Lighting fuse blowing


Postby bigskookers » Sat Jan 19, 2008 9:59 pm

Can anyone help me please - two possibly unrelated problems 1 - Main fuse trips when cooker is on at 190c but does not trip when lower 170c - why is this?

2 - Recently the fuse for the upstairs lights tripped and continues to do so everytime I turn the lights on. In the specifc bedroom where is happens there are 3 50w downlighters. Any thoughts please? The problem has not occurred in any other bedroom or the bathroom on the same circuit. They worked fine before.

Thanks in advance for any advice
Dave
bigskookers
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Joined: Sat Jan 19, 2008 9:47 pm

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Postby kbrownie » Sun Jan 20, 2008 7:07 am

Hi bigskookers
you need to check the wiring/cables in your upstairs lights sounds like you have a short in that room. Check in the ceiling rose for loose connection and touching bare cables and do the same in the switch that operates these lights.
Cooker:A few question first, SORRY! how long have you had cooker, has this just started to happen is the cooker on a circuit dependant to it's self or is part of the kitchen power circuit, what's the kilowatt output and fuse rating of the cooker? like I said just a few questions, reason being the fact that it runs then trips at certain temp, it could be that the design current for the fuse/mcb are not correctly match i.e. not enough amps to run it. But could still be a fault within cooker it's self.
Remember safety first and safely isolate the circuit at the consumer unit before carrying out any work.
Good Luck
KB
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Joined: Mon Mar 05, 2007 9:36 pm


Postby bigskookers » Sat Feb 02, 2008 6:45 pm

Thanks KB - you were spot on with the lighting problem - when I checked the attic space the wires were bare so I replaced - all works fine now. I need to have a think on the cooker issue but thanks meantime.
Best wishes
bigskookers
Posts: 2
Joined: Sat Jan 19, 2008 9:47 pm


Postby ericmark » Sat Feb 02, 2008 9:13 pm

First the lights, If you remove bulbs does MCB still trip? Some cheap bulbs don't have built in fuses and can go short circuit. Also where multi-spots are used they can cause a MCB to trip when they are switched on as they use more power on first switch on but don't think this is problem with your house.

Second is cooker, MCB's do not trip as soon as they are overloaded but take some time they work using heat and if the load is switched on and off it is cumulative average which will cause it to trip. So what size is the MCB which trips? If under 30 amp this could be cause. But inside cookers insulation is often by porcelain beads and expansion and contraction can allow these to touch something they shouldn't as they expand which could be dangerous and possible it will only be found by stripping cooker meters may not find it. Not really a DIY job. If it is the supply then using rings etc on the cooker should make it trip also but if cooker they most likely will not affect when it trips.

I am assuming it is a MCB that is tripping not the RCD? The latter normally has yellow test button. A RBCO also has test button but still not very common. RCD normally double thickness to MCB or RBCO and RBCO will normally have letter B, C or D in front of number of amps i.e. B32.

Once we have more information maybe we can help more but please be careful you may consider safety first and call in an electrician?
ericmark


Postby ericmark » Sat Feb 02, 2008 9:27 pm

First the lights, If you remove bulbs does MCB still trip? Some cheap bulbs don't have built in fuses and can go short circuit. Also where multi-spots are used they can cause a MCB to trip when they are switched on as they use more power on first switch on but don't think this is problem with your house.

Second is cooker, MCB's do not trip as soon as they are overloaded but take some time they work using heat and if the load is switched on and off it is cumulative average which will cause it to trip. So what size is the MCB which trips? If under 30 amp this could be cause. But inside cookers insulation is often by porcelain beads and expansion and contraction can allow these to touch something they shouldn't as they expand which could be dangerous and possible it will only be found by stripping cooker meters may not find it. Not really a DIY job. If it is the supply then using rings etc on the cooker should make it trip also but if cooker they most likely will not affect when it trips.

I am assuming it is a MCB that is tripping not the RCD? The latter normally has yellow test button. A RBCO also has test button but still not very common. RCD normally double thickness to MCB or RBCO and RBCO will normally have letter B, C or D in front of number of amps i.e. B32.

Once we have more information maybe we can help more but please be careful you may consider safety first and call in an electrician?
ericmark


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