Weird 2-Phase Wiring
I was looking in the service panel to label all breakers. It has 30A breaker for drier, which is connected to 12-2 BX cable. Two hot wires from the breaker connected to black and white wires and the neutral from the panel is connected to the BX shield of the cable. Looks like professional job….
I was looking in the service panel to label all breakers.
It has 30A breaker for drier, which is connected to 12-2 BX cable. Two hot wires from the breaker connected to black and white wires and the neutral from the panel is connected to the BX shield of the cable. Looks like professional job. I am not an electrician, but this seems strange. I would expect 12-3 wire instead and no link between shield and neutral.
Is this something unusual and should I call electrician to look at it?
I don’t recommend it, but the 220V on 12-2 is common, although counter-intuitive.
phwhite, of course! now i remember this from my engg classes long ago. duhhh
OP: each leg (wire) can carry 30A. So in wattage it’s 30×220=6600w Dryers are typically 4500w heating + a small motor, which is where I got 22A from.
cmu. thanks for explanation. Since there is no drier connected to the outlet at this time, I will just disconnect the whole circuit and come back to the point, whenever the tenant will want to install the drier.
A one more follow up: does 30A 2-phase breaker caries 30A on each phase or on both phases combined?
Cmu, You can only use a common neutral if the circuits that they are supporting are on opposite phases. This way, the current cancels each other out rather than adding up.
You need (if msr) 10/3 bx cable; 12 is for 20A. Metal ground should not be used as neutral, though they are connected together at the box.
From a practical viewpoint, the 2-wire setup may work but it’s not up to code, and the 12 gauge might be marginal…you have to realize that dryers use abt 22A, and also the 20A for 12g is over-specified for safety (for instance you can supply 2 20A circuits with a common 12g neutral, which is then loaded at 40A and is up to code).