Larger breaker than required

[thomas88]

I am looking at installing a hard-wired device (a UPS). The UPS states that its full load amperage is 35-amps and it should be hard-wired with an 8-guage wire and a 50-amp breaker (240 Volt).

According to CEC, 50-amps would require a 6-guage wire.

Since a 6-guage wire will handle 60-amps, would it be acceptable to have a 60-amp breaker protecting this system? The breaker would protect the wiring to the UPS, but I have no idea what is inside of the UPS for wiring/protection. I already have a 60-amp breaker, so if I can use this, it would be nice.

[twh]

I think you already know the answer to this - I'll confirm it.

You can't use a larger breaker than the name plate requires. That's why it's there.

I think #8 wire was once rated at 50 Amps, and 45 Amp breakers are new. I'm not surprised to see equipment that requires #8 wire and a 50 Amp breaker.

The breaker size is usually listed as a max; but, since you are buying a breaker, anyway, why not buy a 45 Amp one?

[thomas88]

Ok, that makes sense.

However why can you put 20-amp outlets on 12-guage wire in your house, and plug in a 15-amp rated device. The device is only rated for 15-amps max, so if something went wrong, you could end up with 20+ amps going through it before the breaker triped. The wiring in the house would be fine, because it is 12 guage, but the wiring in the device may be much smaller. Wouldn't the same thing apply to my previous situation?

Maybe I have overlooked something here.

[twh]

That's an interesting point.

You can protect wire or equipment with any size breaker allowed in the rules. I am, though, unable to find a rule that requires us to follow the name plate. I'm quite sure it's there; and, if it isn't, what would the limits be?