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?
The Eaton catalog clearly says that the breaker can accept anything between and including #14 - #4 AWG.
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.
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.
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.
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.