I.S. 2 inch rule

[justdavemamm]

Now when you don't/can't have 2 inches of separation between I.S. and non I.S. circuits, you can use 20 gauge sheet metal between then per 504.30, FPN.

504.30 (A)(2) Exception No.1 lets me also separate them (when closer than 2") by ..."approved insulation partition."


Anyone know of a such partition ? Or what defines it ?

I've got a case where there are I.S. devices (PB's & LED LT's) mounted on the door of a panel and when the door is closed, the wire loops / connection points coming off them are about 1 3/4" away from wires & devices mounted on the back panel of the enclosure. Cannot make it further away.

Unfortunately, the enclosure isn't big enough to get inside and measure precisely, so were doing that by measuring offsets from reference points.

I could take some 2 ft x 2 ft sheet metal and mount in over the wiring inside the door. But that would add screw holes to the door, as none are there now. And look terible.

Or I could do the same inside the enclosure, mounting the sheet metal over the components.

I'd like to use something other than sheet metal. Any thoughts.


BTW, next time this machine is built, I'm going to get a deeper enclosure.

Tx, Dave

 

[rbalex]

Re: I.S. 2 inch rule

The magic word is "approved."

A bit of history: prior to 2002, "approved" was dotted throughout Articles 500 ? 516. In the 1999 cycle there were wholesale Proposals to replace ?approved? with ?listed.? This was almost completely rejected. During the 2002 cycle there was a wholesale set of Proposals to replace ?approved? with ?identified.? This received CMP14 acceptance as long as the CMP could substitute it?s own definition of ?identified.? That didn?t set well with the TCC, so it was back to the drawing board.

A CMP Task Group then went through 500 ? 516 and, during the Comment stage, carefully chose those Sections where ?identified? was consistent with the current Article 100 definition.

Oddly enough, for the 504.30 Exceptions ?identified? was never accepted because an ?? insulated partition? can?t be ?identified? for the application.

All that being said, do a Google search on ?split loom.?

 

[justdavemamm]

Re: I.S. 2 inch rule

OK, so you're saying split loom tubing, if approved / designed by the mfg as an insulating partition, would be able to be used in place of a metal partition.

Since the mfg has designed & made this product for this use, vs a piece of, lets say, cardboard, which is made with no specific use in mind.

And a plastic drinking straw, which is a tube that has some insulating properties, cannot be used because the mfg has not made / designed / approved it for insulating wires.

So, it's all in what the mfg has designed it for and approves what it's to be used for. In this case, split loom tuning is designed and approved by the mfg as an insulating partition, right ?

 

[rbalex]

Re: I.S. 2 inch rule

Not Quite.

?Listed? or ?labeled? requires third-party certification; ?identified? does not. However, the FPN to the definition of ?identified? strongly implies that it does. That was one of the reasons CMP14 wanted it?s own definition. CMP14 wanted it clear that the definition could also mean a manufacture?s self-certification or product application recommendations.

?Approved? dumps everything back on the AHJ with the expectation that they can make the appropriate ?judgment call.?

With regard to a ?grounded metal partition,? the FPN is actually only a ?suggestion? ? not a requirement. The manufacture of the 20-gauge sheet metal had no idea what his product would be used for, so they couldn?t ?identify? it, but the CMP could ?suggest? via the FPN that it would be acceptable.

With regard to an ?approved insulating partition,? the CMP expects the AHJ to use the laundry list in 110.3(A) to examine the product. Again, the split-loom manufacture can?t ?identify? that the product would be used properly for this specific application,(IS partition) but other appropriate data the manufacture could supply, if necessary, would allow an AHJ to make an intelligent call. Theoretically, if the AHJ felt a piece of cardboard could do the job, it would be acceptable.