldn't 110.3 (B) and N (C) Listing apply? (NEC 2017)

This is feeding a cooking appliance that only requires 2 wires.

First I would imagine the manufacture of the cooking appliance intended the appliance to be connected to two phases of a 120/208v 3ph 4w grounded power system.
But what IF? We could, what if, all day long. Who bought the 480v to 208v 1ph transformer?

My gut feeling is the secondary of the 480v to 208v 1ph transformer is floating above ground.
.

 

[kwired]

I can say it would be very odd to see a white conductor pulled to a strictly 208v single phase load.


Jap>

Odd, probably is to most. Grounded conductors still required to be white or gray. Corner grounded delta should also have white or gray for the grounded phase conductor.

 

[kwired]

One orange, one white.

Kind of logical, until you realize orange is already one of your 480 volt system colors.

 

[jap]

I said odd because I've never pulled a white or gray or and grounded conductor color for that matter to a strictly 208v load, nor ever would I.

JAP>

 

[jap]

A buck-boost is slang for an autotransformer arrangement of windings. In an autotransformer there is a conductor which is common to both the HV and the LV sides of the transformer. The output is not a separately derived system

The OP has an isolation transformer which does not have a conductor (other than ground) common to both sides of the transformer. The out is a separately derived system.

Yea, that was a misfire on my part.

I agree.

JAP>

 

[kwired]

My question is who designs an appliance that is 208 volt rated at ~30kVA that isn't three phase or is at least able to change some connections to switch between single/three phase?

 

[roger]

But if you were hired to supply power to a piece of equipment wouldn't 110.3 (B) and N (C) Listing apply? (NEC 2017)

That is exactly what I'm saying. If the equipment has specific instructions I would have to follow them, if they do not then I will supply what is available and convenient regardless of the internal components.

Roger

 

[kwired]

I said odd because I've never pulled a white or gray or and grounded conductor color for that matter to a strictly 208v load, nor ever would I.

JAP>

But every time you have done it before you didn't have a grounded conductor involved, OP's application would be, unless he leaves this secondary ungrounded, but then he really needs to have ground detection installed.