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#1
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Dull thud, and all the lights dim momentarily.
I am trying to help some friends discover what is wrong with their
electrics. The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. My friends had not attached any significance to these events until I called them catastrophic explosions, now they are worried. They hadn't noticed the lights flicker at all, they had heard the thuds but put it down to their neighbours door slamming, which isn't unreasonable having heard it. All the circuits are affected, lights and power. For the record, his consumer unit is an old MK type with rewireable fuses, one lighting cct has a retrofit 5 or 6 amp MCB, one of the later lever type. There is no history of any fuse blowing. The house is a semi, the meter and CU are in the hall cupboard far away from the party wall. The supply incomer, I imagine, enters from the street. The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. There is a conservatory with a solid floor at the back of the house. I thought water would be involved, and we have had torrential rain recently, however not a drop has fallen this week and I witnessed 3 of these events last night. I have an idea or two of diagnostic measures to try next time I visit, but what does the team say? -- Graham. %Profound_observation% |
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#2
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Dull thud, and all the lights dim momentarily.
Graham. wrote:
I am trying to help some friends discover what is wrong with their electrics. The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. My friends had not attached any significance to these events until I called them catastrophic explosions, now they are worried. They hadn't noticed the lights flicker at all, they had heard the thuds but put it down to their neighbours door slamming, which isn't unreasonable having heard it. All the circuits are affected, lights and power. For the record, his consumer unit is an old MK type with rewireable fuses, one lighting cct has a retrofit 5 or 6 amp MCB, one of the later lever type. There is no history of any fuse blowing. The house is a semi, the meter and CU are in the hall cupboard far away from the party wall. The supply incomer, I imagine, enters from the street. The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. There is a conservatory with a solid floor at the back of the house. I thought water would be involved, and we have had torrential rain recently, however not a drop has fallen this week and I witnessed 3 of these events last night. I have an idea or two of diagnostic measures to try next time I visit, but what does the team say? The zombie they buried under rhe floor is reaching out to get powered up? Might be a damaged incoming underground. -- Ineptocracy (in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers. |
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#3
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Dull thud, and all the lights dim momentarily.
On Fri, 07 Sep 2012 22:12:01 +0100, Graham.
wrote: I am trying to help some friends discover what is wrong with their electrics. The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. My friends had not attached any significance to these events until I called them catastrophic explosions, now they are worried. They hadn't noticed the lights flicker at all, they had heard the thuds but put it down to their neighbours door slamming, which isn't unreasonable having heard it. All the circuits are affected, lights and power. For the record, his consumer unit is an old MK type with rewireable fuses, one lighting cct has a retrofit 5 or 6 amp MCB, one of the later lever type. There is no history of any fuse blowing. The house is a semi, the meter and CU are in the hall cupboard far away from the party wall. The supply incomer, I imagine, enters from the street. The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. There is a conservatory with a solid floor at the back of the house. I thought water would be involved, and we have had torrential rain recently, however not a drop has fallen this week and I witnessed 3 of these events last night. I have an idea or two of diagnostic measures to try next time I visit, but what does the team say? Where's the refrigerator? My late mother had a fridge that used to create some sort of pulse when the thermostat switched it off. I imagine a capacitor had died, or something. (Probably the 'or something.') The lights would flicker and the TV would get confused for a moment or two and then everything would be normal until the next time. Nick |
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#4
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Dull thud, and all the lights dim momentarily.
On Fri, 07 Sep 2012 22:20:04 +0100, Nick Odell
wrote: On Fri, 07 Sep 2012 22:12:01 +0100, Graham. wrote: I am trying to help some friends discover what is wrong with their electrics. The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. My friends had not attached any significance to these events until I called them catastrophic explosions, now they are worried. They hadn't noticed the lights flicker at all, they had heard the thuds but put it down to their neighbours door slamming, which isn't unreasonable having heard it. All the circuits are affected, lights and power. For the record, his consumer unit is an old MK type with rewireable fuses, one lighting cct has a retrofit 5 or 6 amp MCB, one of the later lever type. There is no history of any fuse blowing. The house is a semi, the meter and CU are in the hall cupboard far away from the party wall. The supply incomer, I imagine, enters from the street. The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. There is a conservatory with a solid floor at the back of the house. I thought water would be involved, and we have had torrential rain recently, however not a drop has fallen this week and I witnessed 3 of these events last night. I have an idea or two of diagnostic measures to try next time I visit, but what does the team say? Where's the refrigerator? My late mother had a fridge that used to create some sort of pulse when the thermostat switched it off. I imagine a capacitor had died, or something. (Probably the 'or something.') The lights would flicker and the TV would get confused for a moment or two and then everything would be normal until the next time. I should have added that it made a loud noise and then shivered with the vibration as the motor ran down. Hence, noise, lights, EMP etc. N |
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#5
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Dull thud, and all the lights dim momentarily.
