3 phase 125A 120/208 breakers?

[Whale Rage Forever]

I don't typically deal with 3 phase product, but I have a customer for a commercial kitchen saying they want to add two electric ovens that-apparently-are each rated for 125A loads at 208v.

Being that 125A is a standard OCPD size in the nec, I didn't think much of this. But as I have contacted suppliers I quickly discovered that everyone is telling me that there are seemingly no 3 phase breakers above 100A that they can provide for 120/208.

So, what am I supposed to do? I find it hard to believe that no one has ever had an individual 3 phase load above 100A. How are you supposed to feed them if you can't get the appropriate ocpd? Use a fusible disconnect at the appliance fed directly from a higher amperage OCPD at the switchgear instead of a breaker at a panel?

 

[Seven-Delta-FortyOne]

That’s certainly one option, to use a fused disconnect.

Or a sub panel, or main panel, to a fused disco, using tap rules.

There‘s a few 125A 3P breakers out there, mostly, or maybe all, are bolt in. What brand and model of panel do you have there?

I most familiar with Eaton, and I’ve only seen above 100A as bolt on.

 

[Whale Rage Forever]

They have to add a sub panel regardless. They have 3 existing 400A rated feed through main lug panels bunched together in the kitchen all jam packed full of other stuff.

I am planning on adding a 400A fusible switch unit to an existing GE switchgear. From there I'd have to run feeders over for a new panel. At that point, it does not technically matter what brand the panel is.

 

[augie47]

It may not be a simple as locating a breaker....
You need to see what the available fault current will be so you can select the correct breaker.
You might have to match the existing gear to series rate or if you are adding a fusible switch, select a breaker that will rate with the fuses.

 

[infinity]

So, what am I supposed to do? I find it hard to believe that no one has ever had an individual 3 phase load above 100A. How are you supposed to feed them if you can't get the appropriate ocpd? Use a fusible disconnect at the appliance fed directly from a higher amperage OCPD at the switchgear instead of a breaker at a panel?

Of course they make 125 amp 3 pole circuit breakers but maybe they don't make them for the specific panel you're using. If you're adding a sub-panel just make sure that it accepts whatever breakers that you need.

 

[Whale Rage Forever]

@infinity
I cannot help but notice that-much as my suppliers have stated-that that breaker, though rated up to 600VAC, does not possess a listed short circuit rating for 208V systems. Given that this is for a 120/208v 3p system, would I be able to use that specific breaker? My suspicion is that the answer is no.

I am gathering that 208v 3 phase is somewhat more limited in equipment that is available for installation.

It may not be a simple as locating a breaker....
You need to see what the available fault current will be so you can select the correct breaker.
You might have to match the existing gear to series rate or if you are adding a fusible switch, select a breaker that will rate with the fuses.

You are likely correct.

There is ample space available in the switchgear to add new fusible switches, and though I would love to assume that it has capacity to add another 400A fusible switch, I certainly haven't checked yet.

Also, I am not clear as to your last sentence. What do you mean by "matching the existing gear to series rate" and "selecting a breaker that will rate with the fuses." Please elaborate.

 

[tortuga]

For 3 phase 208 I always use 240 or 250 Volt, or 600V breakers like infnity posted, never in my entire career have I installed a 208 breaker.
and I see 208 pretty often.

 

[Whale Rage Forever]

For 3 phase 208 I always use 240 or 250 Volt, or 600V breakers like infnity posted, never in my entire career have I installed a 208 breaker.
and I see 208 pretty often.

I understand that it can go up to 600v and this shouldn't matter at all. I am just curious that since it did not specify the 208v AIC if that meant it was specifically not listed for use with a 208v system.

 

[electrofelon]

You will not find a 3 pole 125 in a plug on, only 2 pole (I think its a product standard or UL limitation). Even a bolt on you won't find many that fit in a "standard" space. Siemens has one, the mighty NGB which is 600v and goes up to 125 in a three pole and fits in a standard BL/BQD space. Other options are subfeed or feed thru lugs, a tap off the main conductors, or a sub feed terminal block:

Not Authorized NorthEast Electrical

www.needco.com

 

[winnie]

I understand that it can go up to 600v and this shouldn't matter at all. I am just curious that since it did not specify the 208v AIC if that meant it was specifically not listed for use with a 208v system.

My understanding is that the voltage rating of a breaker is the _maximum_ value it can be used at. In which case a 240V breaker is perfectly acceptable at 208V.

Jon

 

[infinity]

My understanding is that the voltage rating of a breaker is the _maximum_ value it can be used at. In which case a 240V breaker is perfectly acceptable at 208V.

I agree. With the 600 volt circuit breakers get you a higher interrupting rating at 240 or 208 volts which may be a design choice based on the system. For 208 volt systems all I've seen is 240 volt rated CB's.

 

[Fred B]

My understanding is that the voltage rating of a breaker is the _maximum_ value it can be used at. In which case a 240V breaker is perfectly acceptable at 208V.

Jon

A slash rated breaker that is at least or exceeding the highest L-G and L-L available is allowed. The slash Rated 120/240 would be allowed on a 120/208 that is 120-G and not over 240 L-L, but not be allowed on a circuit with 208-G. (NEC240.85)

 

[augie47]

Since you are looking at installing a fusible disconnect either from a breaker or the buss you might consider just installing two and fuse them at 125 amp and forget the breaker altogether. Considering you will need a panelboard for the breakers the two disconnects will be less expensive.

 

[Jraef]

My understanding is that the voltage rating of a breaker is the _maximum_ value it can be used at. In which case a 240V breaker is perfectly acceptable at 208V.

Jon

That is absolutely correct.

Being that 125A is a standard OCPD size in the nec, I didn't think much of this. But as I have contacted suppliers I quickly discovered that everyone is telling me that there are seemingly no 3 phase breakers above 100A that they can provide for 120/208.

I strongly suspect that you were looking for a PLUG-IN breaker. Those are typically limited to 100A max, after than they become bolt-in and the panel has to have provisions for bolt-in feeders. Bolt-in and plug-on are generally not mixed.

 

[Birken Vogt]

Plug in breakers such as CH-BR and Siemens Q-whatever are commonly available up to 125 amp in 2 pole. However, they do not seem to exist in 3 pole. This also holds true for the panel mount equivalents of the same thing.

 

[electrofelon]

Plug in breakers such as CH-BR and Siemens Q-whatever are commonly available up to 125 amp in 2 pole. However, they do not seem to exist in 3 pole. This also holds true for the panel mount equivalents of the same thing.

Siemens does have a 125 bolt on that fits in a standard space, see post #9

 

[Birken Vogt]

I was responding to Jraef who was saying that plug on breakers are commonly limited to 100A, and there are plug on 2 pole 125A. Although now I see he may have been meaning plug on 3 pole breakers are limited to 100A.

I have always wondered why plug on 3 poles had no 125 available.

 

[Birken Vogt]

I would also point out that bolt on 3 pole QO are a common small size breaker easy to get. They also make QO panels that accept both plug on and bolt on breakers.