Use of Resistors in Class I, Division 1 locations...revisit of similar topic.

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DM2-Inc

Senior Member
Location
Houston, Texas
In the closed thread Terminal Block in Non-Hazardous Enclosure Located in Class 1, Div 2 Location, BPoindexter provided a follow up questions concerning resistors in hazardous locations.

Robert B. Alexander responded with a reference
The basic concepts for applications of heat producing items in Division 2 are found in 501.105(B)(2) Exception:

While the thread addressed issues related to Division 2 locations, 501.105(A), which addresses Division 1 locations, states:
Class I, Division 1. In Class I, Division 1 locations, meters, instruments, and relays, including kilowatt-hour meters, instrument transformers, resistors, rectifiers, and thermionic tubes, shall be provided with enclosures identified for Class I, Division 1 locations. Enclosures for Class I, Division 1 locations include explosionproof enclosures and purged and pressurized enclosures.

I take this to mean that for Class I, Division 1, locations, the resistor must be in an enclosure rated for Division 1 locations (agreed and understood).

I've had a long standing debate over the qualifications of that resistor. One of our suppliers insists that we can't install this resistor, and that it has to be installed at the factory, which adds a significant lead time to the equipment for a single resistor (not to mention cost). I've been trying to find language in the NEC which states "...installed at the factory..." or something similar but haven't found it.

Considering the language in 501.105(A), and it's absence to requiring this to be installed at the factory, I'm of the opinion that the code doesn't prohibit me from installing the resistor at all.

Am I interpreting this correctly?
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I apologize for the very late response. I was going to write a fairly long essay; but I have just been too sick.

The short answer is the resistor is not required to be factory installed.
 

DM2-Inc

Senior Member
Location
Houston, Texas
Bob,
Thank you for your response.

I've read many of your posts and noticed that you provide great supporting references to your response. I hope you feel better soon and have the time to provide that "...fairly long essay..."
 
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