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How can I on-off-on a 30 amp 10 gauge line with an ac switch?

How can I on-off-on a 30 amp 10 gauge line with an ac switch?

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  #1  
Old 09-26-13, 11:46 AM
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How can I on-off-on a 30 amp 10 gauge line with an ac switch?

I am wired for a hot water heater off a 30 amp breaker in my panel, I want to use the same circuit for an electric dryer (old plug type) but not at the same time. I need to switch off the circuit at the hot water heater and turn on that same circuit when using the clothes dryer at that spot, then back again. (The dryer and heater are physically right next to each other) What kind of switch do I need, DPST?, and how do I wire it? Thanks
 
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Old 09-26-13, 12:25 PM
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I am wired for a hot water heater off a 30 amp breaker in my panel, I want to use the same circuit for an electric dryer (old plug type) but not at the same time.
You probably can't. The water heater requires a 30 amp 240 volt circuit and the dryer requires a 30 amp 120/240 volt circuit. The water heater circuit likely has two insulated conductors and a ground, but you need three insulated conductors and a ground for the dryer (1 Blk, 1 Red, 1 Wht and 1 bare or Grn ground). Your best bet is to install a new circuit with 10-3 NM B cable.
 
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Old 09-26-13, 12:37 PM
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Thx Joe, my dryer has a 3 prong plug, would that work?
 
  #4  
Old 09-26-13, 12:51 PM
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Your water heater is most likely wired with 10/2 NM and that has NEVER been allowed for a 3-wire dryer.

You can use a 3 wire for a dryer only if it is existing, otherwise it needs a 4 wire.
 
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Old 09-26-13, 03:51 PM
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Yes the hot water heater is wired with 10/2, black, white, and bare ground. Pre 1995, how did they wire the 3 prong plug dryer cord,220v, to the breaker box?
 
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Old 09-26-13, 04:04 PM
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Used SE cable or some older 10/3 had 2 hots and a neutral.
 
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Old 09-26-13, 06:21 PM
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Yes the hot water heater is wired with 10/2, black, white, and bare ground. Pre 1995, how did they wire the 3 prong plug dryer cord,220v, to the breaker box?
Most likely they used 10-3/G NM cable and just didn't use the ground. 30 years ago they would have used 10-3 Plain NM cable, it had no ground, just 1 Blk, 1 Red and 1 Wht.
 
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Old 09-26-13, 09:10 PM
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30 years ago they would have used 10-3 Plain NM cable, it had no ground, just 1 Blk, 1 Red and 1 Wht.
Maybe a little earlier than that. All of the NM that I ran when I rewired our old house, starting in 1982, had a ground wire in the cable. The only noticeable difference that I remember between that cable and what we run today was that the jacket was white for all gauges.
 
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Old 09-27-13, 07:39 AM
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Maybe a little earlier than that. All of the NM that I ran when I rewired our old house, starting in 1982, had a ground wire in the cable. The only noticeable difference that I remember between that cable and what we run today was that the jacket was white for all gauges.
From what I recall in the '70s and early '80s, NM cable was available either with a ground or plain, with no ground, but some supply houses only stocked the NM cable with the ground.
 
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Old 09-27-13, 08:25 AM
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To get back on topic:
my dryer has a 3 prong plug, would that work?
No. Since there is no existing wiring that will work a new cable must be run that is compliant with current code and the dryer cord must be changed to four prong. The cable will need to be 10-3 NM-b on a 30 amp two pole breaker. The bonding conductor will need to be removed from the dryer terminal block neutral connection when the four wire cord set is installed.
 
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