True minimum clear distances, Table 110.26(A)

[Jhall18]

I have been having a disagreement on what is meant by working clearance depths according to 110.26(A). On the project the switch gear, 277/480v, is located in a CMU block main electrical room. The distance from the dead front of the gear to the opposite back wall is approximately 12 feet. Some say the minimum clearance is 3' since the back wall is so far back and does not effect the working clearance, a condition 1. I disagree and say 42" because the block makes it a condition 2. The back wall is beyond the working clearance distance, but it is part of the room and would technically be considered in calculating clearance distances. How far do the conditions need to be in order to effect, or not to, working clearance? Any thoughts?

 

[jumper]

I got lost somewhere.

If there 12 feet between equipment and wall, what working clearance of 110.26 is being violated?

I am missing some detail in the description.

Maybe a diagram of the layout......?

 

[infinity]

Not sure what you mean by the distance to the back wall but regarding the three conditions, a block wall is considered a grounded surface so the distance needs to be 42" or condition 2.

 

[Adamjamma]

So, is the gear being put on a small work wall or partition wall?
But, my old boss who trained me would always say, if in doubt, use the bigger number for clearances as it makes it easier for a fat boy like me to deal with it later...

 

[MasterTheNEC]

I got lost somewhere.

If there 12 feet between equipment and wall, what working clearance of 110.26 is being violated?

I am missing some detail in the description.

Maybe a diagram of the layout......?

Greetings Jumper,

Me being slightly lost in the review as well I believe the OP simply want's to know if the required working clearance for their condition is either 1 or 2. Since their is 12' this seems moot.

However, based on what is being presented I will go with 42 in. In reality, i usually teach the minimum of 3' unless something impinges on that minimum based in a condition of 110.26(A)(1), like condition 2 and a wall then i demand the increase to 42 in., based on voltages of course.

Anyway since you are here and he isn't...let's say you win and use 42 in.....

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17

 

[jumper]

Okay, let’s go with 42, it seems to be the answer for a lotta stuff......

 

[MasterTheNEC]

Okay, let’s go with 42, it seems to be the answer for a lotta stuff......

Works for me...

Paul W. Abernathy
Electrical Code Academy, Inc.
CMP #5 and #17

 

[Carultch]

I have been having a disagreement on what is meant by working clearance depths according to 110.26(A). On the project the switch gear, 277/480v, is located in a CMU block main electrical room. The distance from the dead front of the gear to the opposite back wall is approximately 12 feet. Some say the minimum clearance is 3' since the back wall is so far back and does not effect the working clearance, a condition 1. I disagree and say 42" because the block makes it a condition 2. The back wall is beyond the working clearance distance, but it is part of the room and would technically be considered in calculating clearance distances. How far do the conditions need to be in order to effect, or not to, working clearance? Any thoughts?

Is there a job specification to label working space, or a need to build a platform specifically for the working space? If so, I would go by condition 2, since the block wall will currently be behind you, after the installation is complete.

One might raise the point that the 9 feet of air behind you is an insulator, which might be a reason to call it condition 1. If it is really important to only use 3 ft of working space, you could put in wood/fiberglass/plastic fencing to guarantee an insulator is behind you. But I would default to condition 2, if there is no compelling reason to only reserve 3 ft.

 

[ggunn]

Okay, let’s go with 42, it seems to be the answer for a lotta stuff......

So long, and thanks for all the fish.

 

[Strathead]

Not sure what you mean by the distance to the back wall but regarding the three conditions, a block wall is considered a grounded surface so the distance needs to be 42" or condition 2.

I wonder. This is kind of like going down the rabbit hole, but the OP threw in the word "clearance" that would make me wonder if part of the discussion was marking off the required space on the ground, or storing things in the space not designated.

As such I would contend that condition 1 is the right condition. The back side of any defined working space for this gear is air. That is not a grounded component requiring expanded working space. From a purely argumentative place, the clear work space per 110 is from the dead front to the minimum clear distance defined by condition 1 2 or 3 of table 110.34 (A)

[edit] It is kind of a useless intellectual question of who is smarter. Bottom line, there is plenty of room so who should really give a rat's butt.

 

[infinity]

I wonder. This is kind of like going down the rabbit hole, but the OP threw in the word "clearance" that would make me wonder if part of the discussion was marking off the required space on the ground, or storing things in the space not designated.

As such I would contend that condition 1 is the right condition. The back side of any defined working space for this gear is air. That is not a grounded component requiring expanded working space. From a purely argumentative place, the clear work space per 110 is from the dead front to the minimum clear distance defined by condition 1 2 or 3 of table 110.34 (A)

[edit] It is kind of a useless intellectual question of who is smarter. Bottom line, there is plenty of room so who should really give a rat's butt.

I think that you meant 110.26(A)(1), 110.34(A) is for over 600 volts.

Back to the OP, he has a dead front and opposite of that is a block wall which is a grounded surface so the minimum distance between the two is Condition 2 or 42". Of course as it's been stated since he actually has 12' the point is moot.

