#14 Cu on a 100A breaker

[wwhitney]

I agree it isnt clear, but 240.4 sets a maximum. Then 430 sets a minimum higher than the max, so what to do in that case? I would say the min is now also the max, but they should say that or cover it explicitly somehow.

240.4 does not set a maximum, as the base requirement in the first sentence of 240.4 is "unless otherwise permitted or required in 240.4(A) through (G)." And 240.4(G) tells us that for "motor circuit conductors" Article 430 Parts II through VII control instead.

So that means it's up to Article 430 Parts II through VII to set a maximum. Which 430.62 does, but 430.63 does not.

Cheers, Wayne

 

[don_resqcapt19]

So is the "not less than" language in 430.63 simply a longstanding mistake? Should it be "not greater than" when conductors are sized per 430.24?

Cheers, Wayne

not sure what it should be, but "not less than" is incorrect.

 

[don_resqcapt19]

Other than current limiters for cales, I do not remember ever seeing a true Instantaneous fuse.

I don't think I have ever seen one either, but I think that is what a "motor short-circuit protector" in 430.52(B)(7) is.

 

[jim dungar]

I don't think I have ever seen one either, but I think that is what a "motor short-circuit protector" in 430.52(B)(7) is.

Yes, the codes specifically calls it a fused device, however they do not say it is instantaneous.
It is relatively easy to build an electromagnetic device that has a vertical pickup characteristic. I know of no fuse element with that capability, the ones I have seen have some long time melt point. Maybe the 430.52(B)(7) device has a minimum melt point that is extremely high, kind of like cable limiters?

 

[Little Bill]

Yes, the codes specifically calls it a fused device, however they do not say it is instantaneous.
It is relatively easy to build an electromagnetic device that has a vertical pickup characteristic. I know of no fuse element with that capability, the ones I have seen have some long time melt point. Maybe the 430.52(B)(7) device has a minimum melt point that is extremely high, kind of like cable limiters?

Would a "fast blow" fuse be what they're talking about?

 

[jim dungar]

Would a "fast blow" fuse be what they're talking about?

No, they call that a non-time delay fuse.

 

[ramsy]

No, they call that a non-time delay fuse.

Little Fuse, and other OEM's prefer the term "fast-acting" vs "time delay"
See Time Current Curve on Page 4

 

[ramsy]

not sure what it should be, but "not less than" is incorrect.

430.63 is for OCP only, not conductor size.
"not less than" refers to non-motor loads, before motors are factored into OCP size.

In post #16, wwhitney mixed 430.24 for conductor sizing, with 430.63 for OCP

 

[wwhitney]

In post #16, wwhitney mixed 430.24 for conductor sizing, with 430.63 for OCP

Incorrect, if you mean "mixed up". The two are related issues though, as generally allowable OCPD size depends on conductor size.

The omission in the NEC is that for feeders subject to 430.63, there is nothing that provides an upper bound on the OCPD size. The computation in 430.63 is comparable to the computation in 430.62, and in 430.62 the result is an upper bound. In 430.63, the result is said to be a lower bound. I believe that's a mistake.

Just trying to get my ducks in a row for a PI and checking if I've overlooked something.

Cheers, Wayne

 

[jim dungar]

Little Fuse, and other OEM's prefer the term "fast-acting" vs "time delay"
See Time Current Curve on Page 4

What does the NEC call them?

 

[Tulsa Electrician]

The omission in the NEC is that for feeders subject to 430.63, there is nothing that provides an upper bound on the OCPD size. The computation in 430.63 is comparable to the computation in 430.62, and in 430.62 the result is an upper bound. In 430.63, the result is said to be a lower bound. I believe that's a mistake.

Just trying to get my ducks in a row for a PI and checking if I've overlooked something.

Cheers, Wayne

The way I read it, I agree.

 

[ramsy]

Incorrect, if you mean "mixed up". The two are related issues though, as generally allowable OCPD size depends on conductor size.

