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I want to add a branch circuit to the control panel using 12/3 wire and protected by 20 amp double pole circuit breaker. Is it safe to connect multiple duplex receptacles 120 volts and 240 volts on the same circuit? In this setup, I'd use black, red, and ground for the duplex 240 volts 20 amp receptacle and I'd use black, white and ground for the other 110 volts 20 amp duplex receptacle.

I live in Ontario, Canada.

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    Can you post a make/model number or photo for said double pole breaker?
    – ThreePhaseEel
    Oct 9, 2019 at 3:29
  • It's the federated pioneer stablok (NC) model NC0220CP. homedepot.ca/product/….
    – Ehab Teima
    Oct 9, 2019 at 11:05
  • Here we go again.
    – JACK
    Oct 9, 2019 at 13:12

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This works, as long as your breaker is common trip (most are)

The mixing of 120 and 240V loads/receptacles on the same multi-wire branch circuit is permitted, provided the breaker is common trip (so that a fault on one leg can't be backfed by the other leg of the circuit via the 240V load(s)). From an electrical standpoint, this is no different from a range or dryer circuit, and the resulting imbalance is not an issue from a safety standpoint.

This is permitted (in the US at least) by NEC 240.4(C) Exception 2:

(C) Line-to-Neutral Loads. Multiwire branch circuits shall supply only line-to-neutral loads.

Exception No. 1: A multiwire branch circuit that supplies only one utilization equipment.

Exception No. 2: Where all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch-circuit overcurrent device.

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  • "this is no different from a range or dryer circuit" - except those are always dedicated circuits. I wouldn't appreciate plugging my desktop into that... Permissible, yes. But a good idea?
    – Mazura
    Oct 10, 2019 at 0:19
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    @Mazura -- not all range/cooker circuits are as dedicated as you think (think of a cooktop + two separate single ovens)
    – ThreePhaseEel
    Oct 10, 2019 at 1:54
  • Thanks for the answer. This simplifies it for me.
    – Ehab Teima
    Oct 10, 2019 at 2:52
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    I have a 240v 4-wire going to a oven/microwave combo. Oven is 240V and the microwave is 120V ....
    – JACK
    Oct 10, 2019 at 17:43
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Just so there is no confusion, I am only answering this question.

Is it safe to connect multiple duplex receptacles 120 volts and 240 volts on the same circuit?

When you say safe do you mean will it cause a burn or shock hazard causing an injury or death? Probably not.

But if you are asking is it safe use this circuit and not cause any damage or failure to the circuit or the equipment used on it? It is not safe.

In simple terms. Using two different pieces of equipment one a 240V and one a 120V on the same circuit will cause an imbalance in the circuit.

Example: One piece of equipment is a 240V motor pulling 4.7A and one the other is a flood light pulling 3.3A. One leg of the 240V circuit is pulling 4.7A and the other leg is pulling 11A. This creates and impedance in the circuit which the causing overheating and an imbalance in the 240V motor reducing its life and over heating in the conductors reducing their life. I know there is more than that, but as I said I want to keep it simple and short.

So, from a design standpoint, it is never a good idea to have multiple voltage device circuits unless all equipment is designed to work in tandem.

Hope this helps.

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    You're going to have to explain that motor example some more. The way you wrote that is simply not true.
    – longneck
    Oct 9, 2019 at 16:20
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    TL:DR (I think): 'It creates a situation where it's likely to be an unbalanced circuit.' ... but nobody really balances a load center anyway, not after it gets installed. That being said, on shear principle and conformity, I'd find another breaker to double tap the outlets on and have the 2-pole by itself as expected.
    – Mazura
    Oct 10, 2019 at 0:08
  • It creates a situation where it can't but not be an unbalanced circuit. Motor runs: balanced. Anytime you use an outlet: unbalanced. ... unless you have outlets on both phases. Again: conformity. If I show up, this not what I'd expect.
    – Mazura
    Oct 10, 2019 at 0:11
  • @longneck - I stand by my answer. You need to explain why it is not true and in terms someone with no background in electrical engineering.
    – Retired Master Electrician
    Oct 10, 2019 at 13:38
  • @RetiredMasterElectrician a 240v motor only has 2 poles. there is no way to unbalance one pole.
    – longneck
    Oct 10, 2019 at 15:42

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