 

[Strathead]

I think that you meant 110.26(A)(1), 110.34(A) is for over 600 volts.

Back to the OP, he has a dead front and opposite of that is a block wall which is a grounded surface so the minimum distance between the two is Condition 2 or 42". Of course as it's been stated since he actually has 12' the point is moot.

That is bizarre, I was looking at .26 I

Just to be difficult I contend that opposite the dead front is the insulator air. Condition 1. Well not actually just to be difficult. 110.26B requires the space not be used for storage. I contend in the situation described only 36" must remain clear.

 

[infinity]

Just to be difficult I contend that opposite the dead front is the insulator air. Condition 1. Well not actually just to be difficult. 110.26B requires the space not be used for storage. I contend in the situation described only 36" must remain clear.

Assuming that you already have the required width there are two sides of the working space that is of interest to 110.26(A)(1) that is the dead front side and the wall opposite the dead front which is about 12' away. Being 12' away that wall meets the minimum requirement of 42".

Condition 2 — Exposed live parts on one side of the working space
and grounded parts on the other side of the working space. Concrete,
brick, or tile walls shall be considered as grounded.

 

[Carultch]

Assuming that you already have the required width there are two sides of the working space that is of interest to 110.26(A)(1) that is the dead front side and the wall opposite the dead front which is about 12' away. Being 12' away that wall meets the minimum requirement of 42".

So if the issue were marking the workspace floor, or locating floor space that is OK for storage, or building a platform over muddy/irregular terrain in an outdoor application, which workspace would apply, given a condition 2 surface that is 12 feet away? 36" or 42"?

 

[infinity]

So if the issue were marking the workspace floor, or locating floor space that is OK for storage, or building a platform over muddy/irregular terrain in an outdoor application, which workspace would apply, given a condition 2 surface that is 12 feet away? 36" or 42"?

36", the 42" minimum dimension is because a grounded surface is opposite the dead front. Once the wall opposite is more than 42" away then it is no longer considered which I believe Strathead was saying.

 

[jumper]

So long, and thanks for all the fish.

:thumbsup:

 

[Strathead]

36", the 42" minimum dimension is because a grounded surface is opposite the dead front. Once the wall opposite is more than 42" away then it is no longer considered which I believe Strathead was saying.

Yes that is what I was saying.

 

[charlie b]

The extreme version of this issue would be a panel located outdoors, with nothing located in front of the panel and in the immediate vicinity. I would call that Condition 1, as there are no live or grounded parts on the other side of the working space. The discussion here seems to be whether 12 feet is sufficiently similar to “wide open spaces” as to also fit into Condition 1. My answer is that it is not. There is a room. It has walls. That puts you into Condition 2. If you are marking the working space on the floor, I would put it at 42 inches. That would the space where no storage is allowed. If they come back later and want to install other equipment or to bring in office furniture, then that action requires a separate evaluation of the working space requirements.

 

[Strathead]

The extreme version of this issue would be a panel located outdoors, with nothing located in front of the panel and in the immediate vicinity. I would call that Condition 1, as there are no live or grounded parts on the other side of the working space. The discussion here seems to be whether 12 feet is sufficiently similar to “wide open spaces” as to also fit into Condition 1. My answer is that it is not. There is a room. It has walls. That puts you into Condition 2. If you are marking the working space on the floor, I would put it at 42 inches. That would the space where no storage is allowed. If they come back later and want to install other equipment or to bring in office furniture, then that action requires a separate evaluation of the working space requirements.

Why would you draw that conclusion? I almost used a similar example, to draw the other conclusion. Why do you decide 12 feet is inside the "boundary" but outside isn't. How about a warehouse where the panel is on the wall and the other wall is 100 feet, 200 feet, 30 feet, 50 feet, away? The more I type the more I am convinced it is condition 1. How about an open ball park with a cyclone fence around it, etc. To me the bottom line is that it exceeds all of the conditions, so the conditions aren't really applicable and you now need minimum working space, of 36 inches at that voltage. We could pretend the code needs to add additional clarification, but this is part of what has made it go from a 5 oz book to a 5 pound book.

 

[jumper]

Why would you draw that conclusion? I almost used a similar example, to draw the other conclusion. Why do you decide 12 feet is inside the "boundary" but outside isn't. How about a warehouse where the panel is on the wall and the other wall is 100 feet, 200 feet, 30 feet, 50 feet, away? The more I type the more I am convinced it is condition 1. How about an open ball park with a cyclone fence around it, etc. To me the bottom line is that it exceeds all of the conditions, so the conditions aren't really applicable and you now need minimum working space, of 36 inches at that voltage. We could pretend the code needs to add additional clarification, but this is part of what has made it go from a 5 oz book to a 5 pound book.

Strat, if the working space is now at 36” because that is all that is needed since the wall is 12’ , what stops someone from building a wall 41” away? 42” of clearance is now needed.