The omission in the NEC is that for feeders subject to 430.63, there is nothing that provides an upper bound on the OCPD size. The computation in 430.63 is comparable to the computation in 430.62, and in 430.62 the result is an upper bound. In 430.63, the result is said to be a lower bound. I believe that's a mistake.

Just trying to get my ducks in a row for a PI and checking if I've overlooked something.

Cheers, Wayne

430.63 upper limit appears governed by “other load(s)”

The bottom of Example D8 wont use “Next size up” rule, like my calc in post #4

 

[Sberry]

I did a motor change out a while back. 100 hp. There was a big cab and a small tranny in it for 120. All I can say was that tap wire feeding it looked wayyyyyyyyyyyyyyyyyyyyyyyy tiny. As I recall might have looked it up in the book or forum after. `

 

[wwhitney]

430.63 upper limit appears governed by “other load(s)”

430.63 provides no upper limit.

The bottom of Example D8

Example D8 is not relevant, as it is motors only, and so falls under 430.62, not 430.63.

Cheers, Wayne

 

[jim dungar]

There was a big cab and a small tranny in it for 120.

If this was a Listed controller its internals are not subject the NEC.

 

[Sberry]

No, was field added after by sparkie

 

[tortuga]

The specification in the original question adds a load other than the motor so 430.62 does not apply.

I am not sure how you get that?

430.62(A) A feeder supplying a specific fixed motor
load(s) and consisting of conductor sizes in accordance with 430.24
shall be provided with a protective device having a rating
or setting not greater than the largest rating or setting of the
branch-circuit short-circuit and ground-fault protective device
for any motor supplied by the feeder [based on the maximum
permitted value for the specific type of a protective device in
accordance with 430.52, or 440.22(A) for hermetic refrigerant
motor-compressors], plus the sum of the full-load currents of
the other motors of the group.

The high-level object is a "feeder"
"supplying a" is inclusive, not exclusive.
Then referencing "430.24 Several Motors or a Motor(s) and Other Load(s) ", is a inclusive relative clause since 430.24 is included this "feeder" might carry more than just motors.
Then the terms "specific" and "fixed" are adjectives that function as prenominal modifiers for the noun "motor." not the feeder it can really be any feeder that supplies a fixed motor.

 

[wwhitney]

I am not sure how you get that?

The title of 430.62 is "Rating or Setting--Motor Load". While the title of 430.63 is "Rating or Setting — Motor Load and Other Load(s)." 430.62 only applies when the load is entirely motors and motor driven equipment.

Plus the computation detailed does not include any contribution for other loads, so it had best not apply when there are non-motor loads present. It would make no sense for 430.24 minimum conductor ampacity to include an allowance for other loads (as it does), and then for 430.62's maximum OCPD computation to apply when there are other loads but not include any allowance for those other loads.

Cheers, Wayne

 

[kwired]

Say I have a 240V 2-wire feeder supplying a 1 HP motor (Table 430.248 FLC = 8A) plus a 3A non-continuous non-motor load. It is wired with a 100A breaker (nothing smaller upstream) supplying #14 Cu 90C conductors. What NEC section is violated?

Of relevance are 240.4(G) and 430.63, but I'm not finding a violation.

Thanks,
Wayne

You could have an outdoor feeder tap with no length limitation here but still eventually need to have a branch circuit device in the mix.

 

[tortuga]

The title of 430.62 is "Rating or Setting--Motor Load". While the title of 430.63 is "Rating or Setting — Motor Load and Other Load(s)." 430.62 only applies when the load is entirely motors and motor driven equipment.

In legal and code interpretation, the title of a section cannot limit the plain meaning of the text. See Trainmen v. Baltimore & Ohio R. Co. (1947)
"The title of a statute and the heading of a section cannot limit the plain meaning of the text. For interpretative purposes, they [titles] are of use only when they shed light on some ambiguous word or phrase." -- Supreme Court
430.62(A) pulls in 430.24 with an and "and consisting of conductor sizes in accordance with 430.24"