Fixture wattage rating

[nizak]

I have a recessed housing and trim ( same brand) that is giving a maximum wattage rating and lamp type. It does not differentiate between LED , Halogen, or Incandescent .

90 watt Par 38 is what’s listed.


Does that rating pertain to the amount of wattage that can safely be carried through the socket?

Can an LED lamp that produces more lumens than a 90watt Par 38 incandescent for instance be used as long as the consumption does not exceed 90 watts?

Thanks

 

[GoldDigger]

The maximum lamp size rating is based on several factors.
One of them is the temperature and heat carrying capacity of the socket, even though for most lamps conduction through the socket is not the major heat rejection path.
Another is the ventilation and air flow around the lamp and through the fixture.
Normally the electrical capacity of the socket is not an issue.
For a recessed housing the air flow will be restricted by a large PAR lamp shell compared to an A type lamp, but less visible and IR output from the lamp will hit the inside of the fixture.
Bottom line, the fixture itself can certainly handle an LED lamp of the same light output as the 90 watt PAR. But depending on the details of the particular LED lamp the fixture may not be able to keep that wattage or a larger LED lamp at the far lower ambient temperature it can withstand.
Particularly if the fixture has any sort of a lens or other cover over the opening.

 

[James L]

The lamp rating is all about how much heat it emits up inside the can. Most likely it is related to how much heat the fixture wires can handle.

There's almost undoubtedly a thermal coupling, which should make the lamp blink on and off if there's too much heat up inside there.

If you use a lamp that has a reflector, and an open trim, so that the heat is almost all directed downward, you can use a much larger lamp like 90 watts incan or halogen

If you use a type A lamp and put a shower trim over it, it's usually going to be limited to about 25 watts incan

 

[Flicker Index]

Incandescent lamps get rid of 90%+ of input power as radiant energy. (visible + invisible combined), but LEDs have to get rid of all input energy except the photometric power (in watts) radiated. Not only is this percentage much higher than incadnescent's <10%, the temperature tolerance is much lower.

This is why a 300W halogen can operate in still air but even a 25W laptop CPU needs a fan. Often time, in downlight applications, the brim or ring is used as a heat sink and made to look it's just decorative.

 

[Dennis Alwon]

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