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#189545 - 10/16/09 07:25 AM Dimmer Blown Out  
shortcircuit  Offline
Joined: Jun 2004
Posts: 608
I use Lutron AY600 and AY1000 watt dimmers alot in residential work. The problem I'm having with some of the jobs is the dimmers are blowing out when the incandecent lamps blow out.

I have had dimmer failure with a simple 60 watt candle bulb in a dining room light, a 75 watt par30 in a recessed light and with a 100 watt bi-pin halogen bulb.

Can anyone recomend a dimmer that can better withstand light bulb blow outs?



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#189549 - 10/16/09 11:57 AM Re: Dimmer Blown Out [Re: shortcircuit]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,142
A lot of the lamp failures I see involve a bolted fault between the stanchions that hold up the filaments. Next time you have one of these carefully break the envelope of the bulb and I bet you will see them welded together.
I don't know what this fault current is but it often trips the breaker.

The fix is probably better lamps but I am not sure where they would come from. Everyone is building to a price point these days, not a performance standard.

An alternative fix might be some kind of supplemental over current protection but if it takes a service call to replace the fuse, you didn't really save much.

Greg Fretwell

#189552 - 10/16/09 02:05 PM Re: Dimmer Blown Out [Re: shortcircuit]  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,223
SI,New Zealand
Are these bulbs used in an inverted position (upside-down) by any chance?
I read somewhere some time back that that sort of thing is to be avoided,as it is easier for the broken portion of the filament to bridge the filament stanchions.

As Greg mentioned, there isn't really an easy fix as long as you want to go fusing your switch wires (feeding the lamp circuits.

The only other thing I could suggest is (not sure if they exist in the US) rough service lamps, where the filament has more filament supports than a standard bulb.

#189554 - 10/16/09 02:34 PM Re: Dimmer Blown Out [Re: Trumpy]  
geoff in UK  Offline
Joined: Dec 2002
Posts: 185
I've observed that some good quality bulbs have an internal fuse in the base, which I think can save a lot of problems. I've also seen cheap bulbs fail explosively, showering broken glass and taking out the circuit breaker.

#189556 - 10/16/09 04:40 PM Re: Dimmer Blown Out [Re: geoff in UK]  
shortcircuit  Offline
Joined: Jun 2004
Posts: 608
Thanks for the replies guys. I spent hours today reading and researhing this because I have an unhappy customer who doesn't want to pay for the new dimmer or bulbs that have failed on a job with very low use on the installation, maybe 8hrs use.

Trumpy...I used a 1000watt Lutron dimmer on 3 outside bullet style double flood lights with G8 base 120volt 100watt halogen capsule bi-pin style bulbs.

I found some light bulb info in another thread here on this site...

I also called Philips technical assistance who said the bulb failure would never cause a dimmer to blow out. They said it must have been a power surge/spike or some problem with the dimmer.

I called Lutron technical assistance who said that it is possible that bulb failure in some instances can blow the dimmer.

Both companies offered replacements and Philips said to send the failed bulbs in so they could have a look.

Greg...I have 3 failed bulbs from the job and 1 bulb has evidence of a violent condition when it failed. There are burn marks on the glass inside the bulb and the filament supports have broken apart completely.

I suspect this failed bulb caused the dimmer failure.


#189612 - 10/19/09 07:03 PM Re: Dimmer Blown Out [Re: shortcircuit]  
Tesla  Offline
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Someone needs to put a scope on that dimmer.

I suspect that astounding peak transitory voltages are stacking up. It's the dimmer that's causing the spiking.


#189621 - 10/19/09 11:24 PM Re: Dimmer Blown Out [Re: Tesla]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,142
If those filament supports short it is a bolted fault until something gives and that will usually be the dimmer.
If the breaker trips the dimmer will probably be shorted "on" or the triac could just blow open before the breaker trips.

Greg Fretwell

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