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Old 05-16-2010, 01:14 PM   #1
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Dimmer switch is warm even when lights are off!


Hello,

I have a 2 way 2 gang light switch which controls our 2 wall lights (one switch) and main light (other switch). Today I replaced it with a 2 way 2 gang dimmer switch (250w) and I found it very difficult to replace. Anyway I managed to do it and I could dim the main light and the wall lights separately. I found the switch to get quite warm, but from reading I know dimmers can get warm and it's quite normal. However my switch seems to be warm even when the lights are off, is this normal?

I have:

2 halogen wall lights = 6 x 10w = 60w
1 halogen main light = 6 x 15w = 90w

total = 150w and my dimmer can handle 250w

If you need it I can upload a diagram?

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Old 05-16-2010, 03:08 PM   #2
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Dimmer switch is warm even when lights are off!


Ideally there is zero power dissipated in a perfect dimmer at any setting. Practically, I'd expect ~1w dissipation at full brightness for your dimmer.
10vac output instead of zero volts output at the lowest setting can also give you 1w or more when using incand. bulbs because the cold filament resistance can be 10x to 15x lower than the hot filament resistance. The dimmer might be intentionally designed to do this.

At the lowest setting I'd check the voltage across the lamps. True RMS readings are preferable since the voltage is not sinusoidal.


Last edited by Yoyizit; 05-16-2010 at 03:49 PM.
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Old 05-16-2010, 05:52 PM   #3
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Dimmer switch is warm even when lights are off!


The dimmer switch should have a specific "off" position either with a click you can feel or where you push the knob in to get to the off position.

Simply turning it down all the way may or may not turn off the flow of electricity.
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Old 05-16-2010, 05:53 PM   #4
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Dimmer switch is warm even when lights are off!


Yoyzit,

Is there an answer somewhere in your response? It went over my head.

Gonzo,
WHen you say the dimmer is warm when off, how soon after you turn it off are your touching it? I assume if 8 hours have gone by it is not warm? If so, something is amiss.
Is it too hot to leave your finger on it? Most dimmers get warm when in use. Your's is running about 60% of rated capacity. You could get another dimmer rated for a higher wattage (say 600w) and it would likely run cooler.
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Old 05-16-2010, 07:55 PM   #5
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Dimmer switch is warm even when lights are off!


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Originally Posted by bob22 View Post
Yoyzit,
Is there an answer somewhere in your response? It went over my head.
My bad. Sorry.

I will not get drunk and then reply or post.
will not get drunk
will not

Last edited by Yoyizit; 05-16-2010 at 08:27 PM.
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Old 05-17-2010, 02:35 AM   #6
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Dimmer switch is warm even when lights are off!


I left the lights "off" for about 1-2hours and it was still warm, if I turn the mains off for my downstairs lights the front plate goes cooll after 10 mins.

This is the light switch

I haven't tried for 8 hours, at the moment I have put the old switch back on.

One thing I had to do different (from the normal 2w 2g switch) on the dimmer switch was leave a cable out and insulate the end off with tape as I couldn't turn the main light off, it would go off for a second and come back on at a very low dim. It was a blue cable with red sleeve (is that neutral?) that went into the dimmers slave point then everything worked well. This main light can also be turned on via a single switch over the other side of the room.

As I say all worked well, but the constant heat when off is a worry.
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Old 05-17-2010, 07:53 AM   #7
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Dimmer switch is warm even when lights are off!


Dunno' what 'trailing edge technology' is, but I think the clue is in the phrase 'soft start'.
The dimmer continuously lets some current into the lamps and that's why it's warm. It's probably just a power resistor inside the unit in parallel with the controller circuitry. This is more to prolong the dimmer life than the lamp life.

If this is true you should measure some voltage across the bulbs when the dimmer is set to minimum.
Also, in total darkness you may see the bulbs glow very dimly.
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Old 05-17-2010, 08:12 AM   #8
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Dimmer switch is warm even when lights are off!


These dimemrs can be controller via a remote so would that mean they are always on so some degree? I guess this must be soft start, I just have to brush the front to turn them on, and hold in to increase the power and then press in again to decrease power. Would a diagram help, I worrys me I had to take a cable out to get it to work, a bit of trial and error?

I don't have a device to measure the voltage, are you thinking there is a higher voltage or something else using more power?
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Old 05-17-2010, 08:22 AM   #9
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Dimmer switch is warm even when lights are off!


Quote:
Originally Posted by gonzo View Post
I don't have a device to measure the voltage, are you thinking there is a higher voltage or something else using more power?
To troubleshoot this you will need a voltmeter or an ammeter.
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Old 05-18-2010, 09:37 AM   #10
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Dimmer switch is warm even when lights are off!


Do you think there is some sort of additional voltage going through this switch?

Why do you think leaving the blue cable (with read sleeve) helped turn he main light off, but if I use the existing 2w 2g switch it requires it?

Thanks
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Old 05-18-2010, 02:39 PM   #11
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Dimmer switch is warm even when lights are off!


Quote:
Originally Posted by gonzo View Post
Do you think there is some sort of additional voltage going through this switch?

Why do you think leaving the blue cable (with read sleeve) helped turn he main light off, but if I use the existing 2w 2g switch it requires it?

Thanks
Warmth implies a few watts of power being dissipated, which can be checked with meters.

Dunno' about blue cables.
I'd need a detailed schematic of the switch gizzards and they won't give it to you because it's proprietary.

I'm assuming you followed the install instructions to the letter.
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Old 05-18-2010, 05:46 PM   #12
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Dimmer switch is warm even when lights are off!


......

Last edited by Jim Port; 05-18-2010 at 06:50 PM. Reason: did not see link
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Old 05-18-2010, 06:45 PM   #13
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Dimmer switch is warm even when lights are off!


I went to your link and noticed that this in the UK if that is relevant at all.
I think the website says you need to use a slave unit to replace the other switch if this is a 3-way (lights controlled by two switches). DId you do so?
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Old 05-19-2010, 02:30 AM   #14
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Dimmer switch is warm even when lights are off!


Hi,

You are right I haven't changed the single switch to a slave, would this fix the heat issue? This single seems to almost be on a separate circuit or something let me explain:

If I turn the main light on fromthe double switch I can't turn it off from the single switch, you have to use the original switch to turn it on or off, does that make sense. I thought about getting a slave but it's as if the ligths are on different feeds, what do you think?

This is identical to the instructions I have.

Last edited by gonzo; 05-19-2010 at 02:35 AM.
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Old 05-21-2010, 04:20 AM   #15
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Dimmer switch is warm even when lights are off!


Just wondered if anyone made sense of those instructions I provided in a link above, do I need a slave? does it help with the heat from the other switch?

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