240VAC 2pole Breakers

[kwb]

I have a question that I can't figure out.

My 240V breakers are from all outward appearances just 2 120V breakers stuck together and a pin placed between the levers.

The question is - if I go buy a 40A 240 breaker is that really 2 20A strapped together or 2 40A breakers?

 

[sberry]

It's 2 40A breakers.

 

[metlmunchr]

I think there's also an internal common trip mechanism in a 2 pole breaker so that a short on one leg to ground (or an overload on one leg) causes both sections of the breaker to trip. It doesn't rely on the tie between the levers to trip both legs. As a result, its not a good idea to use a pair of common single pole breakers for a 2 pole load.

Something that's always been something of a head scratcher for me is the cost of 3 pole breakers. My shop has an 800 amp 208V 3phase service with two 200 amp and two 150 amp 3 phase Siemens panels and a mix of single pole, 2 pole, and 3 pole breakers. A 2 pole costs roughly twice as much as a single pole, not exactly but in that ballpark. But a 3 pole costs more like 6x to 8x as much as a single pole, depending on amperage. I can see some premium based on lower production numbers, but the actual multiple seems more like one of those "gotcha" prices.

 

[theoldwizard1]

I am pretty sure Square D sells a "kit" to tie to 120V breakers together for 240V operation.

 

[Bert_]

I am pretty sure Square D sells a "kit" to tie to 120V breakers together for 240V operation.

That would be a handle tie. It is for multi wire circuits that are required be simultaneously disconnected. If you turn off the breaker with the handle both breaker will be off, but if one of the breakers trips it will not trip the second breaker.

It is NOT for 240v circuits since those breakers need to have the common trip feature.

A 2 pole breaker has a common trip feature so that if one side trips the other side will trip also.

 

[PoorOwner]

That would be a handle tie. It is for multi wire circuits that are required be simultaneously disconnected. If you turn off the breaker with the handle both breaker will be off, but if one of the breakers trips it will not trip the second breaker.

It is NOT for 240v circuits since those breakers need to have the common trip feature.

A 2 pole breaker has a common trip feature so that if one side trips the other side will trip also.

So.. could you use a 2 pole breaker for multi wire circuits?

 

[Matt Matt]

Yes, they are 2 40A 1 pole breakers with handle tie but they do have a internal Cam that assists in short and overload trips.

2 pole 240 amp breaker’s with handle ties(pin or plate) that are riveted together usually have a heat Cam trip too. When you handle tie 2 =>1 pole you are solely relying on handle ties to trip the second pole.

This is why usually when you trip a breaker it is left in the middle position. Same as when you buy them(if they haven’t been flipped or tampered with in the store).

 

[Stuff]

In general, it is simplest to always buy a 2 pole breaker as it has the internal trip mechanism and will cover almost every situation. Using a handle tie is for specific applications that most will never run into.

 

[sberry]

I just added some circuits to a church. Used all multi wire and used 2 pole breakers. They can't get in to the overloaded situation they were in, gave them so much available power they won't be fussing with breakers.