How can I wire a circuit for this table saw and stay code compliant?

Question

I'm getting ready to install a new, dedicated 240 V circuit for a 4 hp table saw that I just bought¹. The saw hasn't actually arrived yet, so I'm working off information in the user manual I found on the product's website.

The wiring diagram in the manual shows a 6-20 plug (snippet below). The power requirements elsewhere in the same manual shows that a 30 A breaker is required (snippet also below).

But 210.21(B)(1) of NEC states

Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

Exception No. 1: A receptacle installed in accordance with 430.81(B).

Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug connected arc welder shall be permitted to have an ampere rating not less than the minimum branch-circuit conductor ampacity determined by 630.11(A) for arc welders.

430.81(B) states

Portable Motor of 1⁄3 Horsepower or Less. For a portable motor rated at 1⁄3 hp or less, the controller shall be permitted to be an attachment plug and receptacle or cord connector.

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After several hours of extensive Googling, I've discovered a few things:

1. 20 A < 30 A
2. 4 hp > 1/3 hp
3. Table saw ≠ arc welder

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Question

How do I satisfy the power requirements for this machine and stay code compliant? The 30 A breaker (with 10 AWG wire) and 6-20 plug seem to violate code. Is there something I'm missing? Are there exceptions for situations like this?

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From the user manual, page 6:

and page 17:

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¹ Actually, I'm getting ready to install a sub-panel for the whole workshop. This circuit will be in that sub-panel.

Answer 1

After several hours of extensive Googling, I've discovered a few things:

Long enough to read most of a book. Like I always say, googling doesn't work: Google only answers questions, it doesn't tell you which questions to ask. For that, you need a well-rounded primer on the subject. A book.

Heck... NEC 90.1(A) even says it's a Code violation to use NEC as an instruction manual for untrained persons :)

What's got you confused is the statement "ampere rating not less than the branch circuit". You're going "well that must be the breaker then", and it's not. It's the wire. See Article 100.

So, 210.21(B)(1), Receptacle is 20A, branch circuit (wire) is 20A, we're all good. (B)(2), (B)(3) and 210.23 do not apply since it's a 1-socket circuit labeled "4 HP saw only".

Now how big can the breaker be? Off we go to 240.3, which refers you to the relevant code for a long list of specialized equipment. Motors, motor circuits and controllers refers you to Article 430. This gets restated again in 240.4(G) pointing you to Article 430 parts II-VII again.

And 430 says consult the equipment nameplate because UL will have specified maximum breaker when certifying the motor (based on performance of its onboard overcurrent protection).

The minimum breaker is also on the nameplate, and/or called out in NEC 210.23(A)(2) since remember, nothing prevents you from plugging that saw into a multi-outlet 240V/20A branch circuit. 16A ampacity is 80% of 20A, so it's welcome on a 240V/20A multi-outlet branch circuit which is breakered at 20A per Table 210.21(B)(3).

Yes, there is a range of allowable breakers. Why is that? Because with larger motors, overload protection tends to be on the motor itself, where it has able to be savvy to the motor's temperature. When that is so, the breaker no longer needs to provide overcurrent protection, and only needs to protect against hot-neutral shorts or hot-ground shorts. They allow larger breakers to reduce nuisance trips from (redundant) overcurrent protection. If a 20A breaker holds to your satisfaction, you're perfectly welcome to install it on a 20A circuit including a multi-outlet circuit, and then the rest of 210.21 and 210.23 apply.

For a cord-and-plug connected appliance, The only thing the "dedicated circuit" really buys you is the right to over-breaker to reduce nuisance trips.