Saint Germain

Hello All,

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!
Saint Germain

Dennis Alwon

In terms of requirements for the NEC there would need to be a 5th wire or a separate equipment ground.

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wildleg

I'm not sure the Nec applies to offshore oil rigs, but what does the alarm manufacturer's literature have to say ? What kind of power system(s) are used ? how is the rig anchored ? how is the rig grounded ? who is the ahj ? what is the jurisdiction ?

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Saint Germain

Dennis, That is what I was thinking but I can not find the verbage in the NEC to support this. Could you please share with me where it sais this in the NEC?

Thank you in advance!

Saint Germain

Do you know exactly where in the code it says this? I need some hard evidence to be able to make a case.

Dennis Alwon

try anywhere in 250 part VI. 250.110 & 250.112

Also 250.112(I) for signal and fire alarms says if it operates at 50V or more than an equipment grounding conductor is needed assuming this is class 1 wiring which it seems to be.

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Saint Germain

Thanks, I will check there.