Cable tray restrictions where power and data share a common tray

[Paul the BIG Finn]

I have surveyed a site where power wiring and data wiring share the same 18inch cable tray mounted above the racks in an article 645 space (with no raised floor?). The power wiring is type 'TC' cable, but the data wring is un-marked. I have three questions regarding the installation.

1. As a general practice my company does not run data and power in the same cable tray, but Article 392.6 (E) seems to allow it, "Multi-conductor cables rated 600V or less shall be permitted to be installed in the same cable tray." Section 392.9 (A) (2), which describes the condition we found, specifically addresses "any mixture of cable." Will the insulation levels of the data conductors have to meet the same requirements as the power conductors?

2. The actual installation has uses combinations of 3#12, 3#10 and 3#8 TC cables (either P,N,G or P,P,G @ 120 or 208V single phase). Where ever the 3#8 cables are found the 18" cable tray is more than 80% of the 21 sq. in. allowance from table 392.9, column 2. Apparently the original engineer sized the tray for power only and the owner in the last +10 years has laid many (20 to 30) data cables and individual 22 gauge 'bell' wires on top of the power cable, violating the fill of the power cable fill requirements. Is there any other NEC requirement this installation violates.

3. At least 25% of the power cables are no longer in use, but still terminate at a receptacle mounted on the side of the cable tray. The owner has proposed disconnecting these power cables from the panelboard and the receptacles and abandoning them in place in the cable tray (It would be difficult to remove them from underneath the data cables and among the other active power cables, claiming since they are not in use, they should not count. Since the table makes no distinction, I have told the owner that this isn't a viable solution. It isn't is it?

This is basically an existing condition that only marginally impacts the small add we have been contracted to engineer. We have told the owner we can't run the new circuits in cable tray and have shown them in conduit, but I suspect the owner will direct the electrician to install them in the cable tray. Our firm does not have inspection as part of our contract.

Past delivering the signed and sealed documents and notifying the owner in writing of the existing violations, what is one to do?

 

[raider1]

I have surveyed a site where power wiring and data wiring share the same 18inch cable tray mounted above the racks in an article 645 space (with no raised floor?). The power wiring is type 'TC' cable, but the data wring is un-marked. I have three questions regarding the installation.

1. As a general practice my company does not run data and power in the same cable tray, but Article 392.6 (E) seems to allow it, "Multi-conductor cables rated 600V or less shall be permitted to be installed in the same cable tray." Section 392.9 (A) (2), which describes the condition we found, specifically addresses "any mixture of cable." Will the insulation levels of the data conductors have to meet the same requirements as the power conductors?

Take a look at 800.133(A)(1)(c) for the separation requirements of communications cables from power conductors in a cable tray.

2. The actual installation has uses combinations of 3#12, 3#10 and 3#8 TC cables (either P,N,G or P,P,G @ 120 or 208V single phase). Where ever the 3#8 cables are found the 18" cable tray is more than 80% of the 21 sq. in. allowance from table 392.9, column 2. Apparently the original engineer sized the tray for power only and the owner in the last +10 years has laid many (20 to 30) data cables and individual 22 gauge 'bell' wires on top of the power cable, violating the fill of the power cable fill requirements. Is there any other NEC requirement this installation violates.

Again, 800.133(A)(1)(c) would not permit the intermixing of TC power cables and communications cables.

3. At least 25% of the power cables are no longer in use, but still terminate at a receptacle mounted on the side of the cable tray. The owner has proposed disconnecting these power cables from the panelboard and the receptacles and abandoning them in place in the cable tray (It would be difficult to remove them from underneath the data cables and among the other active power cables, claiming since they are not in use, they should not count. Since the table makes no distinction, I have told the owner that this isn't a viable solution. It isn't is it?

This is basically an existing condition that only marginally impacts the small add we have been contracted to engineer. We have told the owner we can't run the new circuits in cable tray and have shown them in conduit, but I suspect the owner will direct the electrician to install them in the cable tray. Our firm does not have inspection as part of our contract.

Past delivering the signed and sealed documents and notifying the owner in writing of the existing violations, what is one to do?

I agree that if the cables are left in the cable tray even if they are abandoned they must still be counted in accordance with 392.9.

Chris

 

[kingpb]

You cannot protect the owner from himself. As long as your drawings indicate the proper way to do it, (maybe add a CYA note that specifically states that adding them to existing tray will violate NEC) and you provide the info to the owner, he can do with it whatever he wants.

Inspector should also catch it. Make sure you keep good records, so you can get an extra from the Owner for any issue's that arise because of it.

You are only responsible for the work you design. You are making the right choice to completely stay out of the tray, and have done you due diligence by making the owner aware of the situation, in writing of course.

 

[steve66]

Take a look at 800.133(A)(1)(c) for the separation requirements of communications cables from power conductors in a cable tray.


Again, 800.133(A)(1)(c) would not permit the intermixing of TC power cables and communications cables.

But Tray Cable is a chapter 3 wiring method, and 800.133 talks about comm cables in the same tray as "conductors". I'm not sure if "conductors" was intended to include conductors in another wiring method.

I'm not saying you are wrong, but it (the code paragraph) doesn't seem that clear to me. I'd be interested in what opinion others have.

Steve