Combining two 120v circuits

[John Kogel]

A client has two 120 volt 15 amp circuits going from his breaker panel to a detached cottage, what we call a garden cottage. I called out the use of a portable space heater. He should install a 120 volt wall heater for safety.
He wants to know if he can install a 240 volt baseboard heater by combining the two feeders in a junction box. I agree he can get 240 volts this way because the breakers are on opposing bus bars. But I believe this is prohibited by the Canadian EC. He needs to install a new 240 feeder and a breaker panel if he wants 240 volts in the cabin. What does the NEC say about this?
What is the reasoning for not allowing the two branch circuits to be combined downstream?

[Jim Port]

The NEC limits an outbuilding to one circuit or feeder. A MWBC counts as one circuit.

[Chris McIntyre]

Why combine the circuits? Could you not use a double pole breaker on one of the circuits for the 240v heater, or is the baseboard heater 120/240?

[Jerry Peck]

The NEC limits an outbuilding to one circuit or feeder. A MWBC counts as one circuit.

Jim,

(bold and underlining are mine)
"The NEC limits an outbuilding to one circuit or feeder."

I must have missed that part, which section is that? Thank you.

[John Kogel]

Why combine the circuits? Could you not use a double pole breaker on one of the circuits for the 240v heater, or is the baseboard heater 120/240?You are right, Chris. The load has to be kept below 15 amps, not hard to do.

The CEC allows for ONE 15 amp branch circuit to a detached building. These guys got two somehow. :confused:
I checked the pics and it turns out this guy has a 240 volt circuit, not presently in use in the cabin.

[John Kogel]

I'll ask a different question.
'May' a 240 volt circuit be supplied by two separate 120 volt circuits, on single, adjacent breakers, by bringing the far ends together in a junction box?
He'll have 120 v appliances on two branches and a 240 volt heater at the ends of the two branches.

[Jim Port]

Jim,

(bold and underlining are mine)
"The NEC limits an outbuilding to one circuit or feeder."

I must have missed that part, which section is that? Thank you.

225.30. I could have worded this a little more clearly.

[Jerry Peck]

225.30. I could have worded this a little more clearly.

You mean like the part which says: "unless" ... got it now. :D

[Jim Port]

I was more referring to the one circuit part. Someone may take that as the outbuilding could only have one circuit, instead of being supplied by one circuit or feeder.

I doubt that any of the conditions in (A) through (E) would have applied so I did not even mention them.

[Jerry Peck]

I was more referring to the one circuit part. Someone may take that as the outbuilding could only have one circuit, instead of being supplied by one circuit or feeder.

I doubt that any of the conditions in (A) through (E) would have applied so I did not even mention them.

Got what you mean now:
- Instead of 'only one circuit', you were meaning:
- - The outbuilding would most likely be supplied by only one feeder ... but that the outbuilding is allowed to have multiple circuits originating from the panel supplied by that one feeder set.

Yes, I was thinking you were going with the 'one circuit' and did not realign my thinking with your followup 'one circuit or one feeder' comment until now.

Thank you for clarifying what you were meaning.