push buttons/pilot lites in cl1 div2

Status
Not open for further replies.
E

eeggoorr

Member
This is something some engineer concocted. I'm not sure it's possible. What do you say?

A control panel in a cl1 div2 area built with fiberglass nema 4x panel, all thats in the panel are some push to test pilot lights, a selector switch, a potentiometer, & terminal blocks. The pilot lites & selector switches are allen bradley 800H style. The pot requires the use of a intrinsically safe barrier within the 4x with the safe wiring actually leaving the classified area. (I'm not lying) And they think this is going to fly. I don't know if the switches and lights are rated for this. And I've never seen anything done like that with a pot and intrinsically safe barrier INSIDE a cl1 div2 area.

I think he's full of it, what do you folks think?
 
Yes ,factory sealed pushbuttons ,pilot lights and potentiometers are all available and can be mounted it a gasketed polyester box that are good for Cl1,Div2,,,,,, breaker panels are also available in polyester boxes.Check Crouse Hines N2PB Panelboards and also N2RS switch and device enclosures.

dick
 
I use the 800H devices with sealed contacts in non-metallic enclosures in Class I, Division 2 areas all the time. They are suitable for that application. The pot will require that the IS barrier be in the non-classified area.
 
I read somewhere ,where you could buy Ex-Proof parts and pieces for a pot and field assemble but am not sure if it is listed / tested for Class I,Div 2,probably not yet.

dick
 
don_resqcapt19 said:
... The pot will require that the IS barrier be in the non-classified area.
Click to expand...
I am of the understanding that an IS barrier can be installed in classified areas as long as it and the non-intrinsically safe wiring is within an area rated enclosure. See 504.30(A)(2) for requirements for separation of the IS and non-IS wiring.

The question I have is whether the pot (assuming it is panel mounted through and not entirely within in same enclosure as other non-IS apparatus) maintains the enclosure's classified rating, as an IS pot can be installed using any wiring method suitable for unclassified areas.
 
The magic term with respect to the IS part of the installation is control drawing. Without it there is no legitimate installation method.
 
rbalex said:
The magic term with respect to the IS part of the installation is control drawing. Without it there is no legitimate installation method.
Click to expand...
Quite true...

I've read product manuals and datasheets which state the particular IS barrier can be installed in hazardous areas [conditionally], but I've yet to see a control drawing depicting such an installation. I haven't worked with IS barriers much, so not having seen such a control drawing isn't really saying much ;)
 
Smart $ said:
...
The question I have is whether the pot (assuming it is panel mounted through and not entirely within in same enclosure as other non-IS apparatus) maintains the enclosure's classified rating, as an IS pot can be installed using any wiring method suitable for unclassified areas.
Click to expand...
The box I use is rated NEMA 4x. There are any number of pots that will maintain the 4X rating. The issue is if the pot itself can be used in the classified area. That issue goes away with an IS barrier, assuming you meet the installation rule for the IS wiring.
 
don_resqcapt19 said:
The box I use is rated NEMA 4x. There are any number of pots that will maintain the 4X rating. The issue is if the pot itself can be used in the classified area. That issue goes away with an IS barrier, assuming you meet the installation rule for the IS wiring.
Click to expand...
The pot must maintain the enclosure's rating when the enclosure also contains non-IS apparatus and/or wiring (assuming the non-IS contents are the reason for such rating). The requirement does not go away until all contents are IS. Additionally, wiring must meet the requirements of 504.30(A)(2). This has nothing to do with where the IS barrier is located.
 
Smart $ said:
The pot must maintain the enclosure's rating when the enclosure also contains non-IS apparatus and/or wiring (assuming the non-IS contents are the reason for such rating). The requirement does not go away until all contents are IS. Additionally, wiring must meet the requirements of 504.30(A)(2). This has nothing to do with where the IS barrier is located.
Click to expand...
Using the sealed contacts for a Class I, Division 2 installation does not require the use of an explosion proof enclosure. There would be no requirement to have all of the devices be IS. Most of the industrial pots I have seen are rated for use in 4X enclosures.

The installation of the barrier in the classified area may change the type of enclosure that is required. The real advantage of an IS is the fact that when the barrier is in the non classified area, you can use any Chapter 3 wiring method for the classified area. I don't see a real advantage in installing the barrier in an enclosure in the classified area.

There are also industrial pots that are suitable for use in Class I, Division 2 areas without an IS barrier.
 
The AB catalog specifically says their pot units aren't suitable for class 1, div2 applications.

