Frost Heave Prevention Heat Tape - Class 1, Division 1 Area

[meisenb]

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?

 

[kwired]

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?

Let me ask you if conductors or all other equipment within the raceways or enclosures are rated CL1 DIV1?

Part of the reasoning of the enclosure is to protect what is within from the environment outside, or to protect the environment outside from what is inside.

 

[petersonra]

if the heat tape is not rated for the area how will you prevent it from exceeding the temperature limits of the classified area?

 

[meisenb]

I'm a little unclear what it is you are asking. I am using rigid galvanized steel conduit with threaded couplings. The termination point of the heat tape to the power conductors will be inside a terminal junction box in a Class 1, Div 2 area, and rated for such. The wire inside the conduit will be XHHW.

The Class 1, Div 1 area is a below grade dike near a flammable gas storage structure. The area above grade is rated Class 1, Div. 2.

The power wire that will terminate the heat tape will be XHHW. I'm not aware of any wire ratings for Class 1,Div. 1. Is this the direction you are leading me?

 

[rbalex]

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.

 

[petersonra]

I'm a little unclear what it is you are asking. I am using rigid galvanized steel conduit with threaded couplings. The termination point of the heat tape to the power conductors will be inside a terminal junction box in a Class 1, Div 2 area, and rated for such. The wire inside the conduit will be XHHW.

The Class 1, Div 1 area is a below grade dike near a flammable gas storage structure. The area above grade is rated Class 1, Div. 2.

The power wire that will terminate the heat tape will be XHHW. I'm not aware of any wire ratings for Class 1,Div. 1. Is this the direction you are leading me?

The XHHW wire in rigid steel conduit (but not the heat trace cable) is a wiring method allowed by article 501.

I would only be worried about how you plan to make sure the temperature around the heat trace cable in the CID1 area does not get high enough to be an issue if you are not using heat trace cable listed for CID1.

i wonder why the ground is classified as C1D1.

 

[kwired]

The XHHW wire in rigid steel conduit (but not the heat trace cable) is a wiring method allowed by article 501.

I would only be worried about how you plan to make sure the temperature around the heat trace cable in the CID1 area does not get high enough to be an issue if you are not using heat trace cable listed for CID1.

i wonder why the ground is classified as C1D1.

XHHW is not an art 501 wiring method, the rigid steel conduit is. You can pull almost any conductor allowed by NEC through the raceway. I think the main concern with the heat trace would be first is it allowed in the raceway, even if this were not a classified location? And then if it is allowed the next concern is whether or not ignition temperature of the classified material can be reached. One other concern that would apply to any location is how much heat is developed and effects of conductor ampacity?

I don't see this much different than having switches, relays, contactors in enclosures rated for CL1 locations. The enclosure is rated for the environment but what is inside doesn't have to be. It is the enclosure's job to effectively separate the non rated equipment from the environment.