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Best option for wiring 110v. in-floor radiant heat on existing 220v. circuit?

Best option for wiring 110v. in-floor radiant heat on existing 220v. circuit?

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  #1  
Old 09-03-16, 02:41 PM
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Best option for wiring 110v. in-floor radiant heat on existing 220v. circuit?

Location is USA, Idaho. Have unused 20 amp 220v. water heater circuit (converted elec. water heater to gas). Am installing in-floor radiant heat mat in the small bathroom I'm remodeling--300 watt system. System came with 110v. thermostat, but 220v. is available. I assume the heating system needs a dedicated circuit.

Seems my options are:
1) Get the 220v. thermostat--hopefully can swap 110v. unit for 220v. for cost of shipping--if not, cost for new thermostat is ~$90. This seems like kind of a waste of capacity, esp. for an older house with a 100 amp main panel.
2) Replace the 220v. breaker with two 110v. breakers, giving me a dedicated 110v. circuit for the heating system, plus a spare 20 amp 110v. circuit for future. I'd hire an electrician to do the work at the panel.

Best choice? Are there other decent options I'm not considering?
 
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  #2  
Old 09-03-16, 02:47 PM
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Your house has 120 volts and 240 volts not 110v/220v.
System came with 110v. thermostat, but 220v. is available.
If the heater is 120v then you should use the 120 thermostat that came with it.
Replace the 220v. breaker with two 110v. breakers, giving me a dedicated 110v. circuit
Yes, replace the double pole breaker with two single pole breakers or one single pole and a blank insert. A 300 watt heater would only need a 15 amp breaker and #14 wire.
 

Last edited by ray2047; 09-03-16 at 03:13 PM.
  #3  
Old 09-03-16, 03:36 PM
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Thanks for the reply. 120/240 noted. Out of curiosity, do you know why 110/220 is a common misconception? Is it an older standard?
 
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Old 09-03-16, 04:17 PM
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You will only have the capability of one circuit from the old cable. The two conductors give you a hot and a neutral. It should also have a ground.
 
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Old 09-03-16, 05:44 PM
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do you know why 110/220 is a common misconception?
When Westinghouse started promoting AC instead of Edison's DC he made it the same voltage as Edison's just so it would seem familiar but AC is better at higher voltages so gradually it was increased over the last 100 years.
 
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Old 09-04-16, 06:13 PM
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2) Replace the 220v. breaker with two 110v. breakers, giving me a dedicated 110v. circuit for the heating system, plus a spare 20 amp 110v. circuit for future. I'd hire an electrician to do the work at the panel.
Pay special attention to post #4 by pcboss, he is correct. You have no neutral in a 240 volt circuit, just two insulated conductors and one ground; probably one black and one white and one bare ground. You CANNOT get two 120 volt circuits from this cable!
 
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Old 09-04-16, 07:16 PM
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A 300 watt floor would not require a dedicated circuit.
 
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