Applying higer rated voltage breakers on lower voltage equipment

[Pitt123]

Is it o.k. to apply a higher rated voltage breaker to a lower voltage rated piece of equipment. In other words if I have a 100A 2-pole 480V breaker can I use this same breaker on a 2-pole 208V circuit?

If so is the only difference the avaliable short circuit rating used at different voltages?

 

[shockin]

Not uncommon to do this. It is usually done to increase the AIC rating of the breaker as you said. But I suppose you could do it if you just happen to have the breaker sitting around and want to use it somewhere.

 

[kingpb]

In general, if the breaker type is designed for the panel it should be usable. There could be issues if it's a delta derived system.

You should check with the manufacturer/manufacturer data before using.

 

[Pitt123]

Not uncommon to do this. It is usually done to increase the AIC rating of the breaker as you said. But I suppose you could do it if you just happen to have the breaker sitting around and want to use it somewhere.

So basically you are saying that a 600V breaker may have a higher AIC rating at the 240V level then a 240V breaker would?

 

[defears]

http://www.relectric.com/Store/Circuit-Breakers/PAF20361021

Look at the middle pdf. On the left side is the AIC rating at the diffrent voltage levels. Most breakers are like this.

 

[Jraef]

Breaker voltage ratings are MAXIMUM, anything less is technically OK. Lower voltage ratings are usually offered because they are slightly less expensive and/or smaller (spacings between terminals can be lower, smaller arc chutes etc.).

But as kingpb said, there may be an issue with mounting it in a panelboard (if that's what you are doing). In other words a 120/208V rated panel may not have a UL listed method of bolting in a 600V rated branch breaker. The only way to tell is to look at all of the breaker types officially listed for that panelboard.

If it's stand-alone, like in a control panel, then no problem at all, but I would add a very clear label on the panel surface near the terminals that the feed is 208V so that someone in the future doesn't think it's 480V by looking at the breaker rating. Just a courtesy for the next guy though.

 

[Pitt123]

In looking at some manufacturers data it looks like the higer voltage breakers have higher interrupting ratings. For example a 600V rated breaker may have a 65kA rating at 240V where a 240V rated breaker may only have a 22kA rating.

I guess price is also an issue as mentioned above.

 

[infinity]

We've been using these 277 volt SP CB's for 120 volt loads since the engineer wanted a 65 Kaic rating:

 

[weressl]

We've been using these 277 volt SP CB's for 120 volt loads since the engineer wanted a 65 Kaic rating:

..and the 'engineer' wanted this because? (There is a reason why CB's rating goes to a certain maximum. Hint: because there is no practical reason to market to THAT interrupting level.)

 

[infinity]

..and the 'engineer' wanted this because? (There is a reason why CB's rating goes to a certain maximum. Hint: because there is no practical reason to market to THAT interrupting level.)

I don't know why but I'm guessing that it has something to do with the available fault current. He gets paid to design, I get paid to install. :roll:

 

[Pitt123]

We've been using these 277 volt SP CB's for 120 volt loads since the engineer wanted a 65 Kaic rating:

I guess if these breakers were only 120V or 240V rated the interrupting rating at 120V mostly likely would have been some value less than 65kA?