Halogen Ceiling Lights - insulation on live wire melted

[EdwardPeck]

We have just had a disasterous building company install a bathroom for us. In the end we had to ask them to leave. I am gradually looking at their work to see what needs to be redone, and what can stay.

Today one of the ceiling halogens stopped working in the bathroom. We replaced the bulb, but it still doesnt work. On investigation I found that the live wire insulation close to the unit into which you plug the bulb has melted.

I have looked at the wiring above, and it appears that each light has its own transformer.

Is it possible that the wire has melted because the voltage being supplied to the light is too high? And if so how do I check? Or is there some other explanation?

The light socket appears to have 25v 45A written on it. 6 lights. On one dimmer outside room.

The transformer says:

Model T02 Electronic Transformer for LV - Halogen Lamps. Dimmable. PRI: 240V - 50Hz
60VA. COS0=0.99 SEC:11.6v - eff Max: 4.9A TA=50C TX 85C

Hope someone can advise!

 

[breezer]

either cable too small

covered in loft insulation

lamp too big

 

[tim west]

more likely caused by heat of the lamp, you have to make sure the wiring is kept away from the lamp itself and also suitable heat resistant cable or heat sleeved, halogens(MR16) output most of their heat out the back of the lamp due to the dichroic reflector

 

[EdwardPeck]

Thanks. They put in 12V 50W bulbs. The wiring is mostly contained within a white sleeve (which I assume is the heat sleeve). There is no loft insulation.

 

[tim west]

Thanks. They put in 12V 50W bulbs. The wiring is mostly contained within a white sleeve (which I assume is the heat sleeve). There is no loft insulation.

50W's give off a heck of a lot of heat. As they are 50's also check the wiring to the lampholder is of correct size(ie fitting is rated at 50w) as breezer suggested

 

[EdwardPeck]

Sorry. I am not an expert.

How do I check the spec for the wiring?

 

[tim west]

Sorry. I am not an expert.

How do I check the spec for the wiring?

I realised that was the case so i suggested looking for a wattage sticker on the fitting as you may be putting too high a wattage lamp into the fitting?

 

[EdwardPeck]

There is no sticker (that would be too easy!).

The wires are 18 AWG

 

[tim west]

I believe thats close to 0.75mmsq so dependant on length of cable from transformer you may be pretty close to the limit!

 

[EdwardPeck]

OK so drop the wattage of bulb to 40W?

Thanks for your advice.

 

[Steve]

With a bit of modification, you could use low energy mains voltage lamps. No transformer and very cool running.

 

[securespark]

Oh, sorry...that's "Cool Runnings"!