Old 04-04-01, 05:42 PM
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The max breaker size does say 30a on ac unit.
Old 04-05-01, 03:48 AM
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so it would be to code, listing, and unit rating to change out your 20 to said 30!
Old 04-05-01, 06:22 PM
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Just to warn people from increasing your fuse or breaker size allowing that breaker or fuse to have a rating in amp more than the rating of the ampacity of the conductor it protects.

Wirenuts told him that he can have a 30 amp breaker because on a previous post on this project told us he had a 30 amp rated wire.

Good Luck

Old 04-06-01, 10:28 AM
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Location: Fayetteville, NY, USA
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A couple specifics so that people can determine this themselves. The NEC requires specific wire gauges to be used based exclusively on what size breaker is protecting the whole circuit.

Three common circuit breaker sizes and their corresponding wire gauges:

15 amp breaker: #14 min.

20 amp breaker: #12 min.

30 amp breaker: #10 min.

Obviously, the smaller the gauge number the larger the wire diameter, and thus the more amps it can carry.

All the wiring in a circuit must be of the minimum sizes listed above for that size breaker or you cannot increase it. If, for example, you have a 15 amp breaker and a set of #12 wires goes from the breaker to various areas of your home, but you find that a couple receptacles on that same circuit have #14 wire powering them for some reason. Even though #12 wire is connected to the breaker you cannot increase that breaker to 20 amps. Theoretically, you could plug a 20 amp power tool into that receptacle that's wired with #14 and overload that wire. Wire will try to carry as many amps as you ask it to, but it will heat up when it goes above the number of amps it is rated to safely carry. This heat is what causes many house fires. The 15 amp breaker will not permit more than 15 amps to head out over those wires, so the wire is safe.

So, if you are thinking of increasing the size of a breaker that keeps tripping, you should very carefully determine if all the wiring on that circuit is rated for the larger breaker and only change it if the answer is unequivocally YES.

For you fusebox owners out there please note: If you have knob & tube wiring on any of your present circuits, you should not install a fuse of greater than 15 amps on any such circuits. Knob & tube is typically 14 gauge, but was made before gauge numbers were printed on the insulation, so you can't tell. If you get nuisance tripping, such as when you plug in your hair dryer and the fridge kicks on, you can install time-delay fused of 15 amps. This type will permit the momentary increase to exceed 15 amps but will blow if the increase is continuous. They will blow before the wire has a chance to overheat. Unfortunately, many, many people just buy bigger fuses and think the problem went away 'cause the fuses don't blow anymore. Running down to the basement to change a fuse a couple times a month is nothing compared to the inconvenience of replacing ALL YOUR STUFF! And you don't even want to think about loss of life.

Until last year I had a fusebox, and I practiced what I'm preaching. The idiots that owned my home before me had THIRTY AMP FUSES protecting knob & tube circuits. Surprises me that I ever got the opportunity to buy it!

So, be safe out there!


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