How to open dimmer switch box and replace fuse ? :-(

nicofars · 6 Mar 2009

Semes like a stupid question, but it seems that my dimmer swithc (stainless still touch from Screwfix) is dead or I gues the fuse.
I have tested the power from the + and - and up to the light and it's fine. So must be problem at the switch box. The box is transparent inside so I can ee CLEARLY the fuse (not black, not appearing burnt) but the problem is : How can I open this box.. it seems all glued together

There are 3 screws around the box, but don't do anything.
Help ? please...

switch looks like http://www.ozonefortis.net/pcat-gifs/products-small/BT-004.jpg without the drawing

securespark · 6 Mar 2009

You sure it's a fuse?

Older dimmers (white plastic) used to have BS646 fuses in, but not modern dimmers, AFAICT.

Have you checked voltage at the light fitting?

Have you shorted the switch wires out (using safe isolation methods) to see if the light comes on?

laughingjester · 6 Mar 2009

buy a new one should'nt really fiddle about whith manufactured sealed bits of kitt.

ban-all-sheds · 6 Mar 2009

What's the purpose of a fuse in a dimmer?

Spark123 · 6 Mar 2009

I'm thinking that it will have a lower I²t than a lighting circuit fuse therefore there is a slight chance it will pop before enough energy has got through to destroy the triac when a lamp goes.

sparkyspike · 6 Mar 2009

It's a thermal protection fuse and can't be replaced, as far as I know.

securespark · 6 Mar 2009

ban-all-sheds said:
What's the purpose of a fuse in a dimmer?

Well, in the olden days, when you were young (

), dimmers often had fuse protection in the form of a 1, 2 or 3A BS646 fuse. MK and Volex (believe it or not!) were two manufacturers that spring to mind.

It was there to protect the dimmer from damage when the lamp failed. IME, it worked very well.

I often wish dimmers had fuses now. The number I change because customers insist on buying cheap lamps is phenomenal.

One of the last jobs I did self employed, I fitted (against my better judgement) some GU10 downlighters and an MK dimmer. In the box for the dimmer was a big notice in red stating something like:

"LAMPS CONTROLLED BY THIS DIMMER MUST BE OF THE FUSED TYPE OTHERWISE DAMAGE TO THE DIMMER WILL OCCUR WHEN THE LAMPS FAIL."

Yet another example of MK cutting costs in its range.

Ho hum.

ban-all-sheds · 6 Mar 2009

Spark123 said:
I'm thinking that it will have a lower I²t than a lighting circuit fuse therefore there is a slight chance it will pop before enough energy has got through to destroy the triac when a lamp goes.

Sounds good to me - that's what I always thought the fuse would be for.

sparkyspike said:
It's a thermal protection fuse and can't be replaced, as far as I know.

So the point of it is....?

ban-all-sheds · 6 Mar 2009

securespark said:
ban-all-sheds said:

What's the purpose of a fuse in a dimmer?

Click to expand...

Well, in the olden days, when you were young ( ), dimmers often had fuse protection in the form of a 1, 2 or 3A BS646 fuse.

Ha! - When I was young you couldn't buy dimmers - if you wanted one you had to make your own from a design in Practical Electronics.

I often wish dimmers had fuses now. The number I change because customers insist on buying cheap lamps is phenomenal.

I've had a 4-gang dimmer (Wickes finest, IIRC

) in my living room for >20 years (100W GLS & RO80 lamps).

All sorts of makes.

Lost track of the number of times a lamp failure has taken out the MCB.

Never had to replace a fuse in the dimmers (there aren't any), or a dimmer...

nicofars · 7 Mar 2009

few hours after I postd I got my answer,
so basically:
- fuse in dimmer are just for decoration , no just jocking, but cannot replaced anyway
- it's not surprising/rare to change the whole dimmer switch

so I will get a new switch now (or a couple just in case)

thanks guys !

bernardgreen · 7 Mar 2009

ban-all-sheds said:
sparkyspike said:

It's a thermal protection fuse and can't be replaced, as far as I know.

Click to expand...

So the point of it is....?

Urrmm.. could it be to shut the dimmer down when for some reason it is starting to get hot. To shut it down before it gets hot enough to do some damage.

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How to open dimmer switch box and replace fuse ? :-(

sparkyspike

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