501.135

[natfuelbill]

The enclosure is planned to be used as a junction box for the wiring connections for a Chromolux OCE (open element heater) that is inserted into a pipe. THe 2" pipe (one end threaded and the other end closed) is welded into a tank. The controls are PLC based temperature and low level controls which open/close a contactor to provide power to the heater, the heater is meant to provide freeze protection.

The design engineer defines the location as a Class 1 Div 1 hazardous location due to a vent fitting on top of the tank.

Is this field constructed assembly required to be listed C1D1 being that the heater is installed inside the pipe and XP junction box?

 

[rbalex]

I?m making some assumptions about your description. Feel free to correct them if necessary. One is that the terminal housing (terminal box) is in the Division 1 location; two, the heater is not directly exposed to the classified location; three, the heater elements are inside tubes that are in direct contact with the material(s) of concern. I also believe that the design engineer?s classification is correct as you have described it.
With respect to hazardous locations identified can have several meanings that are consistent with the Art 100 definition, but are more specific in application. See 500.8(A). The entire heater assembly does not necessarily need to be listed for Division 1; however ,before I personally would consider it identified, say under 500.8(A)(3), I would review the installation carefully in context of Section 501.15(F)(3).