installing garden lights

[ban-all-sheds]

but i still disagree.

may i suggest the following

you said 105W of 12V lighting - length limit for the 1mm flex supplied is 1.1m

that sounds wrong for a start (105w =1.1m)
@ 12v that is 8.75 A
8.7A down a 1mm cable means the cable can be longer than (as you said) 1.1 metres

Not for 4% volt drop.

i have a set of 12v "garden lights" its much longer than 1.1 metres, yes granted its about 10.9 volts at the other end (havent checked it) but its sure is a lot longer than 1.1 m

9.2% volt drop. Of course you can go longer distances if you don't mind higher volt drop....

 

[cottie1972]

hi the lights i have are micomark LED lights that come in sets of four which can be linked together (somehow!) hope this helps! - cheers for all the advice you have been giving me, they are going in next weekend so ill print out all the tips you have given me - cheers all!

 

[Scoby_Beasley]

W're running a "malibu" weatherproof 120W transformer/timer onto roughly 60m of cable, but connected as a ring, 2 x 20w pond spots 10 x 7w garden spots no probs.I don't know if the furthest spots are dimmer than the nearer ones but I do know you can't look directly at them without temporarily blinding yourself !!

 

[mapj1]

One of the nice things about filament lamps, is if you under-run them a bit, the filament resitance drops, thus keeping the current up- the loss of power with vltage is not as serious as the square law one might think.

From charts in my dog-eared copy of 'Lamps and lighting' by Heewitt and Vause, I see a 10% change in voltage modifies watts by ~15%, efficiecncy (lumens/watt) by 20% and light output (lumens) by 30%.
This difference will be a noticable nuisence if 2 lamps are side by side, but probably not so serious otherwise.

Notice also that lamp life varies as v/Vnominal to the power of 13 (ow!), so underrunning is recommended rather than over. I'd suggest a 1V drop at the extremes on a 12V system is likely to be OK

 

[ban-all-sheds]

Notice also that lamp life varies as v/Vnominal to the power of 13 (ow!), so underrunning is recommended rather than over. I'd suggest a 1V drop at the extremes on a 12V system is likely to be OK

Halogens don't like undervoltage.....

 

[mapj1]

I know, in normal use the filament is constantly dissolving and re-depositing, but, in practive 10% voltage drop is no more destructive than an obscuration of the glass. http://www.gilway.com/html/appl-halogenlamps.html

I have used the cheap linear Q/H lamps on dimmers for theatrical use, frequently at well below half power for the whole show, and yes they do aquire an internally frosted look after a few 100 hours of such use, but an hour or two at full voltage this dissappears again.
I practice I'd really not be that worried about it, as full light output is not usually as much an issue as lamp life.
If the experimental results here (for nominal 110V lamps) http://photoweb.net/pw_tech/colortemp.pdf scale for lower voltages then the color rendering changes will be scarcely perceptable.
Yes its out of spec - does it matter? I'm not so sure.