NEC 110-26 history

[kwired]

Let me know if you get one.

Where do you find this stuff? Everything I run into seems to be from the 70-80's which was built 20" deep instead of today's 24".:weeping:

I have often replaced older switchboards or panelboards with a panelboard that is much smaller dimension (and has more branch circuit possibilities). Sometimes the original didn't have proper 110.26 clearances but the smaller replacement has room to spare.

Somewhat recently replaced a 1970's switchboard in a school building - we needed more circuits but had plenty of ampacity and they already were at six switch limit for service disconnecting means. This switchboard didn't have sufficient clearance in front of it as it was, but my I line panel I replaced it with was only ~8 inches deep instead of 14 and was also much narrower which was also needed.

 

[jim dungar]

.... panel I replaced it with was only ~8 inches deep instead of 14 and was also much narrower which was also needed.

Wonderful, unless your bottom entry conduits were 16" from the wall.

 

[Carultch]

Where do you find this stuff? Everything I run into seems to be from the 70-80's which was built 20" deep instead of today's 24".:weeping:

Absolutely nowhere. That was more of a wild guess than anything else. That's why I said it would be a matter of luck.

 

[don_resqcapt19]

Not too surprised, that would be .9 meters, I'm a little more surprised they didn't increase it to 1 meter (39.37 inches)

Yes, the current code says 914mm(3') and the 2017 will say 900mm(3').

 

[kwired]

Wonderful, unless your bottom entry conduits were 16" from the wall.

I recall needing a pull box below panel to account for this problem, was able to place it right next to new panel so service conductors entered bottom and exited one side of the pull box. Did have to relocate a smaller panelboard (QO series was what was installed) to make it fit and it ended up above that pull box on a unistrut rack to get it spaced out enough that the pull box didn't extend more then 6" into workspace of the QO panel.

 

[kwired]

Yes, the current code says 914mm(3') and the 2017 will say 900mm(3').

They seem to have issues with their unit conversions:huh:

 

[Carultch]

They seem to have issues with their unit conversions:huh:

I think they are simply allowing you to round 1 inch to 25 mm, so that metric thinkers have an easy to memorize number.

If it comes down to a fraction of the inch, it likely will go unnoticed.

 

[kwired]

I think they are simply allowing you to round 1 inch to 25 mm, so that metric thinkers have an easy to memorize number.

If it comes down to a fraction of the inch, it likely will go unnoticed.

I doubt it goes unnoticed in some jurisdictions, in those close call cases you better have both SAE tape measure and a metric tape measure, there are inspectors out there that in past will not give you even a half inch leeway when you could really use it in an existing installation - that 14mm difference change for 2017 (yet they still convert both values to even 3 feet) is a little more then the half inch those guys won't let go.

 

[don_resqcapt19]

They seem to have issues with their unit conversions:huh:

See Informational Note 1 to 90.0 and if you have the hand book, see Table 90.1. The 2014 code is using a "soft" conversion between the two systems, and the 2017 will use a "hard" conversion.
90.9(D) says you can use either the inch pound system values or the SI system values for compliance.

 

[mwm1752]

I doubt it goes unnoticed in some jurisdictions, in those close call cases you better have both SAE tape measure and a metric tape measure, there are inspectors out there that in past will not give you even a half inch leeway when you could really use it in an existing installation - that 14mm difference change for 2017 (yet they still convert both values to even 3 feet) is a little more then the half inch those guys won't let go.

Somtimes it is prudent not using a tape measure when experience has taught you what 3' looks like -- I still find quite a few panels in closets which was an arbitrary place until NEC 1981.