Double Pole Vs Single pole Breakers

Supervstech

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I would not use a double pole for two seperate circuits. One reason is the mechanical force to keep the breaker closed is double that of a single breaker (harder to trip, i'd assume?). I just don't see the reason to even bother doing it that way?
The force to trip is calculated into the breaker design. An overload condition on either leg will trip both sides of a double pole breaker.
I run multiwire circuits all the time, where both legs of a split phase panel are fed on a 4 wire feeder with a shared neutral. It is required to tie BOTH hot phases to a double pole common trip breaker on these circuits, so if one is off, BOTH are off.
 

SolarRat

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Ground should NEVER pass through a breaker... grounding, where needed should be a PERMANENT path.
On 240V split phase circuits, each hot leg is fed through a breaker, and the grounding conductor is not broken, and it shouldn’t be.
On DC systems, the ground is not broken. The PV SUPPLY & RETURN path of the circuit should be broken by a breaker, and often the negative side is bonded to ground, or chassis.

That was my point
 

offgriddle

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Nec 2017 is going to require that both positive and negative feeds are opened on the pv input, I am pretty sure it’s been require on ungrounded pv for quite a while as well

Just had this question pop up on another thread.

What are the advantages/disadvantages of a double pole breaker compared to a single pole breaker for use in our systems.

I have been using double pole breakers because 3 years ago when I searched DC breakers that's what popped up.
Interesting, a double pole breaker in the AC world handles the two hot power wires that feed a single appliance. While there may be extremely rare exceptions that I am not aware of, only the hot wire is protected by a circuit breaker or fuse.
 

Supervstech

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Interesting, a double pole breaker in the AC world handles the two hot power wires that feed a single appliance. While there may be extremely rare exceptions that I am not aware of, only the hot wire is protected by a circuit breaker or fuse.
Gfci also opens the neutral when tripped...
 

offgriddle

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The force to trip is calculated into the breaker design. An overload condition on either leg will trip both sides of a double pole breaker.
I run multiwire circuits all the time, where both legs of a split phase panel are fed on a 4 wire feeder with a shared neutral. It is required to tie BOTH hot phases to a double pole common trip breaker on these circuits, so if one is off, BOTH are off.
Shared neutral ... Hmmmm ... Is it a super neutral at least?
 

Supervstech

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Shared neutral ... Hmmmm ... Is it a super neutral at least?
No.
It shares equally the load on both phases, so with 20Amps on each hot to neutral circuit, it need only be rated for the 20 amp load...

Individual circuits must have a 20 amp neutral conductor for each 20Amp hot, but multi wire can share the conductor without upsizing the neutral due to phase tie.
 

Rider

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No.
It shares equally the load on both phases, so with 20Amps on each hot to neutral circuit, it need only be rated for the 20 amp load...

Individual circuits must have a 20 amp neutral conductor for each 20Amp hot, but multi wire can share the conductor without upsizing the neutral due to phase tie.
And that's evident if you've ever wired a dryer or stove. All 3 conductors, 2 hot, 1 neutral, are all the same size. I'd say the ground too, but I've come across wire bundles where the copper ground is one size smaller than the hot/neutral wires. Not entirely sure under what circumstances that's allowable. I like to keep the ground the same wire size as the other wires.
 

Supervstech

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And that's evident if you've ever wired a dryer or stove. All 3 conductors, 2 hot, 1 neutral, are all the same size. I'd say the ground too, but I've come across wire bundles where the copper ground is one size smaller than the hot/neutral wires. Not entirely sure under what circumstances that's allowable. I like to keep the ground the same wire size as the other wires.
Well, keep in mind the ground is for fault current. No load is placed on it.

ALL circuits are allowed smaller ground conductors than the load conductors.
Look at your breaker panel.
A 200A service will have 4/0 hots and Neutral, and a #4 ground wire... several sizes smaller than the service conductors...

And the dryer and stove could get by with a #16 neutral on a 50Amp 240v feeder, because the 120V load is only for the computers...
The neutral is only the same size because some brands use 120v motors and 240v heaters...
 

Supervstech

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Actually the residential code book only requires #6 ground conductor for the entire house! In NC code is superceded to require #4
 

Xolar

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Interesting, a double pole breaker in the AC world handles the two hot power wires that feed a single appliance. While there may be extremely rare exceptions that I am not aware of, only the hot wire is protected by a circuit breaker or fuse.
This is because un grounded arrays can
All but one of my circuits in the whole panel, ground is the same size as the hot/neutrals.

But thanx for the education.
in residential wiring all three are the same size up to #10 after that they are smaller then the current carrying conductor
 

offgriddle

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[O QUOTE="Supervstech, post: 40980, member: 249"]
No.
It shares equally the load on both phases, so with 20Amps on each hot to neutral circuit, it need only be rated for the 20 amp load...

Individual circuits must have a 20 amp neutral conductor for each 20Amp hot, but multi wire can share the conductor without upsizing the neutral due to phase tie.
[/QUOTE] I see, it's a phase thing. Makes sense why there's only one neutral for a 240 VAC appliance.
The neutral serves as the return path for each phase but the phases peak in different time domains, like a time share for multiple phases!
 

Supervstech

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No.
It shares equally the load on both phases, so with 20Amps on each hot to neutral circuit, it need only be rated for the 20 amp load...

Individual circuits must have a 20 amp neutral conductor for each 20Amp hot, but multi wire can share the conductor without upsizing the neutral due to phase tie.
I see, it's a phase thing. Makes sense why there's only one neutral for a 240 VAC appliance.
The neutral serves as the return path for each phase but the phases peak in different time domains, like a time share for multiple phases!

correct. Phase shift balances the neutral load.
 

Supervstech

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Are you saying that we exist on multiple planes simultaneously? If so, do you think I can get one of my other selfs to wire me some money?
Unfortunately, no... as that would unbalance the entire system and collapse the whole thing.

ya gots ya make do.

sorry.
 

Abby Smith

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I would not use a double pole for two seperate circuits. One reason is the mechanical force to keep the breaker closed is double that of a single breaker (harder to trip, i'd assume?). I just don't see the reason to even bother doing it that way?

It is very commonly used in 220V AC systems. Typically L1 and L2 are through circuit breakers and Neutral is permanent. I won't go in details about that because it isn't relative to the question.

I'm not 100% sure why it is done for DC circuits, maybe for electrical isolation? You don't want the ground to gain voltage through a reactive component like a capacitor, but that's just a guess.
 
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