symean
3rd August 2009, 07:58 PM
We have been installing a 12-volt garden lighting system over the last few weeks, and we've got it all done, except the transformer keeps blowing up! Here's the set-up:
The transformer, cable and lights are all from the same manufacturer, and we're using about 35m of cable and 15W total in lights (all LED) on a 20W transformer. Wherever we cut the cable to install a light we kept the wires matches up, ie: one of them has some writing stamped into it and one doesn't and we kept these matched up all the way around. We've tested this with a multimeter. The 12V cable also runs alongside a 240V cable (for our water feature pump) for about 9m in total...not very close, I'd say the two are within 2" of each other over the 9m. The transformer, which is an indoors one, is (I should say WAS...read below) enclosed in an outdoors box which is waterproof.
At first we had about 25m of cable, and started adding 1W lights one by one. Each evening we had it on for several hours while we played around with light placement. Eventually we built up to 15W of lights and added an extra 10m of cable to loop the cable back to the transformer, which is what the manufacturer recommends if you want to go over 25m of cable length (not required, just recommended so lights don't dim too much).
However once we finished that task, and put the waterproof box under the decking boards to hide it, the transformer burnt out. We have now gone through about 5 transformers, trying the following:
- moving the outdoors box holding the transformer back above the decking
- as above, plus opening the box so the transformer is in open air (not in the sun, only on at night)
- as above, plus opening the loop again so it's a single run of cable
In every case, it burns out after about 90 minutes. The transformer is almost too hot to touch. The only thing we haven't tried is moving the 12V cable away from the 240V cable as this would be a big hassle now that it's all installed and the cable is hidden away. I'm also not convinced it could be the cause because for most of the time that it worked OK we had the cables running side by side for about 6m, it was only on the last day when we finished the loop we ran the end of the loop back alongside for another 3m.
Anyway...I was wondering whether there's an easy way to test that this is the problem. Can we test it somehow while it's on to see if there's some errant charge being generated by the 240V cable? Or is the test as simple as trying it without turning on the water feature? Any ideas or help appreciated.
Cheers :)
Sam
The transformer, cable and lights are all from the same manufacturer, and we're using about 35m of cable and 15W total in lights (all LED) on a 20W transformer. Wherever we cut the cable to install a light we kept the wires matches up, ie: one of them has some writing stamped into it and one doesn't and we kept these matched up all the way around. We've tested this with a multimeter. The 12V cable also runs alongside a 240V cable (for our water feature pump) for about 9m in total...not very close, I'd say the two are within 2" of each other over the 9m. The transformer, which is an indoors one, is (I should say WAS...read below) enclosed in an outdoors box which is waterproof.
At first we had about 25m of cable, and started adding 1W lights one by one. Each evening we had it on for several hours while we played around with light placement. Eventually we built up to 15W of lights and added an extra 10m of cable to loop the cable back to the transformer, which is what the manufacturer recommends if you want to go over 25m of cable length (not required, just recommended so lights don't dim too much).
However once we finished that task, and put the waterproof box under the decking boards to hide it, the transformer burnt out. We have now gone through about 5 transformers, trying the following:
- moving the outdoors box holding the transformer back above the decking
- as above, plus opening the box so the transformer is in open air (not in the sun, only on at night)
- as above, plus opening the loop again so it's a single run of cable
In every case, it burns out after about 90 minutes. The transformer is almost too hot to touch. The only thing we haven't tried is moving the 12V cable away from the 240V cable as this would be a big hassle now that it's all installed and the cable is hidden away. I'm also not convinced it could be the cause because for most of the time that it worked OK we had the cables running side by side for about 6m, it was only on the last day when we finished the loop we ran the end of the loop back alongside for another 3m.
Anyway...I was wondering whether there's an easy way to test that this is the problem. Can we test it somehow while it's on to see if there's some errant charge being generated by the 240V cable? Or is the test as simple as trying it without turning on the water feature? Any ideas or help appreciated.
Cheers :)
Sam