X10 Dimmers, fire safe?

[wirelady]

I recently installed Leviton Dimmer switches in each of my childrens room. I have them setup to dim at bedtime for a night light. My husband is concerned about fire safety, stating that, \"many home fires are due to dimmer switches.\" Our house is only 1 year old, so the wiring is up to date. Do any of you leave a light dimmed for extended periods of time? What are your feelings on overheating? Any comments would be appreciated.

[JimMcGowanInlet]

If your only dimming for an few hours a night thats fine but leaving a module in dimmer mode, all night, 365 days a year, is looking for a failure. If thats the case, although its unlikely to cause a fire the potential to overheat is present, so I'd have to agree with your husband.

Use a regular night light in a X10 Wall module as an option or just dim at bed time for a few hours or both.
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[Nathan]

I have a good friend in the fire department, and I am told that cheap incandescent night-lights are a far greater risk of fire (mainly due to curtains and such getting in contact with the bulb) than dimmers. So be careful.

I'm not sure I can completely agree with the basic premise that dimmers are a fire hazard, or that using them for a night light particularly invites a failure.

Yes dimmers fail, and fires get started. Everything has some risk. But those are extreme exceptions and usually related to poor installations.

The usual failure mode is that because the dimmer is bulky and difficult to install, the electrical connection is poor due to the wire-nut being worked slightly loose in the battle to cram the thing in the wall-box. Over time, this compromised connection will arc and burn thru and fail in one mode or another. Even so, actual fires are fairly rare.

Of course anything can be mis-used or installed improperly and be hazardous. But properly installed dimmers should produce minimal risk of fire, assuming they are properly certified (i.e. UL or similar) and properly installed.

Having been on the other side of obtaining UL certification for devices my then-company manufactured, I can tell you from direct experience it is most thorough, and nothing even the slighted bit questionable gets thru. Of course no process is perfect, but in general they are quite tough. I cannot believe that quality UL certified dimmers are really a fire hazard.

I have a 600 watt light in my dining room which is on a Leviton X10 dimmer. It is often run at 25% or so for hours. Yes the dimmer gets quite hot. But it remains well below any possible ignition temperature of anything one might expect to come in contact with it. Including curtains (which I don't have there). But if you place your hand on the wallplate, you will pull it away quickly.

I also have a number of Switchlinc dimmers that control smaller lights (120 to 180 watts) that are operated as night lights in evening mode. They do not run nearly as hot as the Leviton (they aren't controlling as much load) and I have never had a failure. I do use motion sensors to sense occupancy and dim them very low when no one is present and brighten them a bit based on motion. They work well, although they destroy radio reception.

So I would say that if you have quality, UL approved dimmers, installed properly, I wouldn't worry about it.

One sidebar comment....

In recent construction, the tendency has been to to use plastic switchboxes (They're cheaper and easier to work with) for wall switches, whereas older homes used metal boxes.

In the case of dimmers, metal boxes are preferred because they will help dissipate the heat. Plastic is not a good heat conductor, and a dimmer will run a bit warmer in a plastic box. Likewise, a stainless steel wall plate will also help reduce the temperature a bit, although it will feel hotter to the touch than a plastic one.

For the benefit of anyone building a new house today, I make note of the issue and advise metal boxes for dimmers and possibly steel plates as just a simple extra precaution. I also advise oversized boxes for dimmers as I noted before, they can be bulky and a bit difficult to fit in a standard box.

If you have a choice, either during construction, or you are a capable DIY person who can change out a box, I would place metal boxes for any dimmer that is carrying a heavy load, such as my Leviton 600 watts loaded one, which is indeed in a metal box. But this is an extreme case and not worth worrying about in most cases. The lightly-loaded dimmers do not run hot enough to be concerned in any case.

So in summary, I would say don't worry about it. Use fairly low wattage lights (say 25% of the rating of the dimmer) and it will not even run very warm.

Just my two cents worth..... Your mileage may vary.... etc. etc.

Cheers,
Nathan

[JimMcGowanInlet]

[quote:5ed20d9981=\"Nathan\"]I have a good friend in the fire department, and I am told that cheap incandescent night-lights are a far greater risk of fire (mainly due to curtains and such getting in contact with the bulb) than dimmers. So be careful.[/quote:5ed20d9981]

All the night lights sold near me either use led's or 7w bulbs. Either one can be held in your hand and you can barely feel heat. Although any type of a short near curtains isn't a good thing :shock:

[quote:5ed20d9981=\"Nathan\"]I have a 600 watt light in my dining room which is on a Leviton X10 dimmer. It is often run at 25% or so for hours. Yes the dimmer gets quite hot. But it remains well below any possible ignition temperature of anything one might expect to come in contact with it. Including curtains (which I don't have there). But if you place your hand on the wallplate, you will pull it away quickly.[/quote:5ed20d9981]

The issues I have with dimmers is heat. The more you dim the more heat is generated. That amount of heat isn't bad right off but heat buildup over 10-12 hours will shorten the life of most components. When and how that component fails is my major concern. Like Nathan says you need to disapte the heat somehow. A metal box would help and is also not combustable. Still I would prefer a cooler method.

