foam in switch box

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Jhaney

Senior Member
Location
owensboro, ky
Well yesterday I was called to a customers house for a trouble call about a light that won't come on. When I get there I start trouble shooting and find that the offending light is on a 3 way, so I open up both switches and find that the one on the outside wall is full of that spray foam insulation. After spending 30 minutes pulling out the foam I find the switch is bad and replace it. I recommended to the customer to never ever put foam in the switch box but too use cover insulation.

Isn't that spray foam a extreme fire hazard? Or am I being overly cautious?

The customers second problem is that the offending light constantly blows bulbs at least one a month. So I start trouble shooting the light fixture and find no issues. So I check voltage and get 125 volts at the fixture but when the switch is off I get 18 volts. So now I'm thinking bad splice somewhere so I put my attic monkey outfit on and start tracing the circuit, I made sure everything was grounded properly, all splices were redone, and since that didn't help I removed everything but the light from the circuit and still had 18v with the switch off.

Where else can I be getting this 18v and before you ask I used 2 different meters to verify my results.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I would not be all that worried about the foam catching fire.

If there really is 125V on the line, the bulb is probably burning out faster because of the higher voltage. There are bulbs made specifically to handle slightly above norm voltages. You might want to suggest the customer try them.
 

gar

Senior Member
091008-1114 EST

You need to search for information on lamp life vs voltage for a tungsten filament incandescent lamp. For a specific bulb the visible light energy to power input increases with increasing voltage because the filament is hotter and the color temperature is higher. On the the hand as voltage increases lamp life decreases. By lowering applied voltage you can tremendously increase lamp life. My front hall lights are small low wattage bulbs with very thin filaments that are on a dimmer and always on and usually at very low intensity. These bulbs are 30 years old with no failures, 263,000 hours. About 260 times their rated life.

My guess on CFLs is that lamp life will be degraded on both high and low applied AC voltage. A greater problem with these devices may be location and heat buildup around the electronics elements in the base.

An interesting aspect of the GE dimmable CFL is that with sine wave input, no phase shift dimming control, that the light intensity is moderately constant down to about 100 V where it quits. This tends to eliminate the momentary light flicker that occurs when a high inrush load turns on, like an air conditioner.

The reason for using a 130 V bulb is that at 125 V you will be operating below its design voltage and thus increase life, but there will be less light output compared to a comparable wattage bulb of 120 V rating.

.
 

SG-1

Senior Member
Wouldn't CFL's handle the higher voltage better? I ask because thats what the customer decided to put in.

I started switching over to CFLs long before they were pushing the changeout. I used to change the incandesents every six months or so. They would always go out with a brilliant flash of light. I have not lost a CFL yet. I have had one outdoor type ( Earth Light ) burning in the hallway as a night light now for over 10 years, all night, every night. I started printing the install dates on the last ones I put in.

I did have a problem with the POCO transformer supplying high voltage for several months - 128V at the outlet for short periods of time, but usually never lower than 125Volts.

CFLs pull their current off the tops of the sin wave, this design may make them more tolerant of an elevated supply voltage. I have one light fixture that has one of each type, CFL & incandesent installed. I have not had to change that incandesent now for a very long time. I wonder if the CFL is keeping the peak voltage lower when it is switch on, or supressing the arc that the switch would produce ?
 

mxslick

Senior Member
Location
SE Idaho
Are you kidding me?

Are you kidding me?

petersonra said:
I would not be all that worried about the foam catching fire.

I would. The heat from a loose or arcing connection could easily ignite the foam. Some foam products are highly flammable even when cured. There may be some brands that claim to be safe around electrical equipment, but who's gonna stick their neck out and say that a given foam job is safe?
 

Jhaney

Senior Member
Location
owensboro, ky
I was worried about that as well so I scraped every bit that I could out. Luckily that foam didn't do anything to the wire insulation. Some types of foam can melt stuff.
 
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