Access to terminal lugs

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Access to terminal lugs

  • Yes

    Votes: 5 38.5%

  • No

    Votes: 8 61.5%
  • Total voters
    13
  • Poll closed .
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smcglynn

Member
Location
Detroit, MI, USA
We are doing a project where we have to replace the conductors feeding a motor control center. The MCC is old and the lugs are located in the back of the MCC (only accessible from a removed rear panel). The problem is, the MCC is mounted against the wall. It is our contention that this is an NEC violation. Would others concur? I've enclosed a photo of the MCC by placing the camera into the MCC from the front and snapping a photo looking up the section.
 

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smcglynn said:
We are doing a project where we have to replace the conductors feeding a motor control center. The MCC is old and the lugs are located in the back of the MCC (only accessible from a removed rear panel). The problem is, the MCC is mounted against the wall. It is our contention that this is an NEC violation. Would others concur? I've enclosed a photo of the MCC by placing the camera into the MCC from the front and snapping a photo looking up the section.
Click to expand...

How did they get the wires in there in the first place?:blink:





Welcome to the forum......:thumbsup:
 
smcglynn said:
We are doing a project where we have to replace the conductors feeding a motor control center. The MCC is old and the lugs are located in the back of the MCC (only accessible from a removed rear panel). The problem is, the MCC is mounted against the wall. It is our contention that this is an NEC violation. Would others concur? I've enclosed a photo of the MCC by placing the camera into the MCC from the front and snapping a photo looking up the section.
Click to expand...

I'm not very familiar with MCC installation methods. Was this configuration ever allowed? Sounds like an "oops" during installation. Are the original installation docs still floating around? Maybe there was a letter from the AHJ blessing this (unlikely, I would think).
 
Thanks, you guys are validating my limited field experience. I did field engineering for 10 years, then moved to PM. Never ACTUALLY worked in the field, though have a pretty good working knowledge of the NEC and what is acceptable in the field.

I have an engineer trying to tell me this is a code compliant installation. Every journeyman I've talked to is saying no way. According to the engineer they "do this all the time", in fact, just finished a similar installation, though he won't tell me where. When I asked how, his response was

"You just set the MCC about a foot a way from the wall, make the connections, then, with the wires connected, lift the MCC over the conduit and set it in place . . ."

To answer the questions, this is at a municipal facility that has a long history of NOT pulling permits with the AHJ. I suspect this original installation, circa 1970 was never inspected. In their defense, since I've pulled the permit, I have trouble getting the AHJ to actually show up for inspections when called.
 
NEC Article

NEC Article

I believe this is not in compliance with article 110.26 as there is no working clearance provided on the back of the MCC. Am I referencing the right section or is there something about lugs having to be accessible?
 
Most large gear details exactly where the power is fed to.
IE One cant run circuits that are in front of the red poly-board and
required to be in the lug area, your closed space.

It looks like the front panel is removable, I can see compartment rails for the
vertical support of the "dead front panel". I think you could remove the plate
behind the front door.

It's not the installers fault if things change at a later date and the owner now
wanted the space behind the gear and installs a wall.

You need to find the exact instructions of the equipment, you could compliment
the argument with the original drawings.
 
To me, its clearly a violation of 110.26, first paragraph:

Access and working space shall be provided and maintained about all electrical equipment to permit ready and safe operation and maintenance of such equipment.

110.26A1a basically states that "working space is not required in the back....where all connections.... are accessible from locations other than the back."
 
smcglynn said:
We are doing a project where we have to replace the conductors feeding a motor control center. The MCC is old and the lugs are located in the back of the MCC (only accessible from a removed rear panel). The problem is, the MCC is mounted against the wall. It is our contention that this is an NEC violation. Would others concur? I've enclosed a photo of the MCC by placing the camera into the MCC from the front and snapping a photo looking up the section.
Click to expand...

what code provision do you think is being violated?
 
petersonra said:
what code provision do you think is being violated?
Click to expand...

It very much depends, I think, on the manufacturer's installation instructions, but at first blush I'd agree with steve66. It appears, based on the OP's description and pictures, that the lugs were designed to be accessed from the rear of the cabinet.
 
NEC Article

NEC Article

petersonra said:
what code provision do you think is being violated?
Click to expand...

I'm thinking it is 110.26 (working clearance around the eqiupment. It is my contention that working space is required behind the equipment to maintain these lugs. At this point, the only method of replacing these conductors is to completely disassembe this motor control cener (including the vertical bus in this section) to get at the lugs.

However, Steve66 above seems to indicate that 110.26(A)(1)(a) negates the need for rear access in the case of Dead front assemblies. IMHO, however, I think the last sentence "Where rear access is required to work on non-electrical parts on the back of enclosed equipment, a minimum horizontal working space of 762mm (30") shall be provided.

The way I see it, 110.26 covers the need for clearance when the gear is energized. Obviously, you won't be changing lugs when it is energized, however, 110.26(A)(1)(a) requires that you have at least have 30" of access behind if there is something back there that needs to be maintained (in this case the lugs).

Hopefully that clarifies this.
 
Access to Terminal Lugs

Access to Terminal Lugs

Yes, that is correct. If they are "Electrical", then they are covered under 110.26(A)(1). IF they are non-electrical, they are covered under the last sentence of 110.26(A)(1)(a). the 2002 NEC hand book uses an example of a UPS that has filters in the back.

This is the 2002 NEC Hand book comment after 110.26(A)(1)(a).

"The intent of this section is to point out that work space is required only from the side(s) of the enclosure that requires access. The general rule still applies: Equipment that requires front, rear, or side access for electrical activities described in 110.26(A) must meet the requirements of the table 110.26(A)(1). In many cases, equipment of "dead front" assemblies requires only front access. For equipment taht required rear access for non-electrical activity, however, a reduced working space of at least 762mm (30 in.) mus be provided."

So, if the back of the gear has to be accessed while energized, table 110.26(A)(1) applies requiring 36, 42, or 48" of space depending on voltage. If, however, the gear is designed for rear access for non-energized or non-electrical work (changing filters, accessing lugs), then at least 30" of space are required.

Based on the above paragraph, would you not agree that a minimum of 30" of space for rear access should be provided to work on the lugs?
 
I have no idea if this installation was or is code compliant. But, you said it's been in place since 1970ish so I wouldn't get to worked up about it.

As a workaround, would it be possible to leave the 5' of conductor running up to the lugs and simply butt splice/insulated tap onto them with the new wires at the bottom of the MCC where I assume there is access? Otherwise, I'd uncouple the bussing to the adjacent section, pull it away from the wall and get on with it.

EDIT: On second thought, it's old gear that could probably be replaced. Why not kill two birds with one stone and get something new with lugs in an accessible location?
 
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