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Home Depot's 30A circuit breakers are available in double pole or single pole embodiments. A new electrical line is to be installed for a 240V 30A dryer: it will require a 30A 240V rated circuit breaker.

What is the line of thinking that determines whether a double pole or single pole breaker is used? What is best practice and why?

Update: a double pole is used for 240V high current applications. Maybe this is because of two 120-Volt phases?

Any feedback or edits (preferred) to the question are appreciated.

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  • My understanding is you need double pole for 240 volts, but you can have a 30 amp 120 volt circuit with a single pole(not common), double with another single pole to make 240 volts. Buy two singles or one double.
    – crip659
    Aug 14, 2022 at 0:06

3 Answers 3

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To provide a 240V circuit, you must have a two-space, two-pole breaker.

A single-pole breaker obviously can supply only 120V loads, as it has only one terminal.

Single-space "tandem" breakers won't do because both halves will be on the same leg of your service, giving 0V difference between the two load terminals. Your dryer motor and light might work, but the heating element will do nothing. You'd also run the risk of overloading neutral.

There are some cases (mostly multi-wire branch circuits) where it is/was legal to handle-tie two adjacent single-pole breakers, but that's not relevant here. The dryer is a mixed 240V/120V load and requires common trip which is only available from a two-pole unit. It should be easier (and maybe cheaper) to just get the two-pole unit (instead of two singles plus a handle tie).

This is purely due to voltage, and has nothing to do with current. You can have two-pole 15A breakers, two-pole 200A breakers (or more), and many increments in between. It's true that single-pole breakers over 30A basically don't exist, but that's because delivering thousands of watts of power is more efficient at 240V (voltage drop is less of a factor), not because it's not possible.

Finally, "Home Depot" is not a breaker type. You must use breakers that are specifically listed for your breaker panel. Many will appear to fit, but will actually arc and destroy the bus.

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  • Thanks for the good explanation. It would seem that that a breaker with two nodes are required: one for each 120V leg? Thanks for the advice to use the breaker specifically listed for the breaker panel. I would hate to destroy the bus or worse: start a fire.
    – gatorback
    Aug 14, 2022 at 0:30
  • Yes, you need a two-pole (two space) breaker for your dryer circuit.
    – nobody
    Aug 14, 2022 at 0:41
  • This (and the question) are of course locale-specific to USA/Canada and perhaps a few other places that use the USA/Canada electric distribution model. Most of the world a single-pole breaker is 220-240V 50Hz...
    – Ecnerwal
    Aug 14, 2022 at 14:00
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30A/120V breakers are practically useless. I bought a bunch by accident, and there's no application for them except small travel trailers (TT30 outlets).

To understand what the 1-pole and 2-pole thing is all about, you need to understand the North American approach to 120V and 240V power. This video teases Europeans but it gets the point across very well. Watch it and I think your eyes will be opened.



What's the deal with handle-ties? Fairly simple. Breakers have a feature called "Trip-Free": they will trip even if the handle is held in the "on" position. (e.g. a fire alarm breaker might be locked "on").

The direct result of "Trip-Free" is that handle ties are NOT a reliable way to get both sides to trip if one side overloads. For that, you need a 2-pole breaker that has an internal mechanism to guarantee common trip.



So what are handle-ties for, then? Well, not every load needs common trip. Common trip is only needed when a 240V load also takes a neutral. Dryers, ranges. (the problem is if one side tripped, the effect would be to put the 240V section and the 120V section in series but still energized).

Straight 240V loads (water heater, A/C) don't have a risk of that so they don't need common trip. Also, Multi-Wire Branch Circuits or MWBCs aka shared neutral circuits don't need common trip if they don't serve 240V loads.

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  • Thank you: the video enables visualization of the alternating 120V phases presented at the breaker slots. This is visualized at youtu.be/jMmUoZh3Hq4?t=559b. I am having a little difficulty following the paragraph "What the deal with handle-ties", however, I think that the bottom line is that both poles must be tripped as a pair via some internal mechanism (the fuse will have only one external switch).
    – gatorback
    Aug 14, 2022 at 12:35
  • Also useful for large UPSes. ;^) (though it is amazing how often I have to get someone to put in the correct 5-30L instead of the 5-20L they slapped in there without paying attention...they look similar, but don't fit the other plug quite deliberately.)
    – Ecnerwal
    Aug 14, 2022 at 13:57
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You need two single breakers or one double breaker for 240 volts, in the North American electrical system.

You can use a double pole breaker for two(or half of a breaker for one) 120 volts circuits.

Most double pole breakers are just two singles made as one.

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    No, most double-pole breakers are not just two singles stuck together. The have an extra "common trip" mechanism added that will cause an overload on just one pole to disconnect both poles.
    – nobody
    Aug 14, 2022 at 1:20
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    Crip, you're a pretty bright guy and usually your posts are good, but in this case you gave bad advice. No way should a dryer be on 2 30 amp 120v breakers, even if handle tied. like "nobody" said, a 240 v breaker will trip both poles if overloaded. That may or may not happen with 2 120v breakers. Aug 14, 2022 at 2:01

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