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Electrical outlet above fireplace, wired through build-out

Electrical outlet above fireplace, wired through build-out

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Old 01-30-14, 12:09 PM
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Electrical outlet above fireplace, wired through build-out

We have a new fireplace installed along an existing external wall. So the fireplace sits 18 inches out from the wall. I am going to frame in a box around it that is 5 feet wide and goes from the floor to the ceiling. So the box dimensions will be 18" D x 5' W x 8' H. This box will then be covered in cement board and finished with stack stone. Pretty standard stuff.

I want to put a 42" TV above the fireplace, with the middle of the TV being roughly 5' off the floor. This will place it well clear of the "non-combustible" area above the fireplace.

I am going to run conduit (like 1.5" or 2") for the AV wires (HDMI, ethernet, etc) that the TV may require now and in the future. I could run the power cable from the TV through this same conduit, but I am worried about interference and the size of the power cable end fitting through the conduit.

I was thinking about running romex through the built out fireplace box and then terminating it with a regular power receptacle behind where the TV will be mounted. Is this safe to do, or would I be better running the power cable through the conduit with the HDMI/ethernet/etc cabling?
 
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Old 01-30-14, 12:17 PM
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I could run the power cable from the TV through this same conduit,
No you really couldn't unless the AV cables were all rated at or more then the voltage rating of the NM-b cable and they almost certainly aren't. If the NM-b won't be exposed to excessive heat it could be run inside the build out. The NM-b should be placed far enough back that it is unlikely to be pierced by fasteners or nail plates used.
 
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Old 01-30-14, 12:43 PM
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What is the drawback of the AV cables not being rated for the voltage in the romex? So for instance if the HDMI cable isn't rated for the voltage of the romex, will I experience interference? Or what other things can happen?

If interference (or some other problem) can't be avoided in the same conduit. I suppose I could run a 2nd piece of conduit, but they would still be run in parallel more than likely, with only 2 walls of PVC separating the romex from the AV cables.

What is considered "excessive" heat? I could easily enough put a thermometer where I plan on running the wire and let the fireplace run for a few hours to see what the temperature gets up to. This page seems to indicate 90 celcius for romex (Romex ® - Southwire: The Official Home of Romex ® Wire). So can I assume that if my thermometer doesnèt get above 90 C that I am okay as far as heat goes.

As far as being placed back far enough to avoid being punctured, that won't be a problem as the romex would be attached to the inside of the 2x4 framing. So unless I am drilling 4 inch screws into my stack stone, I'll be okay in that regard.
 
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Old 01-30-14, 01:19 PM
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If you run power and data together the data signal will be compromised by the electromagnetic field generated sound the power conductors. Separate conduits should eliminate that. Steel (EMT) will be more effective than PVC. One steel conduit for the data should be suffucient.

What is considered "excessive" heat? I could easily enough put a thermometer where I plan on running the wire and let the fireplace run for a few hours to see what the temperature gets up to.
You could, but it wouldn't give you any useful information. It's the ambient temperature that the conductors - or, more importantly, the insulation on the conductors - are exposed to when they are in operation that matters. In addition, the terminals that the conductors will be attached to aren't rated anywhere close to 90[SUP]o[/SUP] C.

The short answer is don't worry about it. If the temperature inside your fireplace surround gets up to anything like 90[SUP]o[/SUP] C. (194[SUP]o[/SUP] F.) you'll have more to worry about than your wiring.

Be sure to bring all power and data out through appropriate outlets mounted in boxes that are sealed into the stone work.
 
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Old 01-30-14, 06:09 PM
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If the temperature inside your fireplace surround gets up to anything like 90o C. (194o F.) you'll have more to worry about than your wiring.
Yep, like fire insurance.
 
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Old 01-30-14, 06:24 PM
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So by the sounds of it, I should be able to run romex to an outlet within the fireplace surround, as long as I make sure to keep it away from heat. Then run my conduit for the AV cables through another area, keeping it away from the romex to avoid any interference.

Does that sound about right?
 
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Old 01-30-14, 06:34 PM
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I should be able to run romex to an outlet within the fireplace surround, as long as I make sure to keep it away from heat. Then run my conduit for the AV cables through another area, keeping it away from the romex to avoid any interference.
Be sure to check with your AHJ on how far away from the fireplace and pre-fab flue the wood framing needs to be. If you meet that regulation, you can run NM-B cable through that framing. I would use EMT conduit for communications cabling and then not worry about how far from the power wiring the cables are. The steel EMT should be sufficient shielding against interference. Of course, you'll have to stub the conduit out somewhere accessible is this is also for future requirements.
 
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Old 01-30-14, 06:48 PM
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I'm sorry, but what is AHJ? The fireplace instructions state how far away any combustible materials need to be from any part of the fireplace. So if I follow those distances, I'm assuming I should be good to go.
 
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Old 01-30-14, 06:52 PM
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AHJ = Authority Having Jurisdiction or your local building department. Some municipalities have codes and clearances to be maintained that are more strict than the manufacturers. Be sure you do what they want since they are the ones to inspect and give the final OK on your project.

So if I follow those distances, I'm assuming I should be good to go.
Don't assume anything, ask.
 
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Old 01-30-14, 07:17 PM
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Yeah, I'm gonna be talking to the company that installed the fireplace tomorrow to run this all past them.
 
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Old 01-30-14, 08:20 PM
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I'm gonna be talking to the company that installed the fireplace tomorrow to run this all past them.
If they pulled a permit and got the work inspected, and it's still pending final inspection, then talking to them may be enough. If not, you need to talk to your local permit office yourself.
 
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Old 01-30-14, 08:42 PM
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Yeah they got permits for their electrical work (for the ignition switch), as well as the gas work of course. However, I would be adding on to their electrical work, so would need a separate permit I would imagine.

The idea of "final inspection" is laughable in my city though. We are in a huge economic boom, and you have maybe a 40% chance of somebody even stepping foot in your house when you get a permit.
 
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Old 01-31-14, 12:02 PM
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We are in a huge economic boom
Be thankful, I wish we had a boom going on here.
 
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Old 01-31-14, 01:20 PM
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Oh I am, its just that there are definite problems that come with it.
 
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Old 01-31-14, 01:40 PM
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Oh I am, its just that there are definite problems that come with it.
Those would be good problems to have.
 
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