Any Sparky's - And I mean Electricians! ;-)

[Rabbit171]

Hi all,

just wondering if there are any electricians amongst us who could help me with a small electrical dilemma?

I have some low voltage garden lights that I've had in the garden for years and they work wonderfully. The problem is that the missus has re-landscaped the garden meaning I now have to add two more lights. Not a problem as I have the lights. There are 4 lights, all of which are 12v 7w running off a 32w transformer. Now here's the question, if I added two more 12v 7w to the line what would happen? Would the transformer blow up, all the lights would run dim, or it just wouldn't work? I could get away with adding only one extra light as I have two separate chains. Or is it a case of trying to source a higher rated transformer. Of course I could just get 12v 5w bulbs instead. Which is the best option?

Any help would be greatly appreciated! Thanks in advance

 

[hamster]

Well, overloading will cause extra heating of the transformer.
If it's well designed, it will have a thermal cutout and possibly an overload circuit as well - it will then shut down to protect itself.

If it's a nasty cheap one it may work...and then overheat, short a few turns and blow a fuse. If it's a really nasty cheap one from China it might just burst into flames instead.

At the very best, it'll run hot, and have a drastically reduced life. When I designed power systems for aircraft we worked on a design rule that a 15C rise in temperature halved insulation life.

Your two suggestions are good - lower power lights or a bigger transformer. Personally I'd go with lower power lamps.

 

[john the sparky]

yeah, as above...

I reckon from what I see of faulty transformers, you will melt the transformer, which will then stop working or cause a fire.... but if you put that load on I reckon it would too hot to hold after 30 minutes (and I reckon the transformer will be cheap and therefore will have no protection on it)

I agree, to derate the lamps is a lot cheaper and easier than sourcing the transformer then fitting it....

but as a sparky... I just gave my wife a headtorch electrical aparthy sets in when I get home

John

 

[Harryburgundy]

Go on John...tell 'em your surname...go on go on go on

 

[john the sparky]

Circuit

 

[Harryburgundy]

Brilliant.

 

[john the sparky]

I always wanted to be a florist... but noone would take me seriously :cry:



John

 

[FluffyChicken]

There is a electrical goods place near you (well compared to me one in Cardiff the other in Swansea) called TLC
http://www.tlc-direct.co.uk/ I've used the online store before and they where fine and dandy.

other online electronics stores (Farnell/Rapid) should have LV PSU's as well.
Think I got my last one from Farnell.

 

[Rabbit171]

Thank you very much one and all

I'll go down the route of lower wattage bulbs, the wife would never forgive me if I burnt the house down

Thanks once again