Requirement for a ground conductor in multiconductor cables??
We have an alarm system that is installed on an offshore platform and the alarm strobes and horn operates on 120VAC. There is currently only a 4 conductor cable used to power the alarms. 1 for Neutral, 1 for Red Strobe, 1 for Amber Strobe, and 1 For the horn. The alarm stations are made of aluminum so they are conductive. The argument has been made by others that the alarm stations are connected to the metal platform, therefore they are grounded. However, I feel that there should be a 5th conductor in the cable to be used as a ground. I have looked through NFPA-70 to find something thatr states this, but I have only found information that talks about the ground conductor when used. I am looking for something more specific that I can present to management that states clearly that we should have a seperate ground conductor in the cable.
Does anyone know where I can find this in the code?
Thank you in advance!