MOV (Varistors) in Class I Zone 2 PLC Panel


New member
Hi there,

First time posting.

I have a client who has put varistors(mov) Littlefuse LF9's in the NEMA 4X panel. My understanding is that it shall be considered as non arcing or sparking device.

Wanted to hear your opinion on this?

The panel will be located inside Class I Zone 2 or Div 2 area.

Thanks in advance.


Staff member
Mission Viejo, CA
Professional Electrical Engineer
While it's possible to "mix and match" Divisions and Zones a bit in the NEC, the same is not necessarily true with the Canadian Electrical Code (CEC). First, the CEC adopted the IEC rules "whole hog" and there is no such thining as Class I, Zone 2, it is simply "Zone 2". Second, and most importantly, a Type 4X enclosure is not recognized in IEC nomenclature. It must include an "Ex" designation. Third, while the NEC will permit some fuse applications in an "ordinary locations" enclosure, the fuse must be a non-expulsion type for short circuit or ground-fault protection only. [See Section 501.105(B)(5) in the NEC, I'm not sure about the corresponding CEC rule for Divisions; IEC rules would require an Ex mark.]