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what size are the lights i.e wattage?
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Without knowing your circuit breaker size, and wattage of lights, difficult to give accurate figure.
I had 6 off 5 foot lights, but just changed for 36 2 foots, with no problems at all, running off 6 amp trip.

Just checked. 6 no 40 watts is about 1 amp, so assuming you have 6 amp breaker, you can go to 36 @ 40 watts
 

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probably around 40W ? need to check
At 40w each you could theoretically have about 30 on a 5amp fuse but I wouldn't really go above half that many
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Discussion Starter · #6 ·
OK, so this is what I know, separate feed off consumer unit (from house), splitls into two fused breakers, each using 15A fuses (fat blue ones) One circuit goes to power the sockets, the other to the lights. Its only a single garage but lights are too dim. I have one double 5 foot strip and one single 5 foot strip, would like to upgrade to 3 x 5 foot doubles, cheers for any input
 

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"call 0-800 Apocalypse"
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Can the existing lighting circuit support the extra light fittings?

Lighting circuits are usually on 6 amp circuit breakers often know as MCB’s (Miniature Circuit Breakers). To calculate how many Amps are loaded onto the lighting circuit a simple calculation is made. UK voltage is 230 volts, now assume that each light on the circuit is 100 watts, and you have got 12 lights on the circuit.

The calculation would be:

Total Watts ÷ Voltage = Amps

So taking the above information the calculation would be:

1200 watts ÷ 230 volts = 5.22 amps

So now we can see that the above described lighting circuit is using 5.22 amps meaning that the circuit breaker of 6 amps is not being overloaded.

Now to confuse things a little but very helpful on lighting circuits when you are wishing to add more lights. On lighting circuits once you have worked out the amps you can now apply a thing called Diversity, which for lighting circuits is 66% of the total load. So to work out this calculation we can do the following sum:

5.22amps ÷ 100 x 66 = 3.45 amps

So now we can see that we are able to add more lights to the circuit now that diversity has been applied to it.

Remember to carry out your calculations before you start any work!
 

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And then to confuse it even more, if the cables that feed lights are in free space, they will carry more than if they are plastered into wall.

I reckon you will be fine with your intended amount of lighting.
 

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And of course what type of cable is used? It can be dangerous to ask a "simple " question on here:bigsmile:
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Look for the newer flicker free tubes/fittings too as they are cheaper to run and brighter.
Go for cool white tubes (very white) or even daylight tubes (ultra white) as they are far brighter than std white (yellowish colour).

Single 6 foot cool white fittings will be ok, no real need for doubles, put in as many as you possibly can, (you can never have enough light).

Change your 15 amp breaker! it's dangerous as the wiring will fail before the breaker. Fit a 6 amp one.

I'd recommend these ones 6ft 70w HF Fluorescent Fitting - Less Tube

With these tubes 6ft 70w Daylight Triphosphor Fluorescent Tube T8

The other good investment is a paintbrush & a gallon of brilliant white vinyl silk emusion. Paint the ceiling & walls and you will be astonished how a few lights will light every corner of the workshop.
 
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