Since I Swapped To Led Lightbulbs, My Rheostat Has Become Noisey!

[Impret-Sir]

Hi, I replaced the three 40W incandescent bulbs in my lounge light fitting with 6.2v LED bulbs.
However, the wall rotary dimming control now makes a loud 'buzzing' noise on all but its maximum setting. I swapped the old bulbs back in, and the noise went, suggesting to me that the switch has not developed a fault. These bulbs were sold as being suitable for dimming, (they actually dim just fine), but this noise is audible above conversation, and is unacceptable. Do I need a different rheostat or is mine on its way out?

[Fitzer]

If your dimmer is more than a few years old it is unlikely to be suitable for dimming LEDs, they draw such little power that the older dimmers have problems as the minimum draw through it is too low so yes you do need to replace the dimmer.

[Kidas]

I hope they are 6.2W rather than 6.2 V, as the latter would not work well on mains voltages...

As said, these things draw very little current, so older dimmers (and wiring) sometimes need updating before they work properly with the low-current systems.

I replaced some dimmable 300W halogen bulbs with 19W (dimmable) LEDs, and wnen on full power it's fine, but as soon as we try to reduce the power, the bulbs flash in an unacceptable way.

If you want all three bulbs to be LEDs, then you will probably need to either replace the dimmer switch, or add some ballast (more resistance) to the circuit.

Alternatively, things will probably be OK if you have 2 LEDs and one incandescent bulb in the fitting. It will save energy, but may look a little weird..

Incidentally, dimmers tend not to be rheostats (pure resistance) that reduce the level of the power, but electronic devices that chop up the current into a series of pulses.

I replaced all bulbs on our house with LEDs a couple of years ago and it is a big saving, but there are a few small compromises to be made.

[MTbowels]

Your using a something called a leading edge dimmer in your circuit. You need to change it to a trailing edge dimmer. The buzzing will then disappear and you'll have full control over the LED lamps as long as they are of the dimmable variety. Don't continue to use your present dimmer in circuit as you'll cause permanent damage to it like this.

I'd suggest you visit you local Screwfix and have a chat with the boys behind the counter as to the most suitable trailing edge dimmer to buy. A quick look at the reviews online of their product number 94816 seems to show it being recommended for just the purpose you need. Check out the reviews online yourself. Trailing edge dimmers tend to be marginally more expensive but do the job.

[beso]

The are different dimmer technologies, known as "leading edge" and "trailing edge".

LEDs required a trailing edge dimmer.

[The Builder]

Something like this, ................

Amazon.co.uk User Recommendation

Be careful buying dimmers. LED loads (wattage) are so low, that you need a dimmer that can operate properly at your load. The one above has a minimum requirement of 10watts. Your load is 18watts .. so Ok.

[Ryzen]

You need to fit a trailing edge dimmer to the switch.However not all dimmers are compatible with all lamps.When you choose a dimmer check on the website to check compatibility.As suggested you could introduce more resistance/ load into the circuit but this could negate the cost saving of LED lamps.

[Impret-Sir]

Thanks for all your answers guys, I should point out that thte set up, (in our lounge) has a dimmer at one end of the room, and a conventional on/off switch at the other, by the main door. Will this need a particular type of dimmer? (2 way?).

[The Builder]

Yes, that's right... a 2-way dimmer :o)

[Impret-Sir]

Once again, thx for all answers!

[Impret-Sir]

Now I discover that the correct dimmer will not fit in the box in the wall, so that has to be changed, which means deepening the hole in the wall....... wow, I thought I was just going to buy some new lamps and save some money on my electric bill!

[The Builder]

Ah... so you have a standard 13mm deep box? Not deep enough of course. You could fix a plastic surface back-box over the existing, and use that.

[Hopkirk]

Either that or don't use LEDs in that fitment.

[Old_Geezer]

You could forego the dimmer function.
Gets a bit messy trying to get old box out and new one in without damaging cable.

[Impret-Sir]

As this fitment is the one used most throughout the house not using the LEDs here would rather do away with the whole point of buying them. Similarly, the dimming function is very popular in the room in the evenings! So, I guess I will have to replace the back box, it seems to be just held in place with one screw directly into the plaster, which I presume I will then have to chip away to get the depth I need, not sure it will be deep enough to take another screw though. Its a plasterboard partion wall, and I have seen some plastic boxes with fitting lugs that snap out from the sides to hold against the plasterboard, maybe I will try one of those.