Shock off shower

[Deleted member 9648]

I doubt the problem is on the shower...(IR test on the element might prove otherwise)...if there is a working RCD protecting the circuit that should have tripped if there was any earth leakage....still think you need to IR test the entire installation and eliminate any low readings,and get rid of that ELCB which doesnt provide adequate fault protection.

 

[ericks]

Hi there Justinsane,
You most likely have a potential difference between ground and the tap. This means you have a bad earth to your installation. Knock in an earth spike close to your db or shower window. Test ac volts between the spike and the shower tap, or between the spike and the earth bar on your db. Make sure the earth spike is in wet soil or you can wet the area with a hosepipe. I would start with this test before cosidering changing rcd's and wiring. If you find a pd let me know and i can assist you further.

 

[Deleted member 9648]

Hi there Justinsane,
You most likely have a potential difference between ground and the tap. This means you have a bad earth to your installation. Knock in an earth spike close to your db or shower window. Test ac volts between the spike and the shower tap, or between the spike and the earth bar on your db. Make sure the earth spike is in wet soil or you can wet the area with a hosepipe. I would start with this test before cosidering changing rcd's and wiring. If you find a pd let me know and i can assist you further.

He knows he has a potential difference between ground and tap or the owner wouldnt be getting shocks.It will be because of a low IR to earth on one or more of the circuits in the house and inadequate earth fault protection....improving the earth is only part of the answer,you have to eliminate the cause of the potential difference as well.

 

[Justinsane]

Thanks for all the replies. The voltage reading on the pipework is only there when the shower is switched on which is why I thought it was probably the shower....The earth spike for the new part of the installation is about 10 feet away and the consumer unit it is connected through is less than that. There are only three circuits on the new part of the installation but all of the bonding is there as well...

I'm going back there next week and will do IR tests on all circuits (old and new) as well as continuity of bonding etc.

any further advice is well appreciated......

 

[Justinsane]

Well, I just tested the installation.

Continuity of the bonding is good, even though some of the cables are not the right size...
Bonding to water and gas all good.
IR tests were 500 megaohms on all circuits bar one. I had a reading of 256 between neutral and earth on one of the lighting circuits, I wouldn't normally worry about that...

There is no earth continuity on the two lighting circuits ( have removed two metal fittings)

Earth loop tests were all around 221ohms. They were 181 the first day i was there but i guess the weather probably affected that.

One thing though....the boiler has been getting an intermittent warning light stating reverse polarity somewhere in the installation which has been switching the boiler off.....I have removed all plug tops of every appliance in the house and they are all fine.

There is an old electric bar heater in the bathroom with a pull cord....looks well dodgy. The customer phoned me last night and she thinks that the boiler cuts out when this is switched on....is it possible that this would cause the shock in the shower as well? The ELCB can't be doing its job of this is the case....it works on its test button though........

A boiler engineer is coming next week week but I am completely lost.....

 

[Deleted member 9648]

The IR test results are fine but then it could be intermittent.....I still think the ELCB is unreliable, you should install an acceptable method of earthing and fault protection,with that in place and all bonding verified if there is an intermittent earth leakage the risk of shock will be greatly reduced.

 

[chris gray]

so there is the potential that the fault is on the load side of the bathroom electric heater? did you IR the load side?
DP sw?

 

[adversecamber]

I had a similar fault years ago at a friends house.

When the shower was on you could "feel" power in the taps and pipework, just enough to give you worryingly uncomfortable pins and needles, not like a real shock.

It turned out to be wet woodwork and damaged insulation causing it.

The power cable to the shower had been damaged when the house was built so the copper conducter was touching the wood of the partition wall that the shower was mounted on.
8 inches away the shower waterpipe was clipped to the same wood with copper saddles.

When the shower was used the water leaked behind the bath and made the wood wet (and conductive) causing the pipework to go "tingly".

I cant remember what trip was installed, but it didnt drop out.

It took ages to find as they only got me in to look at it when the shower hadnt been used and so the wood had dried out,so I couldnt find a problem.

it only went wrong after about 10 min shower use when the wall got damp.

 

[Justinsane]

I haven't tested the load side of the heater yet. I'm going back at the end of this week to remove the heater and change the elcb and the old consumer unit for a new one. Still not sure why she got a shock in the shower. The shower circuit is fed from a new unit with RCD protection.....

The fact that it is an intermittent problem makes it difficult to find......

 

[Jason Smith]

The shower circuit is fed from the new consumer unit with RCD protection, your saying as I would, that it should therfore trip. We need to think "outside of the box " on this one. We have got a very old house, a new system, and an old one. Heaven knows what has happened to the shower cable on its its run through history. Touching a hot pipe? a small nible from our rodent friends ? My first thought is to run a cable from the CU to the shower,yes, acros the carpets, then do a test. if the fault is cleared, the customer then cannot argue with the fact that the old cable has to come out and new one be installed properly. I think this test should be done first as a new cu may not standup with a known faulty circuit on it mate........