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Old 07-11-2011, 12:30 AM   #31
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Originally Posted by kbsparky View Post
Interesting that in a different message from you when you show the actual caculations you state thus:




In one message, you stated a 35 Amp breaker can be used, but in another one, only a 25 Amp breaker is needed. Which one did you intend?
The first message is the original post. The second message is from a later post where I stated that the exception is not applicable but if it could be what the new calculations would be.

If 430.6(A)(1) exception 3 could be applyed then the lesser breakers would be needed. Since the exception does not apply it could be the larger breakers. But it cannot be used.

I will admit that the large breakers in my original post are shocking. But that is what the NEC calls for. If I had to install this in the field I would start with smaller breakers and if they didn't hold increase as needed. Two seperate circuits are still required. They both could be #14 though.

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Last edited by electures; 07-11-2011 at 12:33 AM.
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Old 07-14-2011, 10:03 PM   #32
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Insinkerator 5
6.9 x 125% = 8.625 amps. #14 awg is needed.

6.9 x 250% = 17.5. A 20 amp breaker can be used.

Insinkerator 5X
8.1 x 125% = 10.125. #14 awg is needed.

8.1 x 250% = 20.25. A 25 amp breaker can be used.
Now I'm a complete arm chair electrician when it comes to these things...but something stands out here to me. Doesn't code also state that the max amperage on a 14 gauge wire is 15 amps? If you are "protecting" a wire that couldn't handle the amperage allowed by the breaker in the first place what good is the breaker doing?

It'd be like putting a 10 amp fuse on a 22 gauge wire....
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Old 07-14-2011, 10:57 PM   #33
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Now I'm a complete arm chair electrician when it comes to these things...but something stands out here to me. Doesn't code also state that the max amperage on a 14 gauge wire is 15 amps? If you are "protecting" a wire that couldn't handle the amperage allowed by the breaker in the first place what good is the breaker doing?

It'd be like putting a 10 amp fuse on a 22 gauge wire....
240.4(G) allows 20 amps on #14
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Old 07-14-2011, 11:07 PM   #34
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The 3/4HP will need a dedicated #14 circuit with a 35A breaker.
Quote:
8.1 x 250% = 20.25. A 25 amp breaker can be used.
Quote:
240.4(G) allows 20 amps on #14
So are we going with a 20 amp circuit breaker for both then? Or are we going to potentially overload the wire with a 25 or 35 amp breaker?

Personally I'd go with two #12 circuits on 15 amp breakers... (20 for the GD if it tripped the circuit breaker, but I don't think it would.)
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Old 07-15-2011, 12:16 AM   #35
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So are we going with a 20 amp circuit breaker for both then? Or are we going to potentially overload the wire with a 25 or 35 amp breaker?

Personally I'd go with two #12 circuits on 15 amp breakers... (20 for the GD if it tripped the circuit breaker, but I don't think it would.)
The conductors are not going to be overloaded by using a 25 or 35 amp breaker. The NEC allows this for motors.

There is nothing wrong with #12 on 15 amp breakers.
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Old 07-15-2011, 09:15 AM   #36
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The conductors are not going to be overloaded by using a 25 or 35 amp breaker. The NEC allows this for motors.
NEC 240.4D(4) seems to state that having other than a 15 amp breaker on a #14 circuit is not allowed. Up to a 20 amp breaker on #12.

But I guess we will just agree to disagree.
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Old 07-15-2011, 03:14 PM   #37
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NEC 240.4D(4) seems to state that having other than a 15 amp breaker on a #14 circuit is not allowed. Up to a 20 amp breaker on #12.

But I guess we will just agree to disagree.
(D) Small Conductors.
Unless specifically permitted in
240.4(E) or (G), the overcurrent protection shall not exceed
that required by (D)(1) through (D)(7) after any correction
factors for ambient temperature and number of conductors

have been applied.

240.4(G) refers back to 430 which allows higher ampacity on motor branch circuit conductors. Article 430 is one of the most misunderstood atricles in the NEC. At least you didn't call me "ludicrous".
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Old 07-15-2011, 03:33 PM   #38
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Originally Posted by electures View Post
The conductors are not going to be overloaded by using a 25 or 35 amp breaker. The NEC allows this for motors.

