Blew up lighting system - how much to repair?

[Pardroid]

Dear group,

I'm a first time poster and I've done something monumentally stupid, which was to replace 5 20w halogen light bulbs with 5 50w halogen light buls because they were cheaper (I'm used to "normal" bulbs, where it never seemed to matter what wattage I use).

Two days later, and the circuit that's feeding electricity to these bulbs seems to have blown. After a bit of research on Google it sounds like the transformer failed and needs to be replaced.

To cut a long story short, I'm intending to pay someone to sort this out for me as I don't really want to start fiddling with it myself. I've never had to hire an electrician before and was hoping someone may have an idea what kind of price is "reasonable" for this sort of repair, as I'd rather like to avoid getting ripped off.

Thanks in advance!

[Pardroid]

Dear group,

I'm a first time poster and I've done something monumentally stupid, which was to replace 5 20w halogen light bulbs with 5 50w halogen light buls because they were cheaper (I'm used to "normal" bulbs, where it never seemed to matter what wattage I use).

Two days later, and the circuit that's feeding electricity to these bulbs seems to have blown. After a bit of research on Google it sounds like the transformer failed and needs to be replaced.

To cut a long story short, I'm intending to pay someone to sort this out for me as I don't really want to start fiddling with it myself. I've never had to hire an electrician before and was hoping someone may have an idea what kind of price is "reasonable" for this sort of repair, as I'd rather like to avoid getting ripped off.

Thanks in advance!

[Colin Wilson]

I haven`t worked with low voltage halogens, but...

The transformer may have some sort of thermal trip (which may even reset itself when it cools) - have you tried putting 20W lamps back in to see if its "really" dead ?

As a sideline safety issue, what type of fittings are they - are they rated as being capable of taking a larger wattage lamp ? Does it take a specific lamp type i.e. dichroic, as that may also be a factor in the type of fitting / installation.

[robgraham]

I would agree with Colin that these tranformers are normally self protecting and you should try replacing the 20W bulbs - on the other hand just try taking out all the 50W bulbs bar one or two (2x 50 =3D 5 X

20 after all) which may be easier. On the basis that you've only been drawing 250W which is 1 amp you won't have damaged anything else as the cables and switches will be rated at 5A minimum.

As to costs - less than =A310 for a 100W transformer and it's a 10 minute job if the transformer is easily accessible, so say an hour's work plus =A310 plus call out time so I would reckon on =A350 as reasonable.

Rob

[Dave Liquorice]

Yep, you are fortunate that the devices protection activated before a fire started. Oh and well done on knowing that you have been stupid and =

what your limitations are instead of blindly trying to fix it yourself.

5 x 20W lamps is 100W load, 5 x 50W is 250W more than double. "Normal" bulbs don't have a problem because they are connected directly to the mains and the typical 6A lighting circuit can run something over 1,300W =

of lighting. Low voltage halogen bulbs are fed via a transformer. These =

transformers have maximum power rating, exceed it and they go phut or catch fire...

At a guesstimate around =A325/hr plus another =A325 callout fee (ie =A35=

0 first hour) plus parts. If access to the transformer is easy and no wiring has= been damaged it shouldn't take more than 30 mins to fix so bill of aroun= d =A375 + VAT (very roughly).

[Dave Liquorice]

At mains voltage it is 1A, at 12v its 20A... The LV wiring may have got a bit warm before the protection went.

[Dave Plowman (News)]

I've not come across a transformer for this use which has some form of auto re-set - the fire protection is likely a thermal fuse buried in the windings. An electronic type *could* have over current protection but at the low price they sell at I doubt it.

[Paradroid]

Thanks for the responses!

The fittings are rated as 20w. I only noticed after I had the 50w bulbs in for a day or so. By the time I removed the 50w ones, the damage had evidently been done.

The transformer (or something else related to the circuit) is definitely fried (so to say). I tried with a 20w bulb that I know works this morning and again nothing.

I think I've spotted the transformer. Does a white thing around the size of a board rubber sound about right? It's next to one of the recessed holes, so I'm tempted to switch the electrics off at the mains and see if I can get it out to have a look but I can't see any obvious way of actually removing it (there's a sort of crawl space between the real ceiling and the "fake" ceiling with all the recessed bulbs and no particularly obvious way of accessing it).

Talk about learning from ones mistakes :)

[robgraham]

You've spotted the transformer correctly - interesting comparison, suggests your'e a teacher !

Screwfix sell a 105W one (part number 39220) for =A37.79 inc VAT - it was probably fed through the light hole in the ceiling. =20

Rob

[Dave Liquorice]

For an electronic "transformer" (really a small SMPS) yes. It might just be a fuse in the output but I've had them die for no reason at all.

Through the hole?