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Dimmer switch question

Readie

Readie

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Just a quick question please.

Thinking of fitting new spotlights in our lounge and think dimmable might be the way to go.

Do the majority of these switches fit in a standard depth box or is there a possibility of having to chop out wall for a deeper box ?

TIA
 
Hey, don’t fit a dimmer if you’re wanting to save money. They use the same power if they’re turned down or fully on.

Just thought I’d give you a heads up…

EDIT: Sorry, you will save money but only on LED lights. 👍

With incandescent bulbs….

When you dim the lights, you put less current through the bulb by putting a "resistor" in the way. Turning the switch gives a greater resistance, and hence a lower current through the bulb. However, the power that doesn't come out of the bulb is disappated across this resistor (it will get hot). So if a bulb is 50 Watts, but you turn it to half power, 25W will come from the bulb, but the resistor will also dissipate 25W.

Physics lesson over…. Boring or what! 😂👍😂
 
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You can buy LED bulbs that will change brightness just by flicking the lightswitch. Might be easier and cheaper just to change the bulbs instead of the lightswitch ?
 
Jay Butts said:
When you dim the lights, you put less current through the bulb by putting a "resistor" in the way. Turning the switch gives a greater resistance, and hence a lower current through the bulb. However, the power that doesn't come out of the bulb is disappated across this resistor (it will get hot). So if a bulb is 50 Watts, but you turn it to half power, 25W will come from the bulb, but the resistor will also dissipate 25W.
Click to expand...
I think you need to relearn your physics.
P=V^2/R
The electricity supply will be maintained at constant voltage so increasing the resistance in the circuit cuts the power (Watts).
 
Jay Butts said:
When you dim the lights, you put less current through the bulb by putting a "resistor" in the way. Turning the switch gives a greater resistance, and hence a lower current through the bulb. However, the power that doesn't come out of the bulb is disappated across this resistor (it will get hot). So if a bulb is 50 Watts, but you turn it to half power, 25W will come from the bulb, but the resistor will also dissipate 25W
Click to expand...

Most dimmer switches work by reducing the voltage, usually by means of a triac semi conductor, reducing voltage also reduces current, so there is indeed a slight reduction in power.
 
Splitpin said:
Most dimmer switches work by reducing the voltage, usually by means of a triac semi conductor, reducing voltage also reduces current, so there is indeed a slight reduction in power.
Click to expand...
Yeah, I’ve been absolutely corrected mate. 😂

Back in the day dimmers used to use a variable resistor to put a false load across the voltage so the bulb would lessen in brightness and the dimmer switch would get warm to dissipate the power. Sometimes even dangerously hot. It really didn’t make a difference to power consumption.

Just guilty of not digging myself out of the dark ages! 😂😂😂
 
@Readie, just make sure the LED spotlights you get are dimmer compatible buddy. I found out the hard way a few years ago as not all LED lights can be dimmed. I ended up changing both a dimmer and the LED.

And back when they weren’t cheap like today. 😂😂😂
 
To be sure, I would switch off the power to the switch unscrew the 2 fixing screws and measure the depth you have in the back box.
Then you will know what you have and see if you can find a suitable dimmable switch to fit.
I also depends on which way the wires enter the back of the switch or in the top .
Cheers Maz.
 
Be sure it’s a deep box and not a plaster depth box 😉👍.
Assuming it’s flush 🤔
 
Back to the original question...
*Most* dimmer switches will fit in a standard wallbox - but not all.
If you have problems you can buy a sort of spacer (dunno the proper name) which fits between the switch and the wallbox.
I think I got mine from Screwfix. (Loong time ago)
You will probably need extra-length screws as well.
 
And just when you thought it could not get any more complicated :eek:

I've just been through this with a recent renovation, all the above is correct, but there are also two types of dimmer switch, so you have to make sure you buy one which is compatible with LED lighting, and watch out for transformers, some LEDs need them, so again, just watch that everything is compatible before you buy it (y)
 
Blimey,

Thanks for all the replies guys.

Yes, I can remove face plate and measure depth, I was just kind of thinking that dimmers would be extra deep.

Anyway, SWMBO, is now saying she doesn’t want spotlights…..

So it will be dimmable GU10 LED bulbs I’m looking at, if I get my way

Maybe I’ll just wait until she goes away for a day and fit them….🤞

Cheers ..🍻
 
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