Grounding conduit carrying class two and three wiring from sound aplifiers

[ctown]

I posted this comment in the low voltage thread and realized that this thread is probably a better for my question. Sorry for the duplicate question.

Here is my question:
I've been doing my research and I understand that power limited circuits with class 2 wiring (i.e. speaker wire from sound amplifiers) is not required to be in raceways when exposed on walls and in ceilings (NEC Art. 725). But, what if class 2 cabling was put in a metallic conduit (such as Flexible Metal Conduit or EMT) to protect the cables? I figure the conduit needs to be grounded and metallic parts bonded because the class 2 circuit output wiring on the amplifier can reach over 50 volts (70volt distributed sound systems). Is it ok to bond the conduit and metal switch boxes to a steel beam framing member and the amplifier will be grounded by the branch circuit receptacle ground conductor? They will both be connected to the electrode grounding system right? Is this method accepted or is there a risk of a potential difference to ground or other hazards. If this is unacceptable, how would I accomplish this ensuring a safe grounded installation?

This is a question I have been pondering for a while and I keep going in circles around NEC codes. Most of the codes are tailored to contractors working with new construction installations. The type of system I mentioned and other sound systems I am concerned with are added well after the initial inspections and construction of the building.

If you have any insight, it would be vastly appreciated.

 

[cpal]

look at 640.7

 

[wbalsam1]

How about using a non-metallic flexible raceway system, such as "smurf tube"? I've used it in my recording studio to great benefit and it keeps ground loops from occuring between the technical ground and the premises ground. I ty-wrap it to other low-volt cables from my control room monitors to the console. :smile:

To my knowledge I have not violated any code provisions with this system.

 

[ctown]

How about using a non-metallic flexible raceway system, such as "smurf tube"? I've used it in my recording studio to great benefit and it keeps ground loops from occuring between the technical ground and the premises ground. I ty-wrap it to other low-volt cables from my control room monitors to the console. :smile:

To my knowledge I have not violated any code provisions with this system.

The scenario I'm talking about would be running cable for ceiling speakers in a restaurant. I would like to you use flexible metallic conduit to make sure the wires are protected and also to make a clean connection to the KO's in the ballast around the ceiling speaker which is mounted in a suspended ceiling tile. Im a little new to this and not sure if restaurants have always have a technical ground in place and where to find and access it.