8 Comments

Kelly – seeking clarification of “Two Cords”.

Normally, 220/240 is supplied via a single cord: two hots (120 each), with a ground wire – in the vernacular this is 12/2, with ground (12 guage – rated at 20amps, 2 hot (if you’re running 220/240) or one hot & one neutral (if you’re running 110/120). The ground wire exists in either case. When you want to support a 220/240 load, such as a dust collector, and support a 110/120 load with the same wire, you would need a 12/3, with ground – the extra wire is the white neutral – you would wire two hots to the 220/240 device, and use one of these ‘leads’ plus the white to support the 110/120 device.
The term “two cords” leads me to believe, perhaps incorrectly, that you’ve supplied 110/120 from two different wires to drive a 220/240 load. If this is the case, you may want to rethink this – my guess is it doesn’t meet local code requirements…
Again, just seeking clarification.
MJCD

MJCD:
“you would wire two hots to the 220/240 device, and use one of these ‘leads’ plus the white to support the 110/120 device”
I have been tempted to the that for a while but I chickened out for fear of current imbalance. Is there such a problem?

Consider the application. You have to get the two hots and ground to the [remote] switch, which breaks both hots, if 240, or the hot and neutral, if 120. Then you have to return it to the motor. As such, you either need two cables, or one with five conductors.

The collector [currently] operating off 120 could have been altered with a single conductor, just as you would a household light, but a second would have to be added when the collector was switched for 240 operation. Might as well do it now, while everything was open, rather than reinvent the wheel later.

Another side note: Other than extending the position of the switch, wiring is exactly as Jet sends them out. As such, there would no more current imbalance than if you plugged the units in as they came from the factory.

I have a similar question/situation. I currently have an outlet connected to my table saw switch so that my shop vac comes on simultaneously. Both are 110v. I’m considering converting my saw motor to 220 and I want to keep the same setup. If I run 12/3 and connect one of the switch poles to the outlet, it can be done. However, the “neutral” for 220 operation is the other hot leg. Therefore I’m worried that the saw motor may back feed the outlet which could damage my vac. I reached out to an electrical engineer friend just now. Will advise later what he says.

Lanwater:

No imbalance. For a 220 load, each hot acts as both a neutral AND a hot (the current ‘returns’ to the electrical box in an Alternating sequence). In a 110 load, you need the white to provide a return to the electrical box. I have several circuits wired this way, and it is per-Code.

Kelly – I’ll defer to you on this. Suffice it to say that any 220/240 load has to be supported by the same breaker.

Brian – if you run 12/3, with ground, you have two hots, the neutral and ground; so the two hots support the 220 (the neutral is not used); the 110 is supported by one hot and the neutral..
MJCD

My electrical engineer friend said it’s OK. I was worried about phasing from the other hot leg.

ditto