Why is Ventilated Cable Tray Cover Not in the Code???

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EEDude

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Am I missing something???

392.80(A)(2)(a)
600MCM or larger, single or grouped...
  • You can install cable in tray at 75% free-air current rating in uncovered tray.
  • You can install cable in tray at 70% free-air current rating if covered more than 6' with "SOLID UNVENTILATED covers". It is very specific to unventilated covers.
Well...
I plan on using ventilated covers.

Would we simply interpret the implicit omission of ventilated covers as equivalent to uncovered and no need to consider? Just use the 75% free-air rating?
 
Those ratings are probably specific to those types of cable trays because if we go back to 392.22(B), the rules for cable spacing is different for cable trays with ventilated covers.
 
drktmplr12 said:
It's specifically 75% if uncovered. Ventilated is not uncovered if you are asking me.
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But it's also clearly not unventilated. Why is 'unventilated' in the code if covers of any type require a 70 % derate? The code describes only two scenarios, both if which exclude what the OP is using. I see his point.

Conservatively you would use the 70% factor.
 
steve66 said:
Those ratings are probably specific to those types of cable trays because if we go back to 392.22(B), the rules for cable spacing is different for cable trays with ventilated covers.
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That is referring to conductor fill in ventilated (or ladder) tray vs solid tray. Covers aren’t considered.
 
jaggedben said:
But it's also clearly not unventilated. Why is 'unventilated' in the code if covers of any type require a 70 % derate? The code describes only two scenarios, both if which exclude what the OP is using. I see his point.

Conservatively you would use the 70% factor.
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Exactly…
It’s just not written great.

At the end of the day, it’s not a huge deal (or difference), I can adjust the trip unit accordingly. But now it’s one of those things that’s just going to bother me 🤷🏼‍♂️.
 
EEDude said:
That is referring to conductor fill in ventilated (or ladder) tray vs solid tray. Covers aren’t considered.
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I see what you mean. But your paragraph 392.80(A)(2)(a) specifically refers to 392.22B, and 392.22 B only mentions ladder trays, ventilated trough, and ventilated channel trays.

So what kind of tray are you using?
 
I don't do a lot of cable trays, and I guess I'm not sure why you would put a solid cover on a ladder type cable tray?
 
steve66 said:
I don't do a lot of cable trays, and I guess I'm not sure why you would put a solid cover on a ladder type cable tray?
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I have seen this style in some snow areas. Solid covers can still be ventilated by being mounted so there is an air gap above the side rail. The tray brand I used to sell had these types of clips as a standard offer.
 
steve66 said:
I don't do a lot of cable trays, and I guess I'm not sure why you would put a solid cover on a ladder type cable tray?
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I'm my 45+ yr old plant, we utilize covered tray for overhead protection from over spray of dyes and inks and possible falling objects that could damage a wire or cable. Also, places that run a lot of fiber run "boxed" tray with full bottoms to prevent sag and covered top for protection.
 
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