480v on 208v buss

[kwired]

We don’t know that it’s even “probably fine”. Aside from the breakers, panel bus and terminal separation and creepage distances are greater at 600V than at 300V, the two design and testing standards for gear. The panel mfr did not have to think about 600V separation when designing a panel to be listed and labeled at 240V. Neither would they have done fault with Stan /SCCR testing at the higher voltage, they didn’t have to. So for all we know, the bus bars are too close in that panel, regardless of the breaker ratings and even BEFORE the first breaker has to trip there may be serious problems. So saying “it’s probably fine” is potentially giving a nod to something that may catch fire. We have no way of knowing, so we should not even remotely condone this.

NO was a sufficient answer.

There is a difference between telling the truth about something and condoning it. It's like the inappropriate use of slash breakers. Probably never going to matter. Think about all the sites that have inappropriately rated equipment short circuit rating wise. Is there any evidence that this has resulted in any injuries? I am not aware of any.

I earlier posted that it probably isn't going to blow up the moment it gets energized. But that don't mean it will withstand that voltage over time and may have a catastrophic failure when it does fail. Stuff that is insulated for 600 volts still does have catastrophic failure on 480/277 more often then you see such failures on 208-240/120 volts.

 

[JFletcher]

No is a sufficient answer if you don't want to know the reason why something cannot be done.

And I hardly think that others or my post were condoning putting 480 on a 208 panel. I prefaced my post with the word "no" and followed it up by stating that a breaker tripping could possibly cause an explosion and dead front failure.

In the interest of safety, and someone reading only what they want to read, feel free to edit my post to remove any language that someone may misconstrue as permission or endorsement of putting 480 to a 208 panel, which is not only several NEC violations, but a gross violation of safety that could result in death.

 

[kwired]

No is a sufficient answer if you don't want to know the reason why something cannot be done.

And I hardly think that others or my post were condoning putting 480 on a 208 panel. I prefaced my post with the word "no" and followed it up by stating that a breaker tripping could possibly cause an explosion and dead front failure.

In the interest of safety, and someone reading only what they want to read, feel free to edit my post to remove any language that someone may misconstrue as permission or endorsement of putting 480 to a 208 panel, which is not only several NEC violations, but a gross violation of safety that could result in death.

If breaker is interrupting a short circuit or ground fault, if it is tripping on overload it shouldn't cause such an explosion. Now the fact it isn't designed for that high of voltage does increase chances of short circuit or ground fault conditions once insulation breakdown occurs.

 

[JFletcher]

If breaker is interrupting a short circuit or ground fault, if it is tripping on overload it shouldn't cause such an explosion. Now the fact it isn't designed for that high of voltage does increase chances of short circuit or ground fault conditions once insulation breakdown occurs.

Was thinking that under a short circuit condition, as the breaker opens an arc forms within the breaker which does not extinguish itself, basically grenades the breaker(AIC greatly exceeded) and then forms an arc across the bus bars, which in turn blows the dead front off the presumably-lesser-designed-208V panel, due to the rapid vaporization of metal and plastic parts.

As I stated above it was just an initial thought of a worst-case scenario. I do not know if this is actually possible, melodramatic, or otherwise.

 

[Besoeker]

No is a sufficient answer if you don't want to know the reason why something cannot be done.

For more or less the same reason you wouldn't put 240V on a 120V rated appliance.
But the OP didn't ask why.
So NO is a complete and sufficient answer to the question posed.

If he come back and asks why then would be the time to give a more convoluted response.

 

[kwired]

Was thinking that under a short circuit condition, as the breaker opens an arc forms within the breaker which does not extinguish itself, basically grenades the breaker(AIC greatly exceeded) and then forms an arc across the bus bars, which in turn blows the dead front off the presumably-lesser-designed-208V panel, due to the rapid vaporization of metal and plastic parts.

As I stated above it was just an initial thought of a worst-case scenario. I do not know if this is actually possible, melodramatic, or otherwise.

That is a worst case scenario. Destroying the breaker could be a little more common possibility, blowing dead front off maybe not going to be something that would be so likely. A system that has the kind of available fault current to do that has a good chance of having GFP somewhere upstream.

 

[electrofelon]

For more or less the same reason you wouldn't put 240V on a 120V rated appliance.
But the OP didn't ask why.
So NO is a complete and sufficient answer to the question posed.

If he come back and asks why then would be the time to give a more convoluted response.

I have no issue with the way we handled this thread. The first 4 responses were pretty much a direct no. Then we expanded into some cases where the panelboard may be rated for a higher voltage, noting some like I-line, are the same regardless of voltage. Seems like a textbook thread to me :?

