effing dangerous light switch or am I dumb?

O

opps

Joined
16 Jun 2006
Messages
10,202
Reaction score
2,229
Location
London
Country
United Kingdom
A while ago I fitted a new digital dimmer from Homebase

Today I changed the ceiling light only to discover that since fitting the digital switch the feed to the light is constantly live when no light is fitted.

being a lazy so and so I decided against throwing the lighting MCB in the consumer unit, after all, I assumed that a light switch that is not turned on is by definition off. Silly me.

Have I inadvertently wired the switch back to front? There are only two terminals on the switch, I put the live cable in the hole marked L and the cable that supplies the light into the hole that has a wavy line with an arrow intersecting it (which I assumed was the load).
 
Sponsored Links
Well congratulations on still being alive to tell the tale.....

Where are the neutrals? Behind the light switch or above the light fitting? Possibly these have been reversed, so you are switching neutral not live....
 
Mmm, digital dimmer. I wonder if it never actually switches off (isolates) and with no load at all looks live (or is quite live).

Maybe it never switches off and always seeps a little current (hardly green then).
 
Sponsored Links
I am guessing the dimmer has no neutral, and it's digital circuitry is powered by it being in series with a load (the lamp). This would put 230v on the sw live (and the lamp holder) wen the lamp is removed. Similar to 'switch locating' neons.
 
Hi all

The wires that would have been previously connected to the ceiling rose are all hidden away in the cavity. At the light fitting there is a terminal block with the live from the switch and the return.

I fitted the previous light (a couple of years ago), at the time the switch was a standard on/off rocker. From memory when the old switch was turned off there was no power going to the light (had there been I would have sorted it).

Today I only noticed that the switched live at the light is live when I touched it whilst extending it.

assuming that I had wired the digital switch correctly, it seems that when the light fitting is removed from the circuit the current LED on the switch goes out. It was the absence of any visual evidence of power at the LED that lead me to believe that no power was running into the switched live to the light fitting.

My multi meter is elsewhere at the moment but my mains tester screwdriver glows equally bright on both terminals of the switch when no light fitting is connected.

I cannot verify that the shock that I got was 240v. Unlike earlier shocks I didn't feel nauseous or feel the after effect tingling all the way down my legs. It was largely limited to my hand and arm. I was standing on a fake leather swivel stool at the time (yeah, I know- even dumber than not testing for current first).
 
phatboy said:
Well congratulations on still being alive to tell the tale.....

Where are the neutrals? Behind the light switch or above the light fitting? Possibly these have been reversed, so you are switching neutral not live....
Click to expand...

The neutrals are in the ceiling cavity.

If that were the case then with the light fitting removed there would not be any power at the switch, which there was.
 
JM2 said:
Mmm, digital dimmer. I wonder if it never actually switches off (isolates) and with no load at all looks live (or is quite live).

Maybe it never switches off and always seeps a little current (hardly green then).
Click to expand...

Will double check when I have my multi-meter.
 
As its sold in a DIY shed, it is designed asa direct replacement, and so i bet will not require a neutral (as more often than not, there isn't one). It will therefore (as its digital, and things to do), extract power by being in series with the load. This inherently will cause the lamp holder to become live with the lamp removed.

I would say no wiring fault.
 
Lectrician said:
I am guessing the dimmer has no neutral, and it's digital circuitry is powered by it being in series with a load (the lamp). This would put 230v on the sw live (and the lamp holder) wen the lamp is removed. Similar to 'switch locating' neons.
Click to expand...

I suspect that you might be correct.

The switch does have a green LED so that you can see it in the dark, this turns red when the light is turned on.

Until reading your post it hadn't dawned on me that most neon lights on switches use a neutral. something missing from the standard wiring supplying a light switch.

It would have been nice for the maker or retailer to warn customers that their digital switch doesn't isolate power all of the time. I guess it also means that if a bulb blows the fitting's wires are live which is scary given that the light fitting is insulated and thus has no earth.

How are they legal?



Edit- sorry Lectrician, I was answering your first reply and hadn't seen your latest, hence I have pretty much repeated what you said.

Thanks for your replies they have been a great help.
 
If you'd properly safely isolated you'd be fine. :rolleyes:

Let this be your lesson, and work safely in future. You might not be so lucky next time.
 
D

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
You must log in or register to reply here.
Sponsored Links

Similar threads

C
Need to check please?
Replies
3
Views
584
Taylortwocities
Taylortwocities
M
Dimmer switch on cabinet lighting
2
Replies
18
Views
2K
ban-all-sheds
ban-all-sheds
T
2 way dimmer switch wiring
Replies
8
Views
38K
breezer
B
B
What would make a light flicker when using dimmer switch?
Replies
11
Views
45K
festa
F
S
Change switch to dimmer confusion
Replies
1
Views
885
PrenticeBoyofDerry
PrenticeBoyofDerry
Back
Top