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Thread: Water and conductivity

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    Water and conductivity

    Googled the conductivity of tap water and it is said that because of certain additives, tap water is a conductor of electricity, therefore one should not come into contact with a socket outlet or light switch if your hands are wet. So far ........ understood.

    Proof of this is when there's a slight breakdown of the insulation resistance in either a geyser, kettle or iron element and the earth leakage keeps on tripping.

    Also in damp weather when that exposed twin & earth feeding the outbuilding, trips the earth leakage relay. So far ...... still understood.

    Now I need the guys with more brain matter than myself to explain the following ......


    I recently installed an electric showerhead, wired through the earth leakage and as per instructions, with its own 30 Amp circuit breaker and 4mm sq wire.
    The unit consists of an uninsulated 5 kw bare element that heats the water passing over it instantly. There is also an earth wire that earths the water not more than 2 cm's from the element. Million dollar question : Why does it not trip the earth leakage relay ?

    Derek

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    Diamond Member adrianh's Avatar
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    I remember watching a video about this on Youtube.

    How Safe Is the SHOWER HEAD OF DOOM?! - by EletroBOOM


    https://www.youtube.com/watch?v=06w3-l1AzFk
    “Why, sometimes I've believed as many as six impossible things before breakfast.”
    ― Lewis Carroll, Alice in Wonderland

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    An update

    Earth leakage started tripping.
    Switched to tank water, no problem.
    Back to municipal water, earth leakage tripping.

    Resistivity of municipal water too low.

    Installed 3 filters on municipal water. Sediment filter and 2 carbon filters.
    No go. Earth leakage still tripping.

    Back to tank water, no problem.

    Conclusion: Instant shower heads are fine if used with harvested rain water, but do not work with municipal water. The conductivity of municipal water is such that the earth
    leakage relay trips. With the new regulation that all water heaters need to be on earth leakage, these shower heads even although they can save a stack on the
    electricity bill and are sold with a letter of authority, are useless if installed according to regulations.

    Cheers and peace out
    Derek

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    New Member MrZakeQina's Avatar
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    Quote Originally Posted by Derlyn View Post
    Googled the conductivity of tap water and it is said that because of certain additives, tap water is a conductor of electricity, therefore one should not come into contact with a socket outlet or light switch if your hands are wet. So far ........ understood.

    Proof of this is when there's a slight breakdown of the insulation resistance in either a geyser, kettle or iron element and the earth leakage keeps on tripping.

    Also in damp weather when that exposed twin & earth feeding the outbuilding, trips the earth leakage relay. So far ...... still understood.

    Now I need the guys with more brain matter than myself to explain the following ......


    I recently installed an electric showerhead, wired through the earth leakage and as per instructions, with its own 30 Amp circuit breaker and 4mm sq wire.
    The unit consists of an uninsulated 5 kw bare element that heats the water passing over it instantly. There is also an earth wire that earths the water not more than 2 cm's from the element. Million dollar question : Why does it not trip the earth leakage relay ?

    Derek
    Very interesting Actually never thought about it. Okay. You have the answer yet?

    Sent from my SM-A305F using Tapatalk

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    Diamond Member AndyD's Avatar
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    Quote Originally Posted by Derlyn View Post
    ....I recently installed an electric showerhead, wired through the earth leakage and as per instructions, with its own 30 Amp circuit breaker and 4mm sq wire.
    The unit consists of an uninsulated 5 kw bare element that heats the water passing over it instantly.....
    An 'element' is a heating device where the internal heater wire is electrically insulated from the outer tube that contacts the water.

    I suspect you're talking about an electrode heater although I've never come across one of these in South Africa apart from commercial and industrial types, only in central Africa. The ones I've seen have the electrodes close together and inside a plastic tank where the water is heated. Current takes the easiest route (least resistance) so because the neutral electrode is so close to the live electrode there's relatively little leakage, but, even that small amount of leakage would almost certainly trip and earth leakage breaker.

