Single phase appliance on a 3 phase panel?

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wondervamp said:
So funny and true indeed - that is exactly what I was looking at when I thought I was going to be able to just move a breaker where these third space breakers were open! When I took off the dead front this was exactly what was going on! lol


how so?


What do you look for?
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Read post #36... For how so. You gotta try when these guys are trying...
 
Jraef said:
Slight correction: don’t use the high leg for any single POLE loads. The “high” leg is only high with relation to neutral (and ground), leg to leg it’s just 240V.

2 pole single phase loads (that don’t need a neutral wire for 120V) are fine in the high leg.
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Slight correction spelling wise but HUGE correction in theory. So if I take one for the team and use the "high leg" as one of the phases for this 208/230V appliance that doesn't require a neutral, CAN I use a slash rated 120/240V breaker for this appliance or does it need to be a "straight" 240V breaker which is harder to find?

Most of the folks are implying that it will be in violation and can potentially fry anything requiring a neutral downstream.
 
As far as slash rated breakers are concerned, it is a code violation, but I know of quite a few installations that have been using them for 40-50 years now with no issue. Using the high leg with a load that uses that phase and a neutral will fry anything rated for 120 volts. Most single phase motor loads using the high leg and one of the other phases don’t care, but I did have a cooktop that was straight 240 blow a burner, but it may have just been a manufacture defect, as the replacement has been working for about 10 years now.
 
rambojoe said:
That works too... Which ever is easy. Oh... Meter works too :) but you know that... I know yer an electrician. I dont even remember the op's issue! Op, are you talking resi or comm or ag?
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I used to wire up commercially for a short run a years ago but I'm rusty. This is for a business in an older structure so the wiring is all over the place with several older panels. Hell you should see the original panel - it's a crusty old Federal Pacific panel that is still carrying some loads - I know those panels are bad news. You'd be surprised how many are still operating here in the SF bay area.
 
hillbilly1 said:
As far as slash rated breakers are concerned, it is a code violation, but I know of quite a few installations that have been using them for 40-50 years now with no issue. Using the high leg with a load that uses that phase and a neutral will fry anything rated for 120 volts. Most single phase motor loads using the high leg and one of the other phases don’t care, but I did have a cooktop that was straight 240 blow a burner, but it may have just been a manufacture defect, as the replacement has been working for about 10 years now.
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There seems to be some confustion as to if it is safe to utilize the "high leg" as one of the phases on a double pole circuit that doesn't require a neut. with one of these 120/240v slash breakers. And from what I'm reading, those straight 240V rated breakers are harder and/or expensive.
 
wondervamp said:
There seems to be some confustion as to if it is safe to utilize the "high leg" as one of the phases on a double pole circuit that doesn't require a neut. with one of these 120/240v slash breakers. And from what I'm reading, those straight 240V rated breakers are harder and/or expensive.
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I'll take one for the team and admit I have used a slash rated breaker connected to the high leg. Honestly in my experience everyone does it. There are worse sins in the world.
 
wondervamp said:
There seems to be some confustion as to if it is safe to utilize the "high leg" as one of the phases on a double pole circuit that doesn't require a neut. with one of these 120/240v slash breakers. And from what I'm reading, those straight 240V rated breakers are harder and/or expensive.
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If it doesn’t require a neutral, the load doesn’t care if you use the high leg or not, (the only exception I can think of, is possible surge protection on freq drives) as far as the breaker goes, other than making more money for the manufacturer, I’ve never seen a slash one fail on a delta system.
 
Ok here is a question. What is the physical difference between the following (assume two pole, same amperage):
1. A slash rated breaker, 10kaic
2. A straight rated breaker, 10 kaic
3 A slash rated breaker, say 65 KAIC

Is it just the insulation rating of the plastic case?
 
wondervamp said:
Slight correction spelling wise but HUGE correction in theory. So if I take one for the team and use the "high leg" as one of the phases for this 208/230V appliance that doesn't require a neutral, CAN I use a slash rated 120/240V breaker for this appliance or does it need to be a "straight" 240V breaker which is harder to find?

Most of the folks are implying that it will be in violation and can potentially fry anything requiring a neutral downstream.
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You can use the slash rated breaker if neither pole of the breaker is connected to the high leg. If a pole is connected to the high leg, you need the straight rated breaker.
After looking at the code again, and at some UL documents, it doesn't matter what phases the breaker is connected to. All breakers used on a high leg system must be straight rated.
The article I was looking at used outdated references to both UL 489 and the NEC.

