What is the depth of a 6" cable tray to be used in a cable tray fill calculation? 5" ?
What is the depth of a 6" cable tray to be used in a cable tray fill calculation? 5" ?
(OP)
2011 NEC Section 392.22(A)(2) says that 6" is to be used in the calculation for any tray with a usuable depth of more than 6"...but what about a standard 6" cable tray? Most standard cable tray has a 6" side rail, and the rungs take up inside space so should you always use 5"?
This makes a difference in the allowable fill calculations...
This makes a difference in the allowable fill calculations...






RE: What is the depth of a 6" cable tray to be used in a cable tray fill calculation? 5" ?
Bill
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"Why not the best?"
Jimmy Carter
RE: What is the depth of a 6" cable tray to be used in a cable tray fill calculation? 5" ?
I don't know how a modern program could calculate the ampacity. In power station we used only solid bottom open top tray and the ampacity is calculated as per the Stolpe/ICEA Cable Tray Model [1970] and adopted in ICEA P-54-440 standard "Ampacities of cables in Open-Top Cable Trays."
I my opinion it will be very conservative to follow Stolpe for ventilated cable tray.
Sandia National Laboratories publicized a very interesting article [July 2000]:
"Ampacity Derating and Cable Functionality for Raceway Fire Barriers"
However, in my opinion, NEC is simpler to follow and is not so conservative.
By-the-way, NEC 2014 keep art.392.22(A).2 unchanged.
RE: What is the depth of a 6" cable tray to be used in a cable tray fill calculation? 5" ?
Bill
--------------------
"Why not the best?"
Jimmy Carter