My old wall heater is 240v. See all the wires from the first photo. The new heater is 120v. See second photo. The green ground wire is on the box. How do I connect the new heater to all that wires coming out of the wall?

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It looks like you have red , black, white & ground. You could connect a 120v unit to the black , white, and ground with the black, white and ground of the heater. This should be 120v if properly wired. The question would be is this the only heater on this circuit? Also what is the wattage of the new heater. A 120v heater will draw 2x the amperage of the same sized 240v unit and the wiring may not be large enough. If the new heater is 1/2 the wattage of the old one using the black or red wire for the line voltage and then white for neutral and bare copper to the ground will work.

  • Thanks Ed. As far as I can tell, the circuit of this bathroom heater is shared by a base board heater outside the bathroom. The wattage of the old heater is 1000w and the new one is 750w. This bathroom heater is on all the time to keep the pipes from freezing. – P. Eng Jan 12 '17 at 11:11
  • Your 750w 120v heater is more expensive to operate than a 1000w 240v heater and produces less heat. The current draw 750/120=6.25 amps whereas 1000/240=4.16 amps. – Tyson Jan 12 '17 at 19:17
  • Since you pay for electricity by the wattage used is really doesn't cost more. Straight heat packs like these are not the same as motor loads that are more efficient at higher voltages. – Ed Beal Jan 12 '17 at 19:29
  • Is it safe to use/connect a 120v heater on a 240v outlet? The circuit is a double breaker of 20 amp each. – P. Eng Jan 12 '17 at 23:22
  • Using 1 side the white & black or red wipe provide 120 at 20 amps of over loaded on 1 leg it will trip the breaker. Since it is a 20 amp breaker the only question is the wire size 12 awg is required. This is similar to a very common circuit called a multi wire branch circuit where the red / white feed one set of 120v outlets and the black white feeds a second set of 120v outlets both circuits share the neutral (white) this configuration is both safe and code compliant with a 240v breaker both single Handel or by using 2 breakers with a listed handle tie. – Ed Beal Jan 12 '17 at 23:57

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