Halogen and circuit breakers

[Sput]

Ahoy all, my lights have just gone out! Whenever I turn on my lovely 12V lighting in the kitchen, the breaker in the main fuse box trips. The secondary 12V lighting in there doesn't trip it though. Could this be due to a blown bulb or is it more likely to be something to call the landlord over?

[Nick Harvey]

It sounds like the transformer winding shorting out, but who can be sure?

Best get the landlord out, so he can call in a very expensive professional. After all, that's what landlords are for.

Anyway, you're the scientist. How does it go? Volts over Amps equals Ohms, or something like that?

The height of the rainforest is inversly proportional to the depth of the mud at the bottom of the tree?

[Sput]

Isn't it just. Especially when they're unnecessary visits - NOT that I would EVER do such a thing! I think my kitchen might be electrically cursed though.

[Gavin Scott]

Ahoy all, my lights have just gone out! Whenever I turn on my lovely 12V lighting in the kitchen, the breaker in the main fuse box trips. The secondary 12V lighting in there doesn't trip it though. Could this be due to a blown bulb or is it more likely to be something to call the landlord over?

This 12v lighting - I'm assuming you have lots of little transformers peppered around in the ceiling cavity? I would guess that there's a short somewhere in the 5amp ring that serves them.

Unless they've been wired by a cretin, individual transformers may fail but shouldn't take out the breaker on repeated re-sets. The GY9.5 lampholders that accept the pins on each lamp are also a common fail point, but again that wouldn't result in the breaker going repeatedly.

NB: Lots of things will cause the breaker to operate - its the constant breaking that indicates something more serious such as a short.

As I say, its probably a short in the mains serving the transformers. If you can't easily access them to see this then yes - get your landlord to call a spark.

[Nick Harvey]

Looks like the landlord ought to call Scott Electrics of Edinburgh.

I understand they're at a loose end at the moment and shouldn't charge too much, plus travelling.

[nidave]

get your landlord to call a spark.

Would an electrician not be a better choice?

[Sput]

Ahoy all, my lights have just gone out! Whenever I turn on my lovely 12V lighting in the kitchen, the breaker in the main fuse box trips. The secondary 12V lighting in there doesn't trip it though. Could this be due to a blown bulb or is it more likely to be something to call the landlord over?

This 12v lighting - I'm assuming you have lots of little transformers peppered around in the ceiling cavity? I would guess that there's a short somewhere in the 5amp ring that serves them.

Unless they've been wired by a cretin, individual transformers may fail but shouldn't take out the breaker on repeated re-sets. The GY9.5 lampholders that accept the pins on each lamp are also a common fail point, but again that wouldn't result in the breaker going repeatedly.

NB: Lots of things will cause the breaker to operate - its the constant breaking that indicates something more serious such as a short.

As I say, its probably a short in the mains serving the transformers. If you can't easily access them to see this then yes - get your landlord to call a spark.

I should also mention that they were running last night for a fair while and then suddenly tripped - that was the first time it happened. Seems unlikely the ring main would suddenly short out, right? I think I'll have to take out all (7, damn) bulbs to make sure it's not just easily rectified but, damnit, I'm lazy.

[Gavin Scott]

Seems unlikely the ring main would suddenly short out, right?

Not right. Circuits that have worked for months and years can short. I've looked at previously "sound" wiring to see loose chock-block connections and terminations that a mouse could dislodge. It depends on the attention to detail at the install.

From what you're telling me you've got a 5amp (perhaps 15amp) lighting ring which spurs off to two sets of LV downlighters. Its the work off that spur which is in question, and most contract lighting installers would have done it with flexible PVC cable, untrunked and left loose in a ceiling cavity.

It could be a faulty transformer (TRX), or a lamp has arced itself into a lampholder - however I believe it is unlikely that either problem alone would cause your RCD to continually break. The more common outcome of either problem is that an individual lamp or TRX would fail.

[marksi]

Unless they've been wired by a cretin

snip

They most likely have been wired by a plumber. I'm serious. Landlords appear to think that plumbers can fix anything. More worrying still, so do plumbers.

And if you think their wiring is bad, you should have a look at their carpentry skills.

[Sput]

You think plumbers are bad? Try scientists. Fucking hell.

[Sput]

Seems unlikely the ring main would suddenly short out, right?

Not right.

Well, I had a good run here on Metropol. Time to move on

From what you're telling me you've got a 5amp (perhaps 15amp) lighting ring which spurs off to two sets of LV downlighters. Its the work off that spur which is in question, and most contract lighting installers would have done it with flexible PVC cable, untrunked and left loose in a ceiling cavity.

I think you're spot on, although it's all on top of cupboards with a big closed terminal block first because there's a (11 year old) transformer for each cupboard unit. It looks fairly neat but within that box, who knows!

While I'm on the topic: I see the transformer's rated at 50VA output, as in volt-amps? As in Watts? What an odd way to write it, if so.

Anyway, ta for your lovely advice. I'll take all the bulbs out at some point then call the landlord if it still trips.