Panel Boards and Disconnects, Oh My

[tommtgun1585]

This is actually a two-part query so if I need to split it up please let me know. We have a number of traffic related panels (3R roadside like you see at an intersection) that powers message signs, cameras, detectors etc. that are going in place of existing cabinets that had a panel board for power distribution mounted to the side of the cabinet. The Incoming feed is 240V single phase going to a combination of 120V and 240V equipment and there are no motor controls. To provide a cleaner installation a new panel board was provided and mounted inside the enclosure. It's a standard panel board with a main breaker and some branch breakers. A local electrician is now stating that 1) the panel board has to have three feet of clearance within the enclosure by NEC 110 and 2) there has to be a lockable disconnect within 50 feet of the enclosure. Everyone seems split 50/50 concerning the panel board and I haven't seen anything specific about their use inside an enclosure. In 35 years of panel design I don't know that I have ever had to provide an external disconnect for a panel with non-motor loads and these panels are often fed from a main panel board that could be a half mile away. I pinged our local UL inspector but haven't heard anything from him for two weeks. Any enlightenment you might provide would be greatly appreciated.

 

[augie47]

Sounds like it might well be a grey enough area that your local inspector may have to make a call.
When you open (or remove) the cover to your panel does the interior panel have clear working space in front of it ??

 

[tommtgun1585]

Sounds like it might well be a grey enough area that your local inspector may have to make a call.
When you open (or remove) the cover to your panel does the interior panel have clear working space in front of it ??

Yes, and that's pretty much been my stance because the cabinets are all roadside with several feet of working distance around them. This installation, at least to my eyes, is no different than a bunch of DIN rail mounted breakers. Regardless, the panel boards are all facing the rear door and are directly accessible when the door is opened.

 

[jim dungar]

Is the panel complete (with tub, interior, and trim) or is it just the interior (busbars and deadfront)?

 

[suemarkp]

What is the code cite for the disconnect? The main breaker in that panel could be the disconnect for the whole cabinet if it has a locking means (whether come integral lock hasp or a LOTTO kit type). What is feeding this panel -- a feeder or a service? Is the panel the first thing the incoming feeder or service conductors hit?

Does the NEC even apply to the internal implementation of this cabinet?

 

[tommtgun1585]

It's a complete SquareD QO style panel board mounted on rails inside the enclosure.

 

[tommtgun1585]

What is the code cite for the disconnect? The main breaker in that panel could be the disconnect for the whole cabinet if it has a locking means (whether come integral lock hasp or a LOTTO kit type). What is feeding this panel -- a feeder or a service? Is the panel the first thing the incoming feeder or service conductors hit?

Does the NEC even apply to the internal implementation of this cabinet?

We're using the main breaker as the disconnect even though it's being fed from a main panel board that may or may not be within line of sight. There are locking means for both the enclosure and for the internal panel board if necessary. I've never had to provide lockout-tagout for these cabinets since they're just providing power for signs and cameras. I am sticking to my guns, at least so far, that once the distribution panel is mounted inside the enclosure it becomes a part of the enclosure and falls under 508a.

 

[Jraef]

The 3 foot rule is for WORKING clearance (article 110.26 ), you do not have to have "working" clearance on the sides for "dead front" assemblies.

a) Dead-Front Assemblies. Working space shall not be
required in the back or sides of assemblies, such as deadfront
switchboards, switchgear, or motor control centers,
where all connections and all renewable or adjustable parts,
such as fuses or switches, are accessible from locations other
than the back or sides.

He is over thinking it.

The requirement for a disconnect is met by the Main breaker of the panel. It is a "Service" panel, regardless of it being fed from another panel a mile away. This is a new site, new service.

If the other guy were correct, probably over 1 million traffic power pedestals are "illegally" installed around the country.

 

[tommtgun1585]

The 3 foot rule is for WORKING clearance (article 110.26 ), you do not have to have "working" clearance on the sides for "dead front" assemblies.

He is over thinking it.

The requirement for a disconnect is met by the Main breaker of the panel. It is a "Service" panel, regardless of it being fed from another panel a mile away. This is a new site, new service.

If the other guy were correct, probably over 1 million traffic power pedestals are "illegally" installed around the country.

Thank you very much.

 

[kwired]

We're using the main breaker as the disconnect even though it's being fed from a main panel board that may or may not be within line of sight. There are locking means for both the enclosure and for the internal panel board if necessary. I've never had to provide lockout-tagout for these cabinets since they're just providing power for signs and cameras. I am sticking to my guns, at least so far, that once the distribution panel is mounted inside the enclosure it becomes a part of the enclosure and falls under 508a.

Which makes the question become is it compliant with 508a after the modifications are done? If modifications are specified by someone 508a qualified, they may be acceptable, IDK details on this. I do know I can't modify it on my own and still call it 508a compliant.

That said I bet there are a lot of modifications that happen to originally 508a compliant panels over time.

 

[tommtgun1585]

Which makes the question become is it compliant with 508a after the modifications are done? If modifications are specified by someone 508a qualified, they may be acceptable, IDK details on this. I do know I can't modify it on my own and still call it 508a compliant.

That said I bet there are a lot of modifications that happen to originally 508a compliant panels over time.

That's true but these are all new assemblies and we're not modifying any existing panels. The existing panel, with an externally mounted panel board, is being removed and these are being put in place. And you're right; I'm very careful about modifying existing assemblies, especially for government entities.