Captivate Contacts in Class I Div 2

[spaceman95]

According to the 2017 NEC Article 501.105(B)(2) enclosures are required for the make-and-break contacts.
A captivate contact has no moving parts, therefore there is nothing to make-and-break.
Although there might be an LED on a capacities contact, it wouldn't have enough power or generate enough heat to be an issue.
Is this logic sound? We are looking options other than hermetically sealed contacts.

 

[fifty60]

For a button like I believe you would be looking at meeting the requirements of 501.150 contacts related to Signalling....not sure if capacitive buttons would meet that requirement or not...capacitors are not technically solid state devices, but they do not have make/or break contacts that I am aware of either.

 

[IntrinsicSafety]

Yes, the logic is (mostly) correct.

I assume we're talking about a solid-state capacitive switch, or some other device without moving physical metallic contacts.


With respect to the ignition safety of solid-state devices in a Div 2 area:

- ISA 12.12.01 governs the certification of non-incendive equipment. The NEC uses the same principles, so we can use ISA 12.12.01 for guidance.

- ISA 12.12.01 only looks at physical make-break contacts, where you have pieces of metal moving around. Such points include relays, buttons, potentiometers and connectors (internal and external).

- Solid-state devices, such as solid-state relays, transistors and capacitors, don't have make-break contacts, so they are not considered.

- Therefore, if you have a solid-state capacitive switch, or other similar device lacking make-break points, it should not be considered an ignition hazard in a Div 2 area.

I've had a lot of Div 2 equipment certified to ISA 12.12.01, so I'm confident the above is correct.


However, ISA 12.12.01 also requires an enclosure suitable for the location. So it isn't OK to just have a device hanging out on an exposed, non-enclosed panel, or the like.

The enclosure can be an ordinary enclosure - it does not need to be explosion-proof or otherwise rated for any hazardous location. But it does need to be present.


From this, you don't need a Div 1 enclosure for a solid-state device like a capacitive switch. But you do need an ordinary (general-purpose) enclosure for it.


Unfortunately - and through no fault of their own - an AHJ inspector unfamiliar with the certification of Div 2 equipment might not understand the above, or be confident it is correct. Lacking certainty, they might not be willing to accept unfamiliar solid-state devices as acceptable in Div 2 without a Div 1 (explosionproof) enclosure.

To get around this, it may be necessary to bring in an agency inspector from UL (or another certifications agency) to field certify the switch assembly as Division 2 equipment. Then there is nothing for the AHJ to worry about.

This would hopefully not be required, as it would cost extra money. But it would definitely work.

So the main risk here will not be >if< the solid-state switch complies. It's how much time/money it's going to take to prove it complies.

 

[fifty60_4802GND]

This is an interesting understanding of the general enclosure rule. Do you think that the general purpose enclosure rule would mean that the the device itself would have to be installed in a separate general purpose enclosure, or that the housing of the device itself can be a general purpose enclosure?