Air tight recessed lighting

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  #1  
Old 11-24-02, 09:44 AM
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frangul
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Air tight recessed lighting

Our attic has blown in insulation. To protect the recessed lighting cans in the attic, metal was formed around each can like a tall crown and taped at the top.

I have since put in air-tight inserts by Cooper Lighting into 20 year old recessed cans to keep air/dust from entering living space.

Do I need to remove the tape from the top of the metal crown to allow the heat from lights to escape?

The dimmer switch on the wall for the recessed lights warms up a bit, which I didn't notice before the inserts were put in. Don't know if that is a normal occurrence that I didn't notice or if it is a clue.

Thank you for any insight.
 
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  #2  
Old 11-24-02, 11:49 AM
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Wgoodrich
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Dimmers commonly warm up some when they are resisting the flow of current. This is normal.

You tank that has a box over the tank is a double box style that uses the air space gap between the two tanks to keep the outside box from heating enough to cause fire of damage when in contact with combusable material.

It does not matter if you install a gasketed inclosed trim or an open trim concerning fire risk. It does matter that each trim has its own watt rating limit of bulbs to be used. Check the label in your tank to match the trim you have to confirm the maximum watt bulb allowed with that certain trim. Do not exceed that watt limit for that certain tank trim.

There is supposed to be a thermo cutout built inside the tanks built after around 1985 or so. Older tanks did not have this thermal cut out. All depends when you tanks were installed whether you have a thermal cut out limit switch to limit overheating built into your recessed tank.

Hope this helps

Wg
 
  #3  
Old 11-24-02, 02:32 PM
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frangul
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So may I assume that since I am using the same wattage bulbs we have for the last 20 years and that the lights are not thermal since they were put in in 1983, all is well with the dimmer switch.

Do I need to give the heat from the recessed lighting a place to exit from the metal crown that is built around each one in the attic, that is taped shut? It was deemed okay with the regular recessed configuration. I don't know if putting the airtight inserts into play would change what would have to be done on the attic side to allow the hot air to go out of the metal crown.

Thank you for your response, past and future.
 
  #4  
Old 11-24-02, 03:58 PM
J
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UL says that it is normal for dimmers to get up to 117 degrees F. I sincerely doubt if anything you did to the trim on the lights had any affect on the temperature of the dimmer. Dimmers get hotter when controlling more watts and when running with the lights near full brightness.
 
  #5  
Old 11-24-02, 04:42 PM
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Wgoodrich
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I agree with John concerning the dimmer, have little or no concern in that subject.

However I do have concern about your recessed lights.

Changing a trim from say an eye ball trim with a hole in it where most the heat of the bulb is exposed at the surface of the trim allows a 75 watt bulb in that tank with that eye ball trim. Also a tank trim that has a hole in it as a downlight trim and the bulb again is exposed at the surface often sticking out about a 1/2" or more allows the heat to dissipate into the room rather than building heat in the tank. This trim also is allowed a 75 watt flood bulb.

Now if you install a trim with a gasket and a flat glass enclosing that trim and bulb then the rating of that bulb is reduced to 60 watt light bulb. This is due to the concern of increased heat being trapped.

Then back in the days your tanks were installed you had one normally used tank. It was a halo H7 tank. This halo H7 tank required a chimney to be installed so that the insulation was held back away from the tank and these tanks were designed so this chimney allowed the heat to dissipate into the attic allowing that tank to keep from overheating.

In personal expeience in my home town I was called to help investigate cause of fires. Three homes burnt because people unknowingly put tape on these tanks and insulated over these tanks trapping the heat. The heat built up and overheated the wood and started the fire in these three homes. On an average about 50% of the home was burnt in the fire causing extensive damage. No one was hurt in any of the three fires that I can think of.

Recessed tanks appeared and was quite popular about 1978. By 1983 UL required the thermals installed because the story above was appearing across the nation.

I would suggest that you take down your trim and remove the mounting screws on that tank and remove the tank. Then go to your electrical wholesale house and buy a matching tank that has the thermal protection. The new tank should fit in place of the old tank. Then you concerns should be relieved. I know of no fires caused by these tanks since the thermals were installed.

I do know that I have ran many a mile on my truck going back to homes that I had wired in the past where the home owner put bigger wattage bulbs in those new thermally protected tanks or changed the trim trapping the heat and started experiencing their light clicking on and off like a xmas tree lighting due to increased heat and the thermal shutting down due to built up heat then cooling off and turning back on again to start the on of cycle all over again. It was irritating but at least we experienced no more fires due to nontheramlly protected recessed lights after that thermal was required.

We have seen a few fires appear over the years when people did what you are doing. They changed the trim and trapped the heat or added insulation onto and covering the tank in that attic and that change as since then caught some houses on fire.

Take a look and do some research. I suggest changing the inside tank with a new thermall protected tank as a repair then you should be fine.

Good Luck

Wg
 
  #6  
Old 11-24-02, 06:54 PM
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joefixit
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John,
Why would a resistive type dimmer run hotter with the load at near full? I always thought a dimmer generated more heat when set to a high resistive value as it is dissipating energy at the switch by becoming part of the load instead of sending it all on to the light. When it is turned to full there is very little resistance, why wouldn't it operate at the same temperature as an ordinary switch with a low resistance connection?
Brian
 
  #7  
Old 11-24-02, 07:43 PM
J
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There's no such thing as a resistive dimmer sold today. Dimmers use a triac (a triode alternating current switch) to chop up the wave form, essentially shutting on and off the current many times a second. This is what sometimes causes the bulb to buzz.
 
  #8  
Old 11-25-02, 03:28 AM
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RickJ6956
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joe,
At low settings, the device is switching on and off at a slower pace, allowing more time for the heat sink to cool it. As you increase the level, the time between cycles decreases, allowing less time for the device to cool.
 
  #9  
Old 11-25-02, 09:03 AM
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frangul
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Thank you for your answer, the air-tight insert is just cone shaped, no bottom enclosure to cover the bulb. It just makes the inside of the recessed can air-tight, with the trim hugging the ceiling, preventing dust and air from coming into the room.

The chimney made around the light in the attic is taped at the top but is not covered by insulation on the sides. Do you still see a problem?
 
  #10  
Old 11-25-02, 09:06 PM
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Wgoodrich
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If you have a trim that has a round hole in it that allows the bulb to stick through that trim then you may install a 75R30 flood bulb in that tank.

If you have a trim that has a plastic or glass closing that tank then you must use a normal light bulb with a maximum watt rating of 60 watts.

The tank you have is not a double insulated tank and is supposed to have a chimney installed aroud the tank leaving air space around that tank into open air. This chimney is normally a 10 or 12" round piece of heat duct that is long enough to be above the insulation keeping the insulation away from the tank and allowing the heat to rise same as through the chimney of a fire place. The top of this chimney is required to be open so heat can excape out the top of that chimney.

If you don't have the set up above then you are asking to overheat that tank. this is why I suggested that you exchange that tank with a new thermally protected recessed tank to protect your house from an overheated recessed tank.

Hope this helps

Wg
 
  #11  
Old 11-26-02, 04:39 PM
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frangul
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Thank you Mr. Goodrich. I now understand and have done as you said. Thank you for your help.
 
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