Any thoughts on how I prove to an inspector and an engineer that a terminal block is not considered an incendive device, so per 501.10 (B) (4) it does not need to be in an explosion proof box? He is asking for documentation that shows nonicendive at 120 volt. I can find Phoenix Blocks with built in fuses that document they are nonincendive, but our argument is over just plain old everyday terminal strips, Curtis Industries DSWT series.
Terminal Blocks in a NEMA 4X Enclosuree in a Class 1 Div 2 environment
- Thread starter toddelec2
- Start date
- Status
cpickett
Senior Member
- Location
- Western Maryland
- Occupation
- Electrical Engineer
If you find out, let me know! That is something I have come up against a few times, my colleagues hear CL I and immediately think explosionproof, even though a Div 2 installation can save quite a bit of money over a Div 1 installation if the area is indeed Div 2.
In the NFPA 70 handbook (2014) it has a note under 501.10 (B) (4) that says 'In Class 1, Division 2 locations, boxes, fittings, and joints are not required to be explosionproof if they contain no arcing devices; or for lighting outlets or enclosures containing non-arcing devices, if the maximum operating temperature of any exposed surface does not exceed 80% of the ignition temperature.'
In the NFPA 70 handbook (2014) it has a note under 501.10 (B) (4) that says 'In Class 1, Division 2 locations, boxes, fittings, and joints are not required to be explosionproof if they contain no arcing devices; or for lighting outlets or enclosures containing non-arcing devices, if the maximum operating temperature of any exposed surface does not exceed 80% of the ignition temperature.'
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
I'm usually on the other side of the "The NEC is a permissive code." argument; however, in this case, if terminals of any kind were considered to be arcing, sparking or high temperature (ASH) equipment, they would be specifically noted somewhere in Article 501, Part III (Sections 501.100 - 501.150). Note that Equipment is a very broadly defined term in Article 100.
I suspect your inspector or engineer has been influenced IEC practices.
I suspect your inspector or engineer has been influenced IEC practices.
Section 501.25 says there shall be no uninsulated exposed parts, except if they are made to be intrinsically safe or non-incendiary. Doesn't that mean that a standard terminal block is not OK? Does it mean that if there is a terminal block rated for a class 1, Div 2 location, it is OK?
I don’t believe a terminal block is considered incendiary. We used standard Thomas & Betts terminal blocks regardless of the area classification.
I believe section 501.25 is talking about the bare wire, not the terminal block. If Cl 1, Div 2, the can't be any exposed parts - bare wire. so a standard block can't be used. There are TBs by Phoenix that are UL listed for Cl 1, Div 2. Isn't that the way we have to go?
- Location
- Mission Viejo, CA
- Occupation
- Professional Electrical Engineer
Exposed (as applied to live parts) is a defined term in Article 100:
Capable of being inadvertently touched or approached nearer than a safe distance by a person. (CMP-1)
See the IN as well
Capable of being inadvertently touched or approached nearer than a safe distance by a person. (CMP-1)
See the IN as well
I assume that a "standard" terminal block has the terminal and wire exposed so that it can be inadvertently touched (I didn't state my point well enough in the last thread). There are UL listed Cl 1 Div 2 TBs for low power level devices that appear to be suitable guarded, isolated or insulated. Don't the "standard" terminal blocks have to be suitably guarded also? Yet I didn't find any 120 volt UL listed TBs for Cl 1, Div 2, only the low signal level - with words for at least one of them that say they are non-incendive. If they provide a product that specifically addresses this issue for low signal level circuits, I assumed that TBs for 120 volt circuits are not available, therefore 120 volt circuit can't be terminated in a cl 1, Div 2 environment. Which results in me referring back on Section 501.25 . Sorry I'm belaboring this, but I still don't see how the requirements of 501.25 are being met for a 120 volt circuit.
- Status