Arc-Resistant Low Voltage MCCs

[nhee2]

I am curious if most are seeing Arc-resistant MCC's specified or required in your projects? I found some earlier threads in the context of arc-resistant MV switchgear, but did not see much related to low voltage MCC's. Is the additional cost worthwhile/do they provide real safety benefits (don't protect you if doors are open)? Issues with installation/venting? Other considerations?

We have not previously spec'd MCC's as arc-resistant, although are considering it for an upcoming project.

Thanks

 

[ron]

Similar to arc resistant low voltage switchgear, I do not specify the arc resistant feature for anything, because they don't help when the doors are open and they require special venting, often needing to be near an exterior wall.

 

[Jraef]

The issue is if there are people working in an area, "interacting" with the MCC, and not needing any special PPE. Interacting can be operating breakers / disconnects, even with the doors closed. If the MCCs are in a locked room only accessible by "qualified workers", i.e. those with specific training on working with the gear and PPE, then the Arc Resistant MCCs (or switchgear for that matter) is redundant. But I mostly see AR gear being used because people don't have that real estate available, so the MCC / gear is on the working floor of a plant with all manner of people being allowed to turn things on and off. In some cases it is used to avoid all the rigmarole of onerous approvals needed to interact with the gear. I was at a Lockheed / Martin plant where the process for a non-electrician to get authorization to turn an MCC starter breaker back on required 2 levels of management approval.

Not all require special venting, at least at 1200A and below.