As for a control drawing, I don't see why a manufacturer's instruction sheet could not be used as the control drawing, as long as it was identified as such. It's certainly pretty common to handle it that way.
 
petersonra said:
...
As for a control drawing, I don't see why a manufacturer's instruction sheet could not be used as the control drawing, as long as it was identified as such. It's certainly pretty common to handle it that way.
Click to expand...
I agree; however, identified is a defined term that may not ideally apply in this case;i.e., it implies an AHJ's judgement call. I have seen several manufacturers specifically indicate that their instruction sheets were indeed control drawings, especially for auxiliary equipment. In those cases, as long as the equipment were properly installed consistent with the instructions, I'd have no problem accepting them. Those instructions would clearly indicate the location of IS barriers with respect to classified boundaries.
 
rbalex said:
I agree; however, identified is a defined term that may not ideally apply in this case;i.e., it implies an AHJ's judgement call. I have seen several manufacturers specifically indicate that their instruction sheets were indeed control drawings, especially for auxiliary equipment. In those cases, as long as the equipment were properly installed consistent with the instructions, I'd have no problem accepting them. Those instructions would clearly indicate the location of IS barriers with respect to classified boundaries.
Click to expand...

You have a point about the use of the term "identified". I was thinking more along the lines of the end user making some kind of indication that the instruction sheet was being used as the control drawing.

My point was more that I don't see any reason anyone would need to create a drawing and label it "control drawing" for something to qualify as a control drawing, as long as it was clearly being used as a control drawing for a specific circuit.
 
petersonra said:
...
My point was more that I don't see any reason anyone would need to create a drawing and label it "control drawing" for something to qualify as a control drawing, as long as it was clearly being used as a control drawing for a specific circuit.
Click to expand...
Actually, a manufacturer creating a control drawing is a fundamental requirement - see the definition in Section 500.2 and then read Section 504.10(A) in light of that definition.
 
don_resqcapt19 said:
... I don't see a real advantage in installing the barrier in an enclosure in the classified area.

...
Click to expand...
When you install IS barriers in the non-classified area, do you install them in an enclosure??? So what's the difference if you install the IS barrier in the classified area, aside from the type of enclosure required?

It's just common sense to install an IS barrier on the non-classified side if your IS circuit source is also on the non-classified side. But what if the circuit source is in the classified area? Do you run the non-IS portion of the circuit to the non-classified area, install your IS barrier in an enclosure then run less-restrictive wiring back into the classified area? IMO it makes more sense to install the IS barrier, under these conditions, in the same enclosure as the source. Obviously, there are more decisions that go into this, such as the reason for using an IS circuit to begin with.
 
Smart $ said:
When you install IS barriers in the non-classified area, do you install them in an enclosure??? So what's the difference if you install the IS barrier in the classified area, aside from the type of enclosure required?
Click to expand...
That could be a huge difference.
It's just common sense to install an IS barrier on the non-classified side if your IS circuit source is also on the non-classified side. But what if the circuit source is in the classified area? Do you run the non-IS portion of the circuit to the non-classified area, install your IS barrier in an enclosure then run less-restrictive wiring back into the classified area? IMO it makes more sense to install the IS barrier, under these conditions, in the same enclosure as the source. Obviously, there are more decisions that go into this, such as the reason for using an IS circuit to begin with.
Click to expand...

If the circuit source is in the classified area, I probably would not even consider the use of an IS circuit. I don't see where it would provide any advantage.
 
don_resqcapt19 said:
There are also industrial pots that are suitable for use in Class I, Division 2 areas without an IS barrier.
Click to expand...

What pots are available for use in Class 1 Div 2? I'm looking to put one in a small control panel to control a VFD and all I have been able to find are general purpose pots that would have to be in an explosionproof box with a sealoff.

Similar installations in the past at my plant have used a pot in an explosionproof box wired to a small gadget that will supply voltage to a 0-10kohm pot and convert the voltage output into a 4-20 mA current loop that we run into a VFD analog input. I'm trying to do something similar in a NEMA 4X box rather than an explosionproof box.
 
jdsmith said:
What pots are available for use in Class 1 Div 2? I'm looking to put one in a small control panel to control a VFD and all I have been able to find are general purpose pots that would have to be in an explosionproof box with a sealoff.

Similar installations in the past at my plant have used a pot in an explosionproof box wired to a small gadget that will supply voltage to a 0-10kohm pot and convert the voltage output into a 4-20 mA current loop that we run into a VFD analog input. I'm trying to do something similar in a NEMA 4X box rather than an explosionproof box.
Click to expand...

In thinking about it, it occurred to me that I am not sure how you could make a pot on its own safe in a div2 area. Something would need to limit the potential for creating an ignition source.

It may be that a small XP box is the best answer, if all you are dealing with is one pot.
 
Status
Not open for further replies.
Top