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I am hooking up a disconnect for heating air unit. The instructions state use a 25 amp 2 pole breaker with 10-2 wire. The breaker says wire size 14-2. It is an Eaton BR225 beaker. Will it work with 10-2?

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    Are you sure you are reading the breaker correctly? a 25A breaker should never have a 14 gauge wire attached. – ratchet freak Jan 30 at 15:26
  • Can you add a photo of the exact instructions? – DaveInCaz Jan 30 at 20:40
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The Eaton catalog clearly says that the breaker can accept anything between and including #14 - #4 AWG.

Screenshot from Eaton Catalog showing acceptable wire sizes

You should follow the instructions that tell you to use #10, as it will fit the breaker, and will be appropriate for the amps you are running.

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    It should be noted that the chart covers all type BR, 1 inch breakers. It isn't specific to the 25 Amp version. – isherwood Jan 30 at 16:28
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    True. The #14-#4 range is for breakers of 10-50 amp ratings. It indicates to me that they just use the same terminal on all of those, which accepts wires within that range. It's up to you to select the wire that falls within that range AND that is rated for the ampacity of your application, right? – PhilippNagel Jan 30 at 16:31
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No, no, no...

The breaker isn't saying it's for "14/2" Romex cable. It's saying the terminal is able to physically attach #14 through #2 wire.

Whereas the 14/2 cable designation means it has #14 wire and 2 conductors (in house cable ground is counted separately, in cordage it is not).

The ability to fit #14 or #12 is irrelevant to you, unless you are mounting the breaker inside the chassis of a piece of equipment that is not part of any building, or your wiring is being done in a very special set of circumstances unlikely to be seen outside an industrial setting.

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    His wire is 10/2 -- he thinks the breaker is labeled to only take 14AWG for some baffling reason – ThreePhaseEel Jan 30 at 23:49
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One thing people often get wrong about wire sizing for HVAC equipment is that the rules strictly adhere to the usual wire/breaker sizing rules for "normal" wiring. The rules for "normal" wiring state, more or less, a specific relationship between the size of the wire and the maximum size breaker that can be used to protect that wire. For example, 14 gauge wiring must be protected by a 15 amp breaker, but no larger. Similarly, 12 gauge and 20 amp breaker, 10 gauge and 30 amp breaker, and so on.

In the case of HVAC equipment, these hard rules don't necessarily apply. It is often (if not usually) acceptable to use a breaker that is, seemingly, too large for the wire size. For example, our heat pump is connected to our service panel by 10 gauge wiring but is protected by a 40 amp breaker. The specific wiring and protection (breaker) requirements are called out on the equipment data tag on your equipment.

This link gives a pretty good explanation of how this works. Pay special attention to the MOCP vs MCA section.

In your case, I can't say specifically that your breaker can take the size wire you want to use, although @PhilippNagel posted some information that makes it sound like you can connect the size wiring you are using to the size breaker that you have.

Good luck!

  • Thanks for posting this answer, good insight from a different angle, and informative link! – PhilippNagel Jan 31 at 2:58
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Possibly #14 copper wire could be used with a 25-A breaker if it was dedicated to supplying certain loads in which the momentary starting draw was above 20 A, but the running amperage was well below 15 A, e.g., 12 A. But for general use a circuit protected by a 25-A breaker would be wired with 10 AWG copper wire. Follow the instructions for the load you have and use #10 copper wire.

Any statement on this 25-A breaker or in an accompanying leaflet about using #14 wire, must actually be a warning that #14 is the minimum size wire under any circumstances. It cannot be a statement that #14 is allowed in general.

  • isn't that what slow-blowing breakers are for? – ratchet freak Jan 31 at 9:46

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