Light Switch Getting Very Hot - Electrical - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 11-17-2009, 11:35 AM   #1
Newbie
 
Join Date: Nov 2009
Posts: 4
Rewards Points: 10
Question

Light Switch getting very hot


I recently bought a house and after a month I noticed that the light switch in the kitchen, which is a dimmer with an on/off switch, gets very hot when the lights are on for more than about five minutes. Almost hot enough that it would hurt to hold your hand on it. Specifically, the metal around the outside of the switch is getting hot. I bought a new switch, the exact same kind of dimmer except this one said 600W instead of 300W, installed it and found the exact same problem. Any idea what's going on? Would replacing it with a standard light switch take care of it?

Advertisement

CletusTSJY is offline   Reply With Quote
Old 11-17-2009, 01:15 PM   #2
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Light Switch getting very hot


Quote:
Originally Posted by CletusTSJY View Post
1 Any idea what's going on?

2 Would replacing it with a standard light switch take care of it?
1 You are abusing the dimmer by dimming something that is not supposed to be dimmed.
2 Almost certainly, Yes.

Advertisement

Yoyizit is offline   Reply With Quote
Old 11-17-2009, 01:25 PM   #3
Newbie
 
Join Date: Nov 2009
Posts: 4
Rewards Points: 10
Default

Light Switch getting very hot


Thanks for your reply. That is weird, the dimmer was installed when we bought the house and the only thing I've done is replace a burnt out lightbulb with another lightbulb that came from the living room- which also has a dimmer! Well I will replace it with a regular light switch...not like I need romantic lighting while cooking my top ramen! :P

Thanks again!
CletusTSJY is offline   Reply With Quote
Old 11-17-2009, 01:28 PM   #4
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default

Light Switch getting very hot


If you are dimming just incandescent lights it should work as long as you stay under the rated wattage
A heavy metal face plate can help dissipate heat
I use the biggest electric box possible for everything
This gives it more air space
Some of the small plastic boxes & older metal boxes are very small
Scuba_Dave is offline   Reply With Quote
Old 11-17-2009, 03:28 PM   #5
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Light Switch getting very hot


Quote:
Originally Posted by CletusTSJY View Post
Thanks for your reply. That is weird, the dimmer was installed when we bought the house and the only thing I've done is replace a burnt out lightbulb with another lightbulb that came from the living room- which also has a dimmer! Well I will replace it with a regular light switch...not like I need romantic lighting while cooking my top ramen! :P

Thanks again!
This is puzzling, if they are incand. lamps.
I guess while you're changing it out you could check the current draw with a clamp-on ammeter.
Maybe there is an overload that
never goes to a short circuit and
never clears, either,
but this is probably unlikely [probably improbable?].

Last edited by Yoyizit; 11-17-2009 at 03:36 PM.
Yoyizit is offline   Reply With Quote
Old 11-17-2009, 03:41 PM   #6
Newbie
 
Join Date: Nov 2009
Posts: 4
Rewards Points: 10
Default

Light Switch getting very hot


Interesting. If that is the case, replacing it with a regular light switch will not fix the problem I'm guessing? Will the regular light switch get hot too?

I did have to really cram the wires into the box just to get the switch close enough to screw it in...could it just be that there isn't enough room inside the box to dissipate the heat? It shares a box with the dining room light switch (which is not a dimmer and never gets hot) and it's pretty crowded in there.
CletusTSJY is offline   Reply With Quote
Old 11-17-2009, 04:31 PM   #7
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Light Switch getting very hot


Quote:
Originally Posted by CletusTSJY View Post
Interesting. If that is the case, replacing it with a regular light switch will not fix the problem I'm guessing? Will the regular light switch get hot too?

I did have to really cram the wires into the box just to get the switch close enough to screw it in...could it just be that there isn't enough room inside the box to dissipate the heat? It shares a box with the dining room light switch (which is not a dimmer and never gets hot) and it's pretty crowded in there.
A regular light switch dissipates ~0.3w, max, and a dimmer, 5w. This few watts spread out over the several sq. inches of surface area of a dimmer shouldn't be very hot.

Crowded or not, I've never had a dimmer that did that.
I guess you could take it out of the wall box and run it for a while in free air. Within 5 minutes or so you'll know if it's still going to get hot.

A bad wirenut connection could also dissipate 5w, but the surface area of a wirenut is so small that the temp. would be too hot to touch.

I suppose a yet-to-be-discovered root cause could have clobbered both dimmers, or
both off-shore-manufactured dimmers were bad from the factory.

Last edited by Yoyizit; 11-17-2009 at 04:42 PM.
Yoyizit is offline   Reply With Quote
Old 11-17-2009, 05:11 PM   #8
Master Electrician
 
Grimlock's Avatar
 
Join Date: Nov 2009
Location: TX
Posts: 13
Rewards Points: 10
Default

Light Switch getting very hot


It is common for dimmers to get warm. If you find that you can't touch it because it is so hot then you most likely have an overloaded dimmer. Count the watt labels on all of your lamps, add them up and compare to the dimmers rating. Some dimmers have tabs on the side that can be removed to allow them to be ganged up next to other large devices, if these tabs are removed than the rating goes down (Look on the dimmer). If you are pushing the load close to the max then you can expect it to get a little more than warm.