 

[Besoeker]

I have no issue with the way we handled this thread. The first 4 responses were pretty much a direct no. Then we expanded into some cases where the panelboard may be rated for a higher voltage, noting some like I-line, are the same regardless of voltage. Seems like a textbook thread to me :?

The obvious question is would you do it?

 

[electrofelon]

The obvious question is would you do it?

Sure, why not?

 

[Besoeker]

Sure, why not?

How would you deal with existing connected loads?
What about non-compliance withe NEC?
What about invalidated warranties?

 

[electrofelon]

How would you deal with existing connected loads?
What about non-compliance withe NEC?
What about invalidated warranties?

Hope everything works until the check clears, or better yet ask for cash. Get out of there quickly and change your phone number....

Seriously though, obviously this would be a situation where a panel is moved, or the loads are being reconfigured.....and I'm talking about a panel board that is rated for the higher voltage.

 

[ggunn]

No is a sufficient answer if you don't want to know the reason why something cannot be done.

Isn't the fact that the applied voltage would be more than twice the voltage rating of the bus sufficient? That's why we have voltage ratings.

 

[Besoeker]

Seriously though, obviously this would be a situation where a panel is moved, or the loads are being reconfigured.....and I'm talking about a panel board that is rated for the higher voltage.

Maybe we should just stick to the OP's question and answer that.
Rather than trying to imagine scenarios where it might be considered.

 

[winnie]

There is a reason that we are not allowed to answer DIY questions on this board, because we presume a certain level of basic knowledge.

I assumed that the OP knows that a panel should not be used above its rated voltage, but was asking if there was a difference between the actual rating of the panel bus bars and the label.

In reading the OP's question, I read between the lines that we were being asked 'What is the actual voltage rating of a panel labeled 120/208V?' The answer is _probably_ not 480V...but as was pointed out there is at least one case where the actual rating of the bus would be 600V.

If I ask 'What is the voltage rating of a plug labeled 120/208V that matches the NEMA configuration for 120/208V 30A?' what would you answer?

-Jon

 

[petersonra]

There is a reason that we are not allowed to answer DIY questions on this board, because we presume a certain level of basic knowledge.

I assumed that the OP knows that a panel should not be used above its rated voltage, but was asking if there was a difference between the actual rating of the panel bus bars and the label.

In reading the OP's question, I read between the lines that we were being asked 'What is the actual voltage rating of a panel labeled 120/208V?' The answer is _probably_ not 480V...but as was pointed out there is at least one case where the actual rating of the bus would be 600V.

If I ask 'What is the voltage rating of a plug labeled 120/208V that matches the NEMA configuration for 120/208V 30A?' what would you answer?

-Jon

My answer is that it depends on what you mean by the voltage rating. I seem to recall being told by one of the manufacturers that the UL standard for receptacles and plugs requires the same clearances and spacings for all plugs 600V and under.

 

[Besoeker]

There is a reason that we are not allowed to answer DIY questions on this board, because we presume a certain level of basic knowledge.

I assumed that the OP knows that a panel should not be used above its rated voltage,

Not sure that assumption is valid

If I ask 'What is the voltage rating of a plug labeled 120/208V that matches the NEMA configuration for 120/208V 30A?' what would you answer?

-Jon

Exactly what it states on the label.

Just in passing something that might give you a smile. We had a television commercial for a fence paint:
"Ronseal does what it says on the tin"

 

[JFletcher]

Isn't the fact that the applied voltage would be more than twice the voltage rating of the bus sufficient? That's why we have voltage ratings.

That's quite true. However there are numerous devices that can accept a range of inputs. High pressure sodium ballast can work on 120 to 480 volts. Although NM type cable is usually wired at 120, possibly 240, it is rated to 600 volts. panels and breakers are neither of those devices, and have to be used at the listed voltage.

And I apologize to you, besoeker, and any others that I may have irritated with my detailed replies. Personally, when I am told no, the usual and immediate question following it up is "why?".

Also, in this watered down safety-conscious PC world we live in, there are warnings and labels on everything, many of which can be disregarded. Labels on breaker panels are not one of those ignorable types.

 

[Jraef]

I'm closing this thread because we are venturing off into discussions of what is allowed vs opinions on what should be allowed or not allowed. The bottom line is that as electrical PROFESSIONALS, we should not be encouraging or even remotely condoning the misuse of equipment just because MAYBE it will not explode. Further discussion is pointless.