Definition of Continuous

[That Man]

Are any of these loads by chance motor loads?

No. I'm pretty sure motor loads are always 125% There aren't any specific loads. I'm adding automation to a cable sizing application. I've run into this problem before, and just punted in the past. I can only do that so much before I need to find an answer.

 

[don_resqcapt19]

No. I'm pretty sure motor loads are always 125% There aren't any specific loads. I'm adding automation to a cable sizing application. I've run into this problem before, and just punted in the past. I can only do that so much before I need to find an answer.

It really doesn't matter if the motor is a "continuous load" per the definition as the code requires the motor circuit conductors to have an ampacity at least 125% of the motor full load current a found in Tables 430.247 through 430.250.

 

[wwhitney]

It really doesn't matter if the motor is a "continuous load" per the definition as the code requires the motor circuit conductors to have an ampacity at least 125% of the motor full load current a found in Tables 430.247 through 430.250.

True for a single motor, but what about conductors supplying multiple motors? Suppose their nameplate FLC = table FLC = actual current drawn and they are running for more than 3 hours.

Cheers, Wayne

 

[That Man]

True for a single motor, but what about conductors supplying multiple motors? Suppose their nameplate FLC = table FLC = actual current drawn and they are running for more than 3 hours.

Cheers, Wayne

Oooh, I think I know this one. 125% of the biggest motor, 100% of the others. there's enough overhead in the feeder to handle the heat.

 

[tortuga]

It really doesn't matter if the motor is a "continuous load" per the definition as the code requires the motor circuit conductors to have an ampacity at least 125% of the motor full load current a found in Tables 430.247 through 430.250.

I think 430.22 refers to conductors that supply a motor in a continuous duty application, see the definitions under 'Duty'. If a single motor is used in a short-time,intermittent, periodic, or varying duty application you can apply T430.22(E) to the motor nameplate ampacity.

 

[Joe.B]

This isn't a code compliance question, it's a code intent question. And it's been answered, thank you.

Understood, and apologies if my remark came off a snarky, that wasn't my intent. I just meant that if someone is stamping a design, I think their opinions (and consensus of a team) would matter more than the intent of the code. The code is a bare minimum safety manual, and as you said, not a design manual. A designer (especially if they're stamping the design) would most likely have a reason for going above and beyond the minimum in their design choices, I would assume that reason would have something to do with desired function.

 

[tortuga]

Here's a source that talks about this from the Canadian code, FYI.

Thats an interesting 2008 article on Canadian Electrical Code Rule 8-104 Maximum Circuit Loading, keep in mind that CEC section got revised to harmonize with the NEC. Also we don't use R90 wire or NM-D cable in the NEC (unless by local amendment like in WA), but we do use the exact same OCPD's.

Rule 8-104 Maximum circuit loading • David Pilon - Electrical Business

April 10, 2017 - The 3rd Memorandum of Revision (MOR) is out, and Rule 8-104 is undergoing some significant changes. Subrule (8) has been deleted from the CE

www.ebmag.com

The CEC is written for certain Canadian products and the NEC is also intended for specific US products (we still use imperial pipe sizes and AWG wire). They are not totally harmonized (yet).

Go to the NFPA web site and search past NEC issues until you find the one where the "continuous load" definition first appeared, then search the ROP's, you may find what you're looking for

That would be 1965 but prior to that they used the term ‘long periods of time’ which was not well defined, the first mention of that would be the 1951 NEC 2125(b) “the total load shall not exceed the branch circuit rating, and shall not exceed 80 percent of the rating where in normal operation the load will continue for long periods of time such as store lighting and similar loads”, similar verbiage later in 1959 for feeders.

 

[roger]

That would be 1965 but prior to that they used the term ‘long periods of time’ which was not well defined, the first mention of that would be the 1951 NEC 2125(b) “the total load shall not exceed the branch circuit rating, and shall not exceed 80 percent of the rating where in normal operation the load will continue for long periods of time such as store lighting and similar loads”, similar verbiage later in 1959 for feeders.

So tortuga gave you a jump start, take it from there and expand your knowledge.