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How can I safely surface run two electrical Romex electrical cable from the attached garage panel through the second floor bedroom closet to the attic, while complying with North Carolina electrical codes and codes for passing wires through a firewall? The bedroom is located directly above the garage, which means there is likely a firewall between the two areas. I'd like to avoid passing new wires through the wall because the wall is spray foamed and is located above the electrical panel. I believe there are many existing wires in the wall that run to the HVAC attic air handler.

Ecnerwal
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Timur Isangulov
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  • If access is possible, drill a hole through the top and bottom plates of the bedroom wall. Use pull sticks to pull the cables through the holes and seal with fireproof caulk. Don't know if the caulk is approved by NC code. Have to wait for the electric experts to chime in. – RMDman Apr 08 '23 at 13:08
  • I'm planning to run wires on surface, I really don't want to pass wires through the wall because of the location. The wall is above the panel so the must be many existing wires in the wall already and the wall is spray foamed. – Timur Isangulov Apr 08 '23 at 13:12
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    That is good info to include in you question. – RMDman Apr 08 '23 at 13:22
  • Sure, thank you. – Timur Isangulov Apr 08 '23 at 13:31
  • Whatcha wanna do with them in the attic? – Huesmann Apr 08 '23 at 13:53
  • I take it the construction of the fire-rated assembly above the garage can be assumed to be 5/8" Type X over wooden trusses or joists? – ThreePhaseEel Apr 08 '23 at 14:00
  • I need wires for the dehumidifiers. – Timur Isangulov Apr 08 '23 at 14:07
  • @TimurIsangulov -- we need to know the construction of the assembly (floor-ceiling) between the garage and the house to be able to give you a good answer here – ThreePhaseEel Apr 08 '23 at 18:04

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Surface running the wires means installing conduit and not using NM cable. You might want to install the conduit up the exterior wall from the garage to the attic. This is done frequently when replacing knob & tube wiring on different levels of a house. This avoids the firewall issue.

If you choose to do it your way, you'll need to get with your local building authority for acceptable fireproofing.

JACK
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    You can also use "wiremold" for a more finished look for surface mounting wire/cable, if desired. – FreeMan Apr 08 '23 at 14:10
  • How can I do fireproofing when running inside house through firewall? – Timur Isangulov Apr 08 '23 at 14:17
  • Consider a new question specific to that question. In short, processes/products referred to as firestopping, and specifically for conduits and pipes, "firestop collars" - but also, as answered by JACK, see what your LAHJ requires/accepts bafore choosing something they may not accept. OP, also learn the difference between cables and wires, for clarity and correctness. – Ecnerwal Apr 08 '23 at 15:27
  • JACK : It is permissible to use NM cable in conduit, you just have to upsize the conduit. In some situations, it can make the complete run without needing a permanantly accessible junction box and associated splices transitioning from THHN/THWN to NM. That or running conduit for the entire run, which in many cases is not practical. – George Anderson Apr 08 '23 at 15:37
  • Should I use metal or pvc conduit? – Timur Isangulov Apr 08 '23 at 16:37
  • You can use either one with the proper fittings. PVC requires separate bend sections or has to be heated for slight bends and would require a ground wire. EMT can be bent with a bender and serves as a ground. Last time I checked, EMT was a little cheaper to install. – JACK Apr 08 '23 at 17:05
  • @JACK Can I pull the Romex through PVC, or should it be separate wires? – Timur Isangulov Apr 08 '23 at 18:47
  • @Ecnerwal thank you for correcting, I really meant Romex cable and not wires. – Timur Isangulov Apr 08 '23 at 18:54
  • @TimurIsangulov You can but it takes up a lot of space and could be hard to pull if you have bends. You'd need to increase the size. I've always used individual wires. – JACK Apr 08 '23 at 19:03
  • @JACK if I pick the EMT should I ground it or can just run the Romex cable inside? – Timur Isangulov Apr 08 '23 at 19:08
  • @TimurIsangulov If you run EMT, it will be grounded when you connect it to your grounded electrical panel. Why would you run NM cable? – JACK Apr 08 '23 at 19:22
  • @JACK I already have the Romex cable for my project that I'm planning to use. Do you know if there are any requirements for the maximum length of the conduit? I will need to pull 2 cables in up to 20 feet conduit. – Timur Isangulov Apr 08 '23 at 19:36
  • @TimurIsangulov No requirements because it's not normally done that way. – JACK Apr 08 '23 at 19:42
  • You'll either need two conduits with one cable each, or one very large conduit. either will probably cost more than buying THHN wire to run in conduit instead, so the cost argument of "but I have the cable already" is moot. One of many reasons running cable in conduit is rarely done - they have to be treated as circles the size of the largest dimension. As for length, there's no limit, and 20 feet is a trivial length of pull. – Ecnerwal Apr 08 '23 at 19:43
  • See https://diy.stackexchange.com/q/31149/18078 for lots of discussion about that. – Ecnerwal Apr 08 '23 at 19:50
  • @Ecnerwal after reading all the information in this thread few times, I'd like to use THHN wires. Do you think I will be able to pull 6 wires of #12 THHN in 1/2 Schedule 80 PVC, or should I use 3/4? – Timur Isangulov Apr 08 '23 at 20:27
  • Learn to use a conduit fill calculator. http://conduitfillcalculator.com is one example. That gives 36.5% fill, so it's legit. You may only need 5 wires (one ground wire can serve both circuits in the conduit.) That would be just over 30% and an easier pull. – Ecnerwal Apr 08 '23 at 20:33