Need Help Again

Bkessler

I was working in an apartment with radiant ceiling heat, and while cuting a hole for a new fan we hit a wire. Now the owner of the apartment was sure there was no wires where the fan was going but unforutunely she was wrong. So this wire is about 18 gauge solid and its embedded between .5 inch drywall and a .375 inch of plaster. And of course there's no heat now. How can this be repaired. She speaks of an electrician that has made repairs in the past but unfortunetly he is not with us anymore. Thanks AGAIN brian go wings!

DaveTap

Its probably not a wire... its your heating element. Without knowing what type it is I can't answer if it can be spliced or crimped but my first guess is no.

Just a suggestion... next time pull out your tone and probe set or spray a light water mist on the ceiling and turn on the heat so you can see where the elements are.

mdshunk

There is no repair for that resistor wire. DO NOT try to fix it. It will be a hazard. The repair is new ceiling radiant heat, a baseboard heater, or highwall electric heat. You can't fix cut cable heat.

Bkessler

Ok I was afraid of that, The owner already has a cove heater ready to install. Thanks again for the info. bk wings 1 edmonton 0

Sparky Joe

Tough break dude.

Though I'd like to ask what would happen if he did butt splice a peice of #12 between the cut wires?

mdshunk

It would turn that piece of #12 into a heating element, and it would get MUCH hotter than the calibrated resistor wire of the actual ceiling heat cable.

Sparky Joe

How do you figure? What would the wattage be, and how is that #12 a worse conductor than the resistive #18 waire that was there.

I would think that where the repair was made you wouldn't get any heat, at most.

mdshunk

Most heat cable is around 10 watts per square foot when installed. At 240 volts, that heat cable would have a resistance of about .016 ohms per inch of heat cable. (1000 watt of heat being about 300 lineal feet of cable). Each inch of cable is dissipating about .27 watts.

The resistance of #12 copper is only .00187 ohms per lineal foot. Or, .789 ohms per 300 lineal feet. Each inch of #12 will dissipate about 20 watts of heat.

Now, I have not plugged in the "series resistor" calculation for a piece of low ohm #12 in with higher ohm ceiling heat cable, which will make it's effective heat dissipation less. I can tell you from days of foolishness past, that this repair section will get very hot.

CE1

You could repair the heating panel by using a non-insulated (preferably a high temp nickel alloy) crimp butt splice. The real problem is insulating the splice by replacing the insulation that the heating element was imbedded in originally. If it is not done right, there will be a hot spot where the splice was made. This is a VERY BIG liability problem. I would be very cautious because the electrician before you maybe did it this way. Always assume that they guy that was there before you most likely did it WRONG until proven otherwise. In commercial and industrial applications it would be possible to splice a heating element with no real problems because the splice location could maybe reinsulated. But for residential applications NO WAY.
Be careful out there.

DaveTap

I think you missed something in there... the resistance of the 12AWG wire is MUCH LOWER than the element wire and would not get hot... except for the resistance at the crimp connections. (Otherwise the 12AWG wires supplying the element would melt). Remember the original element resistance is all still there limiting the current flow. The problem here being that those connections would have to be able to withstand many heating (expansion), cooling (contraction) cycles without breaking contact. Even if you could still crimp them together in a butt splice the expansion and contraction would evetually cause the connection to fail... the question is how long?

I'm curious if the butt splice were of the correct material how long would it last and how much of a danger would it pose if you installed an AFCI breaker. The connection is between fire rated materials and the AFCI should trip if the connection starts to fail. Any Ideas?

Sparky Joe

in my book Watts = I squared x R. With a lower R you have lower watts.

DaveTap

Correct...

CE1

If the butt splice were of the proper material it would last almost indefinably. The material of the butt splice connector would have to be made specifically for splicing the heating resistor wire (most likely Nickel-Chromium) to itself or a piece of high temperature rated insulated wire. There is also the issue of the proper crimping tool for the butt splice connector. The crimping tool would have to be approved to crimp the butt splice connector and most likely the crimping tool and the butt splice connector would be the same brand (expensive). You have to keep in mind that you are trying to duplicate what the manufacturer of the original heating panel did and it would have to be a very good guess as to how it was originally done. I do not think that anybody out there could do this without having some doubt that it would eventually fail; it would be a question of WHEN and not IF it would fail. An AFCI breaker would have minimum impact on adding to the safety of the spliced heating panel because it would not detect the hot spot of an overheated connection, which is most likely to happen.

Again No Way!!

Sparky Joe

In the control box, where the heat trace recieves it's power, how are those splices made?

mdshunk

The current generation of arc faults will not detect series arcs. They would offer no additional margin of safety.

Sparky Joe

Arc Fault breakers are not generators and do not produce any currents

skymaster

Has anyone just called the mfg,state the problem and ask them how to fix? Might just have a kit they use in mfg to repair such problems? This cant be the first time this problem has occurred.
JackM

Bkessler

Read this thread on raidient ceiling heat

Celtic

Buy war bonds

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