sodium lighting

[Dunc]

Design wise your loading would be 9x600=4500W so 19.57A at 230V. Then you need to remember it's 1.8 times the running current on start up so you need to size your breaker properly to allow for this. Im assuming it's similar in some respects to designing a circuit for a motor, if the motor runs at 5A you wouldn't allow for a cable that is capable of handling 6x that just for start up so the same would apply for the lighting. Think youll need atleast a couple of circuits for that lot and maybe a contactor to bring it all on with a type C breaker.

 

[telectrix]

5400 watts 23.5A. assuming SWA cable. i would use 6mm on 40A type C. need to check voltr drop though . depends on the length of the run. about 38meters is your limit

 

[hodaire]

So the 1.8 figure for discharge lighting is for start up only

Will be running at 600 watts when warmed up?

 

[Dunc]

So the 1.8 figure for discharge lighting is for start up only

Will be running at 600 watts when warmed up?

Yep, and i've just noticed that my maths is sh**e! 9x600 is 5400 not 4500, must have been a typo, honest.....

 

[telectrix]

Yep, and i've just noticed that my maths is sh**e! 9x600 is 5400 not 4500, must have been a typo, honest.....

LOL. it's only us old buggers can still remember chanting out times tables parrot fashion, but 50 years on i can usually beat a calculator on simple sums.

 

[davelerave]

the old 1.8 multiplier isn't for 'startup'

-it's for losses ,power factor ,harmonics

http://www.tlc-direct.co.uk/Book/6.2.1.htm

switches and breakers are rated for arcing and startup


with newer lighting i think you may not need 1.8 for design current and volt-drop- if they have electronic gear and high pf

prob best to find out if possible

 

[hodaire]

Thats how i always understood it, think i will be wiring a few up and stickimg a clamp on.

Quite a big difference in results if some use the 1.8 as start up and some for full running load

 

[davelerave]

they don't

if that was the case you'd be using 7*FLA for design current for motors instead of 100-125%

 

[hodaire]

so the total current is either 19.57A or 47 A or somewhere inbetween

 

[parko]

Hodaire,

You'll measure the RMS Amps with a clamp but you won't measure the Harmonic current. The 1.8 is as Dave said and mainly used to compensate for Harmonics.

Electronic ballasts can modify the supply AC waveform producing Harmonic distortion. The Harmonic currents produced as a result of this distortion, particularly the 3rd harmonic, add to the supply - hence the 1.8 factor.

Your current calc should be 42A.

As a rule I always apply the 1.8 factor unless the manufacturer of the fitting says otherwise.

 

[Knobhead]

Harmonics don’t become a problem until you use three phase. Single phase current out = current back, no matter how wobbly it is. Once you introduce three phase in to the equation harmonics affect the neutral current. The 3rd and 5th being the most relevant ones.
Years ago you may have installed 3½ core distribution cables, but now with the problems of harmonics caused by solid state switching a 4 core may now be needed.

 

[mattmoo1974]

Its written on the ballast, Iv seen 6.2 A for a 600w ballast

 

[mogga]

in street lighting circuits we used rule of thumb 6x250w son ts per circuit 16mm swa or concentric 6a at bottom of pole 10 if it was 400w and 20a ctype breaker
the problems arose when you had a faultu ballast n it took out a circuit as the breaker tripped due to the fault taking it out rather than the fuse

ie 9 lights running normaly take 18 a one faulty takes another 10a it would trip MCB before blowing fuse if you get my drift figures Iv used might not be accurate but its to get the jist across

 

[Engineer54]

Single or 3 phase installations, ...both will be a problem where high harmonic currents are generated by the type of loads being supplied. DNOs are getting very worried these days about there distribution TXs becoming overloaded with the amount of harmonics returning to there TXs. These so called energy saving lamps that are becoming more and more prevalent in every household, have more than just a little in the way of detrimental side effects...lol!!!

As far as i'm aware, those half sized neutral multi core cables, are not allowed for general distribution these days, and i reckon there are going to be more than just a few of those already installed, are going to need replacing, ...sooner rather than later too!!! lol!!

 

[Knobhead]

Energy saving my left foot! It’s about time the loony greens were brought to account for their political misinformation.

The supply infrastructure is being damaged as you say 54. Cables are just the tip of the iceberg, switchgear with ½ rated neutrals, transformers and tails.

Someone is going to have to pay for it all, in my view it should be by a surcharge on energy saving lamps, things with switch mode power supplies, etc.