I will soon be installing an A/V system where the TV will be going over a fireplace. This is a remodel, so there will be a demo, then framing, then pre-wire, then finish. I will be running the HDMI, CAT6, and optical cables as usual. However, I want to future proof it as much as possible. That should include conduit. Once the drywall goes up, there is no turning back. It's all there to stay permanently. It's about a 30' run from the TV, through the fireplace, then through 2"x 4" studs to the entertainment center area. I am concerned about 2 issues:
1) Running a large enough conduit through standard studs that will accommodate an HDMI cable 5 years from now. I have used 1.5" Carlon through floor joists in the past, but not wall studs.
2) Using a flexible conduit that won't melt above the fireplace box. Carlon rates their Riser Guard @ 125 degrees. Not sure the inspector will approve that.

Any ideas will be greatly appreciated! Thanks in advance.

i use 1 1/4" carlon smurf tube above fireplaces and have not had an issue. running this through 2x4s, you will remove quite a bit of material, but as long as they are not load bearing walls, then it won't be a problem.

OP: You fail to mention whether it is a Wood burning fire place or Gas burning fire place.

Just dicking with you about Wood burning fire place :)

Depending which region you are at. Here in Houston, I ran into different inspectors: Constructions, Electrical, Fire place Safety (Whose job only inspect the fire place construction to give approval before a shear wall to be up).

All said flex conduits are to be at least 1" or more away from the chimney exhaust pipe would be fine.

Code says you can't run the flexible PVC conduit within a certain distance of the fireplace vent. Stick to that, and you'll be fine. Call your local AHJ.

As someone that only does commercial work, I wonder why you wouldn't just run standard 3/4" conduit. You can pull several cat 6 which I would think is a better idea than long HDMI anyway.

A rigid piece of conduit will allow easy pulling of future wire too.

Right now is a good example, you can NOT run true 4K (18gps) over cat anything cable. It has to be fiber or HDMI cable.
3/4" is just to small to pull some things with significant connectors on it. Need at least 1" size minimum. Wider is better.
And depending on the bends and how many, 1" is absolutely to small for soft, delicate, large head cables.

Neurorad has the key: AHJ

You need to locate the Authority Having Jurisdiction, who should be THE inspector who will review this work. Ask him what he wants to see.

He might suggest (you might suggest) a thin aluminum plate between the fire box and the conduit. This requires some space on each side of it, of course. Or wrapping the flexible conduit with fiberglass. Or... "what would you like to see here for safety, sir?"

If you're worried about conduit being rated at 125°, I would more worry about cables inside said conduit.
Most are only rated at 90°, some as low as 75°.

We recently did a job where we hung a TV above a "high efficient" gas fireplace. There was a 1/2" gap above the 12" minimum fireplace non-combustible requirements. This meant that all of the fireplace heat escaped up through the 1/2" gap into the framing of the fireplace opening. This caused the plastic fiber optic cable to fail 3 different times before we realized what was going on. We replaced the cable with a glass cable and haven't heard anything recently (although it's now summer months....) The plastic carlon conduit never melted. I wouldn't worry about the Carlon even if it's touching the class B venting. In our case, apparently the fireplace was installed according to the mfg but I'm trusting the contractor.

Brad,

What are you running over fiber for true 4K (18gps) ?

I did this on a job several months ago. Used the Carlon orange LV tubing I think 1.5" or 2". If this is a gas fireplace, the width of the cavity is typically much wider then the fireplace box itself, for the stonework, mantle etc. So there is plenty of clearance to the sides.

In this case, the fireplace vented out the back wall so the vent came up like 12" and therefore lots of headroom in the chase above the vent.

I ran the tubing up the side wall, attached to the inside of the stud of the sidewall. Can also put some 2x4 bracing between the side studs to attach the conduit clamps as well. I ran the tubing with a nice long bend/arc and attached the conduit, with some blocking, right above where the top knockout falls on the metal versabox.

I have not run across a fireplace that I could not get the Carlon Riser rated conduit above the fireplace. 16years of passing inspections. Pay close attention to
the manufacturer specs.

Got an ahole for an inspector, then run 1.25" steel conduit down to the box and skip the worries.

"i use 1 1/4" carlon smurf tube above fireplaces and have not had an issue. running this through 2x4s, you will remove quite a bit of material, but as long as they are not load bearing walls, then it won't be a problem."

Chris,
I don't remember if it's a load bearing wall. It's been a few months since I was out there. It's a gigantic house that sprawls out. There would be about 5 studs to cut. at least 2 right below a large window.

btw...I have yet to learn how to paste the comment to which I am replying in the same window as my reply. Can someone ejumicate me?

If the studs are below a window, they are not load bearing. That said, we almost always run 1" carlon....the orange stuff. I have not run into any issues yet with it not being big enough. At least that is what she said.

And nothing is ever permanent. Sheetrock can always be destroyed to get new wiring in. :)

I forget which company Brent said, I don't think it was cheap thou.
I'm not using it, I use passive cables (with Brent's GA1). In addition to a couple of cat6 and a nice SC quad RG6. And sometimes speaker wire and optical cable, depending on distance and where it's going to.
If you ask about the toslink optical cable, I use Liberty for that.