3-pole beaker feeds single phase panel

[kwired]

It may also allow the breaker contacts to last longer, like with relay contacts in series, which behave like they're opening faster.

wouldn't a four pole breaker make more sense if this is the goal. one side has two sets of contacts the other only has one.

 

[K8MHZ]

We have been able to satisfy UL508A and CSA 22.2 with three pole breakers on single-phase loads. But I insist, especially in the case of a moulded case breaker that the two lines coming in are terminated on L1 and L3, a jumper is looped back from T3 to L2 and the load is connected to T1 and T2. This will more evenly distribute heating in the breaker, which undoubtedly leads to more predictable and safer operation of the breaker. It should be obvious as you pass the two lines through all three breaker poles is advantageous. Three phase breakers in so many cases are abundant and often less money.

So one leg has one breaker (L1-T1) and the other gets two in series (L3-T3) + (L2-T2)?

The name Rube Goldberg comes to mind.....

 

[wasasparky]

...This is from the UL Marking Guide, on Molded Case Circuit Breakers: 3–pole circuit breakers are suitable for use on 3-phase systems only, unless marked to indicate use on 1-phase systems...

The exact text in my 08 guide is:

3–pole circuit breakers are suitable for use only on 3-phase systems unless marked to indicate otherwise.

Doesn't a 3-pole breaker installed in a three phase panel meet this requirement? Even if it only utilizes two legs for its load?

The single phase panel is still part of the three phase system. It is just not utilizing all three phases...

 

[LarryFine]

I assume that we are talking about a breaker that is installed in a 3 phase panel being used to supply single phase loads...there is no way to use all 3 poles as you suggest.

Not in a panel, but I have seen fork-lift chargers that can be used on 1ph or 3ph supplies, and the instructions for 1ph use say to wire one line through two poles that way.

 

[LarryFine]

wouldn't a four pole breaker make more sense if this is the goal. one side has two sets of contacts the other only has one.

If we're talking about line-to-line loads, it doesn't matter. They're all effectively in series anyway.

 

[LarryFine]

Doesn't a 3-pole breaker installed in a three phase panel meet this requirement? Even if it only utilizes two legs for its load?

The single phase panel is still part of the three phase system. It is just not utilizing all three phases...

Like a GFCI breaker with no load neutral connection. I can't argue with that.

 

[jim dungar]

The "listing" testing requires each pole of a multi-pole breaker to be overload tested individually.

 

[cripple]

3-pole beaker feeds single phase panel

The use of one or two poles off of a three pole breakers for single phase circuits is permissible by the UL standard #489, but it does have a voltage limitation of 120 volts to ground.
The UL white book states the following:
?Multi-ploe common trip circuit breakers rated 120/240 V ac are suitable for use in a single-phase mulit-wire circuit, with-out the neutral connected to the load, where the voltage to ground does not exceed 120v.?
Which is taken of UL 489 section 6.1.5.1 and reads as follows:
?A multipole circuit breaker shall be constructed so that all poles will make and break simultaneously when operated manually or automatically in the intended manner; except that in a 2- or 3-pole circuit breaker rated at 125/250 V or less and having two operating poles intended for use on the outside (ungrounded) wires of a 3-wire, dc or single-phase ac system, the automatic tripping of either pole shall be permitted to be independent of the other if the independent tripping is indicated.?

 

[Jraef]

Contacts in series do allow the contacts to last longer, on contactors. On breakers, I don't think any of us would live long enough to notice the difference.

 

[Ranch]

I love to extract just a bit of some of the comments in the thread but my computer is about to die.

When we get our heads out of lighting panels and into an industrial contral panel envision an F frame series C 3 pole breaker, (cheap and off the shelf) and we use for the primary of the panels 1P control transformer, let's try an FD3015 for example. Now think that there are several other F frames in there for small 3 phase motors, we end up with a bunch these.

Sigh - And now my battery light is blinking - see you back when I find my charger.

 

[Pierre C Belarge]

Sigh - And now my battery light is blinking - see you back when I find my charger.

If you cannot find your charger, put an attachment plug on one side of a cord of stranded conductors, then remove some strands from the conductor on the other side of the conductors. Plug it in, the reduced number of strands should reduce the voltage for your computer...












I am only playing with you.