ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
nec 110.3 (B)
by gfretwell - 09/22/21 11:11 PM
Grounding electrodes
by gfretwell - 09/07/21 03:41 PM
Looking For Electricians in the Midlands
by Alex247 - 09/06/21 05:26 AM
New in the Gallery:
Now you know.
Now you know.
by Tom_Horne, September 7
February, North East Indiana
February, North East Indiana
by timmp, July 25
Who's Online Now
0 members (), 43 guests, and 25 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Joined: Oct 2006
Posts: 745
E
Member
OK, as professionals, we know that you aren't supposed to use a dimmer on a fluorescent lamp. Problem is, that the general public does not know this. With CFLs being all the rage, it's just a matter of time before we start seeing more and more stories like this:

http://www.wtop.com/?nid=598&sid=1395955

I'm sure that the package containing CFLs states that you should not use them with dimmers, but honestly, who reads the packaging for a light bulb? This could be a huge problem.


---Ed---

"But the guy at Home Depot said it would work."
Arc Flash PPE Clothing, LOTO & Insulated Tools
Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
Not only could be ... it WILL be. With luminaries such as Al Gore making blanket statements about there being dimable fluorescents, I expect we will see a lot more of this.

Joined: Dec 2002
Posts: 205
G
Member
I have to wonder quite how this could happen, and if it indicates a basic design shortfall in the item involved.
There is no indication whether the dimmer or the lamp was the source of ignition, but in either case a safe failure mode should have been designed in. (eg thermal fuse)
After all, if the device has the ability to overheat to ignition point there could be other faults leading to this, without someone mixing incompatible items.

Joined: Mar 2005
Posts: 1,213
S
Member
Geoff, I believe harmonics are to blame. The dimmers are designed to power simple resistive loads and contain transistors that switch on and off very rapidly to dim the lights. The CFLs, on the other hand, contain capacitors which are designed to operate at 60Hz, but are now subjected to much higher frequencies, at which they offer a far lower resistance- essentially becoming a short circuit to ground. These components are super-cheaply designed already, but with the dimmer, they overheat and blow even quicker. The extra current through the dimmer would cause it to overheat quickly, too. A thermal fuse would help immensely in the dimmer, but I don't believe it would do much good in a CFL. Better solution would be an inductor designed to trap the higher frequency harmonics. But this might only give the illusion of being able to work on a dimmer, and still cause problems.

Honestly, consumers have every warning- it's clearly labeled on the CFL package, and clearly labeled on the dimmer package, and 99.9999% of the time, the CFLs just die quickly with no fire, and the consumer learns his/her lesson, and spreads the word to their friends. The Darwin awards exist for a reason.

Joined: Jul 2007
Posts: 1,335
S
Member
All the labeling in the world may reduce but not fix it. As electricians, do we read the packaging and the safety warnings before installing something?


"Live Awesome!" - Kevin Carosa
Joined: Oct 2006
Posts: 745
E
Member
I agree. I've put in thousands of panels and GFIs and assure you that I've never read the instructions or warnings. The sad thing is that I just realized that in my own bedroom, we have CFLs in both lamps since they have flimsy paper shades. I did this because I was afraid that the heat of a standard "A" bulb would scorch the shades. One of the three switches in my 4-way setup is a dimmer! We never dim them, but I honestly never even thought about it. I sure will now.


---Ed---

"But the guy at Home Depot said it would work."
Joined: Jul 2002
Posts: 8,407
Likes: 2
Member
Originally Posted by sparkyinak
All the labeling in the world may reduce but not fix it. As electricians, do we read the packaging and the safety warnings before installing something?

Good point,
This is why it is important for electricians to keep up with the latest and greatest.

There are fish-hooks in installing any new item to the market in somebodies house, etc.

I had an instance of these CFL's nearly catching fire a few years back in the house next door to where I was living at the time, but these weren't on a dimmer.

Just on the subject of dimmers vs CFL's, I recently installed some CFL's for a guy down the road, I told him that I would have to remove the dimmers from his lounge lighting circuits, because the two do not agree with each other.
The guy could not seriously believe that you could not dim a fluorescent lamp!
(I realise that they can be dimmed, but the control gear price is really only for Commercial installations)

Joined: Mar 2007
Posts: 404
Member
There are a number of CFLs that are advertised and marketed as being useable with dimmers. As they are relatively expensive ($15 each) and I don't have any dimmers in my house, I haven't tried any of them.

Joined: Jul 2007
Posts: 1,335
S
Member
Originally Posted by noderaser
There are a number of CFLs that are advertised and marketed as being useable with dimmers
I am carious what their listing states about them dimming.


"Live Awesome!" - Kevin Carosa
Joined: Mar 2007
Posts: 404
Member
Here's an example of one from GE, that says it is dimmable on a standard incandescent dimmer:

http://genet.gelighting.com/LightPr...adCrumbValues=&ModelSelectionFilter=

Page 1 of 2 1 2

Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
timmp
timmp
Leo, IN, USA
Posts: 27
Joined: June 2004
Top Posters(30 Days)
timmp 3
Popular Topics(Views)
283,074 Are you busy
216,812 Re: Forum
203,189 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5