Flourescent lights parallel circuit not very bright

G100917 · Aug 10, 2021

Hi all,
I've wired up 10 flourescent lights in a parallel circuit for a light box as in the picture. Each bulb is 36w and 3250 lumens. The lights are connected to a switch and a plug with a 3a fuse using 1.5mm round cable. When I turn the lights on they don't seem anywhere near 32500 lumens, and several of the lights have a ripple effect which stops after some time. Does anyone know why the lights wouldn't be particularly bright? Any advice is much appreciated thanks.

littlespark · Aug 10, 2021

The accumulation of lumens don’t add up like that. I’m not sure what the long winded formula might be, but it’s not just “lumens times 10”

what size is your light box? You can get 600mm LED square panels fairly cheap, and various outputs and colour temperature.

snowhead · Aug 10, 2021

As above with the lamps so close you have overlapping light so the total output is not straight forward.
I don't know and don't now need to know the formula.

Are all the lamps and controllers the same make and all new?

Personally I could not detect 32500 lumens just by my very experienced eyes, I couldn't even tell if 10 lamps were 10 times brighter than 1, I would need a Lumen meter.

James · Aug 10, 2021

Bear in mind that they will not reach full brightness until they have been on for 10min or so, the tubes have to warm up even after thy have initially lit up.

G100917 · Aug 10, 2021

Many thanks all for the very helpful replies. I hadn't understood how lumens work so was expecting something extremely bright, the lights are all brand new and Philips. It turns out the lights are in fact bright enough for our needs anyway (silkscreen exposure). Thanks again for the insights much appreciated!

Simon47 · Aug 11, 2021

You would have more light if you'd lined the box with something highly reflective before fitting the lamps. As it is, a considerable amount of your light will be going into heating up the back of the box.

UNG · Aug 11, 2021

G100917 said:
Hi all,
I've wired up 10 flourescent lights in a parallel circuit for a light box as in the picture. Each bulb is 36w and 3250 lumens. The lights are connected to a switch and a plug with a 3a fuse using 1.5mm round cable. When I turn the lights on they don't seem anywhere near 32500 lumens, and several of the lights have a ripple effect which stops after some time. Does anyone know why the lights wouldn't be particularly bright? Any advice is much appreciated thanks.

To improve the output you could get yourself some polished thin aluminium sheet and make a reflector to go behind the lamps. If you google fluorescent lamp reflectors it will give you some ideas

G100917 · Aug 11, 2021

UNG said:
To improve the output you could get yourself some polished thin aluminium sheet and make a reflector to go behind the lamps. If you google fluorescent lamp reflectors it will give you some ideas

That's a great idea. I considered painting the back in gloss white or some reflective paint or even using aluminum foil tape, although wondered if that would then create a large conductive area which would be better avoided

G100917 · Aug 11, 2021

Simon47 said:
You would have more light if you'd lined the box with something highly reflective before fitting the lamps. As it is, a considerable amount of your light will be going into heating up the back of the box.

certainly will do that for the next one cheers for the advice