Andrew Zonenberg
Firestopping on cable tray penetrations between my lab and house (cc: @whitequark )
Apr 12 at 5:03amWeb
Show threadarclight2d ago

@azonenberg @whitequark You should never be allowed near a nuclear plant. :)

Aside: I've seen the results of arcing within the potting compound of a cable penetration from a power plant. Safety analysis is weird.

Show threadAndrew Zonenberg2d ago

@arclight @whitequark I only had to pass residential building code and this was more than enough to make the inspector happy, lol.

(this is also only 120VAC not anything crazy)

Show threadwaldi2d ago
@azonenberg @whitequark Those steel pipes look like ideal circuits for stuff to travel through. Here we like plastic tubes for this use case and they require special handling for fire proofing.
Show threadAndrew Zonenberg2d ago

@waldi @whitequark That isn't conduit it's actually a premade cable with hot, neutral, and ground conductor inside a plastic strain relief wrap inside a flexible spiral metal armor.

Flex conduit of a similar construction exists but is larger.

Show threadLambda2d ago
@azonenberg @whitequark huh, you just stuff those pillows in there and caulk up the gaps? I don't think that's allowed here - at least I've never seen it for residential/normal business buildings, it's always fully filled up with white firestop compound.
Show threadAndrew Zonenberg2d ago

@lambda @whitequark Yeah the pillows are great for cable tray configurations that you modify frequently because you don't need caulk between them (only in small voids around the bottom of the tray where the caulk can't reach). Which makes it super easy to open things up and add more cables or something.

See https://www.3m.com/3M/en_US/p/d/b40070037/ (not the exact part i used but similar)

Show threadZOP2d ago
@lambda @azonenberg @whitequark If they’re actually fire stop pillows they’ll char and expand when exposed to flame. Sealing up tight. Until they’re exposed to fire though, they can’t be relied upon to keep smoke from propagating between spaces.
Show threadAndrew Zonenberg2d ago
@zop @lambda @whitequark yeah the caulk and mineral wool in the bottom area helps make it more airtight while still having pillow to pillow joints you can easily remove to add wires
Show threadZOP2d ago
@azonenberg @lambda @whitequark Exactly. I’ve used them a lot in cable trays or larger openings any time there was a chance we’d be in and out of them in the future, or just when there was larger gaps I didn’t want to make sheet metal filler plates for. Do it decent it’ll pass fire inspection anger…except Chicago lol (Chicago made me build sheet metal AND pack pillows AND caulk to make one inspector happy)
Show threadAndrew Zonenberg2d ago
@zop @lambda @whitequark oh this wouldn't pass in Chicago their codes are crazy I'd have to run all of my wiring in EMT instead of using MC