30 amp 120 volt

[Aeyteam]

What prevents a 30 amp 120 volt circuit to be broken down to (2) 15 amp 120 volt circuits at a 2 pole breaker disconnect?

 

[infinity]

Nothing, the 30 amp circuit then becomes a feeder.

 

[MAC702]

It could even serve two 20-A circuits from such, assuming load calcs allow it.

 

[Aeyteam]

It could even serve two 20-A circuits from such, assuming load calcs allow it.

It was always taught the smallest circuit(feeder) that could be broken down to a subpanel is a 30A 120/240V feed. It was grilled into our heads over the years that it became practice. I am not finding it in the Code. So what you are saying is there is nothing wrong with taking an existing 30 amp 120v ciricuit into a 2 circuit breaker panel, using a wirenut to feed the same phase to both hot lugs, and leaving the panel with (2) 15 amp 120 volt circuits? I believe you said that was fine but like I said it was not taught that way in our area. Thanks.

 

[infinity]

Not sure who was teaching you that but it's not supported by the wording of the NEC. You'll end up with a 30 amp, 120 volt feeder which is code complaint.

 

[iceworm]

What prevents a 30 amp 120 volt circuit to be broken down to (2) 15 amp 120 volt circuits at a 2 pole breaker disconnect?

As alluded by others:
The 30A cb does have to be able to support the end load.

I don't see any code reason why you couldn't have a panel full (42) of 15A CBs. The loads would have to be .7A or less, non-continuous.

pretty piss poor design - but meets code

 

[ptonsparky]

Using a 200 amp breaker ahead of CBs totaling over 800 amps is done all the time. As long as the calculated or actual load is no bigger than the 200, go for it.

 

[kwired]

As alluded by others:
The 30A cb does have to be able to support the end load.

I don't see any code reason why you couldn't have a panel full (42) of 15A CBs. The loads would have to be .7A or less, non-continuous.

pretty piss poor design - but meets code

If you had 42 circuits and total load never exceeded 30 amps, it doesn't matter if one load is 20 amps and the others never put it over 30. Can even have several 20 amp loads, if arranged that they never run simultaneously.

 

[kwired]

It was always taught the smallest circuit(feeder) that could be broken down to a subpanel is a 30A 120/240V feed. It was grilled into our heads over the years that it became practice. I am not finding it in the Code. So what you are saying is there is nothing wrong with taking an existing 30 amp 120v ciricuit into a 2 circuit breaker panel, using a wirenut to feed the same phase to both hot lugs, and leaving the panel with (2) 15 amp 120 volt circuits? I believe you said that was fine but like I said it was not taught that way in our area. Thanks.

Start off reading in 215.2(A)(1) "Feeder conductors shall have an ampacity not less than required to supply the load as calculated...."

That is about the most general rule - you do have some situations where a minimum feeder size may be required.

 

[electricman2]

A week or so ago, I saw a small loadcenter in an outbuilding fed with a 120 volt, 20 amp circuit. It had 3 15 amp breakers in it feeding lighting and receptacle circuits. Owner said it had worked fine for years.