Mrs ronmidg switched on hall/landing light this pm and upstairs lights fuse blew straight away (nothing has been disturbed, or anyone gone in loft for months). Replaced fuse. Light came on, fuse blew after 2 or 3 seconds. Turned light off and removed bulbs from this fitting, fuse blew as I re-inserted. Turned every light on upstairs circuit off and replaced fuse, blew about 15 minutes later. Took every upstairs circuit switch fitting off and checked, no signs of electrical burn anywhere, no frayed or trapped wires, did find one loose wire in switch for one bedroom (not the switch the mrs used) and insect case inside, but no burn marks visible. Tightened this and replaced fuse, now been good for about an hour, not switched anything on this circuit on yet. This is 5 amp fuse wire, maximum load if everything on about 250watts, load when first blew about 90 watts. Concern is there is a shorting connection somewhere in the wiring that is variable. Question is under circumstances above what is most likely explanation? mice? not heard any and do have poison down. (Can get by tonight with free standing lamps plugged into ring main. Will probably turn everything off and pull all the other fuses during daylight tomorrow when the house is empty and watch the meter.
Upstairs light circuit fuse blowing.
- Thread starter ronmidg
- Start date
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SaladFingers
Most likely the cable enters a funny angle through the stairs and now the stair has worn it through.
Sounds silly, but it's what I see mostly with situations like this where nothing else has happened.
Get continuity testing.
Sounds silly, but it's what I see mostly with situations like this where nothing else has happened.
Get continuity testing.
This does indeed sound funny, sounds like it could be poor insulation resistance somewhere in the lighting circuit. Have you got an ohm meter of any sort?
SF-the fusebox is indeed under the stairs, but positioned on the wall where the stairs makes 180 degree turn so cables are buried under plaster fuse box about 12 inches below the halfway up the stairs landing, wall is structural as supports roof purlin, is very solid. Having said that it occurs to me that I do not know for sure what the upstairs wiring route is from the fuse box, it cannot be vertical all the way as there is no upstairs above the fusebox, there has to be some horizontal routing somewhere.
Chivers- ohm-meter, do have a small multitester, the sort to keep in car tool box and it does have resistance scales, will this do?
Many thanks for the interest.
Chivers- ohm-meter, do have a small multitester, the sort to keep in car tool box and it does have resistance scales, will this do?
Many thanks for the interest.
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SaladFingers
Hmmm, insulation resistance would be bloody low for that to happen, doesn't often get that low.
An update.
When I checked the fuse I had left in for 24 hours it had blown, no idea when. This fuse circuit is 1st floor lights, 1st and 2nd floor loft lights, mid stairs and 1st floor landing lights. Decided to investigate cables. The meter on outside wall is about 10 feet away from fuse box which is close to outside wall, and is positioned on interior wall underneath the halfway up the stairs landing. So could not figure out the cable routing from the meter, I thought horizontal is a no no, and then to get to loft space above 1st floor passes through the space where the sloping ceiling is directly under the sloping roof, no way to get at. So went to the other end, found some cables in the top loft which ran in a line towards the bedroom lights, disconnected where there are junctions, then started reconnecting individually to figure out the routing. Put each lamp on separate fused plug running of 1st floor ring main to see which lights came on. In order of connecting. First powers one bedroom, the adjacent bathroom, and then the lower loft, next powers the middle bedroom, last powers third bedroom and the stairs and landing lights came on. So power comes up the stairs, then third bedroom, 2nd, 1st, then bathroom, then loft. Now had every light on the original problem circuit running, through three plugs fused at 5 amps, into a single power brick also fused at 5 amps, did not blow fuse. Disconnected the live line from the third bedroom that turned on the stairs and landing lights because these cables go through the space under the sloping roof that I cannot get at. So any clues as to what the problem is? My fuse wire is very old? We do get mice though they are poisoned within a couple of days of entering? Or a 40 year old fuse box? Or?
