I want to ground a bucket/immersion heater:

  • should I build a conductive cage around the underwater resistance and connect it to ground?
  • would it work to just place the ground wire inside the water, maybe close to the heater?
  • \$\begingroup\$ A properly installed and properly chosen heater for the purpose likely has grounding built in, but adding a cage around the heater would prevent the bulk of the water being strongly energised in the even the coil shorted to the water. How much precaution is necessary depends on use. Is the tank metal and is the tank grounded? Are there people in it? \$\endgroup\$
    – K H
    Mar 15, 2021 at 9:43
  • \$\begingroup\$ If you look at a modern hot water boiler for example, the element is inside a grounded metal tube, so if the insulation fails it shorts to the tube, hopefully tripping the overcurrent or GFCI protection. \$\endgroup\$
    – K H
    Mar 15, 2021 at 9:45
  • 1
    \$\begingroup\$ Buy a broken device that happens to have one. Or a new device. Hot water boilers are cheap. At any rate, you need both the means of grounding in case of failure and the means to detect that failure and cut the device out. I'm not sure whether you're allowed to rely on the existing kitchen having ground fault protection, but at the least, a carefully chosen fuse on the line side would be wise. You could also add a line side cutoff switch when you open the lid. \$\endgroup\$
    – K H
    Mar 15, 2021 at 9:51
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    \$\begingroup\$ You didn't look hard enough. I found at least a dozen on Shamazon (not that I recommend buying anything from them). \$\endgroup\$
    – Andy aka
    Mar 15, 2021 at 9:52
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    \$\begingroup\$ For this kind of application the safe allowed way is to have the heater completely encased in a grounded tube. So whatever it happens the ground will catch current leaks before they can do harm. The most common failure is, of course, that the heater tube corrodes (a pinhole, often), water enters and the RCD trips \$\endgroup\$ Mar 15, 2021 at 10:29

1 Answer 1


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Figure 1. Random immersion heater image from Amazon.

Any immersion heater for your application must have a plug with an earth pin. The earth wire must connect the earth pin directly to the element's protective tube.

This method of earthing when used with appropriate circuit breaker and RCD/ELCB/GFCI protects the user from electric shock. It should not be compromised.

If the unit is supplied with a two-pin plug then don't buy it.

  • 1
    \$\begingroup\$ Okay, I finally learned the lesson: any heater with a ground plug is already earthed. The only thing to additionally do, is to couple it with a circuit breaker. \$\endgroup\$
    – Lilla
    Mar 15, 2021 at 11:41
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    \$\begingroup\$ Don't assume that if you're buying junk from Amazon. Test it and open the terminal case to check the connections. \$\endgroup\$
    – Transistor
    Mar 15, 2021 at 11:46
  • \$\begingroup\$ I think if you have a multi-meter, it is more safe not to open the plug but check if the coil thing is very shorted to the big plug pin. \$\endgroup\$
    – tlfong01
    Mar 16, 2021 at 1:17

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