Dividers in wireways/wire troughs - conductor derating

[Carultch]

I understand that in wireways and wire troughs, you are permitted to install up to 30 "current carrying conductors" without adjusting ampacity for bundling. The instant you add a 31st wire, the 31-wire derate factor applies.

How does this work when you install a wire trough divider?
Does the full count of wires on both sides matter?
Or just the count of wires per side of the divider?

 

[petersonra]

I understand that in wireways and wire troughs, you are permitted to install up to 30 "current carrying conductors" without adjusting ampacity for bundling. The instant you add a 31st wire, the 31-wire derate factor applies.

How does this work when you install a wire trough divider?
Does the full count of wires on both sides matter?
Or just the count of wires per side of the divider?

as strange as it may sound, my understanding is that each side of the divider is counted as a separate raceway for most purposes (except maybe installing).

 

[shortcircuit2]

Good question. I would say you treat each side of the divider as a separate enclosure when applying code rules for conductor fill, etc. The same should apply to cable trays with dividers.

Why are you using the divider? 690.31(B)?

 

[Carultch]

Why are you using the divider? 690.31(B)?

Yes. And the fact that the DC side is 1000V.

 

[Carultch]

as strange as it may sound, my understanding is that each side of the divider is counted as a separate raceway for most purposes (except maybe installing).

Do you know of any citation that would support this interpretation?

 

[qcroanoke]

I understand that in wireways and wire troughs, you are permitted to install up to 30 "current carrying conductors" without adjusting ampacity for bundling. The instant you add a 31st wire, the 31-wire derate factor applies.

How does this work when you install a wire trough divider?
Does the full count of wires on both sides matter?
Or just the count of wires per side of the divider?

http://forums.mikeholt.com/showthread.php?t=174197&page=2&highlight=divider

I think Infinity's response in post #12 covers it. For me anyway.

 

[Smart $]

as strange as it may sound, my understanding is that each side of the divider is counted as a separate raceway for most purposes (except maybe installing).

http://forums.mikeholt.com/showthread.php?t=174197&page=2&highlight=divider

I think Infinity's response in post #12 covers it. For me anyway.

I'm of the opposite position. The ampacity adjustment stipulation is regarding the wire... which does not auto-magically become two wireways when a divider is added.

 

[petersonra]

I'm of the opposite position. The ampacity adjustment stipulation is regarding the wire... which does not auto-magically become two wireways when a divider is added.

suppose you ran some of the wires in the wire way inside of another wire way? then you certainly have two wire ways. would you count the wires in the inner wire way with the wires in the outer wire way for derating the outer wire way conductors? you certainly don't have to count the conductors not in the inner wire way for derating those inside the inner wire way.

 

[Carultch]

I'm of the opposite position. The ampacity adjustment stipulation is regarding the wire... which does not auto-magically become two wireways when a divider is added.

Understood. However, it does now becomes two bundling groups, where the wires would be in immediate contact. The divider prevents one portion from being bundled with the other.

 

[qcroanoke]

suppose you ran some of the wires in the wire way inside of another wire way? then you certainly have two wire ways. would you count the wires in the inner wire way with the wires in the outer wire way for derating the outer wire way conductors? you certainly don't have to count the conductors not in the inner wire way for derating those inside the inner wire way.

What? LOL Are you running for office somewhere?

 

[GoldDigger]

Careful application of basic physics and the Neher McGrath equations convinces me that:
1. The conductors in the inner raceway must be counted along with those only in the outer raceway when determining whether to derate conductors in the outer raceway.
2. If that number calls for derating, that same factor also applies to the conductors in the inner raceway.
3. If the number in the inner raceway requires derating, that occurs independently of what is happening in the outer raceway and does not directly apply to the outer raceway conductors. For that, see 1.

 

[Smart $]

Understood. However, it does now becomes two bundling groups, where the wires would be in immediate contact. The divider prevents one portion from being bundled with the other.

The fact remains, it is but one wireway.

