When to use NEC appliance article or motor article

[Jpflex]

I assume at this point that if an appliance is also a motor such as: a kitchen water disposal motor rated in horsepower over 1/8 hp or air compressor rated in HP, then perhaps you would not size the OCPD and conductor according to the NEC motor article unless their is lack of nameplate or info?

According to the NEC appliance article, appliances are not to exceed their nameplate OCPD rating if the value is listed on their nameplate.

otherwise you follow the 20 ampere max OCPD rule for general appliance running at 13.33 amperes or less or 150% of appliances rated running current if listed over 13.33 amperes

It seems NEC calculation books are not following rules in NEC article pertaining to motors even when appliances are motors

So this confuses me on when to interpret a motor appliance as a motor and follow their corresponding distinctive section of rules under NEC motor article or treat the appliance (with a motor) under the appliance article section of NEC and adhere to its distinctive rules when sizing OCPD and branch circuit wiring sizes?

Here’s a test question attached

 

[Jpflex]

I am more familiar with motors than appliances since working in an industrial 3 phase and single phase environment.

If I treated the 3/4 hp 120 volt 8.1 ampere MOTOR (kitchen waste disposal) I would get different calculated size OCPD than what is shown on question answer sheet (NEC appliance article)


I do not have my NEC code book on hand so I won’t be factoring in motor intermittent duty rating, rather for example I’ll treat this as a continuous load motor as I’m more familiar with and for simplicity

Therefore, under the motor article of NEC:

OCPD will be 13.8 FLC (NEC single phase table) x 250% (inverse breaker) = 34.5 or 35 i ampere breaker

Branch circuit conductor = 13.8 FLC x 1.25 (pretend continuous) = 17.25i or #12 AWG conductor good for 20 i amperes at 60 degrees celcius



In comparison the book not treating this MOTOR appliance as a motor calculated the following:

OCPD = 15 amperes (nameplate 8.1 amperes)

Branch circuit = 14 AWG at 60 degrees Celsius


A device does not know nor care if you call it a motor or appliance so why are we treating them different for OCPD and wiring sizes even when both have over load protection and are both motors?

 

[Tulsa Electrician]

Maybe the difference between articles 422 and 430 and why we have them both.

So what would be one of the major differences that would apply.

 

[Tulsa Electrician]

Hint, the ansawer is in the question.

 

[Jpflex]

Hint, the ansawer is in the question.

Yes but why do we have two sections for the same device (a motor) resulting in two different answers for OCPD and branch circuit ampacity?

If a motor is to be protected rules should be consistent

 

[Jpflex]

Maybe the difference between articles 422 and 430 and why we have them both.

So what would be one of the major differences that would apply.

Perhaps a motor air compressor “appliance” would yield different conductor sizes and OCPD just based on whether you call it a motor or appliance and calculate its specs according to either respective NEC article

 

[Tulsa Electrician]

Let's start with the question from the book so we don't jump around.

It says, the disposal name plate indicates.

We can agree it's an appliance,yes.
So head to artical 422
Read 422.3
So 430 applies. However don't stop there and head to 430.
Let read on, the question also states individual branch circuit.

So we have an individual branch circuit and a name plate, yes.
If you agree let's look at part 2 in 422.

422.10 branch circuit rating.
Read first paragraph slowly.
Then we can head to (A)individual circuit.

The first paragraph addresses the marked rating. You first thought is that is it does not say name plate.
This is covered in 422.60
Read (B). Marking is the key word.

Now go to the second paragraph.
If no marked rating head to part 2 artical 430.

We have Marked rating, yes.

Going to eat dinner than I will do more. Try not to get ahead.

 

[Jpflex]

Let's start with the question from the book so we don't jump around.

It says, the disposal name plate indicates.

We can agree it's an appliance,yes.
So head to artical 422
Read 422.3
So 430 applies. However don't stop there and head to 430.
Let read on, the question also states individual branch circuit.

So we have an individual branch circuit and a name plate, yes.
If you agree let's look at part 2 in 422.

422.10 branch circuit rating.
Read first paragraph slowly.
Then we can head to (A)individual circuit.

The first paragraph addresses the marked rating. You first thought is that is it does not say name plate.
This is covered in 422.60
Read (B). Marking is the key word.

Now go to the second paragraph.
If no marked rating head to part 2 artical 430.

We have Marked rating, yes.

Going to eat dinner than I will do more. Try not to get ahead.

Ok yes lol. Thanks and eat dinner. I left my code book at work and just got laid off due to business loosing investor funds. I plan to study more but dang it code book is at work 3 hours away

 

[Tulsa Electrician]

You could down load the 2017 pdf.
Then catch up.

Now lets continue on with the branch circuit sizing.

In the question, is stated intermittent time rated. Artical 100 duty, intermittent. So it is not a continues load so no need for the 125 % adder. Size right off the name plate at 8.1 amps. Again no need to go to artical 430.

You will also read the question states it has a reset overload protection. Not really relevant for this question.

 

[Fred B]

Yes but why do we have two sections for the same device (a motor) resulting in two different answers for OCPD and branch circuit ampacity?

If a motor is to be protected rules should be consistent

If motor is a part of a listed appliance it is tested by a NRTL and allowed by the NEC to operate beyond the typical scope of NEC motor limitations due to the testing.
But a stand alone motor must be provided specific labeling and falls within motor limitations of the NEC.

 

[Jpflex]

You could down load the 2017 pdf.
Then catch up.

Now lets continue on with the branch circuit sizing.

In the question, is stated intermittent time rated. Artical 100 duty, intermittent. So it is not a continues load so no need for the 125 % adder. Size right off the name plate at 8.1 amps. Again no need to go to artical 430.

You will also read the question states it has a reset overload protection. Not really relevant for this question.

But here’s what does make sense and seems to be a contradiction in NEC code:

1x 29.98

Total 49.96



Overcurrent Protection. Section 422.11 requires overcurrent protection for appliances. Subdivision (A) has provisions for appliances with a protective rating on them; the branch-circuit overcurrent device rating is not allowed to exceed the rating on the appliance



Storage-Type Water Heaters are covered under 422.13 with a requirement that the branch-circuit overcurrent device and conductors for fixed storage-type water heaters with a capacity of 450 L (120 gallons) or less have an ampere rating of not less than 125 percent of the ampere rating of the water heater. The branch-circuit rating is determined per 422.10.



Therefore if I size a continuous load appliance to 125% of its rated ampacity, this may exceed the nameplate OCPD rating - two seemingly contradicting statements from NEC?

 

[jim dungar]

...if I size a continuous load appliance to 125% of its rated ampacity, this may exceed the nameplate OCPD rating - two seemingly contradicting statements from NEC?

If the appliance nameplate specifically spells out the OCPD rating that is what you use.
or
If no OCPD rating is given, you make your selection using the appliance's ampacity.