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Is it possible that (isolated) wires carrying high current, such as 200A, passing through water will heat up that water like a boiler?

I have been told by someone that a fuse panel in a building had its bottom immersed in water and apparently this created a lot of heat and steam. Does this make any sense?

I know that inductive heating COULD possibly occur, but we are speaking 50Hz and no coils but straight wires. Usually one would expect that with frequencies in the kHz range. Resistor-type heating would probably not have occured either since wires in a fuse panel would be highly conductive.

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    \$\begingroup\$ You mean like an electric kettle? \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 27 '16 at 17:33
  • \$\begingroup\$ The wires can heat up the water, but only if the wires are hot. If they are designed for 200A, then they probably don't get very hot (I mean, not hot enough to boil water). \$\endgroup\$ – mkeith Nov 27 '16 at 17:34
  • \$\begingroup\$ A kettle would do "resistive" heating with a resistor specifically designed to heat up. Here we are speaking the bottom of a fuse panel. The incoming main wires might not be copper but they aren't heating resistors either. I just wonder if such an effect exists just because of the high current? \$\endgroup\$ – nepdev Nov 27 '16 at 17:36
  • \$\begingroup\$ This is in the context of a fuse panel, the incoming wires might get a bit warm but I was told it was generating steam, which seems weird \$\endgroup\$ – nepdev Nov 27 '16 at 17:37
  • \$\begingroup\$ Why do you believe that copper wire isn't resistive? \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 27 '16 at 17:38
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There is no inductive heating since water is not magnetic (in any working sense). So if only an insulated wire contacted the water there would be no current flow and no heating. So your story (if no wire contacts the water) is incorrect, but since power wiring panels have lots of bare voltage carrying conductors in them, I assume it's just someone got it wrong.

Providing the water is impure enough to conduct there will be current flow and therefore heat generated in the water if the wires contact the fluid. Depending on the voltage available there is likely to be lots of heat and steam. There are many (mostly Chinese) shower and water heaters that use this very method, although it is potentially hazardous.

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  • \$\begingroup\$ In other words - the resistor is the water itself? I believe that would definitely have been possible in a fuse panel, I do recall having seen panels which have bare incoming metal bars as the source \$\endgroup\$ – nepdev Nov 27 '16 at 17:48
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    \$\begingroup\$ Inductive heating does not require that the work piece be magnetic. It does have to be conductive, though. Aluminum and stainless steel can be heated via inductive methods. But I agree that inductive heating cannot explain this phenomenon. \$\endgroup\$ – mkeith Nov 27 '16 at 19:16
  • \$\begingroup\$ Fuse panels are not internally isolated, all internal terminals will be exposed to raw water if the box is immersed. \$\endgroup\$ – Ale..chenski Nov 27 '16 at 20:04
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Yes, it is Joule's heat (I^2R). Electrical energy in the wire is converted into heat (depending on resistance of the material) and the water in contact get heated up.

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  • \$\begingroup\$ Would that make sense if the wires have next to no resistance but do carry a high current such as 200A? The resistance then sort of being the water? \$\endgroup\$ – nepdev Nov 27 '16 at 17:38
  • \$\begingroup\$ Because per what I know it should be P = I x I x R, which would mean wires with next-to-zero resistance do not create this effect. \$\endgroup\$ – nepdev Nov 27 '16 at 17:40
  • \$\begingroup\$ If resistance is too small (like in the case of a wire), the heat will be less. If you know the resistance , with some basic math you can get the idea. mass of water * (100'C - ambient temp) * specific heat water = I^2.R.t \$\endgroup\$ – user3219492 Nov 27 '16 at 17:43
  • \$\begingroup\$ Wires rated to carry 200 A would not heat up (resistive effect) to warm to any significant level any water around it. \$\endgroup\$ – Jack Creasey Nov 27 '16 at 17:47
  • \$\begingroup\$ Or you can substitute all the values (this must not be tough) and find the resistance from the formula. Check if the value will resemble a wire or not \$\endgroup\$ – user3219492 Nov 27 '16 at 17:48
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Fuse panels are not isolated, there is a lot of metal (conductive) terminals between hot wires and returns and earth ground inside, 0.5 -2 inches apart. More importantly, depending on overall electrical hook-up (two phase or three phase), adjacent hot terminals can have 200-300V RMS of relative voltage. The amperage of wires does not matter much in this case.

Now, if the fuse box was immersed into ground waters, it is bad. Ground waters may have high mineral content, and therefore high conductivity. According to this general water chemistry article, ground waters can have conductivity from 50 uS/cm to 50,000 uS/sm. According to conversion from microSiemens to resistance, this range of condictive water can give anywhere from 1k down to 20 Ohms of resistance at terminal distance of 1cm. This is the typical distance we have in a fuse box.

Therefore, in the best case we have 200V over 1kOhm resistor, which gives the Joule heat at 40 Watts, and in worst cases one can have a kW of heat over the water conductor. So, it is pretty feasible to have a water boiler out of immersed fuse box.

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