[carlh6902]

As I see it, there are two possible mechanisms associated with fire risks:

1) An incandescant bulb is dimmed way down, and is thus assumed to be cool-running. If a failure now occurs in the dimmer (see #2 below), the bulb may return to full brightness and normal temperature, and could start a fire if in contact with flammable material. Do not EVER operate an incandescant bulb in close proximity to flammable material, dimmed or not, for this reason.

2) The dimmer itself frequently runs somewhat hotter when dimmed, and this is thought by some to be a fire hazard. It is not a hazard. The devices, if UL rated, are designed to operate at this elevated temperature, and if properly installed in UL-rated junction boxes the chances of starting a fire are very remote indeed. The failure mode of triac-based dimmers (almost always) is a short circuit of the triac. When this occurs, the bulb comes on full intensity and the dimmer actually runs cooler, as the triac is no longer dissipating power.

You should consider the heating effect of multiple dimmers installed in the same junction box. Many manufacturers derate the capacity of their dimmers when used in multiple-gang locations, and this limitation must be
honored, as the UL certification is contigent on that limitation. If a continuously dimmed bulb were a fire hazard, you can bet that the manufacturers would explicitly forbid such operation, as we live in a society chock-full of hungry lawyers, just looking for their next civil suit.

Carl

[Nathan]

I need to get some of your 7W bulbs. Mine run quite hot.

As to dimmers, if they are properly certified and installed they should be able to run at any setting, for any period of time, even 24x365. Yes they get hot, and yes heat is the enemy of electronics. But they should be operating within specifications. If not, there is a bigger issue, as exactly how did they pass UL anyway?

Your mention of LED's causes me to raise another issue. Efficiency. A 100W mulb dimmed to 10% illumination is certainly going to consume much more than a 7W night light. And an LED version probably consumes well under a watt.

I would suggest installing LED night lights, and dimming the room lights for, say, an hour at bedtime, extinguishing them and leaving the rather dim LED lights to serve. You could have a motion sensor brighten the room lights for those nocturnal visits to the bath. That way you have the best of all worlds ;)

Personally, I like it very dark. ;)

re: Heat and electronics. I recently upgraded my Tivo to big harddrives, and was amazed at how hot they ran. They were running a case temperature of 47 deg C. Much too hot, I thought. Wrong. Seagate's spec sheet calls for normal operation up to 60 deg C case temp. I put a heat sink on em anyway, and now they run at 37 deg C. I like it better even though Seagate didn't seem to care. Will they last longer? Dunno. Time will tell.

Cheers,
Nathan

[Nathan]

Carl, your point about lawyers is a good one. Certainly if there was any real hazard, the legal beagles would quickly kill any manufacturer dumb enough to sell such a device.

As I said earlier, from my fireman friends, the hazard with dimmers, or most any other electrical device of this nature is improper installation, where the wire-nuts that tie the wires together do not form a perfect gas-tight connection, and over time arcs and burns until it eventually causes problems. The major culpret is forcing a dimmer into a standard (small) utility box, crushing and stressing the wires. i.e. Poor installation.

Even then the usual failure is to cease working or blow the breaker, albeit it can easily produce some smoke from the burning of the plastic around the wirenut.

Still, a smoking, melting junction *can* cause a fire. This can happen with ordinary switches and outlets as well. This was especially a problem with aluminum wire, which is much harder to get a good joint with, and thus became eventually largely banned because too many good electricians would nonetheless fail to make a good, safe connection. Properly connected, aluminum wire is safe. But getting it properly connected is difficult.

If you run the dimmer with a load (bulbs) of much lower wattage than it is rated at (as I suggested 25%, or 150W for a typical 600W dimmer) they won't run very warm anyway. The one I have that runs really hot is a 1000W dimmer controlling a 600W load. When dimmed to 50% illumination, it is *very* warm, but still within spec. A 60W table lamp controlled by a 600W dimmer will hardly warm the dimmer at all.

Cheers,
Nathan

[JimMcGowanInlet]

[quote:c815dd6985=\"Nathan\"]re: Heat and electronics. I recently upgraded my Tivo to big harddrives, and was amazed at how hot they ran. They were running a case temperature of 47 deg C. Much too hot, I thought. Wrong. Seagate's spec sheet calls for normal operation up to 60 deg C case temp. I put a heat sink on em anyway, and now they run at 37 deg C. I like it better even though Seagate didn't seem to care. Will they last longer? Dunno. Time will tell.

Cheers,
Nathan[/quote:c815dd6985]

I had a different problem with my tivo. After adding a 120G the internal case temp got so hot, the mother board overheated and caused an audio problem. I've removed the cover and now it runs cooler (27c) but the audio problem still comes and goes. (The audio sounds tinny) So now I have to wait until the new season is in repeats to send it out to get fixed. :-(

[wirelady]

Thanks guys, You have helped me to sleep easier! :D

It's a 600W Dimmer, down rated to 500W because it's in a two gang box. It's plastic, but deep. It's got 3-60W bulbs. Maximum bulb rating at 75% is 375W. Looks like I'm running a little below half the max. I'll test it during the day, when I can continually check it's temp.

I think to feel safe I'll follow the suggestion to only run it for an hour at bedtime. I don't have motion sensors on my second floor. Only on the stairs. :cry: I know....I could add them, but I don't see that happening any time in the near future. I prefer hardwire and don't see the time available to fish wire anytime soon.

I really appreciate all the input!

[AutomatedOutlet]

Wirelady,

I don't think you would have any problem even if you ran it 24 hours a day.