LED wafer lights are becoming very popular and are super easy to use for remodeling projects. However I am concerned about the 110F. ambient that is typical with all the manufacturers I have checked. Do they not intend these things to be put in attics? Am I missing something? I have gone up in the attic to secure the driver to the nearest joist recently and found out it was nearly untouchable. Has anyone else had these concerns?
wafer lights
- Thread starter brody
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Coppersmith
Senior Member
- Location
- Tampa, FL, USA
- Occupation
- Electrical Contractor
Are you saying the driver generates enough heat to reach 110F or that the unit is limited to areas of 110F or less? The ambient temperature in Florida attics normally reaches above 110F. Probably 130F during summer.
Coppersmith
Senior Member
- Location
- Tampa, FL, USA
- Occupation
- Electrical Contractor
I did a little further research. Apparently attics can reach 160F in Arizona.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Im taking that to mean that they are not designed to be installed in a location above 110 F . For instance the ambient temperature of installation of electrical conduits affects the conductor ampacity rating. Higher the temperature the lower the ampacity. I have had LED undercabinet light drivers fail because I installed them in the attic. And I have been red tagged on rough in inspections for installing the door bell transformer in the attic. They are not rated for that temperature. Here the attics easily reach 130F all summer.
Coppersmith
Senior Member
- Location
- Tampa, FL, USA
- Occupation
- Electrical Contractor
growler
Senior Member
- Location
- Atlanta,GA
I think that's a real good question and I won't pretend to know the answer. From reading a bit about the problem I found a chart that showed the decrease in the life of an LED driver when used in higher temp environments .
So I would guess that the driver will work OK in the hot attics but will not last as long and I think you will have to de-rate current output for the driver depending on just how hot you expect it to get.
The main problem with "high temp" are the aluminum electrolytic capacitors used in the driver, they're mostly rated 1000 hours @ 105°C
I'll try to calculate the life expectancy of the caps:
160°F = 71.11°C, to simplify the math, lets say 70°C, heat from other (active) components and the caps themselves (from ESR and leakage) add maybe 10°C to the caps.
Life expectancy of the caps are: 1000h * (2^ ((105 - (70 + 10)) / 10)) = 5657 hours.
After 5657 hours of operation, the electrolytic caps capacitance would decrease by about 30%, how would that affect the driver depends on the driver design.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
On which side of the attic floor insulation is the driver typically located?
If the driver is on the conditioned side of the insulation, the driver ambient temperature will be much closer to indoor ambient than attic ambient.
Cheers, Wayne
If the driver is on the conditioned side of the insulation, the driver ambient temperature will be much closer to indoor ambient than attic ambient.
Cheers, Wayne
growler
Senior Member
- Location
- Atlanta,GA
They can place the driver either above or below the insulation but some test have shown that it's stays cooler if above the insulation.
Think about it. An LED driver is really just a power supply and we all know they do generate a certain amount of heat, so would we really want to insulated the driver and contain that heat in and around the driver or would we want it in the free air so it could cool a bit.
It does get really hot in an attic but the highest temperature is near the roof and the coolest in down near the ceiling. I would think that as low as you could get it but still above the insulation would be the best location.
MAC702
Senior Member
- Location
- Clark County, NV
Agreed with growler. Being in free, even though hotter, air is better than being on the conditioned side but trapped between insulation and ceiling.
Coincidentally, I'm about to install some of these for the first time later this week. A realtor client already bought them and asked me to put them in. Some as replacements of existing (smaller) cans and some remodeled into new locations.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
You and growler raise a great point, I was neglecting to consider that the power supply is a heat source. A 15W LED that produces around 900 lumens is only about 20% efficient, so it is still producing 12W of heat. I wonder how that heat production is divided between the driver unit and the LED wafer.
Cheers, Wayne
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
The irreducible minimum of that is in the LED. The rest depends on the efficiency of the driver design. A switching type regulator can be very efficient. An ohmic ballast can be horrible.
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