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broadgage · 19th Jun 2019, 10:51 pm

If the recently purchased bulb is a GENUINE heavy duty/rough service/reinforced construction type then it will have a cooler running and therefore less efficient filament than a regular GLS lamp.

True rough service or similar lamps (as distinct from ordinary lamps marked as rough service to get around the restrictions on filament lamps) may also have a single coil filament rather than the coiled coil construction of ordinary lamps.

A single coil filament reduces the light output by about 15%, in addition to the reduction from a cooler filament, and a further reduction from the extended life.

19th Jun 2019, 10:51 pm	#75
broadgage Nonode Join Date: Jan 2010 Location: North Somerset, UK. Posts: 2,129	Re: The lightbulb conspiracy If the recently purchased bulb is a GENUINE heavy duty/rough service/reinforced construction type then it will have a cooler running and therefore less efficient filament than a regular GLS lamp. True rough service or similar lamps (as distinct from ordinary lamps marked as rough service to get around the restrictions on filament lamps) may also have a single coil filament rather than the coiled coil construction of ordinary lamps. A single coil filament reduces the light output by about 15%, in addition to the reduction from a cooler filament, and a further reduction from the extended life.