Greetings gang I am looking into options for lv shielded cable (22 awg) for wiring the typical probes and sensors on underground fuel tanks at a typical gas station.
There are various probes and sensors in the underground tanks that go back to a control console, these are routed via seal offs all in rigid or rigid -> pvc -> rigid -> seal off again -> wireway -> then raceway to inside the store.
The tank probe area is little hand hole above the tank that is a Class 1 Division 1 area, it typically has rigid stubbed in and a seal off.
My take is in a class-1 division 1 conduit the wire has to be suitable for the vapors or liquids that may collect on, or come in contact with, the insulation on conductors, regardless of how sealed it is --NEC 501.20.
I have seen it done a few ways
One way as a class-1 circuit with just stranded THHN-THWN-2 or TFFN-MTW if smaller than 14 as those are all marked 'Gas and Oil resistant' in raceway its that simple,
however
Some console systems require a shielded cable so each probes data line is wrapped in a foil shield going back to the console.
Now most low voltage cable is plain 300V PVC insulation type CMP, and since 514.4 in the 2023 references 501.20 and older NEC's have it in a note i am thinking this wont fly.
Do low voltage cables used for this purpose need be a type identified as gas and oil resistant?
Like Fluorinated Ethylene Propylene (FEP) insulation?
I see that one manufacturer Veeder-Root recommend Belden 88761which is a FEP type cable.
My 2nd question is if this cable needs to also be sealed as its now a cable going thru the seal off's?
(vapors could pass thru the cable jacket)
My guess is not if its considered a 'Intrinsically Safe' system other wise yes. Most all of these I am seeing are 'Intrinsically Safe' systems.
What kind of cable wire do you all run for these?
Thanks for your input and feedback.
Here is a diagram of what these systems look like:
There are various probes and sensors in the underground tanks that go back to a control console, these are routed via seal offs all in rigid or rigid -> pvc -> rigid -> seal off again -> wireway -> then raceway to inside the store.
The tank probe area is little hand hole above the tank that is a Class 1 Division 1 area, it typically has rigid stubbed in and a seal off.
My take is in a class-1 division 1 conduit the wire has to be suitable for the vapors or liquids that may collect on, or come in contact with, the insulation on conductors, regardless of how sealed it is --NEC 501.20.
I have seen it done a few ways
One way as a class-1 circuit with just stranded THHN-THWN-2 or TFFN-MTW if smaller than 14 as those are all marked 'Gas and Oil resistant' in raceway its that simple,
however
Some console systems require a shielded cable so each probes data line is wrapped in a foil shield going back to the console.
Now most low voltage cable is plain 300V PVC insulation type CMP, and since 514.4 in the 2023 references 501.20 and older NEC's have it in a note i am thinking this wont fly.
Do low voltage cables used for this purpose need be a type identified as gas and oil resistant?
Like Fluorinated Ethylene Propylene (FEP) insulation?
I see that one manufacturer Veeder-Root recommend Belden 88761which is a FEP type cable.
My 2nd question is if this cable needs to also be sealed as its now a cable going thru the seal off's?
(vapors could pass thru the cable jacket)
My guess is not if its considered a 'Intrinsically Safe' system other wise yes. Most all of these I am seeing are 'Intrinsically Safe' systems.
What kind of cable wire do you all run for these?
Thanks for your input and feedback.
Here is a diagram of what these systems look like:
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