We have a residential project. The second floor has a wooden frame structure, the first floor has a ceiling with metal beams at 10 feet. Can we run exposed Romex in the metal beams or do we have to protect the NM cables inside pipes or change it to THHN in pipes?
Unfinished garage/storage metallic structure
- Thread starter Charlypt
- Start date
Are these I type beams, or square box beams where you'd be fishing the cable through? NM cable has to be protected from physical damage, and what is considered protected varies all over the country and from inspector to inspector. Generally, if it is 10 feet up and it is an I beam I would judge it as OK if the cable was run with the C shape of the I beam. You also need a way to secure those cables every 4.5' on that beam which could be a pain. Putting a piece of plywood backer in that I beam would allow you to staple the cable to that plywood and guard boards could be added if needed for damage protection.
If these are box beams, I'd would say they are protected as long as the entry/exit holes to the box beam were rounded and holes aren't being drilled into the beam after the cables are run which could damage them.
Conduit sleeves in the I beam channel should also exceed the requirements as long as you have smooth bushings or clamps at the ends.
If these are box beams, I'd would say they are protected as long as the entry/exit holes to the box beam were rounded and holes aren't being drilled into the beam after the cables are run which could damage them.
Conduit sleeves in the I beam channel should also exceed the requirements as long as you have smooth bushings or clamps at the ends.
Type I beams. Cables could pass between the beams in one direction, but perpendicularly you have only one option under the beams.
The power comes from the 2nd floor, and would run throughout the ceiling of the 1stfloor to power lights, and switches and outlets in the walls.
My idea is that we should run EMT pipe with compression fittings, changing the NM from the second floor to THHN on the first floor. But some colleagues think that we could run the NM exposed and strapped in the beams and use pipes as sleeves to run the NM to the devices to protect against damage.
The problem is how to tie the cables to the beams as you say, you can't put staples if you don't put wood or you would have to find a method to tie them with cable ties. Running pipes may be overkill, but it solves protection against damage and strapping.
The power comes from the 2nd floor, and would run throughout the ceiling of the 1stfloor to power lights, and switches and outlets in the walls.
My idea is that we should run EMT pipe with compression fittings, changing the NM from the second floor to THHN on the first floor. But some colleagues think that we could run the NM exposed and strapped in the beams and use pipes as sleeves to run the NM to the devices to protect against damage.
The problem is how to tie the cables to the beams as you say, you can't put staples if you don't put wood or you would have to find a method to tie them with cable ties. Running pipes may be overkill, but it solves protection against damage and strapping.
Very good for a few cables. It's necessary to install several to avoid bundling.
Also I found this:
Arlington T23F Flat Support
or use a Unistrut H3 and the side holes to secure the NM with cable ties:
But aren't we overcomplicating things?
Besides, the beams are more than 5 feet apart. Wouldn't that violate the NM strapping every 4.5 feet?
I have used bridle rings on many projects, they are simple and quick. As far as bundling , it's no different than running through stud holes be it metal or wood.
You might have to be a little creative to meet the 4.5' supports but one of my early mentors told me that one of the most important qualities of a good electrician is the ability to improvise.
You might have to be a little creative to meet the 4.5' supports but one of my early mentors told me that one of the most important qualities of a good electrician is the ability to improvise.
Good suggestion. But we're also considering whether it's better to use pipes or find a thousand and one ways to attach the NM to metal beams without violating the code. We're divided. I support pipes, but I have to justify why it's better or give in.
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
What type of floor with the dwelling above have? What is the finished ceiling for the garage?
The has to be something between the beams.
The has to be something between the beams.
The garage has an unfinished ceiling, metal I-beams supporting a metal deck, and then poured concrete to form the second floor. The beams occupy the entire space up to the metal deck in one direction, and of course, there's empty space between them. In other words: metal beams, metal deck, concrete. If you're going to run cables across the beams, the only way is underneath. Power for the islands, for example, must run through the garage ceiling, as well as for the lights, outlets, and garage equipment.
The question is whether to continue running exposed NM in the garage ceiling or switch to conduit.
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
I would keep all the wiring for the dwelling above the floor or in the concrete floor as necessary for things like the island. Why penetrate and fire-stop the floor system unnecessarily.
For the garage I would use all EMT. This doesn't seem like a "budget build" so the EMT would fit in much better with this type of construction.
For the garage I would use all EMT. This doesn't seem like a "budget build" so the EMT would fit in much better with this type of construction.
For the island, the electricity must be run underneath, as the concrete is already poured and I doubt they'd agree to cut it (it's 4 inches thick).
The floor is noncombustible and fire-resistant, but I don't think it's considered a fire barrier or maybe it is, but it would need to be certified for that, and I don't think they want to get into that fight.
The plumbers drilled several holes to install the water and drainage systems, although all the entrances are sealed. We tried to avoid drilling into the floor, not only to preserve its integrity, but also because it's harder work than running wires through the second-floor attic and then through the partitions. However, some drilling is necessary to bring the electricity to the first floor.
I also consider the pipes better for the type of construction, which is more type II for the garage and type III for the rest of the house, although I don't believe or think they want to play with the classifications, so the house should be type III as a whole..
The floor is noncombustible and fire-resistant, but I don't think it's considered a fire barrier or maybe it is, but it would need to be certified for that, and I don't think they want to get into that fight.
The plumbers drilled several holes to install the water and drainage systems, although all the entrances are sealed. We tried to avoid drilling into the floor, not only to preserve its integrity, but also because it's harder work than running wires through the second-floor attic and then through the partitions. However, some drilling is necessary to bring the electricity to the first floor.
I also consider the pipes better for the type of construction, which is more type II for the garage and type III for the rest of the house, although I don't believe or think they want to play with the classifications, so the house should be type III as a whole..
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Use raceways, run THHN/THWN in them and place appropriate junction boxes wherever you end up routing an NM cable(s) to the upper floor. Won't look like some non professional did it either. For supply to island could even just run MC or flex instead of NM cable.
Many seem to think you have to run NM cable for everything at dwellings. Not true. Nearly all wiring methods are allowed. NM however does have more limitations than many other wiring methods have.
I agree with you, running exposed NM always looks bad. And you have to consider the type of construction more than whether it's a dwelling.