DIY Doctor UK DIY Forums

Hi all,

Firstly, I have recently moved into a new property and have discovered two problems. These are:

1) I have spot lights " dimmer controlled" not low voltage, in my lounge and a flourscent light in the kitchen. When both the lounge and kitchen lights are lit all is ok, but when I switch OFF the flourscent in the kitchen, the spot lights flash once. They only flash when they are on full and not dimmed. What could the problem be and how could I cure it??.........

2) Also, could some one please explain what the difference is between, supplementary and equipotential bonding and how are they installed in the bathroom????. Which one applies to the bathroom? There is no sign of earth cables on any pipes in there. There is earthing on the gas and water pipes at the intake, will i still need earthing in the bathroom...

I am a confident diy person on most things except electricity, and help would be greatly appreciated????

Thanks in advance.........

Hi CPM,
could be the ballast &/or capacitor causing a 'spike' ie a short-term high volt surge when breaking the circuit, it was at onetime normal to fit a higher rated switch for fluorescent fittings, is your kitchen switch a good branded make? if not try changing it particularly if the light is of 'mature vintage'.
The earthing at source on your gas & water is called 'main equipotential bonding' and is done as the name suggests to keep all conducting metalwork at or about the same potential [voltage]
However due to lengths of pipe / cable runs it is possible under fault conditions for a difference of potential to arise, so in order to keep this to a minimum in areas where skin resistance is likely to be lower than normal due to being wet such as in a bath/shower room 'supplementary bonding' is carried out between any exposed conducting parts such as pipes, and any 'current consuming' devices such as electric towel rails/ fan heaters ect.
This may be done outside the room in a loft or nearby airing cupboard & in the case of T-Rails/heaters can be done from the local circuit Fused Connection Unit instead of from the actual device.
So the bonding may be in place but not obvious, hope this long-winded explanation helps, regards SPARX

[quote="sparx"]Hi CPM,
could be the ballast &/or capacitor causing a 'spike' ie a short-term high volt surge when breaking the circuit, it was at onetime normal to fit a higher rated switch for fluorescent fittings, is your kitchen switch a good branded make? if not try changing it particularly if the light is of 'mature vintage'.
The earthing at source on your gas & water is called 'main equipotential bonding' and is done as the name suggests to keep all conducting metalwork at or about the same potential [voltage]
However due to lengths of pipe / cable runs it is possible under fault conditions for a difference of potential to arise, so in order to keep this to a minimum in areas where skin resistance is likely to be lower than normal due to being wet such as in a bath/shower room 'supplementary bonding' is carried out between any exposed conducting parts such as pipes, and any 'current consuming' devices such as electric towel rails/ fan heaters ect.
This may be done outside the room in a loft or nearby airing cupboard & in the case of T-Rails/heaters can be done from the local circuit Fused Connection Unit instead of from the actual device.
So the bonding may be in place but not obvious, hope this long-winded explanation helps, regards SPARX[/quote]


HI SPARX,

THANK YOU VERY MUCH FOR YOUR ADVICE ON MY FLASHING LIGHTS, INDEED BY REPLACING THE SWITCH, IT HAS CURED THE PROBLEM.

AS FAR AS THE EARTHING IN MY BATROOM GOES, I HAVE FOLLOWED THE PIPE RUNS OUT OF THE ROOM TO MY AIRING CUPBOARD AND I CAN CONFIRM THERE IS NO BONDING TO BE FOUND. COULD I THEREFORE CROSS BOND THE PIPES AND CONNECT IT TO THE EARTH IN THE ELECTRIC SHAVING SOCKET USING 4MM2 CABEL AND THUS MAKE MY BATHROOM SAFER?. IF NOT HOW CAN I DO IT OR DO I NEED TO CALL IN A PROFESSIONAL.....

ONCE AGAIN,
THANKS IN ADVANCE....

Hi agn, yes sounds fine if you can access shaver circuit, might be a bit tight to connect in a 4mm2 if so and you can protect earth wire with say mini trunking then only need 2.5mm which will be easier.
technically if you connect all together out side bathroom then ok to do but if you need to connect to outlet in bathroom then is 'part-p' work, best wishes, it's refreshing when someone wants to 'Do it right'
SPARX