LED Flickering, Demons & Snubbers.

[LeeH]

I replaced x2 20w tamlex LED floods with 2 10w units from YES electrical on the from of my gaff

They flickered when off so had a quick google and bought a contact suppressor from maplin.

I fitted it across L and N in the Wiska box that's houses the joints and photo cell (load side of the photo cell)

The dam things still flicker. Do they need one each as close as possible to the fitting?

Or do I have genuine demons in my twin and earth?

 

[Marvo]

There's afew ways to skin the cat with flickering LED's. Snubbers is just a blanket term, you get snubbers that are just a resistor and you get snubbers that are a resistor and capacitor network. It shouldn't make much difference where in the circuit you locate the snubber (or more likely bleed resistor). You could try fitting multiple snubbers or if you make your own just fit a lower value resistor (calc the wattage requirement when you drop the resistance).

You can also use a 2-pole switch and switch both L+N assuming the N runs through the switch.

You could even use a changeover switch (2-way switch) with the switched live on the common, the supply live on the normally open and an earth on the normally closed. Not sure if this is compliant with the UK regs though and even if it is it would be wise to leave a cct dia in the switch and maybe an explsination for any poor souls who work on it in future . **edit** also an explanation note in the CU for anyone doing testing in future.....

 

[Octopus]

What happens is you remove the photocell?

 

[LeeH]

Not sure, I've ordered another snubber so will have a play when it arrives.

Cheers all.

 

[Lucien Nunes]

Does the photocell have a neutral connection? If it is 2-wire then its operating current has to flow through the snubber as well as the leakage and that could be harder to solve. If your meter will read AC mA you could check the leakage current going into the fittings, and also the minimum voltage at which they flash. From this calculate the maximum permissible reactance of the snubber / load and therefore its minimum capacitance.

switched live on the common, the supply live on the normally open and an earth on the normally closed

That sounds very naughty and I wouldn't do it for a number of reasons, not least that it would then be impossible to test the IR of the circuit with the switch in either position. Dumping the leakage to neutral is better if there is one, but you can still get the situation while changing over where the N/O and N/C are effecively connected together by the arc.

 

[Marvo]

switched live on the common, the supply live on the normally open and an earth on the normally closed

That sounds very naughty and I wouldn't do it for a number of reasons, not least that it would then be impossible to test the IR of the circuit with the switch in either position. Dumping the leakage to neutral is better if there is one, but you can still get the situation while changing over where the N/O and N/C are effecively connected together by the arc.

Yeah, it is pushing the envelope somewhat but in most countries I operate in it wouldn't be forbidden but not sure about the UK. I don't think using the circuit CPC as a return path for leakage is an issue, the earth is a functional element of the circuit as well as a protective one and many electronic appliances use the CPC to sink surge currents etc. As you quite rightly say it would cause confusion for anyone testing circuits at the CU but I did suggest documentation should accompany it. Food for thought though, even though it's not a conventional arrangement it would be an effective one if it wasn't for the photocell.

I've seen photocells that have a triac output to do the switching rather than a potential free contact which is the norm. Switching LED's or CFL's for that matter with a triac could present several issues including flickering when off.

 

[marconi]

A suggestion for a cure. Buy a DPDT relay with a mains voltage coil. Insert the Common/Normally Open contacts into the L and N conductors of the supply to the LED floodlight (after the usual switch or photocell) to introduce double pole switching. Connect the relay coil across the L and N conductors from the usual switch/photocell. So, now the single pole switched source of energisation is converted to double pole switching to the floodlights. Place the relay et al in a suitable IP protected box. (Plus, the relay's coil acts as a snubber when the switch/photocell is off).

Finder 55.34.8.230.0040 230V Relay (4-Pole) AC - https://www.rapidonline.com/finder-55-34-8-230-0040-230v-relay-4-pole-ac-60-1345