Voltage at light fitting that is turned off

[topquark]

Beats using perming solution

 

[BillyTheSparks]

Thank you all for your replies. All were very helpfull. I understand now that it is probably induced/capacitance voltage and that the only way to get around the problem is to use a resistor/snubber. Could anyone point me in the right direction of the size that I would need or a calculation to work it out.

Am I right in guessing that it is Ohms law? I have the voltage (74), but I have no current and therefore no way of working this out at the moment.

many thanks again

 

[topquark]

Depends on the lamp spec (ie min current), I'd go for a 2K7 Ohm resistor, if you've got to buy some then buy a set of standard values. If you think about it you do have a current, the spec of the lamp is 7W (at 230V).

 

[Joe S]

Do you have a dimmer on the lights? I fitted led's back when they were still very new and the dimmer actually lets a little voltage past and the lights never went all the way off. Could only be seen at night though but it was twinkling.

 

[nickblake]

joking appart what would be an idea is to do a complete test on the circuit r1r2 ,r2rn etc etc this voltage could well be caused by a fault or underlying fault so could be well worth checking

 

[BillyTheSparks]

Do you have a dimmer on the lights? I fitted led's back when they were still very new and the dimmer actually lets a little voltage past and the lights never went all the way off. Could only be seen at night though but it was twinkling.

Hi Joe, no dimmers on this circuit or any circuits in the house for that matter. No electrical control gear anywhere either.



It is definitely a capacitance building up (if thats the right way to think about it) on the strappers. I have done all tests possible (R1+R2, R2/R1/RN, Meggered at 1000v between all conductors on the 2way intermediate strappers. Removed all LED lights from the circuit and Meggered the complete circuit again. Disconnected the earth bond to the gas/water to see if I was getting anything from those. Tested for voltage on the water pipework in the house (altough all plastic apart form airing cupboard).

I have litterally been over this with a fine tooth comb, and this is the only thing that it can be. I would like to resolve the issue of the capacitance but it is a no-no as the house is now finished and chasing walls is out of the question.

I even removed the strappers and common from the switches at both ends of the 2way, and connected one strapper (black) to the live, and then tested for voltage at the 2nd 2way switch. I was getting 105v on the common (brown) and 60v on the 2nd strapper (grey).

I then isolated the circuit, put it all back together, and put a 2K2 resistor between the switch live and neutral (at the switch) this stopped the 74v which I had at the fittings, the only problem was it glowed red hot when the switch was on and suppling the fittings. Obviously it can't withstand the 240v running constantly through it.

Could anyone give me a clue on working out the size of resistor that would be needed?
It needs to be able to allow the 74v through it to neutral, but not allow the 240v to do the same.
So would a high resistor i.e 1M or above do this?


God my brain is fried......Please help.....

 

[topquark]

What rating of resistors did you buy? That 2K2 resistor is going to be dissipating about 25W when the lighting is full on. It should be rated at 250V and around 35W to be safe. Perhaps I should have stated that.

 

[BillyTheSparks]

I was in RS and in a hurry, so I brought some 1k and 2k2 both of which are rated at 3w! No wonder it was getting a bit warm. I'm going to look at the RS website now to see if I can find the ones you recommend.

many thanks for your advice, much appriciated

 

[BillyTheSparks]

Hi topquark, is this the type of thing I'm looking for?

http://docs-europe.electrocomponents.com/webdocs/0f73/0900766b80f73c76.pdf

 

[topquark]

That's the spec you'd need, but I'd question the packaging choice. I'll have a nose on the RS site in a bit.

 

[BillyTheSparks]

Thank you that would be handy, you can probably tell I've never done this before

 

[jeremy]

I'm probably barking up the wrong tree entirely, but have come across induced voltage problems before, which seem to have been caused by a disconnected cpc, 90-100V in one case. Have you checked the cpc?

 

[BillyTheSparks]

I'm probably barking up the wrong tree entirely, but have come across induced voltage problems before, which seem to have been caused by a disconnected cpc, 90-100V in one case. Have you checked the cpc?

Thanks for the advice Jeremy, but these have all been checked and cheaked again. Getting the voltage on the brown/grey when not connected to anything is definitely pointing to the conductance.

 

[topquark]

Limited choice on the packaging front. I'd probably go for this given your 2K2 Ohm choice: Buy High Power RESISTOR 50W 2K2 Vishay RCH50S22000JS06 online from RS for next day delivery.

Easy to solder some leads on for use and wrap in heatshrink for use. Should be easy enough to incorporate in the box(es).

 

[BillyTheSparks]

Limited choice on the packaging front. I'd probably go for this given your 2K2 Ohm choice: Buy High Power RESISTOR 50W 2K2 Vishay RCH50S22000JS06 online from RS for next day delivery.

Easy to solder some lugs on for use and wrap in heatshrink for use. Should be easy enough to incorporate in the box(es).

Thank you for your reasearch, a great help!!

If I have any more questions is it ok to bother you?