Open Bottom or Solid Cable Tray

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designer82

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Does anyone know of any requirements where an open bottom or solid type cable tray is required?

I can't remember if there are any, possibly if there are too many cables you may want open bottom? Or if it is in a plenum maybe solid is required?
 
Solid bottom tray gets a bigger derating. Also it tends to collect dirt and debris. So I’ve never used it. If access (such as in a public space) is an issue conduit is a better choice.
 
The problem is there are a lot of ventilated bottom cable tray types. Nor NEC neither NEMA VE-1 or VE-2 present a clear definition.
In my opinion NEC consider a ventilation as per here attached B-Line sketch and this is very close to ladder type. So, a solid bottom cable tray provided with slots for water draining is still a solid bottom type.
 

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I think it's much easier to pull cables in solid bottom cable tray. If you have a large amount of cables in places away from rain and sun as it is in a power plant for example you can pull all these cables in half the time.
 
I also think that if the cable tray is full it doesn't matter if the bottom is solid or ventilated
 
Julius Right said:
I also think that if the cable tray is full it doesn't matter if the bottom is solid or ventilated
Click to expand...

It does. With power cables you are limited to a single layer and/or spaced out and secured. Even if you lay out cables butted up side by side there are still gaps. Plus it is rated about the same as laying inside a “solid bottom” conduit including derating for multiple conductors.

It’s only with control cables that although there is a fill rule, you can all but stuff them. But it is a random pile of cable with low power density. The fill rule applies to all tray types so it doesn’t matter if it is solid bottom or not (worst case).
 
You are right. NEC [art 392] does not permit more than one layer power cables. In power station where NEC it is only for information, we work according ANSI/NEMA WC 51 [ICEA P-54-440]. Sorry. If you intend to follow NEC recommendation [it will waste a lot of space and equipment-cable tray and accessories] you have to employ ladder in order to reduce the cable conductor cross-section area.
 
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