View Full Version : why is cable tray no good for res.
09-21-2007, 06:25 PM
I know table 19 (cdn code, CEC ) states that tray cable is for tray only, BUT on a technical side why isnt it ok to use for residental (beside because the code book says no). when i look at tray cable i can see the jacket is thicker, stronger, and has UV protection but lumex (ect) isnt as strong. so if a product is stonger, better protected, whats the problem Any insight???
also what if you use teck cable without the armor
PS please be kind im a jman and im only asking because iv seen this come up (uses) before
Well, unfortunately it IS because the book says so. Different cables and cable assemblies are tested in different ways for different uses. Tray cable is tested for use in cable trays and not for residential wiring.
I know that is not the answer that you want to read but that IS the way it is. Sorry.
I once worked in a facility where welding cable was being used for something to do with a 400 Hertz frequency changer. The welding cable had an insulation rating sufficient for the voltage and the size was sufficient for the current but the inspector said that unless the cable was "listed" for the express purpose that it was being used for it was not acceptable. It cost the company a pretty penny to make the change but that is what they had to do.
09-22-2007, 08:03 AM
Tray cable (TC) doesn't meet requirements for crush and impact resistance. Cable that does meet those requirements (TC-ER) may be used in certain areas under the conditions of NEC 336.10(7).
Tray cable may also be run in conduit or other raceways where it is protected.
09-22-2007, 04:43 PM
ok i never thought about the crush haz, mind you if its in the wall there shouldn't be a problem. also if crushing is a problem what about when a 24" tray is filled to the top with cable tray (iv seen this) or when some one drops a tool from heights and it lands on the cables (point being how can tray be a safe if the top is open ) any insights??
09-22-2007, 08:25 PM
NM used in residences is subject to crush hazards that tray cable is not exposed to. Staples, NM clamps, and being hauled around drilled holes are examples of what can crush a cable. I have seen NM (Romex) that was shorted by box clamps.
Trays are used in industrial applications where they are subject ot supervision by qualified personnel. If the cable is run out of the tray it must be rated for that condition.
There are requirements for power cables in trays that are similar to the limitations of current carrying conductors in conduit. They can't be stacked without limit.