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I have two baseboard heaters to install on a 240V, 20A circuit. One heater is 1500w and the other is 2000w.

From my panel, I leave the 20A breaker with 12/2 wire to reach the first baseboard. Obviously I will be waiting for my electrician to come and do this but I am curious as to how both heaters will be plugged.

Will these be plugged in series? If so, how does he do this?

P.S: Located in Quebec, Canada

  • @Machavity In Canada – Alex Jan 21 '19 at 19:56
  • When wiring in a series, if the wattage and voltage of each heater is not equal, the heaters will not split the total voltage equally. It would probably be best to wire them in parallel, as only the voltage would need to be the same. Additionally, when wiring heaters in a series, if one has an issue it also affects the other heater. – Jerry_Contrary Jan 21 '19 at 20:02
  • Next question: In CA they typically use 120v. How are you getting 240v on one line? Normally I'd expect to see a split phase over two lines – Machavity Jan 21 '19 at 20:09
  • @Machavity 20A double breaker brings the voltage to 240V – Alex Jan 21 '19 at 20:21
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You would not normally wire two heaters that are rated for 240VAC operation in series on a 240VAC power source. Instead they would be connected in parallel along a daisy chain of wiring like shown here. Note that the below does not depict the safety ground wire connections.

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The cables are in sequence. The wires are in parallel.

The cable will have ground and two hot wires, we'll call them black and red. The "red" wire may be the white wire taped red, or even taped black. Doesn't matter which.

Red and black come from the panel, stop at heater 1, and continue to heater 2.

At heater 2, they terminate with red and black on opposite poles of the heater.

At heater 1, red and black are each tapped. These red and black taps go on opposite poles of the heater.

Don't forget a branch for your thermostat. That must come off the first heater in the chain. It should be 12/3 cable so you have a chance of upgrading to a smart thermostat later. (the third wire isn't neutral, it's always-power for the 'stat). I'm not sure of that's required by Code for 240V heaters, or for Canada, but do it anyway - you'll thank me later :)

You don't want thermostats at the heater, because you want the heat switched based on the room's temperature, not the heater's. Right at the heater is obviously much warmer than the rest of the room. Even a remote thermostat can be thrown off by the heating that occurs inside its wire connections. The cure there is go with a 24V/relay/low voltage system, as a bonus that lets you use modern 'stats like the Nest.

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Loads are generally connected in parallel across the 240 Volt mains. The 1500 Watt heater draws 1500/240 = 6.25 Amps and the 2000 Watt heater draws 2000/240 = 8.33 Amps. Together these loads draw 6.25 + 8.33 = 14.58 Amps, which can safely be serviced by a 20 Amp breaker and 12/2 wiring, provided nothing else is connected to this branch circuit. Each heater must also be grounded.

  • I'm pretty visual ... Is there a diagram of such parallel wiring? – Alex Jan 21 '19 at 20:22

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