Nec 240.15 overcurrent devices

[Jpflex]

240.15 B says circuit breakers must open all ungrounded conductors both manually and automatically, unless permitted in B1, B2, b3, b4

B2 says single pole breakers can serve multi wire branch circuits for line to neutral loads if the breakers have identified handle ties.

However if the ring or tie is available but not installed they still serve as single pole breakers.

Nec does not say the handle ties must be mechanically connected so why require special breakers at all?

if the intent is to disconnect all ungrounded conductors then why not just us 2 pole breakers?

2 same for single phase circuits line to line loads

3 same for 3 and 2 phase systems with ground

 

[jaggedben]

You can use 2 or 3 pole breakers instead of handle ties for MWBCs but the code doesn't require it.

A handle tie is a mechanical connection between the handles of more than one breaker. But it may or may not turn off the other handles if one breaker trips. Many of the manufacturer supplied handle ties I've seen allow one breaker to be in the tripped position while another is on or off, but not one to be on while another is off. So, using handle ties often means that if one pole is turned off manually, all poles get turned off, but if one pole trips the others stay on. Using a 2-pole breaker means that if one trips the customer loses power to all of them.

 

[LarryFine]

The intent is to open all ungrounded poles when manually operated.

You certainly may use 2- and 3-pole breakers when handle ties are required.

 

[don_resqcapt19]

240.15 B says circuit breakers must open all ungrounded conductors both manually and automatically, unless permitted in B1, B2, b3, b4

B2 says single pole breakers can serve multi wire branch circuits for line to neutral loads if the breakers have identified handle ties.

However if the ring or tie is available but not installed they still serve as single pole breakers.

Nec does not say the handle ties must be mechanically connected so why require special breakers at all?

if the intent is to disconnect all ungrounded conductors then why not just us 2 pole breakers?

2 same for single phase circuits line to line loads

3 same for 3 and 2 phase systems with ground

In general a multipole breaker will be more expensive than single pole breakers with handle ties.

 

[jaggedben]

In general a multipole breaker will be more expensive than single pole breakers with handle ties.

Until you count the extra trip to come back with handle ties because those are never on the truck.

 

[electrofelon]

In general a multipole breaker will be more expensive than single pole breakers with handle ties.

Quite a bit too. A 3 pole 20A breaker is somewhere around $65. A single pole is what $7?

 

[roger]

Until you count the extra trip to come back with handle ties because those are never on the truck.

Yeah, but in reality a small nail or piece of #12 is the better way.

 

[don_resqcapt19]

Until you count the extra trip to come back with handle ties because those are never on the truck.

With breakers that have holes in the handles, I have been known to use 6-32 screws and nuts
With one major brand of identified handle ties, the screws work much better than that brands handle tie.

 

[Jaybone812]

You can use 2 or 3 pole breakers instead of handle ties for MWBCs but the code doesn't require it.

A handle tie is a mechanical connection between the handles of more than one breaker. But it may or may not turn off the other handles if one breaker trips. Many of the manufacturer supplied handle ties I've seen allow one breaker to be in the tripped position while another is on or off, but not one to be on while another is off. So, using handle ties often means that if one pole is turned off manually, all poles get turned off, but if one pole trips the others stay on. Using a 2-pole breaker means that if one trips the customer loses power to all of them.

Yup . 210.4(b)says all fbe ungrounded conductors must have the ability to be simultaneously disconnected , doesn’t say anything about a common trip

 

[Jpflex]

For the purpose of the journeyman test, it seems tedious to memorize which circuits can use single pole breakers and i dint see the purpose entirely of this code