Building Automation Systems cable question

[mark richards]

I am being asked to wire the control wiring between a CRAC indoor Liebert unit and its roof mounted condensing unit. I have to install a Canbus Anixter B89207 twinax 20-2C shld. 300V CMP cable. The Liebert technical support line told me this can be installed above a drop ceiling, plenum area, on bridle rings and sleeve it in raceway up to the unit on the roof.
They also specified I furnish a Heat Rejection interlock cable Class 1 600V rated #18AWG twisted pair control cable and tell me it can be ran with the Canbus cable. I asked them what the voltage was on this cable and they answered; "Liebert doesn’t give us the voltage on that connection. I would assume that it is control voltage as you can run it in the same conduit as the CANbus cable. We don’t offer deviation from this wire specification. No one has brought this up as an issue before. I’d recommend getting a Belden cable. Looks like Anixter has Belden Wire 18 gauge twisted pair 600V with reel sizes lest than 500ft or you can get a custom cut. Please note that the Condenser is powered separately and not by Interlock B." I also notice on their submittal data this cable runs through the "low voltage field entrance hole" with the Canbus cable.

Now for the issue, I do not see a Class 1 600V 18TP cable available in plenum. Anixter send me a price for a Type TC-ER (Tray Cable, Exposed Runs). Anixter tells me that they do not make a Class 1 600V cable rated for plenum use. NEC70 doesn't allow for TC-ER cables to be ran on j-hooks with the Canbus cable. It appears, other than the exceptions, it must be in raceway or Tray Cable. Running a separate conduit for this cable is going to blow my budget. It would appear at first glance, because they tell me they don't make a CMP 600V Class 1 cable my only choice is a Tray Cable and Iw ill have to bite the bullet and lose money?

 

[__dan]

Just a guess but the interlock cable, based on the spec but ignoring the Class 1, I would ask them if the cable can be class 2. That would make it a typical Art 725 power limited control application and a CL2 rated cable. For this to happen the upstream or sourcing power supply, device or card, the cable connects to would have to say "Class 2" on it. Usually that's a safely power limited device 40 Watts or less.

My guess is it is typical class 2 equipment or application. This would have been what they tried to do from the start. The interlock cable probably pulls in an ice cube relay or is an input to another Class 2 device. Whoever makes that equipment would have to confirm but that's the question to ask. Then you can get a CL2 cable meeting the rest of the spec. Or a dual rated CM CL2 may have the higher Voltage rating. 600V is non standard and probably not necessary, they're not using it except maybe to run in the same compartment as the power wiring.

Separation barrier would be needed between the CL2 and the power wiring.

If they require class1, afaik you would be in a chapter 3 wiring method, EMT, MC cable, #14 gauge minimum, which is why someone said TC-ER, but idk if TC-ER is plenum rated, and then plus the tray but it is rated for short exposed runs of whip to the equipment.

If an error was made it was when they said class 1 instead of class 2, where Art 725 could be applied.