What’s the best HVAC Building Automation & Control Wiring used for terminating control wiring from 24volts to 600v plus rated wiring?

[Themaintenancenetwork]

Can you make a post about the best stranded wiring with insulation type for building automation and controls for hvac & refrigeration? 600V plus wire types that are good for vfd’s and more.

Very interested to see what you post!

 

[garbo]

Vast majority of automation & controls that I came across was solid wire especially #16 guage & smaller. Any time we ran these in conduit we used solid wire if #16 or 14 guage. If we ran Beldon type of low voltage cable it had stranded conductors. At the 5 million square foot campus that I retired from we had over 500 VFD'S. All had THWW for line & loads on VFD'S. Some were on plain Jane NEMA frame motors from the 1960's. All had a copper properly sized ground conductor from drive to motors. Tried to keep wire length from drives to motors under 100'. Had four VFD'S for 75 HP cooling towers that were several hundred feet away but never gave us any problems. A few months ago a poster stated he now only uses believe he said Type XHHN wire for drives. To me that would be a better choice.

 

[tom baker]

I also prefer XHHW for VFD power, typically for control wiring for PLCs would use THHW/N, or 300 V PLTC shielded, 18-2 as it wet location rated. XHHW is a bit larger on the OD, but the insulation is tougher than THHN, and is best in wet locations.

 

[petersonra]

I don't know there is really a best. For most control wiring purposes the cheapest stuff works about as well as the more expensive stuff. THHN/THWN is quite adequate.

I am personally fond of #18 2C instrument tray cable, either with or without shield for control wiring.

For VFDs, people have been using THHN/THWN for 40+ years and it has worked quite well. I might be inclined to step up a notch to XHHW but I would not get real offended if someone used THHN. However, some VFD instructions now suggest XHHW so it might be that is the way to go rather than fight people over it.

There is no reason to exceed code requirements for this kind of thing. It does not make the installation one iota better.

 

[mikecentola]

Sorry to bump an older thread, but I used 18/7 VNTC for controls cable from a motor controls panel over to a pendant. It was 600V rated so it was overkill since there was only 240 inside the cabinet. I used it for 24VDC control of start/stop and multiple speeds.