Effective lumen of PLC ?

[cwloo]

Hi,

We all know that 18 watts PLC produce about 1200 lumen depending on brand but I am just wondering what's the effective lumen if we put it inside the ceiling downlight which have only 6~8" dia (reflect down).

Any idea ?

 

[jason 77]

Hi,

We all know that 18 watts PLC produce about 1200 lumen depending on brand but I am just wondering what's the effective lumen if we put it inside the ceiling downlight which have only 6~8" dia (reflect down).

Any idea ?

First off, what is a PLC?

 

[cwloo]

First off, what is a PLC?

Sorry, just realize that it was also call "compact fluorescent lamp" in some country.

and it was installed into those ceiling light.

 

[Mkala]

This is difficult to answer - because you need to know the efficiency of the reflector.

I have no experience in this domain (but I am interested - I am on a similar project), according Cree you can expect about 50-60% efficiency (page 6 ) :

http://www.cree.com/products/pdf/LED_Luminaire_Design_Guide.pdf

Just because I am curious, what PLC stand for ? Here we use CFL too...

 

[blasterman]

A fluorescent bulb of any type is going to take a huge 'fixture penalty' mounted like this and directed through a diffuser. Likely 50%...at least. So, it's not fair comparing them to a bare Cree or any other LED.

 

[Mkala]

Yes, but it is precisely the question

The document of Cree is just for reference about the efficiency of a typical light fixture.

 

[lostsoul01]

Here's my light in the ceiling. The reflector is awful and the light fixtures themselves are probably at least 30 years old. I mention this because newer ones are likely more efficient. Originally they had glass, but this has been replaced with cheap plastic.

In it, I use a 26W CFL, which claims to output 1700 lumens.

In a test, I replaced one with a Cree CR6 from Home Depot. This light uses 10.5W and claims to output 575 lumens.

I find the CR6 to be as bright, if not brighter when standing in the area under the light that would normally be lit with the CFL.

Of course I've made no official measurements, but with that "feel" I'm estimating my old lights are putting out 600 lumens to the ground, or 35% efficient. The rest just gets lost up in that fixture.

 

[Random Guy]

A fluorescent bulb of any type is going to take a huge 'fixture penalty' mounted like this and directed through a diffuser. Likely 50%...at least. So, it's not fair comparing them to a bare Cree or any other LED.

This depends on the fixture. The 4x F32T8 fixture in my kitchen has a fixture efficiency of about 75%.

 

[blasterman]

Of course. That's why expensive T5 fixtures cost so much durn money. It's not the bulbs....it's the reflector.