3 Zener Barrier Panel
3.1 Introduction
The optional Zener Barrier Panel (ZBP) is available for connection to PAL-AT when leak detection cables
and probes are installed in hazardous locations. It provides intrinsically safe output circuits for use in Class
I, Division 1 Groups C and D hazardous locations (Zone 0, Group IIB) when used with PAL-AT sensor
cables, jumper cables, and probes, installed in accordance with the instructions in this manual. Refer to
Appendix A, Special Instructions, for intrinsic safety requirements.
The ZBP also functions as a surge suppressor and reduces the chance of damage to the internal Zener
Barrier Assemblies (ZBA) and PAL-AT from external voltage spikes, e.g. nearby lightning strikes.
3.2 Panel Installation
The ZBP is designed to be permanently mounted indoors in a dry, non-hazardous location. The
enclosure is rated Type 4, 12 [IP66] (see figures 3-1, 3-2, and 3.3). The enclosure must not be located in
direct sunlight to prevent excessive heat buildup. In all installations, the ambient temperature
surrounding the panel must not be less than -4°F [-20°C] and not exceed 140°F [60°C]. Relative
humidity must be less than 95% (non-condensing).
The ZBP must be located adjacent to the PAL-AT panel. Each Zener Barrier Assembly (ZBA) in the
panel has a 5 ft [1.5 m] cable connected to the cable plug in the PAL-AT. The cable must be run in
conduit between the two panels.
The jumper cable from the ZBP to the sensing cable in the hazardous location must be routed in
conduit. All conduit fittings must be appropriately rated and installed properly to maintain the rating of the
enclosures. All electrical connections must comply with local codes. Seal-offs may be required to prevent
vapors from traveling into the ZBP.
Figure 3-1
Zener Panel Mounting
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