Breaker question

[Gerry Grzadzinski]

If 30 amps is the max current draw, from my experience with wide belt sanders, you probably won't get anywhere near that, unless the starting load is very high.Last job I worked at, the sander had an ammeter on it, and even with fairly heavy passes, the current draw didn't go up that much.

I just scanned through this, so sorry if it's already been mentioned.

[Roger Frazee]

Craig

I see I made an error in earlier posts about 22 amps needing 10 awg minimum if using nm-b (romex). That should be 12 awg not 10. 12 awg is rated 25 amps in the 60C column of table 310.16. Sorry for my mistake. I have a later post in reply to Alan Schaffter that corrects the earlier examples.

[Craig D Peltier]

If 30 amps is the max current draw, from my experience with wide belt sanders, you probably won't get anywhere near that, unless the starting load is very high.Last job I worked at, the sander had an ammeter on it, and even with fairly heavy passes, the current draw didn't go up that much.

I just scanned through this, so sorry if it's already been mentioned.

When the G9983 Grizzly sander starts the amp meter bumps up to 30 for a nanosecond.

[Rod Sheridan]

Interesting!

No intent to be contentious, but for my own edification, assuming I have a properly configured 240v/30amp circuit, can you give some examples of loads requiring less than 30 amps that cannot be plugged into that circuit. Also assuming the plugs are compatible with the receptacles.

Hi Tom, I have a Hammer A3-31 jointer planer.

Maximum overcurrent protection allowed is 16 amperes, so it cannot be plugged into a 30 ampere receptacle.

regards, Rod.

[Charlie Knauer]

Craig

I see I made an error in earlier posts about 22 amps needing 10 awg minimum if using nm-b (romex). That should be 12 awg not 10. 12 awg is rated 25 amps in the 60C column of table 310.16. Sorry for my mistake. I have a later post in reply to Alan Schaffter that corrects the earlier examples.

The correct wire size for a 22amp load is #10. The 25 amp rating is for derating purposes only.

Charlie

[Rob Russell]

Craig

I see I made an error in earlier posts about 22 amps needing 10 awg minimum if using nm-b (romex). That should be 12 awg not 10. 12 awg is rated 25 amps in the 60C column of table 310.16. Sorry for my mistake. I have a later post in reply to Alan Schaffter that corrects the earlier examples.

That's true if it's THHN/THWN in conduit. If the circuit is wired with NM-cable (aka "Romex"), #12 is only good for 20 amps.

[Charlie Knauer]

That's true if it's THHN/THWN in conduit. If the circuit is wired with NM-cable (aka "Romex"), #12 is only good for 20 amps.

How did you come up with that. 310.16 shows #12 with an *. At the bottom of the page * tells you 240.4d.
240.4d states;
Small conductors. Unless specifically permitted in 240.4e 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.
(D)(5) 12 AWG Copper 20 amps.

Charlie

[Roger Frazee]

The correct wire size for a 22amp load is #10. The 25 amp rating is for derating purposes only.

That's true if it's THHN/THWN in conduit. If the circuit is wired with NM-cable (aka "Romex"), #12 is only good for 20 amps.

Charlie and Rob please follow along with me as I have not looked back at the forum for several days. The underlined and bold is mine.


The ampacity of NM-b cable is ruled by NEC 334.80.

" The ampacity of nm,nmc,nms cable shall be determined in accordance with the 60C (140F) conductor temperature rating....the 90C (194F) rating shall be used for ampacity derating purposes, provided the final derating does not exceed that for a 60C rated wire.

The ampacity of 12 awg Nm cable at 60C = 25 AMPS TABLE 310.16

The ampacity of 12 awg at 90C for derating purposes is 30 amps

There is an asteric next to the 12 awg ... Looking at the footnotes the asteric means to see 240.4D

240.4(D) Small conductors. Unless specifically permitted in 240.4(E) or (G) the overcurrent protection shall not exceed that required by (D)(1) through (D7) after any corrections factors for ambient temperature or number of conductors has been applied.

Overcurrent protection for 12 awg is not to exceed 20 amps 240.4(D)(5).

This has nothing to do with the ampacity of the wire.

12 awg is rated 25 amps whether nm or thhn or thwn. Further .. deration is taken from the 90C column which is 30 amps not 25 amps. NM is a 90C rated insulation....

Now how do we get to have a larger breaker than 20 amps for 12 awg nm or thwn or whatever as specified by 240.4(D) for small conductors?

Please refer to 240.4(G)

"Over current protection for specific conductors shall be permitted to be provided as referenced in table 240.4(G)

It then shows you that breaker protection is amended for motor appliances and motors in accordance with art.422 and 430 among others.

So a 22 amp load can be served for a motor with #12 nm cable (25 amps) as a minimum and not required to be #10 awg . I then am allowed to breaker that nm #12 awg in accordance with table 430.52. This releases me from 240.4(D)(5) limiting me to 20 amp OCPD for #12 awg.

In contrast I am not allowed any amendment to overcurrent protection for 12 awg used for a general purpose branch circuit that can have multiple receptacles.... Only motor circuits or those specified in table 240.4(G). The ampacity of 12 awg is still 25 amps but I cannot use a breaker protecting it that is over 20 amps for anything unless listed in table 240.4(G). This will not work for the motor tools we are discussing in this thread unless we run a individual circuit to a single receptacle serving only these tools.

[Roger Frazee]

When the G9983 Grizzly sander starts the amp meter bumps up to 30 for a nanosecond.

Yep so you should be fine doing as we have been discussing.