Art 501- Class I, Div. 2

[gofish2day]

I have built a panel in a nema 4x box with no intention of it being in a classified area. Now i find out the area is classified. The box has fused terminal blocks with bussman GMA type glass fuses. The smallest fuse that is used in classified areas is bussman KTKR. It is filled and current limiting. These are to large.

The customer states i can use the glass (non-herm. sealed) type fuses in inst. circuit if i add a class 1, div. 2 switch prior to the panel. I am not so sure. He refers to NEC 2002, Art. 501.3 (5) fuses. This mentioned permitted as 501.3 (B)(1).

Please offer any interpretations.

I feel a spark is a spark in a classified area. I there is a fault on one of these 0.5a fuses (24vdc) it can cause a problem. Yes, the switch may help when changing the fuse but not if there is a fault.

Thanks,

Karl

 

[pwhite]

Re: Art 501- Class I, Div. 2

karl,
a nema 4 enclosure is not designed to be placed in a classified area it is not designed for.
if the area is a class 1 div 2, then your nema 4 box will not work. in these areas, a nema 7,9 enclosure is required. these enclosures are designed to contain an explosion within the enclosure itself.
if you can place the enclosure outside the listed area to a non explosive environment, you could use intrensically safe barriers to interface between your panel and the listed area. you also will be required to use seal offs and other materials for the area.

i would check with a PE and have his ruling and see the local ahj.

maybe someone with a better understanding of these areas will post an answer as well.

 

[nhee]

Re: Art 501- Class I, Div. 2

A general purpose enclosure is permitted in a Cl 1, Div 2 location if it contains no arcing or sparking devices. If it does contain arcing/sparking devices then the NEMA 7/9 explosionproof box is required.

Some fuses are permitted by 501.6(3) if a Cl1 Div 2 switch is installed upstream, but I don't believe the glass fuses you mention would be permitted.

[ October 28, 2003, 05:18 PM: Message edited by: nhee ]

 

[nhee]

Re: Art 501- Class I, Div. 2

Sorry, the section I referenced seems to apply to motor control circuits. 501.3(B)(5) would seem to permit the glass fuses you are talking about.

 

[don_resqcapt19]

Re: Art 501- Class I, Div. 2

In my opinion 501.6(B)(3) permits a glass envelope fuse within a general purpose enclosure in a Class 1 Division 2 location.
Don

 

[gofish2day]

Re: Art 501- Class I, Div. 2

Thanks, everyone

I appreciate your input.

Karl