C1D2 Enclosure - External Mounted Devices

[rdkazmier]

Hello - I have an C1D2 application that will be using a NEMA 4X enclosure with a type "Z" purge/pressurization system. This is going to be for a pump skid and house VFD's, their associated circuit protection, and some control circuitry. We are being asked to provide the following external devices on the enclosure: Start/Stop Push button, Pilot Lt indicating ON condition, Speed Potentiometer, Panel Meter displaying motor speed , and Disconnect. I can understand the Start/Stop pushbuttons and Pilot Lt as I can find C1D2 rated operators. The thing that has me concerned is the disconnect (I am assuming that they want a thru-door style) and potentiometer requests.

Being that this will be a purged/pressurized enclosure, does that impact the rating of the devices that are allowed? I can I use a thru-door disconnect that is NEMA 4X (or for that matter a speed potentiometer that is NEMA 4X). What is considered "internal" to the enclosure? Is any part of a device that is mounted through the enclosure considered "external" and need to be rated C1D2? My gut tells everything external should be C1D2 but I am looking for any direction on where to look standard wise to verify what is needed/required

I have already e-mailed the manufacturer of the panel meter's to verify whether their units are suitable for a pressurized enclosure or if they need to be contained within the enclosure behind a window etc. They state that they are "suitable" for C1D2 applications but I would rather be safe than sorry.

Any help/guidance would be greatly appreciated!

 

[dz63]

We are an OEM equipment manufacturer that supplies process equipment with control panels into XP hazardous areas.

For Class 2, Div 2 applications, we use an Allen Bradley 800H-UP29 10K ohm speed potentiometer with a sealing washer in our Type Z purged & pressurized control panels. It has a Class I, Division 1 Group BCD, Class II, Division 1, Group EFG rating.

For the disconnect switches, we use the RStahl disconnect with an 8006/4 series contact block inside our Type Z purged & pressurized control panels. It has a Class I, Division 2 Group ABCD rating.



We've got the latest version of NFPA496 and it does not specifically address mechanical devices on enclosures, like disconnect switches, potentiometers. It's a bit of a gray area. Theoretically any "sparking" of these components is located inside the pressurized enclosure which is considered a safe area, so the above two devices may be overkill. But, easier to defend from a compliance perspective.

FYI. The UL panel shop who build our purge panels, has this statement about external "mechanical devices" in their UL file. So technically a Class I, Division 2 rated disconnect is not actually required for them to certify their Type Z panels.
We request the certified components anyway.

Good luck!

 

[rdkazmier]

Thank you!