In article ,
Graham. writes: I am trying to help some friends discover what is wrong with their electrics. The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. Does it happen all the time, e.g. including all through the night, or only during the day? What about weekends? My friends had not attached any significance to these events until I called them catastrophic explosions, now they are worried. They hadn't noticed the lights flicker at all, they had heard the thuds but put it down to their neighbours door slamming, which isn't unreasonable having heard it. All the circuits are affected, lights and power. Well, it could still be something next door, interfering with the local mains supply. Could the bang be a breaker tripping off next door? Is the flicker a momentary brown-out, or a momentary surge (which can happen if there's a short circuit on another phase which momentarily yanks the neutral part way to that phase voltage)? Brown-outs and surges can show up better with mains filament lamps, because they amplify the effect. -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] |
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#6
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Dull thud, and all the lights dim momentarily.
On Fri, 07 Sep 2012 22:17:50 +0100, The Natural Philosopher wrote:
Might be a damaged incoming underground. Aye, I don't like the description of the sound as a "dull thud" that is too much like a muffled explosion for my likeing. Think I'd be getting onto the local REC, even on Saturday. If it is an underground cable fault it could make considerably more than a dull thud and a little flicker of the lights. -- Cheers Dave. |
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#7
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Dull thud, and all the lights dim momentarily.
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#8
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Dull thud, and all the lights dim momentarily.
In article o.uk,
"Dave Liquorice" writes: On Fri, 07 Sep 2012 22:17:50 +0100, The Natural Philosopher wrote: Might be a damaged incoming underground. Aye, I don't like the description of the sound as a "dull thud" that is too much like a muffled explosion for my likeing. Think I'd be getting onto the local REC, even on Saturday. If it is an underground cable fault it could make considerably more than a dull thud and a little flicker of the lights. A Kentucky Fried Chicken was wrecked by a supply cable fault, which was basically a fire/arc before the main cutout which they couldn't put out. Usually these things eventually turn into a good enough short circuit to blow the upline fuse (typically 400A on a residential street supply), or they end up burning out the cable leaving it open circuit. Until one or other happens, it can be pretty difficult to locate. One of my work colleagues used to do this in the 11/33kV network, but I suspect that doesn't mess around with just the occational pop for so long! -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] |
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#9
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Dull thud, and all the lights dim momentarily.
On Fri, 07 Sep 2012 22:51:06 +0100 (BST), "Dave Liquorice"
wrote: On Fri, 07 Sep 2012 22:17:50 +0100, The Natural Philosopher wrote: Might be a damaged incoming underground. Aye, I don't like the description of the sound as a "dull thud" that is too much like a muffled explosion for my likeing. Think I'd be getting onto the local REC, even on Saturday. If it is an underground cable fault it could make considerably more than a dull thud and a little flicker of the lights. This is my thinking too. 40 years ago I encountered something very similar the lights dimmed and there was a thud, but only after heavy rain. In that case the thud came from across the road under the pavement beneath a street light. My friends house is on an ordinary suburban street with underground distribution. Is it likely his incomer cable will enter from other than the front of the house? If it does enter at the front there is no chance the supply main runs where I can hear the noise, but it's still a worry. I am wondering about the power to the conservatory. If the cable(s) were undersized and the loop impendence high enough could you think of some momentary short circuit scenario that would cause these symptoms but not blow a 30A wire fuse? It could well be that the problem is next doors, I just cannot tell. -- Graham. %Profound_observation% |
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#10
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Dull thud, and all the lights dim momentarily.
