sewage holding tank

[steve66]

Wiring to float switches in a sewage holding tank - I typically see this specified as going through an intrinsic barrier installed in an explosion proof junction box.

Is the explosion proof Jbox required, or can the intrinsic barrier go in a standard jbox??

The wiring comes from a building, the tank is outside the building, and the Jbox is also outside the building in the run to the tank.

 

[rbalex]

Read Article 504 through at least once. It isn?t too long and reading it as a whole helps comprehension.

First, the installation should be done under a Control Drawing [504.10(A)] Depending on the overall application, the control drawing may indicate the enclosure type. NOTE: The barrier itself is Associated Apparatus. [See the definition in 504.2]

If the barrier and its enclosure is outside the classified location, then it does not need an explosionproof enclosure since only the IS circuit will be in the classified location. See the sealing requirements in 504.70. If the barrier and its enclosure are in the classified location, the enclosure must be suitable for the classification.

In either case, still be very careful about grounding/bonding [504.50 & 504.60]; their requirements are just as rigorous as ?regular? classified locations.

 

[steve66]

OK. Read through it. I had forgotten there was a short code section on intrinsically safe circuits.

It doesn't look like an explosion proof box is required, just a regular junction box (since it is located outside of the hazardous location) .

It looks like the float switch is a "simple apparatus". Therefore, it doesn't need to be listed for use with the intrinsically safe barrier.

Thanks. That helps.

 

[tom baker]

One IS wiring requirement that is commonly missed is field wiring is required to be light blue.

 

[steve66]

One IS wiring requirement that is commonly missed is field wiring is required to be light blue.

I didn't know that was a requirement. I usually only see float switches on the IS side. They usually come with a prewired lenght of SO cord. I'm not sure what color of wires they use.

 

[rbalex]

Color coding is permissive - not a requirement. See 504.80(C).