Halogen Pin / holder Corrosion

[steamvalve]

Have just moved into a new house. The kitchen has 10- 50W halogen down lighters fitted into the plaster board ceiling. Two weren't working when we arrived - so I had a look. The holder (push-in pin type) was corroded and the springs weren't holding the lamps firmly. So I went to an electrical shop and got two new lamp holders. I fitted these and everything was OK. Four weeks later they are corroded again and the protective insulation on the back of the lamp holder is falling off! None of the other 8 lamps are affected?! What the hell is happening? Can anyone help? I'm not sure if you can get a more heavy duty lamp holder - higher rating etc. What's even more confusing is that you may expect the ones over the hob or sink to be worse (damp areas) but it's not those ones. Thanks in advance.

 

[Spark123]

Is there plenty of room for heat to dissipate above the lamp?
Did you replace the lamp and the holder, or re-use the old lamp?

 

[STI]

Ignore my original post i missed the last part of your post
But what is above these two lamps anything wet or very cold causing condensation in that area.

Are you certain its corrosion and not burn, what are the connectors like in the terminal box, corroded/burnt too ?

 

[steamvalve]

There's two occupied bedrooms above. No obvious signs of condensation. I think it could be burn - thinking about it. Perhaps these two originally had a lower rating holder than the rest. When i've replaced it, I just asked for a holder - so they probably gave me a 20W holder, when I really need a 50W. I think you may have solved my problem!

 

[RF Lighting]

I don't think those holders have a specific wattage rating. Some are manufactured better than others though.

 

[STI]

I don't think those holders have a specific wattage rating. Some are manufactured better than others though.

Love to claim the glory but i think RF is right no wattage rating but quality could be a cause. However the other thing that could be causing problems is if your lamps are the wrong sort for the fittings ie diochromatic or aluminium. Some fittings should only have the "cool" running lamps fitted. These are designed to reflect more heat forward away from the wiring etc. Guess what they are more expensive.

 

[skenk]

Did you replace the lamp and the holder, or re-use the old lamp?

(lamp=bulb)

 

[steamvalve]

Thanks for this response - this is great!.
To answer - I have no idea what sort of lamps they are - I didn't replace the lamps when I bought the new holders. The fittings are the standard 'can' type. Can you get these 'cool' lamps from B&Q?

 

[electronicsuk]

Is there plenty of room for heat to dissipate above the lamp?

This question seems to have gone unanswered, yet it's pretty important. Thermal insulation will cause quick and successive failure of lamps and lampholders.

I'm not sure if B&Q sell aluminised reflector lamps - searching for the term on their web site only throws up low energy GU10s. It's a shame that Dichroic lamps seem to be the de-facto reflector lamp, when nine times out of ten they are not what you want for household use.

 

[steamvalve]

Not sure how to quantify plenty of room.
All I can say is that it's a typical ground floor installation.
The fittings are cut into the plasterboard ceiling of the kitchen.
The plaster board ceiling is nailed to the joists for the first floor bedrooms to which the bedroom floorboards are fixed to. I guess the clearance between the kitchen plasterboard ceiling and the underside of the bedroom floorboards is about 150mm (the depth of a standard house joist). Should be enough room - I would have thought.

 

[electronicsuk]

Just trying to establish if there is any thermal insulation present around the failed fittings. It sounds as if there isn't, in which case it sounds very likely to be an issue with the holders or lamps themselves.

 

[steamvalve]

Sounds like I need to find these 'cool' lamps.
Anyone know a good on-line stockist?

 

[electronicsuk]

Sounds like I need to find these 'cool' lamps.
Anyone know a good on-line stockist?

Not online, but I seem to recall tool station stocking them. Failing that, google 50w aluminised reflector lamp. Make sure it's got the right base for your fittings, presumably GU10.

 

[ban-all-sheds]

When looking for them, please don't become confused by the some of the muddled and contradictory posts here.

Some fittings should only have the "cool" running lamps fitted. These are designed to reflect more heat forward away from the wiring etc. Guess what they are more expensive.

If you see any lamps labelled "cool beam" then these do the exact opposite of what STI says - they reflect heat back into the light fitting, not away from it.

That's why the beam is (relatively) cool.

I'm not sure if B&Q sell aluminised reflector lamps - searching for the term on their web site only throws up low energy GU10s. It's a shame that Dichroic lamps seem to be the de-facto reflector lamp, when nine times out of ten they are not what you want for household use.

They are what you want if the light fitting is designed for them, unless you want to fry your head.

But if the light fitting is not designed for them then you must not fit dichroic, or "cool beam" lamps, you must use PAR ones (Parabolic Aluminised Reflector).

http://en.wikipedia.org/wiki/Multifaceted_reflector

 

[skenk]

If the old lamp pins were black and pitted then they can quickly cause the new holder to fail, you need to replace both the holder and the lamp.