Discuss Dimmer switch problems in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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christian

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Hi lads.I've just replaced a light fitting in a small box bedroom with a single low voltage down light and changed the switch with a one way dimmer.The problem is it turns the the light on and off but it does'nt dim.Would i be right in thinking the dimmer switch is knackered ???? Its quite a drive away so i would like to know whether its worth buying a new dimmer switch, save coming back on myself...Cheers lads
 
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Spudnik

  • Thread Starter Thread Starter
  • #2
From what you are describing i would say the dimmer was at fault.

Also, most dimmers need a minimum load as well as having a maximum load.
 
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christian

  • Thread Starter Thread Starter
  • #3
From what you are describing i would say the dimmer was at fault.

Also, most dimmers need a minimum load as well as having a maximum load.
So could it be to small a load as well jason ???
 
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claire_r

  • Thread Starter Thread Starter
  • #4
a 250 w dimmer needs 40w to operate, a 400 w dimmer needs 60w....if you have any test equipment just see if you are getting any voltage on the load side to earth when its turned on, if not itll be the dimmer :) id just replace for a switch meself! :D
 
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Chappers

  • Thread Starter Thread Starter
  • #5
A low voltage light fitting, ie., a 12V one with transformer? Not sure how well that'd respond to the variable supply from a dimmer switch. I would say dimmer switch is fine, but once you turn it low enough, the transformer stops supplying voltage from the secondary and so the light goes out (assuming it is 12V type fitting).
 
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Spudnik

  • Thread Starter Thread Starter
  • #6
Yes but the op was stating that the dimmer just turned on the light and wouldn't dim?

I have had this before with faulty dimmers. Not often tho.
 
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Chappers

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  • #7
I've found two types of 12V transformers, dimmable and non-dimmable. Here's a dimmable one: 60Va Dimmable Transformer - 12v Low Voltage Lighting and what could be happening is that when the dimmer's set to full brightness, the transformer behaves normally, but when the dimmer chops the juice up, altering the duty cycle, the transformer doesn't work as it should. I'm not sure of the effects of a low duty cycle on a transformer. Not sure how the dimmable transformers achieve what they do, either. Just a suggestion as missing something like that could create a big headache of a job...
 
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christian

  • Thread Starter Thread Starter
  • #8
I've found two types of 12V transformers, dimmable and non-dimmable. Here's a dimmable one: 60Va Dimmable Transformer - 12v Low Voltage Lighting and what could be happening is that when the dimmer's set to full brightness, the transformer behaves normally, but when the dimmer chops the juice up, altering the duty cycle, the transformer doesn't work as it should. I'm not sure of the effects of a low duty cycle on a transformer. Not sure how the dimmable transformers achieve what they do, either. Just a suggestion as missing something like that could create a big headache of a job...
Thanks to everyone for replying.The transformer is dimmable, and it switches on and off just no dim.It is a big headache aswell mate lol.....
 
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Spudnik

  • Thread Starter Thread Starter
  • #9
If its a long trip to sort out then maybe take a new dimmer and a dimmable transformer with you,

Save you having to go back again.

Good luck!
 
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Chappers

  • Thread Starter Thread Starter
  • #10
Looks like Jason's probably right and the dimmer's knackered. We have loads of problems with transformers at work, they've got low voltage downlights everywhere in every building and the transformers keep packing up. Ends up being a pain in the backside, hope yours is solved easily.
 
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Plan

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  • #11
just to throw another spanner even in installations with 230v fittings (im talking about gu10 & gz10 etc) dimmers can be a nightmare as have to be half rated ie 6 50w gu10 lamps (300w) have to have 600w minimum dimmer
 

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