Voltage at light fitting that is turned off

[Farmelectrics]

ive noticed on here recently problems with leds staying on when switches are off not had any problems my self and fitted quite alot whats the general feeling of why there staying on just in case it happens to me look a fool if you cant tell customer why its happening

 

[Farmelectrics]

have these snubbers got to be fitted end of line or dosnt it matter

 

[BillyTheSparks]

Just trying to re-ignite this one as I'm back there tomorrow to have a go at it.

I'm going to start by taking all the LED lamps out of the circuit, and test again for the voltage. If it is still present (which I'm sure it will be) I'll then start taking the circuit apart.

The thing that is bugging me is that with ALL the light switches of the circuit off, I still get 74v at this particular down light fitting. And I also get approx 58v at the bathroom light fittings.

As said before all the neutrals are in Wago's, the wiring is new, all the conductors are meggering at >499 (I tested at 1000v to make sure). I've meggered the switches, taken the switches off and connected the wires into Wago's.

ANY ideas would be good just for me to try them. The more I think about it the more confuddled I get.

Many thanks for taking the time to read this.

 

[telectrix]

have these snubbers got to be fitted end of line or dosnt it matter

again, a bit of trial and error. don't think it matters where they go as long as it's across sl and n

 

[BillyTheSparks]

again, a bit of trial and error. don't think it matters where they go as long as it's across sl and n

I would like find the problem and fix it, rather than put in a 'solution' that might / might not sort it out.

 

[telectrix]

if it's induced voltage you won't be able to fix it as long as cables run together.

 

[BillyTheSparks]

Do you really think it could be an induced voltage of 74v?? and coming from the black strapper to the grey strapper but by-passing the earth wire?

 

[topquark]

Do you really think it could be an induced voltage of 74v?? and coming from the black strapper to the grey strapper but by-passing the earth wire?

Quite possibly. We're guessing you effectively have the equivalent to this as the overall circuit: http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html with the 3 core for the two way lighting behaving as the capacitor.

The length of one of the strappers will dictate how high a value capacitor you in effect have (the longer the run the higher the capacity) and hence the PD present. You'll find the timing between flashes is a regular period (if only a long time between flashes).

The addition of a snubber resistance will increase the overall resistance to the point where there is insufficient current flow for the led lamps. It can eliminate it completely (but too high a resistance would mean no current flow at 230V either!).

So in this particular case probably not induced from an adjacent circuit, rather from that same circuit; so the only other way to eliminate it would be to run the strappers and common separately (separated by a greater distance, so then no capacitance build up).

 

[nickblake]

its great fun using low ohm resistors 100 ohm x 230 volts = one allmighty pong

 

[nickblake]

did have a problem with commercial hair dryers giving the user a shock when they un plugged them , the suppression capacator was across the incomming side of the switch so was holding charge after it was switched off an zapped any one when unplugged and they touched the pins easily rectified 20 hair dryers later relocated the capacator to the other side of the switch , and wrote to the manufacturers too

 

[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.