Heat & CAT5 Ethernet Cabling

Question

I am wondering what the heat rating is on standard CAT5 cabling or where I can check the heat rating of my cabling by using the information inscribed on the cabling?

In my specific situation, I am trying to decide if the length of CAT5 I have sitting around can be run along and be fixed to the feed line of a old cast-iron radiator (hot water from the boiler would be traveling in that pipe, since the rad is still in use). I am laying down this CAT5 because I want dedicated 100Mbps connection via cable versus the Wi-Fi signal I am using now, so if any sort of impedance would result from having the cable subjected to heat from the pipes, that would be an important thing to know as well.

Hopefully some wise sysadmins or hardware folk know the details of this sort of situation and can advise me on the best way to proceed.

Thanks in advance,

Answer 1

The spec says -55C to +60C so you may be exceeding that rating.

http://en.wikipedia.org/wiki/Category_5_cable#Electrical_characteristics_for_Cat.5e_UTP

Personally I think it will be ok if you lag the cable and possibly by a good quality Cat5e or Cat6 cable.

Answer 2

Personally I wouldn't run a cable like that without some kind of insulation/heat shield, and I would only do that after looking for alternate ways of routing the cable.

Problems I see are:

Electricity doesn't work well with heat (heat negatively affects conductivity) - Dave Cheney already pointed out the specs regarding acceptable temperates for Cat5e.

The cables plastic jacket is likely to melt over time (or rather it will soften up just enough that it begins to fray apart under it's own weight), exposing the wires inside. This will likely result in packet loss over the cable.

And most importantly, you could start a fire. Either from the plastic jacket heating up enough that it catches fire (burning wires are great - it spreads through walls, and releases toxic gases) or after the cable frays, the exposed wire could touch the metal and short, resulting in an electrical fire (the fact that there is water involved isn't great either).

Don't take all this as overly dismissive - I've personally taped RJ12 to the outside of building ducts as a quick way to route in an extra phone - however an old style cast iron system does not sound good. A simple test would be, with the heating jacked up, can you hold onto the pipe for long without getting a burn?

Answer 3

I'm with David on this one: if you're asking about what kind of heat a plastic cable can handle, it sounds like fire is a possibility. Running the cable or not depends on your own judgment, but: If there's a risk of high heat it might be worth looking into plenum-grade cabling. Slightly higher heat tolerance, lower horrible-gas release, etc.:

What Is Plenum Cable, and When Should I Use It?

Answer 4

It's a bad idea. Keep computer stuff away from HVAC whenever possible.

Depending on the type of heating system you're using, the temperature of the water in that pipe will either slightly exceed the rated operating temperature of the cable or exceed it by a significant amount (steam radiators).

The people talking about fires are probably being alarmist IMO. The problems you're going to have are brittle or separated jackets, oddball performance problems, plumbers cutting your network off, etc. Plenum or shielded cable won't make a difference here and won't address any potential building code issues.

Typically, I would recommend having drilling a hole in the floor. If you're in a historical building, there are more exotic options that will cost more money and are dependent on your situation. In one extreme example, transitioning the wiring in a early 1800's courthouse from terminal coax to Ethernet for 250 people cost about $90k. (much of that cost was restoring the damage the mainframe people made in the 70's)

Answer 5

When you have heat problems there are always three components:

A. radiation

Hot things radiate and thus transfer heat to other things. You put some shielding that is not transparent for heat. Any metal foil will do and a lot of other things. The shield must not be in contact with the heated element and cable because of

B. conduction

If you heat a thing up, it will conduct heat to the other side and to all other things in contact. Insulators conduct extremely badly, conductors very well. Put an insulator between which may work also as a shield.

C. convection

Even if you have insulator and shield in place, eventually there will be enough heat slowly coming through to heat your cable. You need to have some, at least minimal, exchange of the air around cable or some other means of getting the heat away continuously.

Convection (moving of the heated medium) will help: install the wire in a larger diameter tube (an inch? depends on length and bends) and make sure there is at least a small draft able to get through. If you have an altitude difference, you can get it to work by itself, otherwise put a ventilator.

A bonus is that you can also monitor the temperature on the exit.

To sum up: as already said I'd try to find another route. If not possible, then put an insulated shield (mineral wool/foam + aluminium foil is available) between and put cable in a large diameter tube to allow for draft to cool the cable.