Standard Ampere Ratings?

[bphgravity]

Article 240.6(B) lists 110-ampere OCD's as standard. This doesn't fit the within the normal intervals.

15-ampere through 50-ampere are at 5-ampere intervals . 50-ampere through 100-ampere at 10-ampere intervals. Then the 110-ampere. It then goes back to several 25-ampere, 50-ampere, and 100-ampere increases. Why the one odd-ball?

Does Table 310.15(B)(6) play a role in this?

 

[roger]

Re: Standard Ampere Ratings?

Actualy the 125 would be the real odd-ball in that it would be a 15 amp increase from the 110.

This would be the only 15 amp jump, where all the others are common with atleast one other.

Roger

 

[bphgravity]

Re: Standard Ampere Ratings?

I see your point.

Had the ratings gone from 100, 125, 150, 175, 200, these would have all been 25-ampere increments. The 110-ampere rating is indeed a continuation from the 10-ampere interval starting at 50-ampere. What significance does 110-ampere have that the code makes that 10-ampere increase, but deosn't need to make it after?

 

[steve66]

Re: Standard Ampere Ratings?

Looks like most of the jumps are limited to a 17% jump (10A/60A for example) for breakers under 1200A. If 110 were skipped, the jump from 100A to 125A would be 25/125 or 20%. That's my best guess. I don't know why the larger sizes have larger jumps (maybe each jump is then a new frame size).

I dont know what they mean when they say 601 is an additional standard size for fuses.

P.S. Whatever you do, don't take a long look at the tables for standard resistors and capacitors. 10,22,33,47,68....

 

[charlie]

Re: Standard Ampere Ratings?

Bryan, I can't answer your question but the 601 is over a standard 600 ampere fuse so it is made to fit the next size fuse holder and labeled as a 601 ampere fuse. In other words, it is a 600 ampere fuse that fits the next size fuse holder without using a reducer to make it fit.

 

[bill addiss]

Re: Standard Ampere Ratings?

Here's an explanation of the 601 rating from Dan Neeser @ Bussmann:

The reason there is a 601 fuse is to give flexibility. Class R and J fuses only go up to 600A. Above 600A, a Class L fuse must be used. Class L fuses range from 601A-6000A. The first case size of a listed Class L fuse is 800A with fuses sizes typically of 601, 650, 700, 750 and 800A.

Thus, if you have a circuit that could be sized at 600A, but may have to be increased in the future due to future expansion or motor inrush issues, Class L is the obvious choice. By going with a 601A Class L fuse, in an 800A disconnect, the fuses could be increased in the future up to 800A, provided conductors with an appropriate ampacity are used.

Thanks,
Dan