halogen downlights in bathroom..

[pmx_super]

Hi,

I have a problem with the 12V halogen down-light kit in my bathroom.

Basically they keep going out, which is accompanied by a buzzing from the transformer. I believe the issue is related to one of the following: they are standard Zone 3 ones but one is directly above the shower cubicle; plus the transformer is not in a ceiling cavity - it's just perched on top of a suspended wooden 'doughnut' shaped frame.

I was told (by the man in B&Q) that whatever zone the lights are rated for the transformer will always be a problem. This leads me to believe I need mains powered ones (G10s?). Problem is, to maintain the aesthetics of the present arrangement I need four 20W lights. Do they make mains halogen spots in 20W? I cant find them anywhere. Or am I missing an obvious alternative solution.

Cheers.

 

[andy]

possibly the tranny is too small. bigger 1 should solve it.

 

[mapj1]

the transformer is probably over heating (given recent weather) - does it have good airflow - and is it man enough for the number of lights and the total wattage involved, or have higher wattage lamps been fitted and the transformer not upgraded. Actually, in a wet area, the low voltage lamps are really a good idea, and the mains fired transformer should be kept in the dry (and cool) at the end of a reasonable length of cable away from the water.

 

[pmx_super]

the transformer is probably over heating (given recent weather) - does it have good airflow - and is it man enough for the number of lights and the total wattage involved, or have higher wattage lamps been fitted and the transformer not upgraded. Actually, in a wet area, the low voltage lamps are really a good idea, and the mains fired transformer should be kept in the dry (and cool) at the end of a reasonable length of cable away from the water.

This has been happening for quite some time.. irrespective of weather conditions.

It has a very good airflow since it's basically out in the open in the bathroom.. which may also be it's problem.

There are 4x20W lights, and it appears to be a sealed unit (i.e. lights and transformer came wired up, though I cant find fours any more, they all come as 3x and 5x).

I'm not sure where I can find a dry spot in my steamy, windowless shower-room (with another flat above), hence why I thought I might need mains voltage downlights.

 

[mapj1]

IF the transformer is cold when it stops working, then check for good contacts at all lamp holders and at the tranny end - the other thing that will make the tranny shut down and sulk is either a short circuit or an overload.

 

[bathjobby]

Alternatively; if the transformer is hot, then 1 of 2 things;
1) What length of cable do you have from the transformer to the lights ? If it is greater than 2 mtrs you will be prone to a sufficient voltage drop on the cables that the lamps will go out. If you have different cable lengths you would expect those on the longer cables to go out and some to stay on. Does this happen or do they all go out together ? If they all go out together then;
2) You are overloading the transformer so get a bigger one OR BETTER STILL, give each lamp its own small transformer. This also means that you can position the transformers fairly close to the lamps to ensure insignificant voltage drop to lamp.

 

[pmx_super]

IF the transformer is cold when it stops working, then check for good contacts at all lamp holders and at the tranny end - the other thing that will make the tranny shut down and sulk is either a short circuit or an overload.

Might moisture cause a short-circuit?

 

[mapj1]

If it causes corrosion, and the corrosion products bridge between the contacts, (or between windings on the transformer itself) it is possible. Otherwise it will cause a leakage current, but not much compared with what the lamps will be taking.
If it is an electronic transformer (i.e. a high frequency transformer plus switching transistors confustication) then all bets are off as to what moisture might make it do, as higher impedances are in involved in the electronics.

 

[pmx_super]

I think I'll try buying a new transformer as an initial experiment.

My question now is .. where do I buy a suitable transformer on it's own? They only seem to come as part of full lighting kits. If I can buy it on it's own, what is good spec. transformer for 240/12V running 4x20W halogen lights?

Thanks for everyone's continued help and patience!

 

[mapj1]

If you have a TLC near you, or can stand the postage
http://www.tlc-direct.co.uk/Main_Index/Transformer_Index/Lighting_Transformers/index.html
As you have 80 watts of lamps, I'd suggest a 100watt trannsformer as a minimum (no point in pushing it to its limit)
Unless you wanted to split the lamps into 2 groups of 2 of course, then a pair of 50 or watters might be OK.
The toroidal transfom,ers, being copper and iron, are more rohbust than the 'electronic' type but they also wiegh and cost noticably more, and can be hard to find a good mechanical fixing for.

CEF (City electrical Factors) have a similar range - try the yellow pages and see what is local to you.

 

[bathjobby]

pmx-super; I've given you the answer in my post above, but for whatever reason you appear to be ignoring it
http://www.screwfix.com/app/sfd/cat/cat.jsp?ts=57511&id=101667

 

[pmx_super]

pmx-super; I've given you the answer in my post above, but for whatever reason you appear to be ignoring it
http://www.screwfix.com/app/sfd/cat/cat.jsp?ts=57511&id=101667

It was your post that prompted me to decide to try a new transformer. Apologies for not acknowledging that... I certainly didn't ignore it.

In answer to your original Q.. yes they all go out together, which is why - on your advice - I decided to try a bigger and better transformer. That's why I asked what might be a suitable one.

Thanks for the links.. I only looked as far as B&Q. I noticed screwfix did a 105VA submersible one. Might this be a good idea to deal with the moist atmosphere in my bathroom? Or is that sledge-hammer / nut kind of thing?

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One more thing... does LV automatically imply 12V? The submersible one mentions 240V.. it doesn't say what it coverts to though. It mentions IP68..