Electric Shower Heater

[thaibeachlovers]

The electrician came to install the shower unit today. I think he was going to just tap in a wire at a plug next to the bathroom door and add an double pole switch ( 250 bht ). I directed him to the circuit breaker box and pointed out a spare breaker that I "suggested" he use! However, he then didn't install the on/ off switch, and claimed the breaker is sufficient. I've always seen an on/ off for electric showers in hotels, so is he right?

When it came bill time he still charged for the switch, till I pointed out he hadn't put one in- naughty!

At least he did use 2.5mm wire, though the earth wire he brought looked like 1mm, probably 1.5mm. However, I gave him my 4mm earth wire, so that's more than adequate. I asked what length earth rod he was going to use- 50cm! so I gave him a spare 1m rod I had, just so I didn't get charged for something useless, and later went to an electrical shop for something longer. Only had 1.8m, so 2 of them in the ground 2m apart. Should do the trick!

Anyway, I now have a hot water shower, with a circuit breaker and a decent earth. Doesn't get better than that!

[Crossy]

Local switching is not required by UK regs, dunno about Oz.

Certainly not required in Thailand but could add that extra bit of safety so long as you can't operate it with wet hands.

I assume that your heater is 3.5kW or thereabouts.

[thaibeachlovers]

Local switching is not required by UK regs, dunno about Oz.

Certainly not required in Thailand but could add that extra bit of safety so long as you can't operate it with wet hands.

I assume that your heater is 3.5kW or thereabouts.

Thanks Crossy.

Yes, I bought a 3.5kw so that if we have to move back to the village I can take it back there.

It doesn't get REALLY hot, but certainly beats either a cold shower, or having to heat a bucket on the gas cooker. Probably saves on the electricity bill.

[Kwasaki]

Local switching is not required by UK regs, dunno about Oz.

Certainly not required in Thailand but could add that extra bit of safety so long as you can't operate it with wet hands.

I assume that your heater is 3.5kW or thereabouts.

Thanks Crossy.

Yes, I bought a 3.5kw so that if we have to move back to the village I can take it back there.

It doesn't get REALLY hot, but certainly beats either a cold shower, or having to heat a bucket on the gas cooker. Probably saves on the electricity bill.

Yeah, I guess what you have done will be OK, just been sorting some of my house electrics thanks to ' Crossy ' helping with information.

I would only say and think one rod would of been OK and not too sure if using two rods at only 2m apart is OK.

The 220volt power to our house is only 15amp anyway, power connected into the unfused Knife switch, then to the RCB, then to the distribution box.

I have our shower unit live on a 15amp MCB in the distribution box and have a safety breaker switch on the outside of the shower room which acts as a isolator.

I ran a 10mm cable as an earth from the shower unit to the distribution box earth bar and a cable out to the 1.8m earth rod.

So I hope I am OK too.

[thaibeachlovers]

Local switching is not required by UK regs, dunno about Oz.

Certainly not required in Thailand but could add that extra bit of safety so long as you can't operate it with wet hands.

I assume that your heater is 3.5kW or thereabouts.

Thanks Crossy.

Yes, I bought a 3.5kw so that if we have to move back to the village I can take it back there.

It doesn't get REALLY hot, but certainly beats either a cold shower, or having to heat a bucket on the gas cooker. Probably saves on the electricity bill.

Yeah, I guess what you have done will be OK, just been sorting some of my house electrics thanks to ' Crossy ' helping with information.

I would only say and think one rod would of been OK and not too sure if using two rods at only 2m apart is OK.

The 220volt power to our house is only 15amp anyway, power connected into the unfused Knife switch, then to the RCB, then to the distribution box.

I have our shower unit live on a 15amp MCB in the distribution box and have a safety breaker switch on the outside of the shower room which acts as a isolator.

I ran a 10mm cable as an earth from the shower unit to the distribution box earth bar and a cable out to the 1.8m earth rod.

So I hope I am OK too.

Actually it was Crossy that said two rods less than 2 meters long 2 meters apart were OK.

Thanks for the reply.

[Crossy]

Actually it was Crossy that said two rods less than 2 meters long 2 meters apart were OK.

