Bathroom lights trip

[ben_m_g]

Just a quick (maybe stupid) question

The bathroom halogen lights trip out, if left on for only an hour or so, then take a while to switch back on and have normal use.
(3 X 40w spots fairly new by the looks of em)

Been in the loft and removed the insulation away from the lamps to no effect.
I assume its an overheat problem? As i carn't see anything installed that would do it.
A quick cursory would seem that the wiring is sound with nothing obvious to my eye..


I've had spot lights for some time and never seen them trip after such a short time.

Obviously this is a pain as after a while as the gf gets left in the dark, thought it doesn't seem to shift her out of the bath though...

Ideas anyone?

 

[jj4091]

You probably will not be able to see any cable fault that is being caused by over heating, you would need to do a resistance check with a multimeter or preferably a megga, but are you sure it is not the fact that the fittings are not suitably rated for the location & steam is getting into them & causing the tripping.

 

[ban-all-sheds]

Ideas anyone?

About the lighting or what to do with your g/f in the dark in the bath?


When you say they trip out, do you mean that they turn themselves off, i.e. just those go off, or that the breaker for the circuit trips?

If they are ELV lights it could be the transformer overheating - have you cleared the insulation from around that?

 

[ban-all-sheds]

you would need to do a resistance check with a multimeter or preferably a megga

1) The two can't possibly measure the same thing.

2) How would either a high circuit resistance or a low insulation resistance cause these symptoms?

 

[sparkyspike]

Do the lamps go out at the same time? Do they have individual transformers, or just one transformer? Are they 12v or 240v?

 

[jj4091]

you would need to do a resistance check with a multimeter or preferably a megga

1) The two can't possibly measure the same thing.

2) How would either a high circuit resistance or a low insulation resistance cause these symptoms?

I presumed when he talked about tripping that an mcb was tripping due to a l-n s/c or l-e s/c which was clearing after the cables cooled, but I think I qualified it with the second part of my response

 

[skenk]

Sounds like the transformer is overheating, then resetting itself when it cools down. 110w(va) transformer trying to power 3x40w=120w bulbs i'll wager. Check by seeing if there's only 1 transformer, check the rating, usually given in va, eg 50-100va. The wattage of the 3 lamps should add up to more than the first number and less than the second.

 

[ban-all-sheds]

I presumed when he talked about tripping that an mcb was tripping

An MCB that only serves the bathroom lighting?

due to a l-n s/c or l-e s/c which was clearing after the cables cooled,

So you think that cables can get so hot that the insulation softens/melts sufficiently for 2 cores to make good enough contact for a high fault current to flow, but not create any smoke or smell of burning, and that once cool the fault would disappear?

How does that work?

but I think I qualified it with the second part of my response

are you sure it is not the fact that the fittings are not suitably rated for the location & steam is getting into them & causing the tripping.

How is steam getting in going to create a fault path of low enough resistance for the MCB to trip?

 

[ben_m_g]

i'll clear things up hopefully, yes all the light go out at once and they look to be pretty standard bathroom fitments.

wiring wise the loft is partially borded so i will have to rip up some boards to try and get a look if thats what is called for.


A moment all i can see is an unswitched fused conection unit feeding the lights, so i will try and find the transformer and report back.

thanks for all the the imput guys

 

[jj4091]

I presumed when he talked about tripping that an mcb was tripping

An MCB that only serves the bathroom lighting?

He may have only had the bathroom light switched on( come on we all have to speculate sometimes)

due to a l-n s/c or l-e s/c which was clearing after the cables cooled,

So you think that cables can get so hot that the insulation softens/melts sufficiently for 2 cores to make good enough contact for a high fault current to flow, but not create any smoke or smell of burning, and that once cool the fault would disappear?

You must have led a sheltered life if you have not had that as a fault

How does that work?

but I think I qualified it with the second part of my response

are you sure it is not the fact that the fittings are not suitably rated for the location & steam is getting into them & causing the tripping.

How is steam getting in going to create a fault path of low enough resistance for the MCB to trip?

If I am wrong I bow to your superior knowledge but I was under the impression that was one of the reasons, fittings had to have a suitable IP rating for bathrooms, or is it purely protection from hazard. People interpret different things in different ways, I interpretted the information I read in a different way to others perhaps.

 

[skenk]

Before you rip the floor up . . . if it's not too late . . . it's likely the transformer will be accessible by taking down one of the light fittings (you will have to take each one down to check). Or try just taking 1 lamp out of it's fitting, leave the lights on and and see if you still get the tripping. If no trip then replace the lamps with ones of a lesser wattage and your problem should be sorted. . . if that is it's the case of an overloaded transformer . . .