Running co-ax

If you bought decent coax like 'CT100' or whatever its latest incarnation is called, then it won't matter what it touches as long as you didn't crush it or bend about 2 inches of it into a

It is not a good idea to have pvc insulation in permanant contact with central heating hot water pipes. Could you not use clips to secure the coax away from the pipes?

Why not ?. It survives UV light out of doors.

I never encountered this problem in my lifetime of working in the aerial and satellite business.

Saw plenty of heat-affected coax, but it was always after house fires!

Bill

Well, I'd personally not want to run coaxial tv cable along with hot pipes myself. I guess what happens and how long it takes to happen depends on your signals in the area. Can you not strap a bit of the coax you are using to a water pipe soomewhere with a couple of loose cable ties and see what occurs? Brian

Yes and some sorts of coax you would be hard pressed to bend it like that anyway, A far cry from the so called low loss stuff we used to use in analogue days with about as much braid as hair on a billiard ball. Brian

Is what you mean ttat the coax may touch the pipes when going through the holes ?

Could you not sheath the co-ax with a couple of turnings of heat resistant tape at those points ? You'd need to slacken it off from end or one or other apply the tape and pulll it back through I'd imagine,

michael adams

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All plastics have melting points above the boiling point of water. Central heating systems do not run at boiling point. A round cross-section cable touching a round cross-section pipe wouldn't have a large area of contact but the cable would have a large surface area with which to dissipate heat.

Like I said before (and it seems nobody was taking a blind bit of notice) in a lifetime of fixing aerials and dishes I never once saw this problem.

Bill

Out of curiosity I found the following

Clip On Hot Water Pipe Thermometer 0-120C 63MM Temperature Gauge

Then there's this

Polyethylene and polyvinyl chloride are used as insulators. These two plastics have relatively low melting points, and can start to soften at temperatures as low as 150 degrees F. [65 C] If the insulation is exposed to low heat over long periods of time, the position of the center conductor in relation to the shielding may shift as the hot plastics yield. If the center conductor and shielding touch, signal never makes it past that point. Coax should be kept away from heatsinks, stage lights, and other sources of heat

It appears its not the actual contact but the heat being radiated (?) by pipes potentially being up to 120C over prolonged periods which may cause the problem

Or not, in your experience apparently.

michael adams

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So you?re taking the calibrated scale of a thermometer as an indication of typical CH water temperatures?

Tim

Boiling point of water at 3 bar is about 134 deg C. IIRC boiler gauges typically go to 3 bar, presumably relief valves are slightly less.

Water doesn't always boil at 100C. Up a mountain where the air pressure is lower, it boils below 100C. If the water in the CH pipes is at 1 Bar above atmospheric (as it is here, f'rinstance), it will boil at, IIRC, 121C, and up Everest it boils at 70C.

Radiated is correct unless the coax is above the hot pipe in which case there's be some heat transfer by convection. Conduction if it's touching the pipe.

But if you clip it on to a CH pipe or domestic hot water pipe the reading will be around <70C.

Er, no ? As I said above, it's the pipes themselves which are 120C, it being a pipe thermometer, after all. Not necessarily a CH water thermometer, at least as far as I know.

Quite what the relationship between the two may be I don't claim to know But it's the temperature of the pipe rather than the water inside it, which is of the most relevance here.

And its relationship of that temperature - in the confined space of a hole don't forget, to the temporaries at which it's claimed the plastic components of a co-ax lead may start to soften which is of most potential interest.

michael adams

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I'm quite prepared to believe you. But then why have thermometers that go up to 120C if there's no need ?

michael adams

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sorry to hijack this

but what does FS do for me.

assuming that I'm not prepared to sub to Netflix or whatever what does it give me

Just the main 5 channel catch up services (plus their baby channels)

or something more?

TIA

tim

michael adams wrote on 14/11/2020 :

It doesn't make any sense, unless it is for use on steam pressurised heating pipes. Maximum you get on a domestic heating system at the flow from a boiler, is 80C.

michael adams presented the following explanation :

..and how might the pipe be hotter than the water in contains?