Under cabinet LEDs running too hot?

[333rocky333]

I wonder if lining the hole with some of that silver reflective sticky tape that laggers use would reflect the heat back into the fitting, i always thought them fittings were designed to fit in a metal surface base

 

[JohnW2]

I wonder if lining the hole with some of that silver reflective sticky tape that laggers use would reflect the heat back into the fitting,....

I'm sure that it would to some extent. However, given that that black finned heatsink is presumably there to remove heat from the fitting, reflecting heat back into the fitting might not be too desirable an idea?

As I recently wrote, I do seriously doubt that the temperature of the contents of, say, a bottle of wine would rise appreciably during thee period of time that the lights are likely to be on, even if it were sitting right on the 'hot spot'.

Kind Regards, John

 

[Paul Goff]

As with many things, there are LED lamps, and then there are LED lamps!

In this case two fairly distinct types, ones in which a resistor is limiting the current flowing through the actual LED, and ones which limit the current electronically.
The resistor type are cheaper, less efficient, run hotter and don't last as long as the electronic ones.

Far be it from me to cast aspersions about what sort may have been fitted by a kitchen company

 

[JohnW2]

As with many things, there are LED lamps, and then there are LED lamps! In this case two fairly distinct types, ones in which a resistor is limiting the current flowing through the actual LED, and ones which limit the current electronically. The resistor type are cheaper, less efficient, run hotter and don't last as long as the electronic ones.

All true, but, no matter what the method of current limitation, I assume that the 2.6W rating relates to the total power consumed by/dissipated in the light - and I don't think that amount of dissipated energy is going to have an appreciable effect on the general temperature within the cabinet.

Let's face it, if 2.6W were able to raise the ambient temp within the cabinet by 10° (which the OP now admits is probably not happening), one would probably only need 40-50W to turn the cupboard into an oven!

Kind Regards, John

 

[bernardgreen]

The resistor type are cheaper, less efficient, run hotter and don't last as long as the electronic ones.

Life time depends on how the current is supplied to the LED elements.

Supplying a resistor + LED element(s) from a smooth DC source ( battery for example ) will result in a longer lifetime than if the supply is from a Switch Mode Power Supply with an output such as 12 volts (eff) The 12 volt (eff)only averages 12 volts and can be 24 volts switched ON and OFF at high frequency. ( some SMPS units were found that were 36 volts paek voltage )

When the voltags is at 24 volts the current through the LED elements can be many times the maximum pulse current for the LED elements. This overcurrent slowly degrades the elements

 

[bernardgreen]

The resistor type are cheaper, less efficient, run hotter and don't last as long as the electronic ones.

The life time depends a lot on the voltage source . Some are smooth constant voltage while others create pulses of voltage which average out to be 12 V DC (eff)

eff = effective when supplied to an incandescent lamp.

The problems with pulse width modulated voltage sources are that the LED elements may be taking high current pulses which could lead to degredation and / or early failure of the LED elements

For example three LED elements in series with a current limiting resistor designed for a 12 volt supply

0v--LED--LED--LED--Resistor--12 volt.

The LEDs will have about 3 volts per element, total 9 volts leaving 3 volts across the current limiting resistor. LED current = 3 divided by R

If the source is a series of 24 volt pulses that average out to be 12 volts (eff)

0v--LED--LED--LED--Resistor--24 volt.

The LEDs will have about 3 volts per element, total 9 volts leaving 15 volts across the current limiting resistor. LED current = 15 divided by R

So the 24 voltage peaks will be driving 5 times the rated current through the LED elements/