240.85 Applications.

A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker’s voltage rating. A two-pole circuit breaker shall not be used for protecting a 3-⁠phase, corner-grounded delta circuit unless the circuit breaker is marked 1φ–3φ to indicate such suitability.

A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker’s voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker’s voltage rating.
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So what I posted first was correct. As long as the breaker does not connect to the high leg it can be a slash rated breaker.
 
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electrofelon said:
Ok here is a question. What is the physical difference between the following (assume two pole, same amperage):
1. A slash rated breaker, 10kaic
2. A straight rated breaker, 10 kaic
3 A slash rated breaker, say 65 KAIC

Is it just the insulation rating of the plastic case?
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Pretty sure it has to do with the heat energy at the contacts. With a properly applied 120/240 volt slash rated breaker, the breaker contacts will only see heat energy of the fault current times 120 volts because only one contact sees the fault for a ground fault and the two contacts are essentially in series for a line to line fault. With a high leg fault the heat energy would be 173% higher.
 
don_resqcapt19 said:
You can use the slash rated breaker if neither pole of the breaker is connected to the high leg. If a pole is connected to the high leg, you need the straight rated breaker.
After looking at the code again, and at some UL documents, it doesn't matter what phases the breaker is connected to. All breakers used on a high leg system must be straight rated.
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Holy moly, now you are saying all breakers on a high leg system have to be straight rated. And by all...you mean ALL?
 
don_resqcapt19 said:
You can use the slash rated breaker if neither pole of the breaker is connected to the high leg. If a pole is connected to the high leg, you need the straight rated breaker.
After looking at the code again, and at some UL documents, it doesn't matter what phases the breaker is connected to. All breakers used on a high leg system must be straight rated.
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Which is kinda strange, because the internal voltages are still 240 phase to phase, even between the high leg and other phases. Voltage to ground shouldn’t matter, as the case insulation is probably exactly the same. If you scratched out the 120 on the breaker, you would probably have the exact same breaker. Probably a pencil pusher figuring if the breaker does not have “120” on it, then it would prevent it from being used for a 120 loads.
 
don_resqcapt19 said:
You can use the slash rated breaker if neither pole of the breaker is connected to the high leg. If a pole is connected to the high leg, you need the straight rated breaker.
After looking at the code again, and at some UL documents, it doesn't matter what phases the breaker is connected to. All breakers used on a high leg system must be straight rated.
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Even in single phase sub panels that don't even have a high leg in the enclosure?

Do they even make 240 rated single pole breakers for those panels?
 
When I sold panel boards the restriction was for breaker used on the high leg only.

I believe slash rates breakers do not contain internal components and construction required to interupt a fault greater than a nominal 120V to ground. The lack of these components and construction likely mean the AIC rating if the breaker will not be 10kA at the 208V seen on the high leg to ground. Conceivably this is no more safe than using any breaker at the wrong voltage or with an excess available fault current.
 
hillbilly1 said:
Which is kinda strange, because the internal voltages are still 240 phase to phase, even between the high leg and other phases. Voltage to ground shouldn’t matter, as the case insulation is probably exactly the same. If you scratched out the 120 on the breaker, you would probably have the exact same breaker. Probably a pencil pusher figuring if the breaker does not have “120” on it, then it would prevent it from being used for a 120 loads.
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see my correction to post 50
 
wondervamp said:
See post #22 - two mods with opposite opinions
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Both are saying it is ok to use the high leg in the panel for any single phase 240V loads that don't need a neutral. Both would agree that a straight rated breaker is required for any two pole breaker that uses the high leg.

One option that hasn't been mentioned is to use a three pole breaker provided there is room in the panel. They are less expensive than straight rated breakers.
 
ActionDave said:
Both are saying it is ok to use the high leg in the panel for any single phase 240V loads that don't need a neutral. Both would agree that a straight rated breaker is required for any two pole breaker that uses the high leg.

One option that hasn't been mentioned is to use a three pole breaker provided there is room in the panel. They are less expensive than straight rated breakers.
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After rereading, I see they agree. I'm just really trying get the lowdown on this for the sake of doing my part to keep the phases in balance.

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