choosing lamp shades

[petermouse]

I am a bit confused (no really). Some lamp shades (B&Qs) are simply marked Max wattage 40W or 60W. Simple enough. Any type of lamp GLS filament, CFL or LED is O.K. up to that wattage. But a lot of other suppliers have their lamps shades marked GLS Max 60w, LED Max 6W, CFL Max 11W. All on the same shade. Surely the filament lamp (GLS) gets hottest. I would not have thought that a 6W LED or an 11W CFL is the largest wattage I could put in. So Why the Limit? Perhaps they do get hotter? If I have a light shade marked up as GLS 40W, LED 3W, CFL 7W Surely I could put a CFL lamp in up to and including 40W? If anyone made them. Perhaps I am thinking too much. I just want to be sure if I can put an 11W CFL (equivalent to 60W filament) in a Lampshade rated at GLS 40W ,LED 3W, CFL 7W

 

[Squid]

Covering their backs, oh and that was a mouthful to read ;o)))))

 

[petermouse]

Covering their backs, oh and that was a mouthful to read ;o)))))

Any thoughts? though.

 

[snowhead]

Presumably arrived at by testing on individual shades.

 

[Squid]

Any thoughts? though.

Companies having to put warnings on everything as not to get sued if something goes up in flames, B+Q most probably get their stuff from China.

You also have to remember to take in to account the room the shade will be in, 3 metre ceiling with a long drop will have more air circulating around it than if in a pokey box room, to be honest I don't want to lead you astray but there used to be a rule of thumb in days gone by which I can't remember.

 

[Marvo]

It's a fair question, a watt rating should be a constant regardless of the item producing it and I can't think of any sensible reason it should be limited to a lower value if an LED lamp is used.

The problem nowadays is that manufacturers instructions carry legal weight so you can't just ignore them or write them off as being an ----covering exercise. Maybe email one of the manufacturers for their reason if you've got the time, I'd be interested to hear their reply.

 

[littlespark]

You can also think along the lines of halogen lamps. Just to confuse you more.
They may be less wattage, but they don’t half get hot, mum. Hotter than a regular old fashioned lamp.

 

[Lucien Nunes]

Those ratings are silly, but the assumption that a 40W tungsten-rated fitting could take a 40W LED is not valid. Much of the power consumed by tungten was wasted as heat, dissipated by a combination of radiation and conduction from the envelope. An LED also produces heat but that is focused within the cap and dissipated mainly by conduction. The electronics inside cannot withstand the same temperatures as a tungsten lamp, so the criterion is not just whether the shade or fitting itself would get too hot, but whether there is enough cooling airflow to keep the lamp electronics happy.

Re. halogen, the envelope temperature may be higher but the amount of heat dissipated in the fitting is slighly less than with GLS tungsten, as a few extra percent of the power consumed leaves the fitting as light (the rest is always dissipated as heat somehow).

 

[static zap]

Remember burning my hand on a hot heat sink on an LED lamp , retaining heat longer than a glass 100W incandescent. Turned off for a while !
... I'm sure poor air circulation is the enemy ...