Can you put a two pole breaker on the high leg for a high delta panel

[Cartoon1]

Would you be able to put a 2 pole branch breaker 240V rated on a high leg delta panel, Leg A,B or leg C,B (assuming the high leg is B)? if for example the load requirement is a 3 wire single phase? Thank you

 

[winnie]

1) A true 240V straight rated 2 pole breaker then it is fine on the high leg, but watch out, many (most??) are 'slash rated' 120/240V, whereas 3 pole breakers are often fully rated.

2) If the load requires 3 wire single phase, that implies a that it uses the neutral, which would not be fine on the high leg.

-Jon

 

[tom baker]

And wholesale houses may not stock a fully rated breaker and they are a lot more expensive. A slash rated breaker on a high leg is not rated to withstand the the higher voltage in a short circuit

 

[Dennis Alwon]

When you say 3 wire single phase that is a red flag. Is a neutral needed?

 

[kwired]

And wholesale houses may not stock a fully rated breaker and they are a lot more expensive. A slash rated breaker on a high leg is not rated to withstand the the higher voltage in a short circuit

Expensive enough they might even be higher cost than a three pole breaker. Not because it cost more to make but is just a supply/demand thing driving the price.

 

[wwhitney]

And wholesale houses may not stock a fully rated breaker and they are a lot more expensive. A slash rated breaker on a high leg is not rated to withstand the the higher voltage in a short circuit

Anyone have any cross section photos showing the internal differences?

Thanks,
Wayne

 

[ptonsparky]

Anyone have any cross section photos showing the internal differences?

Thanks,
Wayne

I didn't keep any but I autopsied some QOs back when we had an issue with corrosive fumes at a dairy. They didn't appear any different that I can remember.

 

[Cartoon1]

When you say 3 wire single phase that is a red flag. Is a neutral needed?

Good Point, thank you!!

 

[Cartoon1]

And wholesale houses may not stock a fully rated breaker and they are a lot more expensive. A slash rated breaker on a high leg is not rated to withstand the the higher voltage in a short circuit

How much more expensive are we talking about? 200 - 300%?

 

[jim dungar]

I didn't keep any but I autopsied some QOs back when we had an issue with corrosive fumes at a dairy. They didn't appear any different that I can remember.

The difference is in the line to ground clearances and path for clearing the products of arc interuption.

 

[Cartoon1]

I appreciate everyone answers. They were all spot-on, helpful, and detailed. Great community!!

 

[electrofelon]

How much more expensive are we talking about? 200 - 300%?

For siemens, the straight rated 2 pole breakers have an R as a suffix, for example a two pole 20 is a Q220R. There arent very many hits on the internet, but I found one for $65. Their use seems to be extremely rare in my experience. Most people seem to either not know about the issue, or dont care. I run across a lot of high leg delta where I am and I dont recall actually EVER seeing a stright rated 2 pole used where required.

Another option, if this is a bolt on panelboard, is to use a 277/480 breaker. For example with siemens this would be a BQD220. I wouldnt be at all surprised if that breaker is actually cheaper than the R breaker.

 

[kwired]

The difference is in the line to ground clearances and path for clearing the products of arc interuption.

Three pole breakers are usually straight 240 rated so you would think those are built to same specifications, if one wanted to take something apart to see any differences.