Dimmer caught on fire?!
David Grant
From: "David Grant" <tho...@sympatico.ca>
Subject: Dimmer caught on fire?!
Date: Sunday, January 05, 2003 10:23 PM
I am wondering if anyone can tell me why this particular dimmer almost cause
a building to burn down.?
The dimmer I installed was to control 120V incadescent track lights. It
would dim about
12 lights at 100W each (1200W). I got the larger dimmer (for 1500W). It
worked fine for months. However when I returned one day I found the dimmer
blackened and black scorch marks 2 feet up the wall. (Scary!) The building
is used maybe once a month.
This did not accur while the lights were on (the lights are turned off when
no one is there)
Maybe the lights were on really dim, but definitly not on full. The breaker
did not trip. I removed the dimmer and found the wires to be in good
condition aside from being lightly covered in soot. The wires going to this
box was just a switch loop (2)
I can only assume there was a fault in the dimmer. In the jboxes for the
track lights was the feed and feed to other lights as well as the switch
loop. The switch loop was copper and the remaining wires were aluminum.
When I made the joints I used NOALOX and when I inspected the jbox after the
fact every joint was still good with no signs of damage/arcing.
Anyone have any ideas to what happened. When I return the dimmer back to
Home Depot I asked them to have someone look at it and give me an
explaination (I'm not really expecting one).
Dave
(P.S. I seem to have little luck with dimmers!)
The dimmer in question was made by LEVITON
Marc_F_Hult
in message <DsnS9.1383$7h3.3...@news20.bellglobal.com>:
Are these X-10 dimmers? What model -- Leviton make many different dimmers.
If you bought it at Home Depot, it probably isn't architectural grade and it
probably isn't X-10.
Does it have one or more of the fins removed (if so it ain't "1500 watts" any
more) ?
Is it mounted in a box with other dimmers (if so, it ain't "1500 watts" any
more.
Is it mounted above another dimmer (not *ever* recommended) ?
It probably failed while dimmed -- neither on nor off -- which is what places
the greatest load on the triacs/SCR's, snubber (capacitor and resistor), and
choke. Get one rated for 1800/2000 watts that has a large _external_ heat
sink and keep it OFF when not in use. Also, check the voltage at the switch
under various loads. (Aluminum wiring gives me the creeps ....)
Consider putting this dimmer on a circuit of its own. At reduced voltage,
the current through the dimmer can go up if the resistance of the filaments
goes down and the heat dissipation required of the TRIAC/SCR's
goes up incrementally, and what was theoretically 80% of rated load
(1200watts/1500watts) goes ... well, you saw it.
HTH ... Marc
Marc_F_Hult <use...@xxxhydrologistxxx.com>
TKM
Marc_F_Hult <use...@xxxhydrologistxxx.com> wrote in message
news:ce8k1vk850atvemkh...@4ax.com...
As mentioned, an electronic dimmer is working at its maximum and is most
vulnerable when it is in the "full dim" position. I'd add to the list above
a voltage surge or lightning strike hitting the line resulting in an
internal arc-over.
TKM
rob
Dimmers usually suffer violent ends if you don't use the correct
dimmer for the job.
For instance: low voltage halogens and Lutron's Spacer system.
Can't use the dimmers on the shelves at Home Depot or Lowes because
they are designed for 120V incadecent bulbs ONLY. No protection for
inductive kickback from any transformer or ballast. Just a momentary
short when it burns out.
Here is a page with their entire Spacer line.
Note the different types...
http://www.lutron.com:80/spacer/components.htm
I have been running for three years without a single failure once I
installed the correct dimmer.
(Spacer is pretty cool too. Special ordered the parts through Home
Depot.)
Ben Willcox
> As mentioned, an electronic dimmer is working at its maximum and is most
> vulnerable when it is in the "full dim" position.
Can you explain how this is so? I would have thought it would be working
at maximum load when the triac is chopping the AC waveform at its peak, i.e.
about 50% brightness.