Two rods that close together (<= rod length apart) will behave as a single longer rod. If they are a long way apart they will provide a better ground but there's a greater danger of getting large currents flowing in your ground wiring in the event of a close lightning strike (with the associated fire risk). This is likely the reason that multiple rods are prohibited by Oz regulations.

If you must use multiple rods make sure you link them outside the house and use a single wire to your earth bar, this means that if there is a large current flowing it will be safely outside.

Better for those of us with poor ground conditions would be to get a galvanised ground mat made up and bury it as deep as possible. Investigating an Ufer ground (Google) may also pay dividends.

[Kwasaki]

Forgive me just trying to get things straight, I am not overly worried about my wiring but still have a thirst for knowledge.

I get a reading of just less than 2 ohms on an earth test, with one 1.8 m rod ( can't get longer around here maybe I could order from somewhere ).

So if I get another 1.8m rod link it 1.8m away with 10mm wire to the first one, I will be improving the earth situation, I take it.

[electau]

Forgive me just trying to get things straight, I am not overly worried about my wiring but still have a thirst for knowledge.

I get a reading of just less than 2 ohms on an earth test, with one 1.8 m rod ( can't get longer around here maybe I could order from somewhere ).

So if I get another 1.8m rod link it 1.8m away with 10mm wire to the first one, I will be improving the earth situation, I take it.

The 2 ohms is measured from the main earth connection at the electrode to any point in the installation.

The earth electrode 12.7mm copper clad steel is regarded as having sufficient contact area with the soil.

With the MEN system negligable current flows in the main earth conductor and may be disregarded.

[Crossy]

Forgive me just trying to get things straight, I am not overly worried about my wiring but still have a thirst for knowledge.

I get a reading of just less than 2 ohms on an earth test, with one 1.8 m rod ( can't get longer around here maybe I could order from somewhere ).

So if I get another 1.8m rod link it 1.8m away with 10mm wire to the first one, I will be improving the earth situation, I take it.

How are you measuring your ground impedance?

If correct 2 ohms is an excellent reading for a simple ground stake and adding another won't add any value.

The limiting factor with a TT system is the resistance between the stake and the mass of the earth, it is this you need to measure.

[Kwasaki]

I get a reading of just less than 2 ohms on an earth test, with one 1.8 m rod ( can't get longer around here maybe I could order from somewhere ).

How are you measuring your ground impedance?

If correct 2 ohms is an excellent reading for a simple ground stake and adding another won't add any value.

The limiting factor with a TT system is the resistance between the stake and the mass of the earth, it is this you need to measure.

Multimeter on ohms setting, one probe to earth connection on wall socket and the other to Neutral point on the wall socket.

[Kwasaki]

Forgive me just trying to get things straight, I am not overly worried about my wiring but still have a thirst for knowledge.

I get a reading of just less than 2 ohms on an earth test, with one 1.8 m rod ( can't get longer around here maybe I could order from somewhere ).

So if I get another 1.8m rod link it 1.8m away with 10mm wire to the first one, I will be improving the earth situation, I take it.

The 2 ohms is measured from the main earth connection at the electrode to any point in the installation.

The earth electrode 12.7mm copper clad steel is regarded as having sufficient contact area with the soil.

With the MEN system negligable current flows in the main earth conductor and may be disregarded.

Thank's for the reply but I'm a DIY sparky you would have to explain that in simpler terms.

I going to post up my present house wiring diagram so will be grateful if all you guys can comment on it.

[Crossy]

Multimeter on ohms setting, one probe to earth connection on wall socket and the other to Neutral point on the wall socket.

OK, so you're likely just measuring the resistance of your MEN link. Actually nothing wrong with that as this is the path current will take in the event of an L - E fault.

To verify the efficiency of your local ground stake make the measurement from the disconnected stake to your neutral (which should be solidly grounded at the transformer).

[electau]

Multimeter on ohms setting, one probe to earth connection on wall socket and the other to Neutral point on the wall socket.

OK, so you're likely just measuring the resistance of your MEN link. Actually nothing wrong with that as this is the path current will take in the event of an L - E fault.

To verify the efficiency of your local ground stake make the measurement from the disconnected stake to your neutral (which should be solidly grounded at the transformer).

That will be anything from 50 ohmsto over 1000 ohms depending on soil conditions. Not required if the MEN system is used. RCDs must be used if the earthing is TT or direct. Based on an electrode depth of 1.2 or 1.8M.

