upstairs lighting circuit and faint tingle from taps

dave68 · 25 Mar 2010

noticed very faint tingle when touching metalwork on thermostatic shower in bathroom . using volt stick measures 12-36 volts.
isolated circuits in cu one at a time and found to only occur when upstairs lighting circuit on .
checked in bathroom all seems pipes are bonded .

also measures 12v on bath taps , but 12-36 on shower metalwork

any suggestions on problems ,
many thanks

bongos · 25 Mar 2010

Is there a cpc (earth) present throughout your lighting circuit? If so is it continuous throughout? Are you able to check for continuity and that you don't have a 'floating' earth?

Is the lighting circuit protected by an RCD?

Is your main earth and protective earth bonds present for gas/water?

Sorry. More questions than answers!

dave68 · 25 Mar 2010

hi ,thanks for reply
earth in upstairs is continuous throughout checked connections.
cu is also earthed to gas/water via 10 mm cable

the upstairs lighting circuit is not rcd protected, however the bathroom has dedicated rcd circuit for lights/ extractor fan.

was wondering should the shower pipework be connected to the cpu of this circuit ?

regards , dave

bongos · 25 Mar 2010

dave68 said:
was wondering should the shower pipework be connected to the cpu of this circuit ?

Have a look here for more info on supplementary bonding in bathrooms.

If all your bathroom circuits are protected by a 30mA RCD (which you say they are) then supplementary bonding would rarely be required.

It sounds like you may have a L/E or N/E fault on the upstairs lighting circuit. If you're lucky you may be able to visually inspect most the upstairs lighting circuit if it runs through the attic. Have a look for any damaged insulation or trapped cables and check the light fittings too. Are there any areas where the cable come into close proximity with the water pipes?

Another option is a sparky with access to an inulsation resistance tester.

OOI, how did you confirm earth continuity throughout the upstairs lighting circuit?

dave68 · 25 Mar 2010

thanks for reply bongos
tested cpu by connecting muti- meter via clamping to cold water pipe in bathroom. then using long piece of flex went round each ceiling rose and checked using buzzer/ continuity ,

so i guess my next option is to disconnect each switch drop and circuit cable and test each piece .

the loft is boarded over so not much to see or check up there .

bongos · 25 Mar 2010

dave68 said:
tested cpu by...

It's CPC.

You're going about finding this fault in the right way but unfortunately it can be a struggle to locate these types of fault without an insulation resistance tester.

Especially if they're intermittent faults.

Let us know how you get on!

ColJack · 25 Mar 2010

12-36 volts with reference to what? ( ie what did you have the other probe on... )?

martinxxxxxx · 25 Mar 2010

Try measuring for volts from the main earth terminal at the consumer unit and all of the pipe work taps and lighting cpcs in the bathroom. If you get any volts then they cannot be connected. If you do get volts then turn off the supply and try resistance. If you get any high/open readings you will have found the non connected earth.

Have there been any leaks in the bathroom at all. As you may have flooded a hidden junction box under the floor. This would have popped the fuse/breaker. And carbonised the surface of the junction box. This can be checked by looking under the floor or measuring the insulation resistance.

Hope this helps

Martin

dave68 · 26 Mar 2010

thanks for replys and information . just got in from night shift so will try advice later . bath and sink taps reading 12 v . shower pipework reading 36v. using volt stick

would this indicate fault is nearer to shower pipework ?

will have look and try later .

dave

ColJack · 26 Mar 2010

again.. 12 V with reference to what?? 36V with reference to what?

to read a voltage you need 2 points of reference, one probe on what you are measuring, one on a reference point.. ( usually earth )..

please post a picture of your "volt stick" or a make and model..

dave68 · 26 Mar 2010

this is the volt stick i have been using to test , not done any fault finding yet in lighting circuit , start over weekend

davelx · 26 Mar 2010

DOes that volt stick have two points of connection to the circuit, so that you can measure accurately between two points?

If not, then before you can effectively fault find this you need a proper multimeter, with TWO test leads. You can get these for a few pounds at Q&B, Maplin etc. A "volt stick" really will not give you a reliable indication of what is going on.

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upstairs lighting circuit and faint tingle from taps

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