Wire amapacities

[Michael Prinsloo]

Where do I get wire ampacities? Also according to one thread for the breaker sizing of the AC or heat pump, you can breaker for the maximum rating and wire for the minimum rating. Where do I find this information?

[James E. Braun, CMI]

I have never seen it in writing but about all heating and cooling contractors say that. It is acceptable in my area.

[Nick Gromicko]

http://www.nachi.org/gallery/electri...ge-ratings.jpg

[Jeffrey R. Pope]

General ampacities are outlined in the link posted by Nick. The NEC (or the Canadian version of the same) will give you much greater detail including wiring requirements for motors and such.

Originally Posted by Michael Prinsloo

Also according to one thread for the breaker sizing of the AC or heat pump, you can breaker for the maximum rating and wire for the minimum rating. Where do I find this information?

This info is available on the data-plate of the appliance.

[James E. Braun, CMI]

The wire size is on the data plate? When did they start doing that?

[Bruce A. King]

These two links and the code book should get you everything you need to know....


http://ecmweb.com/nec/code_calc_072304/


http://www.nachi.org/forum/f19/12-wi...-circuit-5629/

[Jeffrey R. Pope]

Originally Posted by jbraun

The wire size is on the data plate? When did they start doing that?

Not the wire size, the minimum and maximum circuit ampacity.

For instance, the minimum circuit ampacity may be rated at 28.8 amps, so it should be wired with conductors rated for at least 30 amps. Next to that, it will list the maximum breaker or fuse - let's say it says 45 amps.

So in this case, you can have a 45 amp breaker serving 10AWG conductors and the installation would be compliant with both the NEC and the appliance listing.

[James E. Braun, CMI]

Okay, thanks!