If, repeat IF all the switches are off, then any faulty lamp bulbs, or flex drops, would not blow the fuse/cause a short - exceptions might be, two way lighting circuits, where you can never be sure, whether they are on or off.
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Systematic procedure for tracing repeated fuse blowing in domestic 5 amp lighting.
- Thread starter JimboMarimbo
- Start date
If, repeat IF all the switches are off, then any faulty lamp bulbs, or flex drops, would not blow the fuse/cause a short - exceptions might be, two way lighting circuits, where you can never be sure, whether they are on or off.
Exactly. Hence why taking ALL the bulbs out is a good idea
Where there is doubt, about the switch state..
I'm trying to digest all this and reconcile some apparent conflicting views "get a plug in 5A MCB" vs "I absolutely do not suggest the OP should do the above". Anyway I have bought a box of twenty 5A cartridge fuses for starters. And so, the following sounds good...
"Split the circuit in half (disconnect the circuit at a ceiling rose
Repower circuit. That will tell you which half the fault is at.
Then keep splitting down.
It could also get half your lights working again"
Sounds like a process I could manage, apart from "That will tell you which half the fault is at" surely not - it will not point in any one direction to "keep splitting down" or am I missing something here?
As for ceiling roses, they are all plastic, replacements, I would think when the house was split into two flats in 1970s and some rewiring with a WYLEX two way fuse box.
The bell transformer is a 13 A plug type and all the power sockets are working normally - as for the bathroom light just a normal newish pendant.
"Split the circuit in half (disconnect the circuit at a ceiling rose
Repower circuit. That will tell you which half the fault is at.
Then keep splitting down.
It could also get half your lights working again"
Sounds like a process I could manage, apart from "That will tell you which half the fault is at" surely not - it will not point in any one direction to "keep splitting down" or am I missing something here?
As for ceiling roses, they are all plastic, replacements, I would think when the house was split into two flats in 1970s and some rewiring with a WYLEX two way fuse box.
The bell transformer is a 13 A plug type and all the power sockets are working normally - as for the bathroom light just a normal newish pendant.
One extra - I did state in my original post "I removed every light bulb (all LEDs)" - confirming there are NO light bulbs in situ anywhere.
You’re missing something. If you break the circuit in the middle and power on, if the fuse blows the fault is between the fuse and the break. If it doesn’t blow, the fault is beyond the break.
Please have a plan for replacing some or all of this installation.
Thank you, that is perfectly clear - your patient polite response is much appreciated.
I shall take your procedural advice, starting with the ceiling rose above the bulb holder that was 'on' when this whole fuse blowing started.
Fuse box 'off', Disconnect the two (four?) wires in the rose, replace the fuse, set fuse box to 'on' Fuse blows or does not blow. Repeat, guessing which will be next until you find one and follow along one by one.
The logic of this is first rate.
As for a 'plan' for replacing some of the wiring, I have thought no further than pulling the 'bad' end of the wire back to the fuse box end where there must be some sort of distribution board. I dunno, one thing at a time, eh?
I shall take your procedural advice, starting with the ceiling rose above the bulb holder that was 'on' when this whole fuse blowing started.
Fuse box 'off', Disconnect the two (four?) wires in the rose, replace the fuse, set fuse box to 'on' Fuse blows or does not blow. Repeat, guessing which will be next until you find one and follow along one by one.
The logic of this is first rate.
As for a 'plan' for replacing some of the wiring, I have thought no further than pulling the 'bad' end of the wire back to the fuse box end where there must be some sort of distribution board. I dunno, one thing at a time, eh?
Trying to avoid advising someone, who may not be safely able to do this sort of thing, without putting themselves at extreme risk of electrocution.
The usual method of lighting circuit wiring, is via what is called a radial circuit of some variety. The L&N progress from the consumer unit, to each supply light section, on the circuit, in turn. It either goes around the joint boxes, the ceiling roses, or the switches - depending on how/when it was wired. Provide the requested photographs, and we will have a better idea which way it might have been done.
