atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 25-pair cable crossing hot water pipe

Hello,

Background: I just ran a 25-pair cable up to the attic to extend a working 551C KSU. I can see in the hole in the wall cavity header that the cable jacket touches a crossing of a hot water heating pipe at a 90 degree angle. Note: The cable quality/source is Bell System OEM previously removed from a closed NYNEX CO.

Question: Is the cable and lead insulation going to degrade over time due to the 200F heat of the copper pipe? Would you recommend I open up the ceiling and correct this (by insulating the pipe or moving it a few inches away from the cable)?

I would think this situation would happen all the time back in the day and that the cable insulation was designed to take the heat.

Thanks in advance, -Alan

That much heat will make the sheath and eventually the pair insulation brittle and over time it will flake off, it will proably take several years. I've removed cable in a similar situation that were probably in there 20-30 years and moving them just turned the insulation and sheath to dust.

The cable was removed because it was no good, for how long I don't know, it was a feed between floors that hadn't been used in some time and they had a need for it again, I couldn't find one good pair in it. Actually after 6 or 7 bad pairs I just replaced it.

Couldn't you put a plate of asbestos between it? Not the insulation that is illegal, but a hard plate?

"lead" insulation? Are your sure?

"200 degrees" ? Are you sure?

Use a piece of the split foam insulation on the pipe and also put a piece on the cable where it crosses

I once worked with that lead sheath 25pr, the truck driver rolled it off the back and broke the reel. I had to loop it off laying on its side. Like a coil spring, just a pure pleasure to pull.

> "200 degrees" ? Are you sure?

Yes, the boiler is set at 200, so the heating pipe gets close to that temp.

With the advice that the cable insulation will indeed degrade, the ceiling cavity was opened and intersection corrected. I put a 3/4 inch thick piece of wood in as a barrier and sleeved the pipe with split insulation. I left the cable hole alone in case I need to pull another run through.

Thanks, -Alan

Yeah, you really do need to stay away from heat pipes. I remember many years ago one of my guys ran a 4 pair cable for an extension through the same hole in a block wall as a steam pipe. That was during the summer and come October I get a call that an extension is not working. It took awhile to figure it out because the run wasn't easy to see and follow, but when I yanked on the part going through the wall it was all melted and grounding out to the pipe. What made it even more difficult was that I never found the pipe hot so I couldn't tell that it was a heat pipe. With steam heat, the steam comes up and heats the radiators then shuts off and the piping cools down. Maybe it would have been more obvious in January but this customer was real cheap and only turned the heat on for a few minutes first thing in the morning that October. That's all it took.

-Hal

Do it right the 1st time and you won't have problems down the road.