# Estimating your workshop lighting needs



## ivan (10 Jan 2009)

This may be of some help in estimating what fittings you need to get a well lit workshop. 

The degree of illumination is called illuminance, and it's measured in lux (that's lumens per sq M). Fortunately the eye can accomodate to a wide range of illuminance, as daylight provides about 100,000 lux in sun, and moonlight 0.2 lux. Of more practical use, _minimum_ illuminance needed for critical tasks like sewing or reading or woodwork is about 300 lux at the task. _People over 50 may need up to twice this level_.

Light fittings vary in practical effectiveness according to room size, mounting height and overall wall and floor colour. For simplicity, in a workshop with lighting at height 2.5 to 3M and using a good reflector, with white walls and light floor, the Coefficient of Utilisation (C of U) is about 0.5. For a very dingy workshop, could be as low as 0.3.

LIght fittings get dirty, and light is lost as a result. If you spring clean once a year, allow a Maintenance Factor (MF) of about 0.6 (0.8 if you do it monthly!)

You calculate total lumens required (lamp output is given in lumens) thus:

Installed Flux= desired illuminance x floor area/C of U x MF

For workshops, desired illuminace is 300 lux.

My workshop is 5.5M x 5.5M, very light in colur, and cleaned once a year, so the

total flux needed = 300 x 5.5 x 5.5 / 0.5 x 0.6 which comes out to 30,250 lumens

The lumens could come from:

Lumens
1300 - 100W filament bult
3150 - 200W filament bulb

1100 - 20W energy saver fluorescent

2100 - 900mm fluorescent tube
3000 - 1200mm fluorescent tube
4800 - 1500mm fluorescent tube
5200 - 1800mm fluorescent tube

light outputs for tubes allows for fading during life, and is less than the 'new tube' figure

I chose 4 x 1.8M double fittings giving 8 x 5200 = 41,600 lumens, a bit more than was required (I was 45 yrs old then and getting a bit short sighted) 20 years on I find I need additional task lighting for critical jobs (see paragraph one; 6 doubles would have been better)

Data simplified from Electricity Council Publications


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## johnjin (10 Jan 2009)

Thanks for that Ivan
I am starting to get the gist of it.
I think its time I bought some more candles. :wink: 

Best wishes

John


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## jhwbigley (10 Jan 2009)

i had to reseach that for my As project when i made a decorative light, i had 3 A4 side on it :shock: . luckily i found a lot for what i wanted out of my dads eletrical installation books. 

Ivan, u'v done a grand job to condense it done so everyone can work out what lighting they need in there workshop.

jhb


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## Tierney (13 Jan 2009)

Wow, exactly the sort of information I need for my next project - a workshop re-wire.

David


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## joiner_sim (14 Jan 2009)

I am not happy to say this. But my very small tiny shed/workshop is lit by a 500W portable floodlight. It provides decent enough light when its daylight, with addition to the daylight coming thru the windows, but if its a late night working, which is rare.... The shadows that are cast can really be quite bad and at that point I do ask myself is it safe to continue working. Being a small shop though, I am considering the next time I'll be working late, going and buying another 500W portable floodlight, this would provide more than enough light I think.


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## ivan (16 Jan 2009)

Glad to be of use.

The figs given will be OK for most 1 man workshops, provided they're not long and thin, with black walls, or 5m high. Remember, too little light and yer can't see to do the job; too much light and you just waste a bit of electric till yer eyes get dim like mine! Perhaps not very green, though...


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