Nec 770.12

[erickench]

I read the above NEC section and I'm not sure if I believe what I'm reading.
It state's the following:

Listed plenum optical fiber raceway, listed riser optical fiber raceway, or listed general-purpose optical fiber raceway selected in accordance with the provisions of 770.154 shall be permitted to be installed as innerduct in any type of listed raceway permitted in Chapter 3.

The last phrase is what I cannot comprehend. Are we actually installing raceway inside raceway?

 

[suemarkp]

Yes. We have an installation where 3" and 4" conduits were run to every room in a building. Originally, this was filled with fiber and two different purposes were served (call them secure and non-secure).

When it was time to change the fibers, it all had to come out because you can't easily pull new fibers through old ones. Pulling out fibers requires reterminating, and that is a costly and time consuming process (at least it sued to be). Three innerducts were installed in these conduits one for secure, one for non-secure, and one for single mode fibers. If a fiber needs to change size or type, we only have to empty one inner duct instead of all 3. Also helps to differentiate which fiber group a cable belongs to.

 

[lakee911]

Interduct is like a fabric-type sleeve with multiple holes (passages). You pull it off of a roll and it goes into the conduit. Your wire/cable gets pulled through one or more passages. Next time you need to pull new wire it goes through a different passage. Presto ... no tangles. Works nicely when you can't or don't want to pull the old out.

Editted: Well, at least thats what I think of ... but maybe the OP was something different. See http://www.google.com/images?um=1&h...=interduct+fabric&aq=f&aqi=&aql=&oq=&gs_rfai= for pics.

 

[erickench]

Thanks for explaining it to me along with that web page. But there is still a problem with the wording. The rule reads as if plenum raceway is being used as innerduct and is being installed inside another raceway. Here's a link for plenum corrugated innerduct:

http://store.cablesplususa.com/networking-infrastructure-premier-conduit-raceway.html?_vsrefdom=ppc

Now as for interduct which is spelled different from innerduct that would be able to be used inside a raceway. Time for another proposal.