What instructions do you give GC or architect for location of power when the exact TV size/model is TBD? Similarly, how do you address LV placement in that situation? Thanks.

Try to determine where tv will go and smallest size tv it will be, mark location dead center of that.

Dead center could be a total mistake. You have to think past that.

This will be totally affected by the mount you use, so whatever you like, you've got to think of it ahead of time and specify it in the proposal. It would be good to include language stating that the mount cannot be changed without expecting the electrical location to change, and you will not pay for such changes. Some mounts have a solid piece of steel right in the center. Some have a huge open area. Some, particularly low profile mounts, severely limit where the outlet can go; these also sometimes can't be used with stupid TVs where HDMI cables come straight out the back (though I haven't seen any of these for a while.)

Correct. I was saying what "i" would do as i use snap mounts which are wide open.

This always a P.I.A.
We "usually" have the sparky put a whip near the center with some slack. We usually put a conduit to the TV area. The conduit location is normally midway of the TV size, off center, hoping we'll be able to get our cabling in and around the mount. With the conduit being midway, if we have to cut-in a new hole/ plate it can be done a little higher and not really affect the conduit. The power is retrofit after mount is in (usually by us!).
I'd love to see what others are doing about this common "situation" we always are dealing with.

If you can get away with it when it comes to your AHJ, and you're not required to run 120V in a conduit:
1. Have sparky leave romex loose, hanging from top to bottom inside wall cavity
on the other side of the stud
2. Run your conduit from top to half way point in the wall
3. Run your AV cables outside the conduit, again from top hanging down to bottom of the wall.
4. Take pictures of what's in the wall before the drywall covers it

At trim-out, determine TV size and exact location, cut your power and your AV plates and go from there.
I used it several times and it works well enough.

Thanks for the input. I've recently been using mounts that have only a single plate that the arms attach to, which makes this issue much easier to deal with. I've started to spec that the power and A/V should go horizontally centered and and just below the display center point (similar to Zohan.) Wondering how this will fare.

Depending on the size of the TV (For example 50-55") I personally connect the arms for the bracket at 19"...Meaning, the TV will hook to the bracket at 19" (approx).  The TV is approx 29-30" top to bottom.  So that leaves me 10" for them to install the electrical outlet. (I always put the elctrical outlet above the bracket).  In a nutshell, if they install the electrical outlet 23-24" from the bottom of the TV, I'm good.  

I always have them install it sideways....Just in case they're off in their measurement that'll give me an extra inch or two. 

About the same, I try to go horizontally to the top corner of the display, if I think it will be a Samsung recently I've been going top right, Panasonic they go top left.

If either side will be visible when coming into the room I use the other.

I have my sparky run romex inside the wall with some slack. I use the combo old work 2 gang box from Home Depot that is sealed high voltage on one side and open low voltage on other side of the box. That way whatever TV or bracket is used I can put the outlet right where it needs to be behind the TV.

We use Data comm back boxes for large tv's

[Link: datacommelectronics.com]

All tv electrical wires are run back to our rack location. We have the electrician staple his wire along one side of stud about half way down wall. We then run our conduit on other side of cavity stud but only run conduit about 3/4 down from top and loop our wires to close to floor. We mount bracket on finish out and then but in back box at the exact location we need it. pull our electrical to box underneath and our lines to top of box. This has save us a ton of headaches. We have also ran conduit pipe for electrician on one side and conduit pipe on other for us. Leave wires in attic and pull them later to get best results. In our area, contractors have not insulated home until we are finished.

Hope this helps

Thanks, yes this is all very helpful.

On a related note, under what circumstances to you request backing to support the display and how is this backing specified? Thanks.

I see a lot of you saying that the sparky just leaves the wire loose in the wall at prewire, but how does he get away with this to pass code? I know here if the wire is specified for a receptacle it reqires a box at prewire and the inspector wont pass the house until this is completed.

In out area this is no problem. Because it is a home run from our rack to the backbox, this passes inspection because it is not going to be hot until we connect our rack power to it. I don't understand why they let this go. None the less I am thankful that they pass it

Try to have them install and outlet at standard height right under where the tv is going. Then when you mount your tv you run your Romex. If your feeding from the rack just disconnect the power from the outlet and move it to the new location. You can then remove the outlet and replace with a blank or leave the outlet disconnected which shouldn't be an issue.