There is nothing wrong with #12 on 15 amp breakers.
Show me just one(1) Jersey electrician that sizes GD circuits in the manner you demand. It's just nuts.
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Old 07-15-2011, 04:40 PM   #39
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That is TOTAL BS. You do not calculate residential appliance motor circuits using motor calculations.
Read NEC 430.6 in totality. Especially the exceptions.
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Old 07-15-2011, 05:49 PM   #40
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(D) Small Conductors.
Unless specifically permitted in
240.4(E) or (G), the overcurrent protection shall not exceed
that required by (D)(1) through (D)(7) after any correction
factors for ambient temperature and number of conductors

have been applied.

240.4(G) refers back to 430 which allows higher ampacity on motor branch circuit conductors. Article 430 is one of the most misunderstood atricles in the NEC. At least you didn't call me "ludicrous".
Like I said I don't know the NEC very well, but I do have a degree in electrical engineering, so I have a fairly good grasp of power. From everything I looked at in Article 430 it seems to imply a lot of scenarios that are vague at best. It would be nice if a lot of that Article was rewritten to specify if you are dealing with 3 phase vs. 1 phase and industrial vs. residential.

I can certainly see how a 3 phase motor setup using #14 wire could require a 25 or 35 amp breaker in order to work. In a single phase environment however it looks like a 35 amp breaker would be over kill on a motor that only has a plate rating of ~8 amps, at least for residential use.

This is kind of where I feel like Article 430 seems to drift off and becomes unclear. Even if the GD was a 1HP unit, I (personally) wouldn't put it in the same class as a 1HP industrial motor that could be rewired into different configurations.

While 35 amps over 50 ft or so of #14 wire isn't going to result in the wire getting hot enough to set the house on fire, I would be more concerned with wire connections providing excess resistance and overheating.
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Old 07-15-2011, 06:36 PM   #41
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Originally Posted by bcsizemo View Post
Like I said I don't know the NEC very well, but I do have a degree in electrical engineering, so I have a fairly good grasp of power. From everything I looked at in Article 430 it seems to imply a lot of scenarios that are vague at best. It would be nice if a lot of that Article was rewritten to specify if you are dealing with 3 phase vs. 1 phase and industrial vs. residential.

I can certainly see how a 3 phase motor setup using #14 wire could require a 25 or 35 amp breaker in order to work. In a single phase environment however it looks like a 35 amp breaker would be over kill on a motor that only has a plate rating of ~8 amps, at least for residential use.

This is kind of where I feel like Article 430 seems to drift off and becomes unclear. Even if the GD was a 1HP unit, I (personally) wouldn't put it in the same class as a 1HP industrial motor that could be rewired into different configurations.

While 35 amps over 50 ft or so of #14 wire isn't going to result in the wire getting hot enough to set the house on fire, I would be more concerned with wire connections providing excess resistance and overheating.
430.6 (A) (1) exception #3 - correct?

A garbage disposal is an appliance. This article absolutely does apply. Don't see how one can argue it doesn't.
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Old 07-15-2011, 08:13 PM   #42
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Hook `em both to a single 15 Amp circuit. Put a 3-way switch on the 1st one, so if that was turned on, power would be disconnected to the 2nd one.

Betcha you never would want to run `em both at the same time anyways, and something as simple as a $2.00 3-way switch makes them non-coincident loads.
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Old 07-15-2011, 08:13 PM   #43
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430.6 (A) (1) exception #3 - correct?

A garbage disposal is an appliance. This article absolutely does apply. Don't see how one can argue it doesn't.
As far as I am concerned it does apply.
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Old 07-16-2011, 12:20 PM   #44
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Damm -- I thought this was a simple question, lol.
Thanks for everyone's input.
For the record, I decided to put both on a single 20- with 12 guage wire. It's a residential installation. I'll update you all it it fails inspection, burns down, etc.
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Old 07-16-2011, 07:52 PM   #45
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Damm -- I thought this was a simple question, lol.
Thanks for everyone's input.
For the record, I decided to put both on a single 20- with 12 guage wire. It's a residential installation. I'll update you all it it fails inspection, burns down, etc.
It was and the answer was simple also. Until the experts got hold of it.

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