atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring how hot can cable get

hello guys i have a customer in the desert having metal conduit run on top of the roof. it gets up to 120 degrees there, maybe hotter once in a while. palm springs area. the plan is to run some cat 5 and cat 6 cable through, it will be connecting buildings. not sure how hot the inside of the conduit will get. im guessing maybe 150. will this harm the cable.thanks dave

I would ask the manufacture of the cable I intend to use for those specs.
I doubt you'll have a problem, but you mention "connecting building",..... at that point I would highly recommend fiber. Just sayin.

Check your copy of the NEC as I believe there is a table for this. I'm not sure were it is, but have read about it in EC&M magazine. They talked about the de-rating you have to do to wire in conduit on a roof because of the increase in heat. The heat increase was substantial too, not a few degrees, but a considerable amount and it changes on how much separation the conduit has from the roof.

When I lived in Phoenix, we had run some cable through conduit and it did melt the insulation. When the air temp is 120, the roof will be over 140. Keep in mind if it will make the blacktop soft under your feet, it will probably melt cable.

Would small OSP cable be a good fit for an application like this? General cable catalog shows a working rating of 80 Celsius

I believe 80C is 160F.

PVC has a range, depending on the formulation up to 221 degrees F. However, the more common formulations are only good to 140 degrees F. Teflon as a rating, depending on formulation, of over 220 degrees F.

The NEC table regarding cable temperature and derating has to do with ampacity of copper and aluminum wire and not melting point properties. Table B.310.15(B)(2)(1)

OSP cable, generally, will withstand higher temps, but the cable is rated for open air and not conduit.

You would be well served to contact a cable manufacturer and speak to a technical rep and explain your situation. They can offer a cable solution to meet the temp requirements. You must know, if you have the means, that there is cable than can withstand thousands of degrees of heat. It will also cost thousands of dollars for a few feet. A company tech rep can give you the best solution.

Rcaman

tha was a lot of good info. thank you.

He can still melt the sheathing of the fiber.

OP, select the right product for this, whether copper or fiber. Manufacturer should have a rating on the spec sheet.

Make sure the spec sheet is from a reputable manufactuer like Belden.

All too often are specs fudged by the Chinese engineers...just look at the horsepower and RPM ratings on the tools at Harbor Freight Their dust collector is rated at 20A, has a 10A switch and a 14GA power cable.....no problem there!