Estimating your workshop lighting needs

[ivan]

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

 

[johnjin]

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

 

[jhwbigley]

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

 

[Tierney]

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

David

 

[joiner_sim]

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.

 

[ivan]

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...