12v 65va transformer for lighting

Steve_xx

My nephew has a set of spotlights in his kitchen. The transformer has blown. It is rated 12v - 65va. However, after talking with him I've discovered the reason that it's blown, ie he has fitted 50w lamps to each of the three holders, rather than the 20w bulbs it ought to have!

I'm helping him source a new power supply for the lights. I looked on the RS website and I found one that is 12v - 65va, but it's dimmerble and the present transformer is connected to a simple on/off switch. I don't actually know if it's dimmerble or not.

The question is, would a dimmerble transformer be ok to fit on a simple on/off switch? And, the cost of this item, inclusive of delivery from RS is £8.11. Does that sound about right for one of these?

Here's a link to the one I think he needs

http://www.rselectricalsupplies.co.uk/electrical-lighting-supplies/low-voltage-transformers-electronic/low-voltage-transformer-electronic-dimmerble-65va/

mikey72

Dimmable is ok,
scrwfix have one as well
http://www.screwfix.com/prods/39220/Lighting-Lamps/Electronic-Transformers/Electronic-Transformers/Halolite-35-105w-Electronic-Transformer

or

http://www.screwfix.com/prods/48058/Lighting-Lamps/Electronic-Transformers/Electronic-Transformers/Halolite-20-60W-Electronic-Transformer

Steve_xx

mikey72 wrote: »

Dimmable is ok,
scrwfix have one as well
http://www.screwfix.com/prods/39220/Lighting-Lamps/Electronic-Transformers/Electronic-Transformers/Halolite-35-105w-Electronic-Transformer

or

http://www.screwfix.com/prods/48058/Lighting-Lamps/Electronic-Transformers/Electronic-Transformers/Halolite-20-60W-Electronic-Transformer

Ok Thanks for the information. Would the second one on your list really be ok as it's 5va less than the one that's on now?

Steve_xx

Would item 1 and/or 2 on this list be suitable?

http://www.toolstation.com/shop/Lighting/Low+Voltage+Downlights/Electronic+Transformer+12v+105w/d220/sd2638/p67666

zax47

Yes. 3 x 20W = 60W. In this case (not always) 60W = 60VA. So 60 VA tranny is fine.

Steve_xx

zax47 wrote: »

Yes. 3 x 20W = 60W. In this case (not always) 60W = 60VA. So 60 VA tranny is fine.

Would it be as well to get the higher rated one to give a bit of leeway?

zax47

No need. Just don't put 3 x 50W bulbs in!

105VA is for 3 x 35W, 150VA is for 3 x 50W.

Steve_xx

zax47 wrote: »

No need. Just don't put 3 x 50W bulbs in!

105VA is for 3 x 35W, 150VA is for 3 x 50W.

He'd better stick with the 20watt bulbs because he has two sets of these in his kitchen, each set with 3 bulbs on the circuit. He swapped all of the 20w bulbs for 50w. However, only one transformer has gone duff. Everytime he switched the lights on in the kitchen it was tripping the lighting circuit fuse for the whole house. Only when I disconnected the duff transformer did the problem of the circuit tripping stop. We put the bulbs (50w) back into their holders on the working transformer and all was well for about 10 minutes, then the lights went off. It was at that point that he told me that he had changed all the bulbs for higher wattage ones and it was after he'd done that that the problems started. I wish he'd have communicated that to me at the start!

But aside from that, would there be any problem in putting 20w bulbs into a 105va transformer?

zax47

No problem per se, but there really is no need.

Steve_xx

ok Thanks for your help and advice, much appreciated.