    I would avoid using an electrode heater in any domestic water heating application at all costs, the inherent hazards of these things far outweigh any cost benefits.

    By the way, there used to be a specific allowance in the regs for leakage current of electrode heaters to be limited to 10% of their load current so you could install this shower using an earth leakage breaker with an IΔn of 2 Amps......good luck trying to find one though. It's been a while since I saw this reg so might be worth checking it's still there in the latest version.
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    Quote Originally Posted by AndyD View Post
    An 'element' is a heating device where the internal heater wire is electrically insulated from the outer tube that contacts the water.

    I suspect you're talking about an electrode heater although I've never come across one of these in South Africa apart from commercial and industrial types, only in central Africa.
    Hi AndyD

    No, not an electrode heater. These shower heads have a bare, uninsulated element that heats the water. Checked it with the multimeter. 11 ohms from end to end and decreasing resistance as the one lead is moved along the element towards the other end. Definately not electrically insulated from the water.

    see http://lorenzettisa.com/installation/

    This is the unit.

    Cheers and peace out
    Derek

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    Quote Originally Posted by AndyD View Post

    By the way, there used to be a specific allowance in the regs for leakage current of electrode heaters to be limited to 10% of their load current so you could install this shower using an earth leakage breaker with an IΔn of 2 Amps......good luck trying to find one though. It's been a while since I saw this reg so might be worth checking it's still there in the latest version.
    The regulation still exists and is in the new draft with pretty much the same wording - There are other requirements preceding the clause pasted below

    6.16.7.3 Earth leakage protection shall be provided for the circuit that
    supplies an electrode water heater, steam generator or boiler. This
    protection shall be set to operate in the event of a leakage current exceeding
    10 % of the current consumed by the appliance under normal conditions of
    operation. The characteristics of the circuit and of the earth return path shall
    be such that the earth leakage device will operate before the potential
    between earth and the shell of the steam generator or boiler exceeds 50 V,
    including under short-circuit fault conditions

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    Quote Originally Posted by Derlyn View Post
    Hi AndyD

    No, not an electrode heater. These shower heads have a bare, uninsulated element that heats the water. Checked it with the multimeter. 11 ohms from end to end and decreasing resistance as the one lead is moved along the element towards the other end. Definately not electrically insulated from the water.

    see http://lorenzettisa.com/installation/

    This is the unit.

    Cheers and peace out
    Derek
    Looking at the site it does appear that it is an element directly immersed in water if I look at the requirements for replacing the element and positioning of the earth wire , unless the extra earth wire is extra safety.They talk 3 connections to the element - Like Andy said , Don't think I would want that water flowing over my head.

    There will definitely be a leakage to earth that the earth wire will be directing away from a person underneath - Manufacturer seems to stipulate an ELU in there instructions , so even if the regulation was not there I would say you need to fit an ELU ( SANS 10142-1 clause 5.1 ) - Maybe if you have an ELU dedicated to the shower head only you may get away without trips.

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    Quote Originally Posted by Derlyn View Post
    Hi AndyD

    No, not an electrode heater. These shower heads have a bare, uninsulated element that heats the water. Checked it with the multimeter. 11 ohms from end to end and decreasing resistance as the one lead is moved along the element towards the other end. Definately not electrically insulated from the water.

    see http://lorenzettisa.com/installation/

    This is the unit.

    Cheers and peace out
    Derek
    Wow....I can't believe they're selling those here, they're just wrong on so many levels...

    Surely they fall laughably short of the IPx5 requirement in zone 1 for starters?
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    Quote Originally Posted by AndyD View Post
    Wow....I can't believe they're selling those here, they're just wrong on so many levels...

    Surely they fall laughably short of the IPx5 requirement in zone 1 for starters?
    At least the termination is done with a ferrule in the trunking and nicely taped up ... there is no way moisture could affect the earth leakage tripping
    Comments are based on opinion...not always facts....that's why people use an alias.

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