I have a frost heave prevention heat trace system where heat trace cable is installed under a structure. This cable will be located mostly in an Unclassified Area inside conduit. It will route through a Class 1, Division 1 area and Class 1, Division 2 area. I am being told that heat trace cable that is installed in conduit in a Class 1 Division 1 Area does not have to be rated for Class 1, Division 1. Is this accurate? Per NEC, all utilization equipment in C1,D1 has to be rated for C1, D1. How does adding the conduit on the outside of it give this application an exemption?
I don?t intend to do an exhaustive evaluation, but heating conductors in raceway in Division 1
may be ok but it is
not automatically acceptable.
kwired correctly identified a key issue ? that the heat generated inside the raceway will eventually show up as elevated temperatures on the raceway exterior. In most cases a thermostat set to 80% of the AIT of the gas/vapor involved will do the job. Temperature self-limiting cables are also acceptable in either Division 1 or 2.
Again, the magic word in Section 501.135 is
identified which does
not necessarily mean
listed or
labeled although they are an excellent means of identification. There are several manufactured heater cables that are indeed specifically
listed for Class I, Division 1 or 2. There are also several recognized means within the body text of Section 501.135 to address the issues involved. A thermostat is acceptable as is temperature self-limiting cables. Note the overvoltage condition restriction if an active temperature controller is not provided.