1000 Gallon LP Tank NEC Hazardous Area Classification

[JJcrick2]

Hello. I'm a telecommunications engineer for a public utility in Ohio.

We are creating a wiring standard for remotely connecting and monitoring our LP tank fuel levels at our remote telecom sites. The tanks provide fuel for backup generators that are located in our industrialized buildings at the site.

Summarization of the monitoring circuit:

The LP tanks have a Rochester gauge with a hull effect sensor that translates the fuel level to an electrical signal (4.5-5.0 vdc @4.5mA). The electrical signal is carried on a conductor that is ran in a 1” underground conduit to our telecom building. In the buildings, the electrical signal passes through a surge arrestor before it passes through to an analog card in an rtu. The rtu is polled over an internal network and the fuel level is remotely monitored by our NOC Team that monitors our entire AEP internal infrastructure.

We are trying to determine the National Electric Code hazardous location classification of the LP tanks we use at our remote telecom sites. The tanks are located outside, over 10’ away from our un-manned telecom buildings and only are used for the fuel supply of our backup generators. Do you know if the tanks are considered Class I, Division 1 or Class I, Division 2?

Rochester, the manufacturer the fuel gauge indicated this is a Class 1 Division1 environment. However, after talking with the State of Ohio, it seems this is open to NEC interpretation and could be classified and Class 1 Division 2.

Thanks for your assistance,

Jeff

 

[tom baker]

Questions similar to this one come where an area classification is needed come in frequently. Start with section 500.4 Documentation. One of our mods is an expert on Haz Locations and he can answer in more detail, but you will probably need to get a engineer to design you project, You will then have stamped drawings that would be acceptable to an AHJ. The AHJs appreciate this type of document, for me its similar to control panels, if them come UL 508 it makes the job much easier.

 

[oldsparky52]

Are you locked into these gauges? About 10 years ago I worked with a guy that installed wireless gauges that required no wiring and could transmit a signal hundreds of feet. I think it also had an option to connect to a cell phone number. I'm pretty sure they were C1D1 rated.

 

[rbalex]

I endorse tom baker's Post #2. I suggest you also consult Article 515. (I wish the Title were a little clearer about its application - so read its Scope in Section 515.1)

Get someone experienced in classifying locations AND have them create the required documentation of Section 500.4(A).

SIDE NOTE: The device would likely still be certified for Class I, Division 1 even if it were installed in Division 2. This is because the location's classification determines the equipment's certification by its application; the equipment's certification doesn't determine the location's classification.

 

[JJcrick2]

Thanks guys on your comments! Old sparky52 we aren't locked into the wired gauges mentioned above. I believe a wireless solution may be the best from many points of view(safety, cost and ease of installation). I appreciate the suggestion and I'm currently looking into wireless solutions.

Robert B. I also appreciate your comment on the NEC...especially the side note. I will research the NEC but think to be safe we should consider this a c1d1 location.

Jeff

 

[rbalex]

Thanks guys on your comments! Old sparky52 we aren't locked into the wired gauges mentioned above. I believe a wireless solution may be the best from many points of view(safety, cost and ease of installation). I appreciate the suggestion and I'm currently looking into wireless solutions.

Robert B. I also appreciate your comment on the NEC...especially the side note. I will research the NEC but think to be safe we should consider this a c1d1 location.

Jeff

It's OK to do that; however classifying "just to be safe" can create a few additional problems on its own - see Section 500.5(B)(2)(3). A Division 1 location always has an adjacent Division 2 location unless there is a physical barrier or other means to prevent it.