Flashing lamp

[crystal ball]

Wired up a 12v dc fan in a bathroom, picked up the feed from a nearby ceiling rose, now the lamp is flashing when switched off, stops when power supply is switched off so looks like that is the cause, are there any products about that can be placed in circuit to stop this?

 

[ericmark]

I will guess you have connected to a line supply not a neutral in the ceiling rose. Just because it is black or blue does not mean it is a neutral.

 

[crystal ball]

Its connected to L & N

 

[securespark]

Pictures would help.

 

[crystal ball]

Nothing to see really, T&E from rose live loop & neutral to FCU then to 12vdc power supply, flashing stops when fuse pulled

 

[ericmark]

In the main LED and CFL flash because some thing allows a little energy to reach the bulb, which is more than the leak resistor can disperse.

This is normally capacitive or inductive linking, very common with two way switching where the long cable runs allow more AC to transfer. But also happens where electronic switches are used which need a small amount of energy to work.

The fix is normally to fit a load capacitor

These allow more current to flow before the voltage raises to point where the lamp will flash.

However the connection to a fan is unlikely to cause the problem, in fact the reverse, the load from the fan is likely to stop a light which was flashing not start one flashing.

Hence asking for pictures of the connection in the ceiling rose. It seems very likely a black or blue wire was not neutral but a line feed, or some other fault. Does the fan work when it should work? i.e. when the light is on?

 

[bernardgreen]

Does that CAPLOAD device include a series resistor to act as a fuse if the capacitor faults to a short circuit across the supply. ?

An alternative is a Capacitor 0.047uF micro Farads 250 volts AC in series with Resistor 100 ohms connected across the lamp
Which come pre-packaged as a contact suppressor from RS Components.

As a contact suppressor it would be fitted between Live and Switched Live at the switch BUT as a snubber it has to be fitted between Switched Live and Neutral at the lamp..

( If there is a Neutral at the switch it may be more convenient ( space wise ) to fit it in the back box of the switch )
RS Stock No.: 206-7869
Mfr. Part No.: PMR209ME6470M100R30
Brand: KEMET

There are other sources

 

[crystal ball]

In the main LED and CFL flash because some thing allows a little energy to reach the bulb, which is more than the leak resistor can disperse.

This is normally capacitive or inductive linking, very common with two way switching where the long cable runs allow more AC to transfer. But also happens where electronic switches are used which need a small amount of energy to work.

The fix is normally to fit a load capacitor View attachment 266010 These allow more current to flow before the voltage raises to point where the lamp will flash.

However the connection to a fan is unlikely to cause the problem, in fact the reverse, the load from the fan is likely to stop a light which was flashing not start one flashing.

Hence asking for pictures of the connection in the ceiling rose. It seems very likely a black or blue wire was not neutral but a line feed, or some other fault. Does the fan work when it should work? i.e. when the light is on?

Its not a direct connection , it supplies power supply which is full of electronics which made me think it was that causing the problem, going back tomorrow with my trusty incandescent bulb.

 

[crystal ball]

Does that CAPLOAD device include a series resistor to act as a fuse if the capacitor faults to a short circuit across the supply. ?

An alternative is a Capacitor 0.047uF micro Farads 250 volts AC in series with Resistor 100 ohms connected across the lamp
Which come pre-packaged as a contact suppressor from RS Components.

As a contact suppressor it would be fitted between Live and Switched Live at the switch BUT as a snubber it has to be fitted between Switched Live and Neutral at the lamp..

( If there is a Neutral at the switch it may be more convenient ( space wise ) to fit it in the back box of the switch )
RS Stock No.: 206-7869
Mfr. Part No.: PMR209ME6470M100R30
Brand: KEMET

There are other sources

That sounds promising thanks

 

[winston1]

Nothing to see really, T&E from rose live loop & neutral to FCU then to 12vdc power supply, flashing stops when fuse pulled

Don’t need a FCU on a light circuit. A 3 a fuse has no discrimination against a 6a MCB.

 

[magicmushroom666]

Does the fan run 24/7 then? If connected to live and neutral, then there's nothing that would switch it on and off...

Its connected to L & N

 

[ericmark]

Don’t need a FCU on a light circuit. A 3 a fuse has no discrimination against a 6a MCB.

Where does he say he is using a 3 amp fuse? I must admit even with a 1 amp fuse not sure it does anything, don't think it would blow even with a stalled fan, but ability to stop fan being used by removing fuse is good.

I would be looking at cable route, we are taught about correctly terminated with a balanced circuit and use of 50Ω, 75Ω, 95Ω and 300Ω cables, and 300Ω ribbon looks very like twin and earth, so seems likely energy is transmitted from cables which can be received by others, but not enough to light a tungsten bulb, but maybe enough for a LED bulb.

I had it with G9 bulbs the little one flashed and shimmered, the big one worked A1, well one did fail, so opened, and the smoothing capacitor inside was nearly as big as the whole little bulb. Actually found dry joint and fixed and back in service.

But there not only seems to be no standard, but there is nothing on the packet to say how much leak though or what smoothing is included, so it is a suck it and see.

 

[securespark]

Don’t need a FCU on a light circuit. A 3 a fuse has no discrimination against a 6a MCB.

Who says there is a 6A MCB?

 

[SUNRAY]

Don’t need a FCU on a light circuit. A 3 a fuse has no discrimination against a 6a MCB.

That's as maybe... but it also serves as the cheapest way of providing isolation.

Actually I lie, the cheapest way is a 13A socket and plug...

CB you have wasted money, you should have fitted a 13A socket.

 

[winston1]

Cost does not come into it. Do it the correct way with electrics.