Question on Sealing NEC 300.7

[brother]

NEC 2008 300.7

Was having a interesting discussion with another electrician on Sealing. He asked how much differential in temperature would need sealing. I just answered and said I don't know, I guess enough to cause condensation or water LOL whatever that may be. Mostly a judgment call I suppose. there have been times when I thought that sealing would be needed and others argued that since no water formed on the other side of the area then its not needed. What do you think?

Also he asked about the 'location' of the sealing,. Basically are you suppose install a box, LB, or C to install the sealing at the exact location of the transition from the interior to exterior of a building, cold storage etc.. ?? Or is there an amount of distance you can be from it.

I say its that 'portion' which in my opinion is the maxium of 10ft of unbroken length if you really needed a technical length.

I dont see this code section enforced really that much, if any at all.

 

[infinity]

Here's the exact wording from the 2008 NEC:

300.7 Raceways Exposed to Different Temperatures.
(A) Sealing. Where portions of a cable raceway or sleeve are known to be subjected to different temperatures and where condensation is known to be a problem, as in cold storage areas of buildings or where passing from the interior to the exterior of a building, the raceway or sleeve shall be filled with an approved material to prevent the circulation of warm air to a colder section of the raceway or sleeve. An explosionproof seal shall not be required for this purpose.

IMO it doesn't matter where you install the sealant as long as it prevents the exchange of air. For services with raceways we usually install ductseal on the inside of the service panel.