[Kwasaki]

Multimeter on ohms setting, one probe to earth connection on wall socket and the other to Neutral point on the wall socket.

OK, so you're likely just measuring the resistance of your MEN link. Actually nothing wrong with that as this is the path current will take in the event of an L - E fault.

To verify the efficiency of your local ground stake make the measurement from the disconnected stake to your neutral (which should be solidly grounded at the transformer).

Sorry a bit boggled as you can see from my diagram in the other thread posted, I don't think I have a ' MEN link ' no wire is connecting neutral with the earth rod.

As I understand it, to verify the efficiency of my local ground rod ( i.e. my house one ) disconnect wire from ground rod, clamp a wire to my main incoming neutral wire from the street to the house, and then measure ohms on the multimeter. ??

[Crossy]

As I understand it, to verify the efficiency of my local ground rod ( i.e. my house one ) disconnect wire from ground rod, clamp a wire to my main incoming neutral wire from the street to the house, and then measure ohms on the multimeter. ??

Yes, you must measure to the disconnected rod in order to verify the efficiency of the rod itself.

Also measure volts AC between the rod and neutral just in case some volts there are confusing your meter. Using a regular multimeter isn't ideal, but it has to be better than nothing.

If you still get something less than 200 ohms and no N-E voltage you're good to go

[Kwasaki]

As I understand it, to verify the efficiency of my local ground rod ( i.e. my house one ) disconnect wire from ground rod, clamp a wire to my main incoming neutral wire from the street to the house, and then measure ohms on the multimeter. ??

Yes, you must measure to the disconnected rod in order to verify the efficiency of the rod itself.

Also measure volts AC between the rod and neutral just in case some volts there are confusing your meter. Using a regular multimeter isn't ideal, but it has to be better than nothing.

If you still get something less than 200 ohms and no N-E voltage you're good to go

Understand, thanks, I'll get to be a Thai sparky yet.

[electau]

If you try to measure the earth electrode resistance to the general mass of earth the voltage of a multi meter 300mV may be insufficient to break down the initial contact resistance. However you can try using a short electrode in the ground located about 1 metre from the main earth electrode and measure between those two points. This saves you disconnecting the main earth connection.

The main objective is to make sure that the resistance is low enough to operate a RCD or RCBO when the TT or direct earthing system is used ie. no connection between the incoming supply neutral and main earth. A single 12.7mm copper clad steel electrode 1.2 metres into the general mass of earth will meet this requirement.

Indirect contact protection.

Maximum permissable earth resistance.

10mA RCD sensitivity Max earthing resistance 5000 ohms.

30mA RCD sensitivity Max earthing resistance 1666 ohms.

This measured value of earth resistance must be such that the product of this value and the RCD residual operating current does not exceed 50VAC.

Eg. 0.03mA x 1666 ohms = 50V.

An RCD will give protection from direct contact, but in this case the current flow to earth is through the human body. The touch voltage will be much higher ie it will be the supply voltage. A 30mA RCD will operate with a max resistance of 7666ohms on 230V.

For a 220 volt supply this will be 7333ohms.

An RCD is designed to operate and must operate in less than 0.4seconds.

TT or direct earthing resistance will never be low enough in ohms to operate an overcurrent device such as an MCB. This is why an RCD device must be used to protect against earth faults.

[Kwasaki]

If you try to measure the earth electrode resistance to the general mass of earth the voltage of a multi meter 300mV may be insufficient to break down the initial contact resistance. However you can try using a short electrode in the ground located about 1 metre from the main earth electrode and measure between those two points. This saves you disconnecting the main earth connection.

The main objective is to make sure that the resistance is low enough to operate a RCD or RCBO when the TT or direct earthing system is used ie. no connection between the incoming supply neutral and main earth.

Maximum permissable earth resistance.

10mA RCD sensitivity Max earthing resistance 5000 ohms.

30mA RCD sensitivity Max earthing resistance 1666 ohms.

This measured value of earth resistance must be such that the product of this value and the RCD residual operating current does not exceed 50VAC.

Eg. 0.03mA x 1666 ohms = 50V.

An RCD will give protection from direct contact, but in this case the current flow to earth is through the human body. The touch voltage will be much higher ie it will be the supply voltage. A 30mA RCD will operate with a max resistance of 7666ohms on 230V.

