mixing wires in conduit

Correction:

Question: Respecting 1. and 2., any problems with this wire routing? If so, what? And is there a preventative?

You have two conduits. Run ALL of the power cables/wires in one conduit and run your video and audio in the other conduit. This will provide maximum insurance against interference.

You probably will not have a problem with your original scheme, except that when the power switches off and on, you do have a risk of a momentary glitch in your video and audio. That also depends on how well you shield your video and audio cables.

The rules to minimize interference:

* Shielding

* Distance -- Distance away from power conductors or other sources of interference

Just a note in case the project is to be inspected: The low voltage is not permitted to be run in the same conduit as the 120v.

I have tried this but now I always run them seperately, long lenghts of ac power wires running in parralel with low voltage cables will induce large voltages in your low voltage video cabales unless you are very good at screening. these voltages may (probaly will ) damage your low voltage equipment.

Exactly. The low voltage video wires have to be completely shielded from the AC wires and, as one poster already pointed out, the low voltage wires have to be in a different conduit from the AC mains. The reason for the former is interference and power induction and the latter because the low voltage devices won't have the necessary safety circuits to handle the AC should the two make contact.

The low voltage run (assuming the conduit is not conductive) has to be shielded with a braided shield around a pair (or other multiple) of wires. The wires don't have to be twisted in this application, so that's a bit cheaper.

Make sure you separate Class I and Class II wiring to comply with the National Electrical Code. If I recall, Class I is 50 volts and above, or anything over 100 watts.

Before running the DC and Video in the same conduit, insure that it's clean DC.

D.C. derived from a transformer/rectifier bridge power supply will have a considerable
ripple which may effect your video signal.