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

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Jamesco said:
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.
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Without the neutral, only the L-L voltage matters. It doesn't matter if one line conductor is grounded.

If anything in the appliance depended on both lines being hot, there would be a third supply terminal.
 
LarryFine said:
Okay, one purple and one white.
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It could still be orange. Unlike white, gray, and green, orange is not exclusive to one application. In this discussion any ungrounded conductor color can be used.

Roger
 
kwired said:
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.
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Correct.

Most Transformer I've seen that were strictly 480 to 208c Single Phase fell into the custom transformer category.

Not sure where this one came from.

Not your typical Xfmr.

JAP>
 
kwired said:
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?
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We don't know what the KW rating of the cooking appliance is. Who in their right mind would have ordered a 480v to 208v 1ph transformer to fed the the cooking appliance to begin with? For a few more dollars he/she could have special ordered a 480 to 120/208V 1ph transformer and wired the secondary as a 120/208v grounded power system.

To date the OP has not provided any info on the cooking appliance other than it is 208v 1ph.
It appears the OP has left the building.:)
 
kwired said:
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.
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Ground detection..... Qualified personnel to monitor the ground detection? Not the people that work in food preparation.
 
Jamesco said:
We don't know what the KW rating of the cooking appliance is. Who in their right mind would have ordered a 480v to 208v 1ph transformer to fed the the cooking appliance to begin with? For a few more dollars he/she could have special ordered a 480 to 120/208V 1ph transformer and wired the secondary as a 120/208v grounded power system.

To date the OP has not provided any info on the cooking appliance other than it is 208v 1ph.
It appears the OP has left the building.:)
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Is a 480 to 120/208v Single Phase Transformer even an option to be had?

Never heard of one.

JAP>
 
jap said:
Is a 480 to 120/208v Single Phase Transformer even an option to be had?

Never heard of one.
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And you probably never will.
The relationship of 120/208V 1-phase 3-wire can only be derived from a three-phase source and at least two transformer winding sets (i.e. 2 legs of a wye transformer).
 
Jamesco said:
For a few more dollars he/she could have special ordered a 480 to 120/208V 1ph transformer and wired the secondary as a 120/208v grounded power system.
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Um, I don't think that's even possible. The closest you could have is 120/240v 1ph.

If the load had a neutral terminal, then it would need 120v; if it doesn't, it doesn't.
 
jap said:
Is a 480 to 120/208v Single Phase Transformer even an option to be had?
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No. The closest you could get is a 480 to 104/208V single phase transformer.

If the appliance really needs 102/208V 'single phase' derived from a 3 phase system, it should be labeled as such and require more than 2 wires to feed it.

If the appliance is labeled 208V then it _should_ function just fine with 208V 'L-N', 208V 'L-GL' (line - grounded line) or 208V 'L-L'.

-Jon
 
winnie said:
No. The closest you could get is a 480 to 104/208V single phase transformer.

If the appliance really needs 102/208V 'single phase' derived from a 3 phase system, it should be labeled as such and require more than 2 wires to feed it.



-Jon
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The closest you could get is a 480 to 104/208V single phase transformer.
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Link please. I missed it.

If the appliance really needs 102/208V 'single phase' derived from a 3 phase system, it should be labeled as such and require more than 2 wires to feed it.
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No it doesn't need a neutral. Haven't you ever wired a 208V piece of equipment that only required 208V 1ph? I bet you fed it from a 120/208V 3ph 4w grounded power system.

The 480 to 104/208V 1ph transformer fits the bill. Problem solved.
 
Although odd to me because it's something I'm not familiar with, most of the evidence points to the fact that if the secondary of the transformer the OP is showing is grounded, there may not be a problem that needs solved.

JAP>
 
jap said:
Although odd to me because it's something I'm not familiar with, most of the evidence points to the fact that if the secondary of the transformer the OP is showing is grounded, there may not be a problem that needs solved.

JAP>
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What did the manufacturer of the cooking appliance tell you? Did the manufacturer say it would be ok?
 
Jamesco said:
Link please. I missed it.
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A 480V to 104/208V single phase transformer would probably be a custom, I came up with the numbers based on what is physically possible, not based on an available part number.

Jamesco said:
No it doesn't need a neutral. Haven't you ever wired a 208V piece of equipment that only required 208V 1ph? I bet you fed it from a 120/208V 3ph 4w grounded power system.
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I absolutely agree, a 208V single phase device should not need a neutral. The only reason for a neutral at the transformer would be for grounding purposes if, for some reason, the load required 'symmetrical' grounding. But I fully expect that the load would work just fine with one terminal of the 208V grounded.

-Jon
 
winnie said:
A 480V to 104/208V single phase transformer would probably be a custom, I came up with the numbers based on what is physically possible, not based on an available part number.



I absolutely agree, a 208V single phase device should not need a neutral. The only reason for a neutral at the transformer would be for grounding purposes if, for some reason, the load required 'symmetrical' grounding. But I fully expect that the load would work just fine with one terminal of the 208V grounded.

-Jon
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winnie said:
But I fully expect that the load would work just fine with one terminal of the 208V grounded.
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Your best guess?

Just doing a Google search for a 22 KW 1ph 208V cooking appliance I ran across this unit.

www.webstaurantstore.com

Commercial Convection Ovens

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www.webstaurantstore.com www.webstaurantstore.com


Unit shall be electrically heated with three tubular heaters.

Each heating element Individually fused? Both ungrounded phases of each element fused?

$22,086.00..... I think I would contact the manufacturer before I grounded one leg of the transformer.

Who bought the transformer? Who in the end will be responsible for wiring the transformer and connecting it to the appliance?
 
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