My personal contention for looking at it otherwise is compare the one wireway divided to two smaller wireways. You then would not have to derate until going over 30 conductors in either wireway... which allows up to 60 conductors without derating.

My counter to the above contention is to run two smaller wireways and get over it. :angel:

 

[steve66]

From a heat dissipation standpoint, I don't see how a wireway with a divider is any different that two separate wireway's ran side by side against each other.

And there is a 20% max. fill to not derate, and a 4 sq inch minimum on surface raceways. So if you are going to put in a divider and count it as two separate wireways, the minimum cross sectional area doubles. Then you have 2 bundles of wire taking up 1/5th the cross sectional area, with 4/5ths of the cross sectional area being empty space.

So in my opinion it becomes two wireways, and you can install a divider and 60 conductors without derating.

Although I would have reservations about doing this if the wires were really loaded. But I would also have reservations about putting 30 conductors in a single wireway with no derating if they were really loaded even if it is clearly allowed.

 

[Smart $]

From a heat dissipation standpoint, I don't see how a wireway with a divider is any different that two separate wireway's ran side by side against each other.

And there is a 20% max. fill to not derate, and a 4 sq inch minimum on surface raceways. So if you are going to put in a divider and count it as two separate wireways, the minimum cross sectional area doubles. Then you have 2 bundles of wire taking up 1/5th the cross sectional area, with 4/5ths of the cross sectional area being empty space.

So in my opinion it becomes two wireways, and you can install a divider and 60 conductors without derating.

Although I would have reservations about doing this if the wires were really loaded. But I would also have reservations about putting 30 conductors in a single wireway with no derating if they were really loaded even if it is clearly allowed.

Here's a friendly reminder: Where does Code say it is permitted to consider a divided wireway as two wireways for the purpose of derating?

 

[petersonra]

Here's a friendly reminder: Where does Code say it is permitted to consider a divided wireway as two wireways for the purpose of derating?

where does it say it is not?

 

[Smart $]

where does it say it is not?

Manufacturer documentation, listing, and/or labeling, or even trade identification. It's a divided wireway, not two wireways.

I'll agree that Code does not require metal wireways to be listed, labeled, or even identified... so if you want to do so with an "undistinguished" wireway, have at it.
:thumbsdown:

 

[steve66]

Manufacturer documentation, listing, and/or labeling, or even trade identification. It's a divided wireway, not two wireways.

I'll agree that Code does not require metal wireways to be listed, labeled, or even identified... so if you want to do so with an "undistinguished" wireway, have at it.
:thumbsdown:

Actually, the code does require listed for surface raceways, and a manufacturers label for other metal raceways.

I seriously doubt the "manufacturer documentation" states anything about derating, or if a divided raceway is one raceway, or two. If I'm wrong, please provide an example.

 

[Smart $]

Actually, the code does require listed for surface raceways, and a manufacturers label for other metal raceways.

I seriously doubt the "manufacturer documentation" states anything about derating, or if a divided raceway is one raceway, or two. If I'm wrong, please provide an example.

Okay, Mr. Pitnicky Jr. :angel:

I was referring only to Article 376 metal wireways... and requiring manufacturer marking is not the same as requiring equipment to be labeled as per the Article 100 definition.

All I'm really saying is the manufacturer packaging, sticker, etc. will call it wireway. Show me where any one product is marketed as wireways, i.e. plural.

 

[ggunn]

Okay, Mr. Pitnicky Jr. :angel:

I was referring only to Article 376 metal wireways... and requiring manufacturer marking is not the same as requiring equipment to be labeled as per the Article 100 definition.

All I'm really saying is the manufacturer packaging, sticker, etc. will call it wireway. Show me where any one product is marketed as wireways, i.e. plural.

It's not us whom you need to convince, you know. Let us know how the inspection goes.

 

[Smart $]

It's not us whom you need to convince, you know. Let us know how the inspection goes.

Won't be me any time soon. I haven't even done work that gets inspected in that manner in at least the last 5 years as I've been on the POCO side of things and now not-working disabled.