Electronic fuses - class 1 division 2

[przedpel]

Hi,

According to NEC 501.105 B (1)

"Switches, circuit breakers, and make-andbreakcontacts of pushbuttons, relays, alarm bells, andhorns shall have enclosures identified for Class I, Division1 locations in accordance with 501.105(A)."

Does it mean that that if I have a panel located in class 1 division 2, all relays, and circuit breakers assembled inside should be approved to use in class 1 division 1?

If yes, then when we can use components certified for class 1 division 2?


Can I use electronic fuses (link below) for PLC protection and IS barrier in panel located in class 1 division 2? This electronic fuse is approved in use for class 1 division 2.

http://shop.murrelektronik.com/en/E...100600&src=search&srchPage=1&perPage=10&pos=1

 

[rbalex]

Have you read the Section 501.105(B)(1) Exception (4)?

If you wish to install an intrinsically safe system, it must be in compliance with Article 504. Personally, I believe complying with Article 504 is usually far more trouble than it's worth.

 

[przedpel]

Thanks for reply. According to 501.105 B (1):

"Exception: General-purpose enclosures shall be permittedif current-interrupting contacts comply with one of the following:
(4) Are listed for Division 2"


Does it mean that this exception allows to use components class 1 division 2 inside enclosures(panel) located in such an area?

Please for help. Mainly I work with ATEX/IECEx.

 

[przedpel]

OK. Exception 4 of NEC 501.105 (1) allows to use components approved class 1, division 2 inside an enclosure.

According to NEC 501.105 (5):

"Where general-purpose enclosures are permitted in 501.105(B)(1) through (B)(4), fuses for overcurrent protection of instrument circuits not subject to overloading in normal use shall be permitted to be mounted in generalpurpose enclosures if each such fuse is preceded by a switch complying with 501.105(B)(1)."

Can I use in this case standard, non-certified fuse terminals WSI 4/2 (Weidmuller) with minitaure 5x20 fuses preceded by a switch complying with 501.105(B)(1) and excaption 4? So, switch would be for class 1, division 2.

 

[rbalex]

...Can I use in this case standard, non-certified fuse terminals WSI 4/2 (Weidmuller) with minitaure 5x20 fuses preceded by a switch complying with 501.105(B)(1) and excaption 4? So, switch would be for class 1, division 2.

Well, the terminals will still need to be certified (typically UL or other US nationally recognized testing laboratory) but not necessarily specifically for Class I, Division 2. Otherwise, they may indeed be simply preceded by a switch acceptable under Section 501.105(B)(1) Exception(4). It is critical to recognize the fuse is only to provide short circuit or ground fault protection.