Ben.
todesco
When it's on, it's conducting the full load. The voltage drop on the
triac is pretty constant. The dissipated power in the triac is a
function of the
load current and voltage drop on the device. When it's off, there is no
current through the device except for some leakage. Now, if the triac
gets
real leaky, you could get higher voltages across it, and because the
device
dissipation power increases as the square of this voltage, the power can
go up real fast making it heat. Most dimmers I have seen completely
open
the circuit with the mechanical switch when it is off (not X-10 stuff)
so
the dimmer switch must have been on with the dial set low ... I would
think.
Marc_F_Hult
<ben.w...@nospam.blueyonder.co.uk> wrote in message
<pan.2003.01.07....@nospam.blueyonder.co.uk>:
The TRIAC in a dimmer (or back-to-back SCR) doesn't "chop the AC waveform at
its peak". What it does is delay the turn-on until part way into the cycle.
see http://www.saburchill.com/tech/electronics/elect0396.html
David Grant
The case of the dimmer was intact but, it felt kinda soft and squishy is you
were to squeeze the back of it. The front cover/heat sink did not melt but
had black soot on part of it. The soot marks up the wall also covered the
inside of the electrical box and the two wires.
Does anyone what to see a picture of this, I have a few?
Dave
----- Original Message -----
From: "Spehro Pefhany" <sp...@interlog.com>
Newsgroups: alt.engineering.electrical
Sent: Monday, January 06, 2003 8:43 AM
Subject: Re: Dimmer caught on fire?!
> On Mon, 6 Jan 2003 08:39:39 -0500, the renowned "Jim Fincher"
> <jfin...@bellsouth.net> wrote:
>
> >I think your should ask Leviton not Home Depot....
>
> Yes, once you've let go of the thing, good luck in getting any
> information back.
>
> Soot on the wall is different from scorch marks, I suspect you had
> the former.
>
> I'd guess if you looked inside the phenolic dimmer case you'd find
> that a snubber/EMC capacitor (probably) failed and arced away for a
> while, producing a lot of soot. It was contained within the case,
> which is why you didn't see a hole in the case. For a fire to have
> occured it would have had to get through the dimmer case and
> through the electrical box.
>
> Best regards,
> Spehro Pefhany
> --
> "it's the network..." "The Journey is the reward"
> sp...@interlog.com Info for manufacturers:
http://www.trexon.com
> Embedded software/hardware/analog Info for designers:
http://www.speff.com
"David Grant" <tho...@sympatico.ca> wrote in message
news:DsnS9.1383$7h3.3...@news20.bellglobal.com...
J. Clarke
r_fi...@hotmail.com says...
> Flourescents don't normally like to be dimmed.
>
> Dimmers usually suffer violent ends if you don't use the correct
> dimmer for the job.
>
> For instance: low voltage halogens and Lutron's Spacer system.
>
> Can't use the dimmers on the shelves at Home Depot or Lowes because
> they are designed for 120V incadecent bulbs ONLY. No protection for
> inductive kickback from any transformer or ballast. Just a momentary
> short when it burns out.
That's odd. I picked up a Lutron dimmer off the shelf at Home Depot the
other day that was clearly labelled as being suitable for use with
fluorescent lamps.
However, he was using incandescent track lighting so I don't see what
relevance this has.
> Here is a page with their entire Spacer line.
> Note the different types...
>
> http://www.lutron.com:80/spacer/components.htm
>
> I have been running for three years without a single failure once I
> installed the correct dimmer.
>
> (Spacer is pretty cool too. Special ordered the parts through Home
> Depot.)
>
--
--
--John
Reply to jclarke at ae tee tee global dot net
(used to be jclarke at eye bee em dot net)
s
- Do dimmers work with flourescent lamps?
- Do the flourescent lamps actually dim or just shut down at a certain
point?
- Using the flourescents that fit in incandescent fixtures, will a
dimmer work here?