When I checked the fuse I had left in for 24 hours it had blown, no idea when. This fuse circuit is 1st floor lights, 1st and 2nd floor loft lights, mid stairs and 1st floor landing lights. Decided to investigate cables. The meter on outside wall is about 10 feet away from fuse box which is close to outside wall, and is positioned on interior wall underneath the halfway up the stairs landing. So could not figure out the cable routing from the meter, I thought horizontal is a no no, and then to get to loft space above 1st floor passes through the space where the sloping ceiling is directly under the sloping roof, no way to get at. So went to the other end, found some cables in the top loft which ran in a line towards the bedroom lights, disconnected where there are junctions, then started reconnecting individually to figure out the routing. Put each lamp on separate fused plug running of 1st floor ring main to see which lights came on. In order of connecting. First powers one bedroom, the adjacent bathroom, and then the lower loft, next powers the middle bedroom, last powers third bedroom and the stairs and landing lights came on. So power comes up the stairs, then third bedroom, 2nd, 1st, then bathroom, then loft. Now had every light on the original problem circuit running, through three plugs fused at 5 amps, into a single power brick also fused at 5 amps, did not blow fuse. Disconnected the live line from the third bedroom that turned on the stairs and landing lights because these cables go through the space under the sloping roof that I cannot get at. So any clues as to what the problem is? My fuse wire is very old? We do get mice though they are poisoned within a couple of days of entering? Or a 40 year old fuse box? Or?
Could be anything to be honest, I have seen daft things like the fixing screws in a back box going through the cable, melted plastic above light fittings, nails through wires which have been there for years etc.
Best bet is to get a sparks with an insulation resistance tester (AKA Megger) to try and find the fault - you should not keep replacing the fuse wire as this may result in something worse happening.
Best bet is to get a sparks with an insulation resistance tester (AKA Megger) to try and find the fault - you should not keep replacing the fuse wire as this may result in something worse happening.
Agree with not just changing fuse, have split the original circuit into 4, 3 chunks each with its own fuse, and running through a separate power source with fuse, all 5 amps, the fuse box and most of the wiring I cannot get to is not live.
Had a result this pm, had to leave for a couple of hours and returned to find one fuse blown, the other three good, the one for the 'last' chunk in the original circuit, one of bedrooms+bath+lower loft had gone. Currently disconnected will be wiring these three separately tomorrow, and reconnecting the other known good to the fuse box. Will separate the bed and bath, can see the whole cable runs for these when I lift the insulation, and probably replace the loft wiring completely as quite a bit of original wiring I cannot see as hidden between sloping ceiling and roof.
Had a result this pm, had to leave for a couple of hours and returned to find one fuse blown, the other three good, the one for the 'last' chunk in the original circuit, one of bedrooms+bath+lower loft had gone. Currently disconnected will be wiring these three separately tomorrow, and reconnecting the other known good to the fuse box. Will separate the bed and bath, can see the whole cable runs for these when I lift the insulation, and probably replace the loft wiring completely as quite a bit of original wiring I cannot see as hidden between sloping ceiling and roof.
Well, have been running the system with the upstairs lights on 6 separate lines since lunchtime, 3 beds, bath, top loft, middle loft, each with its own 5amp fuse, all plugged into a 6 way brick running through a 5amp fuse off the ring main, everything works, no fuses blowing. The wiring from the fuse box to the 1st floor which is not accessible as it passes along brick walls, through the staircase somehow, and inside the sloping roof, is not being used. Everything that should be working is working. Big but though, downstairs could hear an occasional electric contact noise, like a fuse blowing, or a high amperage contact being broken. But nothing was cutting out. This is in the opposite side of the house to the 1st floor lighting, the part with no upstairs. Taking the boards away revealed lighting weight cable (amongst others) running from above the fuse box to the opposite side of the house and up into the top loft, has mouse damage, and a small burnt section with blue sparking. Immediately removed the ground floor lighting fuse in addition to the 1st floor light fuse, which made no difference, was still live. Then shut off at the master switch, cut the burnt wire, turned the system back on, everything works, have no idea what this wire is for, definitely lighting cable but not connected to either of the light circuit fuses. Is original wiring when house built as is amongst rest of wires to fusebox, fixed same way to joists, using same clips. Shall be trying to find where it disappears to in the top loft tomorrow. House was built in 1977, was it normal then to use lighting cable for anything other than lighting? The original issue appears to be fixed, as someone suggested likely to be a problem somewhere in the stuff now not in the loop, in/under/around the staircase.
Have you left it cut & live now then? Or have you made the cut end(s) safe?[/b]
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