Heat Trace Cable Buried Treasure

[Bluenoser337]

I have access to the wiring from 2 different heat trace cable sets. The wires I have access to are not the actual ends of the heating cables. They are obviously spliced between the heating cable and the junction box I have access to. I read 156 ohms on one set of wires and 95 ohms on the other. My ohm's law tells me that should mean one set is 100 watts (at 120v) and the other 150w. These numbers do not seem correct as these cables are used to keep a "pipe-in-a-pipe" where it crosses under a bridge, from freezing....each run about 75 feet long. I am wondering if this could mean these are "self regulating" cables or maybe I'm missing something else. They were connected originally to old dial type stats, but they were too rusted to get any info from them. Any thoughts? Thanks!

 

[VEBill]

Maybe apply power and monitor the current with a clamp-on meter. Of course, this won't give you the data points for deep winter temperatures (but you're lucky that it is pretty cool/cold here for the next few days).

Insulated pipes? If not, then you could also borrow an IR camera and monitor the pipe temperature to see if you see any heat. Or use a "laser" remote IR thermometer to track the pipe temperaturs.

 

[itsmoked]

Most tapes seem to be self regulating so I'd agree, just an ohmmeter on un-powered tape may offer up a weird number.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Bluenoser337]

Yes itsmoked, I think that must be what is going on. From what I can gather, it should be okay to simply connect these to an ambient sensor to power the traces when the temperature drops below a setpoint...and they regulate themselves all they want after that. VE1BLL, I think that taking the amp reading will be the only way to really see how many watts I am dealing with. Thanks all!!