single phase 208 high leg delta

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Rinpo

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Hello forum

I have a cooktop that wants single phase 208v
High leg delta 208v service
Can I use a 2pole 240v breaker on the high leg of this service to power the unit, meter reads 208v line to neutral.
( I'm only using the 1 pole on the high leg )

thank you
 
Yes but it needs to be a 240 volt rated breaker not 120/240 Maybe special order and much more expensive. You may know this but others may not.,,A 120/240 breaker is not rated for a ground fault at 208v
 
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Is this cooktop straight 208 or is it 120/208? Even it it is straight 208, and while I know of no code that prohibits this, it would be contrary to standard practice it could lead to service issues down the road. If it is 120/208 then you can't do it at all. Is this a commercial cooktop?
 
Rinpo said:
Hello forum

I have a cooktop that wants single phase 208v
High leg delta 208v service
Can I use a 2pole 240v breaker on the high leg of this service to power the unit, meter reads 208v line to neutral.
( I'm only using the 1 pole on the high leg )

thank you
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There is no such thing as a high leg delta 208V service. If you have a high leg, it is a delta 240/120 with the center point grounded (neutral). You will have 208V (or close to it) from the high leg to neutral. As was mentioned, you would have to use a non-slash rated breaker, straight 240V if you use this for the cooktop.
 
Little Bill said:
There is no such thing as a high leg delta 208V service. If you have a high leg, it is a delta 240/120 with the center point grounded (neutral). You will have 208V (or close to it) from the high leg to neutral. As was mentioned, you would have to use a non-slash rated breaker, straight 240V if you use this for the cooktop.
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My take on this is that the OP understands this is a 240/120 3 phase 4 wire supply but he wants to connect the load between the high leg and neutral to get 208 volts. Bad idea. Hence my comments in post #3.
 
My understanding is that the 208V 'high leg' to N has comparatively poor voltage regulation and makes poor use of transformer capacity.

-Jon
 
winnie said:
My understanding is that the 208V 'high leg' to N has comparatively poor voltage regulation and makes poor use of transformer capacity.
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A high leg to neutral load can overload the transformer bank. I have seen analysis that shows a transformer can be overload simply by turning off 120V loads.
 
texie said:
My take on this is that the OP understands this is a 240/120 3 phase 4 wire supply but he wants to connect the load between the high leg and neutral to get 208 volts. Bad idea. Hence my comments in post #3.
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I was going by his statement in the OP. I know he mentioned just using the high leg but I wanted to clarify it's not called a Delta high leg 208V service.
High leg delta 208v service
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So no code issue, but rather a supply issue. My area has very few high leg services left. POCO no longer offers that service
 
texie said:
Is this cooktop straight 208 or is it 120/208? Even it it is straight 208, and while I know of no code that prohibits this, it would be contrary to standard practice it could lead to service issues down the road. If it is 120/208 then you can't do it at all. Is this a commercial cooktop?
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Yes, this is a commercial cooktop in an older building. The specs are asking for single phase 208v. Existing power is supplied by 240/120 3phase 4 wire.
 
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Rinpo said:
Yes, this is a commercial cooktop in an older building. The specs are asking for single phase 208v. Existing power is supplied by 240/120 3phase 4 wire.
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That means that your only practical alternative is to use either isoloation of buck transformer configuration on the A-C phase.
 
Okay so just to add some more info for clarity, unit is asking for 58A on L1 and 55A on L3 at 208v. If my supply is 240/120 would this work? I believe it's wanting a supply from 208/120 Wye not 240/120 Delta, but thats why I'm looking for some advice. Will 208 to neutral work?
 
Rinpo said:
Okay so just to add some more info for clarity, unit is asking for 58A on L1 and 55A on L3 at 208v. If my supply is 240/120 would this work? I believe it's wanting a supply from 208/120 Wye not 240/120 Delta, but thats why I'm looking for some advice. Will 208 to neutral work?
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No.

You answered your own question. Wye is acceptable, not Delta .

Read the posts again as to not using the high leg and neutral.
 
Rinpo said:
Okay so just to add some more info for clarity, unit is asking for 58A on L1 and 55A on L3 at 208v. If my supply is 240/120 would this work? I believe it's wanting a supply from 208/120 Wye not 240/120 Delta, but thats why I'm looking for some advice. Will 208 to neutral work?
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Does the appliance also have 120 volt loads within it? With the two different currents you mentioned it seems it likely does. That would get even more messy trying to make sure you supply correct voltage to the appropriate sub loads if you tried powering this from a high leg and neutral plus another ungrounded conductor.
 
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