EDIT: No normal toggle switch should get warm/hot unless there is a problem.
Grimlock is offline   Reply With Quote
Old 11-18-2009, 03:39 PM   #9
Newbie
 
Join Date: Nov 2009
Posts: 4
Rewards Points: 10
Default

Light Switch getting very hot


Thanks for everyone's help. I put the cover back on the dimer and turned the lights on for a few hours to see how hot the cover and screws got. Although it's still warm, it is definitely much cooler than it was with the previous dimmer. I added up the wattage of all the light bulbs and it came to 390 watts. The previous dimmer said 300 watts on it, and the documentation I read said if there's another switch in the same box, the number of watts it can handle goes down. If that's the case, I'm thinking the dimmer was getting overloaded? This new dimmer is 600 watts and with the extra switch in the box, it comes down to 500 watts, which is still greater than the 390 watts that the bulbs add up to. I'm going to stick with this and see if it ever gets too hot.

Thanks again for everyone's help.
CletusTSJY is offline   Reply With Quote
Old 11-19-2009, 09:34 AM   #10
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 8,035
Rewards Points: 2,868
Default

Light Switch getting very hot


The dimmer would only need to be derated if installed next to another dimmer and the breakoff tab(s) were removed. Installed next to a regular toggle switch does not affect the dimmers rating.

All dimmers generate heat. See this FAQ fron Lutron.

http://www.lutron.com/default.aspx?pid=6#faq6

IIRC the temperature may get to 140 degrees depending on load and amount of dimming.
Jim Port is online now   Reply With Quote
Old 11-19-2009, 10:24 AM   #11
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Light Switch getting very hot


Quote:
Originally Posted by Jim Port View Post
The dimmer would only need to be derated if installed next to another dimmer and the breakoff tab(s) were removed. Installed next to a regular toggle switch does not affect the dimmers rating.

All dimmers generate heat. See this FAQ fron Lutron.

http://www.lutron.com/default.aspx?pid=6#faq6

IIRC the temperature may get to 140 degrees depending on load and amount of dimming.
2% [from the link] of 600w is 12w, dissipated in the volume of a 25w bulb. That's fairly warm, but my dimmers don't run anywhere near capacity.

Adults can be burned in 5 sec at 60C(140F).

Last edited by Yoyizit; 11-19-2009 at 10:27 AM.
Yoyizit is offline   Reply With Quote
Old 11-19-2009, 10:30 PM   #12
Electrical Contractor
 
kbsparky's Avatar
 
Join Date: Sep 2008
Location: Delmarva
Posts: 3,368
Rewards Points: 2,000
Default

Light Switch getting very hot


A hot glue gun only uses 10 watts or so, and those are too hot to touch.

A dimmer with a plastic wall plate (plastic is an insulator) held with metal plate screws can make hot spots out of those screws. The equivalent of touching the nozzle of a plugged in glue gun.

Get a heavy, metal wall plate to help dissipate the heat.
__________________
-KB

Life is uncertain -- eat dessert first!!
kbsparky is offline   Reply With Quote
Old 11-27-2009, 09:56 PM   #13
skidrowpete
 
Join Date: Nov 2007
Location: maryland
Posts: 12
Rewards Points: 12
Default

Light Switch getting very hot


was at a nursing home and older residents were complaining about hot dimmer plates manager wanted them changed but that would not have been cost effective called leviton and talked to engineer and to my disbelief he quoted me the temperature could be as high as 80-90 degrees or about i67 degree c. the only way to cure that was to install regular snap action switches or convert them over to a tmo gang box and install a higherr rated dimmer with heat sinks made in them
skidrowpete is offline   Reply With Quote
Old 11-27-2009, 10:01 PM   #14
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Rewards Points: 2,000
Default

Light Switch getting very hot


I don't really find 80-90 that hot
Body Temp is hotter then that
Scuba_Dave is offline   Reply With Quote
Old 11-27-2009, 10:54 PM   #15
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Light Switch getting very hot


Quote:
Originally Posted by skidrowpete View Post
the temperature could be as high as 80-90 degrees or about i67 degree c.

You mean 80C = 176F?

Quote:
Originally Posted by skidrowpete View Post
was at a nursing home and older residents were complaining about hot dimmer plates
With all the NFPA/NEC rules and regs I can't believe these dimmers pass muster.

Advertisement


Last edited by Yoyizit; 11-28-2009 at 12:02 PM.
Yoyizit is offline   Reply With Quote
Reply

Tags
lighting


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Confused by switch w/indicator light install... WaldenL Electrical 7 08-29-2009 10:02 AM
Tracing light switch to an outlet allanet Electrical 13 04-03-2009 09:44 AM
A simple 2 light --1 switch question? redondo11@msn.com Electrical 7 11-05-2008 09:35 AM
no power going to the light switch baseballfan Electrical 18 09-08-2008 06:35 PM
Problem changing light switch grgryl Electrical 14 08-10-2008 02:26 PM




Top of Page | View New Posts