The circuit is like this... T?= joint box/ceiling rose/switch - depending on the wiring method used. X is the shorted wiring you are trying to trace.
CU.......T1.......T2.......T3.......T4.......T5.......T6...X....T7.......T8.......T9
If you part the wiring at a point between T4 and T5, insert a good fuse, and it doesn't blow, obviously your fault is beyond T5. If try the same again, but between T7 and T8, then it blows, you now know the fault is between T6 and T7.
It is a simple, logical, fault-finding method, which works for many things, but in the case of hidden wiring, you have to make a shrewd guess, at which order the lights may have been wired. T1 will almost certainly be the ground floor light, nearest the consumer unit. The rest may form a semi-circle, or even a crude star pattern.
I meant, replacing the fuse box with something less ancient. For example, having a modern RCD would improve your safety while doing this fault-finding.
If its VIR in conduit, then it's long overdue for a full rewire and if it's not in conduit, then the urgency is even greater due to the potential fire risk.
Okay in theory, but in reality, all the cables could be perished with insulation falling to pieces. Then what would you recommend with an ancient 'fuse box' removed and crumbling insulation on the cables beneath?
I don’t think they’ve said anything about the type of cable, have they? Maybe the ancient rubber wires were replaced with PVC in 1975 and are still fine. Or not! The one thing we do know is that there is a fuse box with cartridge fuses. Get someone to quote for replacing that, and no doubt they’ll also say something about the state of the wiring.
“Photos please”.
Which is why we are asking for some photos!
If you get to a place where the fuse doesn’t blow, then you need to reinsert the led lamps and turn the switches on in each room.
Note down the rooms that the lights works in. You will probably not need to do any work in those rooms that work.
With this investigation, it’s important you take detailed notes to help with the fault finding process. Particularly as this could span days.
Also get yourself some red or brown tape or paint.
Take a picture of each ceiling rose before disconnecting anything.
Ceiling roses typically have 3 block connections in a row.
First a 2 wire block. This will connect to the live wire on the flex drop to the lamp. The wire next to that should have red or brown tape or sleeve on it. (It probably won’t at the house age). Dab a bit of red paint on the ceiling wire so you don’t ever get it mixed up.
The middle block will typically have 3 red wires in it.
The last block should have 3 black wires in it. One of them being the drop to the lamp.
Basically you need to goto the room half way away from the fusebox.
And disconnect the 3 red wires in the middle block so they are apart and repower the circuit.
If the fuse doesn’t pop, goto other rooms and insert lamps and switch rooms on and see what rooms work.
If ban was here , he would say learn how light circuits work. And he has a point.
Note down the rooms that the lights works in. You will probably not need to do any work in those rooms that work.
With this investigation, it’s important you take detailed notes to help with the fault finding process. Particularly as this could span days.
Also get yourself some red or brown tape or paint.
Take a picture of each ceiling rose before disconnecting anything.
Ceiling roses typically have 3 block connections in a row.
First a 2 wire block. This will connect to the live wire on the flex drop to the lamp. The wire next to that should have red or brown tape or sleeve on it. (It probably won’t at the house age). Dab a bit of red paint on the ceiling wire so you don’t ever get it mixed up.
The middle block will typically have 3 red wires in it.
The last block should have 3 black wires in it. One of them being the drop to the lamp.
Basically you need to goto the room half way away from the fusebox.
And disconnect the 3 red wires in the middle block so they are apart and repower the circuit.
If the fuse doesn’t pop, goto other rooms and insert lamps and switch rooms on and see what rooms work.
If ban was here , he would say learn how light circuits work. And he has a point.
This might help a little - https://www.diydata.com/planning/electric-lights/electric-lights.php diagrams at the bottom of the page. It doesn't show the method where both L&N are taken/looped via the switch.
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