I once experienced a camp counselor shocking the piss out of himself when he picked up a wire for the camp PA system. I was around six at the time, and I was the one who knocked down the wire with my knapsack.

Everyone hated him. "Eddie Spaghetti in the can" we called him. I laughed so hard, I was the one who ended up with wet pants, but it was worth it. That was the best day of summer camp!

The reason the tech advised you to ground the 70 volt audio system (which was probably in conduit for part of it's circuit) was so that some poor bastard like larry's camp counsellor wouldn't ground something to your floating conduit and think that itwas properly grounded, then proceed to shock himself to death. As soon as you start putting things in conduit, most electrical codes require that your conduit system be properly grounded, even if it is a very limited system. A welder might pop a ceiling tile and see your un grounded conduit and think that he will have a pipe to ground to.

A good example is a system in which you run all of your 70 volt audio system using let's say 18G or 20 G 2 conductor signal wire in an open ceiling cavity without conduit or a raceway. You run into a situation where you want to protect the conductors mechnically for a short distance such as a publc hallway, or a bridge between concealed ceiling cavities that might protect otherwise vulnerable wiring. Then you use a limited amount of EMT to physically protect those circuits ( a short bridge). That's when you run into having to conform to adhering to 120 volt AC electrical code requirements. All that will be required to meet the code requirements is to bond any of your pipe to the nearest confirmed building electrical ground or a conduit system that is grounded. The circuit within the conduit isn't actually grounded , but the conduit or bridge containing it is.

I recently installed a 70v speaker system in a newly constructed office space. I am also installing cat 6 wiring for 150 desks at the same lication. While completing the data wiring I was using a tone generator and an inductive amplifier to find an unmarked cat 6 wire when I started hearing the music through the toning speaker... I am obviously worried about this because we should not have interference on the data network. I used shielded cable for the speaker systen install ans don't understand why there is stray voltage in the data lines. In addition I made sure not to lay the speaker wires near the data wires. By reading through this forum I found something about the drain wire on the shielded cable which I did not use. I am going to try to hoom that up to ground and see if that helps . In the meantime What would cause this? What are possible solutions? Does it even matter considering data runs at different mhz ? Help

Did a Barnes & Nobel long time ago, and it was contracted work. We had to follow the install as the way it was designed, and we did not run the conduit either. At the headend both the CCTV and 70V systems, which were separate systems and separate conduits, until came together into one conduit that went underground to a counter and there was only (1) 2" conduit and was about 50 feet long. The 70V system was generating hum bars that bounced to the music and at louder volumes the picture was a complete mess. Now weather or not a shielded speaker cable would have helped in this situation is unknow.

It's too bad we didn't hear about that Barnes & Noble system back then. We might have been able to help.

Be cautious when observing that there were hum bars in the video and that the hum bars bounced to the music, then concluding that the 70V system generated the hum bars. You are assigning cause without understanding the problem.  Maybe the 70V system was not the cause but something that happened (an incident) along with (latin "co," meaning "with") the other thing, making them co-incident. Coincidence really means that they happen at the same time but that you don't know enough to assign blame.  All the detective shows say they don't like coincidences, meaning they believe one thing caused the other or some third thing caused both.

It is often simple to erroneously say one thing caused another when the truth is that all we know is they happened at the same time.  Experimentation and solution can tell us if this is true.

Let's let this thread die and post further responses at Joe Bernardo's thread on this exact topic, [Link: remotecentral.com]. 18 minutes after Joe posted here he realized he could start a new thread instead of resurrecting an old one, and that's the new one.