Three spot lamps suddenly stopped working

Longshanks · 11 Apr 2011

Hi Everyone

Had spot lights fitted as part of new bathroom job last year? Recently I fitted these special loft caps so that I was able to put some insulation down above the lights to prevent mould etc etc. Completed that job a few weeks ago and then fitted new pull cord in bathroom last week.

Suddenly, out of the blue, the three spot lights on the left don’t work (the other three do). I’ve checked the wiring in the pull cord and that’s fine but guess that somewhere along the line the connection between the lights has been disrupted. I pulled up the insulation last night and couldn't see anything obvious.

Does it sound like the links between the lights or the rectangular junction box thing that he used when the guy set it all up?

Thought that this would be a quick fix but maybe not!!

Your time and advice would be appreciated as ever. Can also provide piccies if this would help.

Chri5 · 11 Apr 2011

Are the lamps straight 230v or via a 230v down to 12v transformer ?

Have you checked the bulbs (by swapping a good one over and vica a versa)

The overridding doubt that I have is that YOU have knocked or pushed a cable since you have fessed up to having done work recently.

After checking the above suggestions the next thing will be proving the juice gets to the lamp holders via meter / volt stick or contractor.

ban-all-sheds · 11 Apr 2011

Chri5 said:
After checking the above suggestions the next thing will be proving the juice gets to the lamp holders via meter / volt stick or contractor.

No no no no no.

Longshanks · 11 Apr 2011

Thanks

Straight 230v as far as I know.

Don't think it's the bulbs as they all went in unison!

The bathroom installer did the work but it was definitely checked by a spark etc. I'm sure it's my fault but if I did pull or knock a cable why didn't they go immediately? I also need to establish whether its the individual connectors (that now go into these loft caps) or the connections into the rectangular plastic unit which was used. This is what I was getting at.

L

Longshanks · 11 Apr 2011

Hi again

Just surfed and found something similar on tinternet so I think it's the 230 to 12v malarkey that's in use here. I'll check again when I get home and provide piccies.

L

Chri5 · 11 Apr 2011

ban-all-sheds said:
Chri5 said:

After checking the above suggestions the next thing will be proving the juice gets to the lamp holders via meter / volt stick or contractor.

Click to expand...

No no no no no.

Why not ?? (other than the possibility of live working, which has more risk for a DIYer- ladders, 2 probes and finding LN on the lamp holder).

The lamps should have a marking on the side. If there's transformers, it is quite possible that they were done as 2 units each covering 3 x lamps.

They do fail, but equally they do get warm and it's not a good idea to wrap them up in insulation.

xr4x4 · 11 Apr 2011

Chri5 said:
ban-all-sheds said:

Chri5 said:

After checking the above suggestions the next thing will be proving the juice gets to the lamp holders via meter / volt stick or contractor.

Click to expand...

No no no no no.

Click to expand...

Why not ?? (other than the possibility of live working, which has more risk for a DIYer- ladders, 2 probes and finding LN on the lamp holder).

The lamps should have a marking on the side. If there's transformers, it is quite possible that they were done as 2 units each covering 3 x lamps.

They do fail, but equally they do get warm and it's not a good idea to wrap them up in insulation.

Indeed, as long as you check on a known good live source before you test, should be fine.

I've seen two electricians use these now, so I brought one, handy for quick live testing.

Longshanks · 11 Apr 2011

Just to be clear I'm using AICO Thermal Loft caps which have been sealed and (as recommended on this forum) and laying the insualtion over these.

Are you saying this arrangements is unsafe?

Could this account for the bulbs all popping on one side and not the other?

Thanks

Taylortwocities · 11 Apr 2011

You need to determine what you are dealing with.

If the lamps are 12v you may have two transformers up in the loft.
They may be wired so that one transformer powers three lights and the other transformer powers the other three.
If you have piled insulation on top of the transformers one may have cooked itself.

But then you may not have 12v lamps. If they are 230v lamps you need to find how the wiring has been done. You need to find the common point at the start of the wiring for those three lights.

Please investigate what you actually have and report back.

NOTE:
The Voltstick shown above is fine for a very basic checks but it will only detect the presence of 230v in the live(phase/line) conductor.
Your problem may be a wiring problem in the neutral conductor. You would need a multimeter or proper 2-probe voltage indicator to test this out.

Longshanks · 12 Apr 2011

Hi

Many thanks for this helpful reply. Have now added pictures to album to show wiring in loft. Gist is that transformers have been used as indicated. I don't think either could have been cooked as I ensured that they were positioned above insulation as you can see.

From the symptoms and pictures is it more likely to be the left transformer supplying the three lights that don't work? Obviously the power in and out are OK so I guess it has to be the transformer itself or the connections to and from the transformer.

I've also checked the connections to the bulbs and they are fine.

Just don't want to make this into a big production when it's summat simple.

Many thanks for your time.

Longshanks

bernardgreen · 12 Apr 2011

Many of these compact electronic "transformers" are built to the minimum standards of design and cost and need all the help they can get to survive.

I would suggest lifting the units off from that insulation and placing them on fire proof plates such as ceramic tiles or similar to allow free air movement around the unit to help with cooling. When nestling in the insulation as they are now they are not getting free air movement around them.

Is that a metallic coating on the insulation ? These electronic "transformers" use high frequency switching to control the output voltage and seldom have any consideration of electro-magnetic screening or effects on adjacent materials in their design. A metallic or otherwise conductive sheet in close proximity to the unit could affect their operation. Induction warming of the sheet by stray electro-magnetic radiation from the unit is not impossible.

flameport · 12 Apr 2011

Likely to be the transformer. What rating are the lamps (bulbs) - they should be 20w each, however if someone has replaced them with higher wattages, this will cause the transformer to fail.

Longshanks · 12 Apr 2011

Thanks for your advice once more. Will check the ratings of the bulbs when I go home at lunch time. Will also follow your advice in relation to positioning of transformers.

It seems that you can't win. Was advised to insulate the loft above bathroom (using thermal loft caps) to avoid mould and now run into probs with electrickery!!

If the bulbs are above 20w is it likely that replacing them wil work?

From the piccies can you tell what transformers were used. Can I buy any standard 230 to 12v or do they both have to be the same type?

Thanks

flameport · 12 Apr 2011

This transformer would be a direct replacement:
http://www.toolstation.com/shop/d220/sd2638/p55497

If the lamps total more than 60w, changing them to the correct ones might get them working, but only if the transformer has an auto-shutdown feature. (most do not).

Longshanks · 12 Apr 2011

Many thanks again.

Sorry to be thick but when you say "direct replacement" do you mean have to use the same type as original (these were NRE I understand).

Do I also have to replace the one that is still working at the same time (like changing wheels)

Longshanks

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Three spot lamps suddenly stopped working

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