...this is all assuming that the dimmer is rated for flourescent
lamps. (Haven't actually seen one - are then expensive???)
Thanks!
"J. Clarke" <nos...@nospam.invalid> wrote in message
news:avhad...@enews3.newsguy.com...
todesco
There are dimmers rated for fluorescent lamps ... don't know if you have
to have one of these for compact fluorescents. I have used one of these
'special' dimmers to dim low voltage lighting that used an 'electronic'
transformer and it works well.
todesco
There are dimmers rated for fluorescent lamps ... don't know if you have
to have one of these for compact fluorescents. I have used one of these
'special' dimmers to dim low voltage lighting that used an 'electronic'
transformer and it works well.
Ben Willcox
>
> The TRIAC in a dimmer (or back-to-back SCR) doesn't "chop the AC waveform at
> its peak". What it does is delay the turn-on until part way into the cycle.
>
> see http://www.saburchill.com/tech/electronics/elect0396.html
>
Ah yes, you are indeed correct, I got it the wrong way round.
Ben
Ben Willcox
> Well, this is not true, sort of. The triac is either on or off, period.
> When it's on, it's conducting the full load.
Yes I understand that. However, what I meant was, when the circuit is
dimming the lamp the triac is only conducting for a small part of a
cycle, where the voltage (therefore current draw - load) is quite low.
When the lamp is dimmed to 50%, the triac is switching on at the peak of
the cycle (thanks to Marc_F_Hult for correcting me here!), therefore at
this point the load is the greatest.
Of course I am not saying this module burnt out under these conditions,
only that I don't see how maximum load would have been placed on the
module when the lamp is dimmed so low that it's (almost) off.
Ben.
J. Clarke
no....@the.internet says...
> Just a few questions regarding dimmers and flourescent lights...
>
> - Do dimmers work with flourescent lamps?
Depends. If the ballast is dimmable then yes, otherwise no.
> - Do the flourescent lamps actually dim or just shut down at a certain
> point?
They dim to a point then shut down.
> - Using the flourescents that fit in incandescent fixtures, will a
> dimmer work here?
If the lamp is dimmable, yes. Most CFs (Compact Fluorescent, the most
common type that fits in incandescent fixtures) are not but some are.
> ...this is all assuming that the dimmer is rated for flourescent
> lamps. (Haven't actually seen one - are then expensive???)
For a given quality level not all that much more expensive than
incandescent-only IIRC. Been a while since I priced them though.
--
TCS
>In article <1142b779.03010...@posting.google.com>,
>r_fi...@hotmail.com says...
>> Flourescents don't normally like to be dimmed.
>>
>> Dimmers usually suffer violent ends if you don't use the correct
>> dimmer for the job.
>>
>> For instance: low voltage halogens and Lutron's Spacer system.
>>
>> Can't use the dimmers on the shelves at Home Depot or Lowes because
>> they are designed for 120V incadecent bulbs ONLY. No protection for
>> inductive kickback from any transformer or ballast. Just a momentary
>> short when it burns out.
>That's odd. I picked up a Lutron dimmer off the shelf at Home Depot the
>other day that was clearly labelled as being suitable for use with
>fluorescent lamps.
I find that rather hard to believe. Dimmers use a chopper circuit (variable
pulse width by delaying the firing pulse to the triac) and this is incompatible
with flourescent lamps.
How, pray tell, does that dimmer work? Flourescents can't be dimmed. The gas
inside is either ionized, or it isn't.
todesco
TCS
>Wrong!
right!
Dave Houston
http://www.lutron.com/ballast/hilume.asp
There are many others.
---
http://www.laser.com/dhouston/
todesco
Travell3r
You need a dimmable flourescent fitting for the dimmer switch to work with.
The loads drawn are much to high for a dimmer to handle otherwise.
"todesco" <tod...@attbi.com> wrote in message
news:3E20A347...@attbi.com...