I am wondering if a multi wire shared neutral circuit is considered a 240v circuit.
I ask because in the code it says that AFCI breakers are not required on 240v circuits. A 240 20amp breaker costs 16 dollars, a 240v 20amp afci costs 216 dollars. Is a 220 breaker safe on a multi wire circuit, will it trip as quickly as two single breakers?
I would just add a new wire and split the circuits (my first choice) but my attic is full of insulation and I can't see how I can remove enough to put a raceway on the rafter tops. The problem is I have a 4 in 12 roof and have added insulation 4 times over the years to keep up with new standards so I have insulation batts going two directions and one layer of blown in insulation. Does anyone have any tricks on how to work around the insulation?
Would I have to de rate the wires in conduit in the attic?
Best Answer
You could use a subpanel.
I'm assuming you have a series of 120V receptacles on this circuit, at 20A or 15A.
You would keep the 20A 2-pole breaker on the main panel, and the 12/3+G cable.
At the other end, put a very small load center. You can use a "main lug" type, 2-circuit, 4-space. They're under $20. For example: http://www.amazon.com/dp/B000BPOROY/
Then you can put AFCI breakers in this subpanel to branch out as needed.
I haven't gotten a reliable answer as to whether 20A subpanels are allowed in code (30A may be a minimum), but the electrical theory is sound.