Max voltage allowed in a box with IS circuits

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lhwidget

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Location
OKC OK, USA
Occupation
Design Engineer
It's sad, I remember reading this and now I can't find it, been looking for a whole day now...

We use XP control boxes, located in a Class 1, Div 1 areas. These control boxes use 115 VAC transformers to run simple ladder logic, executed with hard-wired relays. The same box contains the 460/380 VAC contactor and OL for our 3 phase motors.

Can I install Intrinsically Safe barriers and circuits in the same control box with the 460 VAC wiring? I realize the IS barriers and wiring must be separated by a 2" boundary or a grounded plate, but what is the maximum voltage permitted in a control box with IS inputs and outputs?
 
NEC 504.30(A)(2). What I'm trying to figure out is whether I can install barriers and IS circuits in the same XP box I have 460 VAC 3 phase switchgear in.
 
It sounds like you are meeting the requirements of 504.(A)(2) with 2in space and either a grounded metal partition or insulated partition.

I don't know what a XP control box is, but the code doesn't specify the type of enclosure or the voltage of the non-IS system.

Though I would be careful as to not violate any Class 1 Div 1 wiring methods. I would also consider wiring space within the enclosure as a design constraint as well.
 
Sorry, shorthand from a noob. We're using Explosion Proof enclosures. Dealing with NEC 504 for Class 1 Div 1 areas. IS lets us move from 3/4" hard conduit & seals to cable trays and simple multiple conductor cables.
 
You would need to make sure the wiring for the non-IS circuits meet the class 1 div 1 wiring methods as they enter or leave the area.
 
Yes, I agree. The IS cables will be sealed as they exit the box. The Explosion Proof portion (the 3phase motor power) will be sealed leaving the box and routed in heavy 3/4" conduit.

I'm still curious about my initial question; Can I use IS wiring in a control box with 460 VAC in it?
 
lhwidget said:
Yes, I agree. The IS cables will be sealed as they exit the box. The Explosion Proof portion (the 3phase motor power) will be sealed leaving the box and routed in heavy 3/4" conduit.

I'm still curious about my initial question; Can I use IS wiring in a control box with 460 VAC in it?
Click to expand...

That is how I read 504.30(A)(2). So long as one of those methods is met.
 
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