Compressor & breaker required?

[Robert Galloway]

Maybe what the electrician meant was that a 40 amp breaker wouldn't offer much protection. It would happily deliver enough amps for the motor to fry without tripping.

rhg

CW wrote:

[CW]

The breaker is there to protect the wiring, and that's all. If you believe as you say, anytime you go to use an appliance, turn them all on as that circuit will be underloaded if you don't. Never use a single corded drill in your shop. Best turn on the dust collector too in order to load the circuit. How's your power bill? Things must work in strange ways around your house.

[Robert Galloway]

Isn't the phase angle supposed to change with load? Near 90 degrees at no load (real power minimum) Near 0 degrees at full load Real power close to apparent power?

rhg

Robert B> >

[CW]

It's not intended to protect the motor.

[Greg O]

Make sure the wiring is sized for the twenty amp breaker. It needs to be at least 12 ga. or larger for a long run. If it is on a 15 amp breaker now, I would suspect 14 ga. wire, much too light for a twenty amp breaker. Greg

[DonkeyHody]

I got a new shotgun. I'm only going to shoot at targets that are close until it's broken in so I won't strain it.

DonkeyHody "We should be careful to get out of an experience only the wisdom that is in it - and stop there; lest we be like the cat that sits down on a hot stove-lid. She will never sit down on a hot stove-lid again---and that is well; but also she will never sit down on a cold one anymore." - Mark Twain

[Mike Marlow]

I know you're trying to be wise, but kindly restate this so that it makes a bit of sense.

-Mike-

[Greg]

What he is talking about is the different facets of protection in a motor circuit. The branch circuit breaker is only there to protect from a short circuit. Overload protection is another part of the system and that is what protects the motor. It is also what keeps the wire from overheating. That is why you can have things like #14 wire on a 40a breaker and still be legal. See the diagram at the beginning of NEC 430 to get a better understanding.

[CW]

Thanks Greg. Saved me the trouble.

[Woodchuck]

I used 8gauge w/g to feed my shop which has a 60 foot run and it's protected by a 40amp breaker.

[Mike Marlow]

Not actually. Greg responded with something intelligble while your response both ignored what I had originally posted and jumped way too fast at the chance to post a wise ass comment. Neither of those characteristics served to credit you.

So let me ask you a question - would you connect your 220V tablesaw directly to the main breaker in your panel? Besides the code requirement for a branch circuit, and wire size, why not? Isn't it because circuits are sized to the application?

[Greg]

Maybe we should just tell people to follow the 240.4(D) rule (15a = 14ga, 20a = 12 ga, 30a =10-ga) and ignore the 430 rules altogether since they seem to be over everyone's head. It just isn't what the code allows.

430 "motor" rules do require the circuit to be sized to the motor served.

[CW]

[Robert Galloway]

and... electric clocks aside, for larger items, like your central air, the circuit and the load are usually matched closely enough to keep the load itself from burning up if there should be a problem.

rhg

CW wrote:

[Mike Marlow]

Not at all Greg - I appreciate you mentioning the 430 rule - something I'm not familiar with and can stand to learn from. My reply was more in response to CW's condescending tone than it was related to anything factual about electricity.

[Mike Marlow]

Unfortunately, it's you with the reading comprehension problem. If you didn't suffer this you would have noted my original point. I'm done with this now - you're a waste of time and not at all entertaining.