For a 220 volt supply this will be 7333ohms.

An RCD is designed to operate and must operate in less than 0.4seconds.

TT or direct earthing resistance will never be low enough in ohms to operate an overcurrent device such as an MCB. This is why an RCD device must be used to protect against earth faults.

Thanks for the info it has brought up a question I was going to ask on the diagram thread, where I am going to post another diagram for you guru's showing what I intend to do to improve things a little more.

I going to carry out the testing first.

[PattayaParent]

Can I get this thread back to an electric shower heater question?

My missus reckons she is getting 'electric tingling' from the water of our electric shower unit wheras I feel nothing.

Is it possible that if there is an electrical fault with the unit this can somehow transfer electricity into the water?

Or is it more likely her imagination / another phenomenon?

Edit: formatting

Edited October 6, 2011 by PattayaParent

[Crossy]

Not directly to the water, but if you have a metal or metalised shower hose then yes, quite possible.

Is the heater correctly grounded?

Do you have an RCD?

[PattayaParent]

Not directly to the water, but if you have a metal or metalised shower hose then yes, quite possible.

Is the heater correctly grounded?

Do you have an RCD?

Not sure I've no idea what an RCD is?

Coudn't get the front cover off the unit to check if there's a ground cable on it. I know the multi point unit on the other shower has a ground cable, that is separate from the shower head which is attached to the bath and is all plastic.

The 'problem' unit is a shower heater with integrated shower head with a metalised hose and only plasctic head.

[Crossy]

RCD, look in your electrical installation for a breaker with a 'Test' button. If you have one press the test button and see if the shower heater goes off (to ensure that it is powering the heater). If you don't see a test button you have no RCD and should investigate installing one ASAP.

Try harder to get the cover off, there's sometimes a screw behind the control knob (should just pull off)

Replace that shower hose with a purely plastic one not a 'chrome' finish one, just to be safe.

[PattayaParent]

Thanks Crossy, I'll check it out when I get home.

It's a rented house I've newly moved into so just finding a few issues with it.

Edit: formatting

Edited October 6, 2011 by PattayaParent

[Kwasaki]

Is the heater correctly grounded?

Do you have an RCD?

Not sure I've no idea what an RCD is?

A temporary plug in one for a quick fix.

Edited October 6, 2011 by Kwasaki

[PattayaParent]

Thanks guys.

Had a look last night and thre's no RCD and no spare sockets to put one in the DB.

Also the shower hose I'm pretty sure is plastic but 'looks' metallic.

Had an electrician test both the water heaters with a meter and there seems to be no problem.

Edit: formatting

Edited October 7, 2011 by PattayaParent

[Crossy]

Had an electrician test both the water heaters with a meter and there seems to be no problem.

What did he measure? What were the results?

In my business if there are no documented test results the test did not happen.

[PattayaParent]

I was holding the meter so I know it happened!!Don't know if it was Amps or Volts he measured but it was less than 1 of them.Edit: Formatting

[Crossy]

I was holding the meter so I know it happened!!Don't know if it was Amps or Volts he measured but it was less than 1 of them.Edit: Formatting

Exactly!

You know something happened, unfortunately you don't know what he measured or whether the results were satisfactory. TBH I doubt your sparks knows either, not that that's anything unusual

If you had results you could put them here for those who know what they're on about (and those who don't) to interpret for you.

As a start, where did he have his end of the test probes?

Assuming the man had the lid off, did you notice whether there was a ground connection?

[Tywais]

Not directly to the water, but if you have a metal or metalised shower hose then yes, quite possible.

Actually you can get it from the water as most is heavy in metals/minerals making it an electrolyte and conductive. Found out the hard way when I was pouring water into a coffee water heater and put my fingers in the stream. Got a serious zap from it.

[Crossy]

Not directly to the water, but if you have a metal or metalised shower hose then yes, quite possible.

Actually you can get it from the water as most is heavy in metals/minerals making it an electrolyte and conductive. Found out the hard way when I was pouring water into a coffee water heater and put my fingers in the stream. Got a serious zap from it.

Ouch! but probably less relevant to a shower where the stream is usually broken into droplets, remember MythBusters pissing on the 3rd rail?

That said, most important to ground the shower and ensure an RCD is protecting the circuit.