Water and conductivity

[Derlyn]

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

[adrianh]

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

[Derlyn]

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

[MrZakeQina]

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 [emoji23][emoji23][emoji23][emoji23]Actually never thought about it. Okay. You have the answer yet?

Sent from my SM-A305F using Tapatalk

[AndyD]

....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.

[Derlyn]

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

[GCE]

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

[GCE]

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.

[AndyD]

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?

[ians]

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

[ians]

IF it takes a 1.5 kw (6.5 amps) element 4 hours (per their university source) to heat a 150 litre geyser and you have an instant heater only uses 19 amps for a few minutes... why isnt everyone rushing out and installing instant heaters?

[Derlyn]

IF it takes a 1.5 kw (6.5 amps) element 4 hours (per their university source) to heat a 150 litre geyser and you have an instant heater only uses 19 amps for a few minutes... why isnt everyone rushing out and installing instant heaters?

Good question Ians

The big problem is the earth leakage tripping.

I have done some experimenting and with municipal water there's a leakage current to earth of +- 100mA. ( earth leakage trips )
Using harvested rain water the leakage current down to earth is +- 5mA. Acceptable.

We use harvested rain water so the earth leakage problem does not affect us.

I have now installed a dedicated extra earth leakage relay for the unit so it is fed through 2 earth leakages just as an extra precaution.

As far as the regulations are concerned, as far as I can see, they pass the muster for appliances in zone 1.

a) Earth leakage protection is provided.
b) Is enclosed in insulating material that it is not possible to touch current carrying-carrying parts with the standard test finger.

We are very happy with the unit so far. Costs about 85 cents for a 5 minute shower. Even less than half the price of a shower using a gas geyser.

As I said earlier, they do not work with municipal water if installed and wired correctly, but with harvested rain water ........... perfect and a good money saver.


Cheers and peace out.
Derek