Graham. wrote:
On Fri, 07 Sep 2012 22:51:06 +0100 (BST), "Dave Liquorice" wrote: On Fri, 07 Sep 2012 22:17:50 +0100, The Natural Philosopher wrote: Might be a damaged incoming underground. Aye, I don't like the description of the sound as a "dull thud" that is too much like a muffled explosion for my likeing. Think I'd be getting onto the local REC, even on Saturday. If it is an underground cable fault it could make considerably more than a dull thud and a little flicker of the lights. This is my thinking too. 40 years ago I encountered something very similar the lights dimmed and there was a thud, but only after heavy rain. In that case the thud came from across the road under the pavement beneath a street light. My friends house is on an ordinary suburban street with underground distribution. Is it likely his incomer cable will enter from other than the front of the house? If it does enter at the front there is no chance the supply main runs where I can hear the noise, but it's still a worry. I am wondering about the power to the conservatory. If the cable(s) were undersized and the loop impendence high enough could you think of some momentary short circuit scenario that would cause these symptoms but not blow a 30A wire fuse? It could well be that the problem is next doors, I just cannot tell. If his house is like mine (1930s ex-council), the incoming mains cable runs along the end of the 4 house terrace, then along the back wall, branching off to each hosue as it goes. -- Tciao for Now! John. |
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#11
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Dull thud, and all the lights dim momentarily.
On 7 Sep,
Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? -- B Thumbs Change lycos to yahoo to reply |
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#12
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Dull thud, and all the lights dim momentarily.
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#14
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Dull thud, and all the lights dim momentarily.
On Fri, 07 Sep 2012 23:51:05 +0100, wrote:
On 7 Sep, Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? I see what you mean, and maybe Nick had this in mind too. It might account for the timing intervals, the inrush surge of the motor starting acting as the cartelist to set whatever it is off upstream. Still odd though because where I hear the noise is not between the kitchen and the CU, Quite the opposite direction in fact. -- Graham. %Profound_observation% |
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#15
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Dull thud, and all the lights dim momentarily.
On 08/09/2012 00:18, Graham. wrote:
On Fri, 07 Sep 2012 23:51:05 +0100, wrote: On 7 Sep, Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? I see what you mean, and maybe Nick had this in mind too. It might account for the timing intervals, the inrush surge of the motor starting acting as the cartelist to set whatever it is off upstream. The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... Still odd though because where I hear the noise is not between the kitchen and the CU, Quite the opposite direction in fact. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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#16
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Dull thud, and all the lights dim momentarily.
On Fri, 07 Sep 2012 22:12:01 +0100, Graham.
wrote: The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. She would say that. What she's not telling you is the basement and attic are full of dope plants and the thud-flicker are when the contactor for the lights cuts in and out via a timer. |
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#17
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Dull thud, and all the lights dim momentarily.
John Rumm wrote:
On 08/09/2012 00:18, Graham. wrote: On Fri, 07 Sep 2012 23:51:05 +0100, wrote: On 7 Sep, Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? I see what you mean, and maybe Nick had this in mind too. It might account for the timing intervals, the inrush surge of the motor starting acting as the cartelist to set whatever it is off upstream. The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... Depends. When I had a 1947 vintage lump of iron up a pole to supply me the microwave would do that all on its own. And trip the RCD when I installed a load of computers and other **** on it NOW I have a freezer sized personal transformer to supply the house, that doesn't happen :-) Still odd though because where I hear the noise is not between the kitchen and the CU, Quite the opposite direction in fact. -- Ineptocracy (in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers. |
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#18
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Dull thud, and all the lights dim momentarily.
On Sat, 08 Sep 2012 00:48:42 +0100, John Rumm
wrote: On 08/09/2012 00:18, Graham. wrote: On Fri, 07 Sep 2012 23:51:05 +0100, wrote: On 7 Sep, Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? I see what you mean, and maybe Nick had this in mind too. It might account for the timing intervals, the inrush surge of the motor starting acting as the cartelist to set whatever it is off upstream. The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... I'd appreciate your view on what might be causing the thud John. -- Graham. %Profound_observation% |
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#19
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Dull thud, and all the lights dim momentarily.
On Sat, 08 Sep 2012 00:54:34 +0100, Grimly Curmudgeon
wrote: On Fri, 07 Sep 2012 22:12:01 +0100, Graham. wrote: The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. She would say that. What she's not telling you is the basement and attic are full of dope plants and the thud-flicker are when the contactor for the lights cuts in and out via a timer. Actually all the plant nursery's the police have raided in the last few years are on my road. -- Graham. %Profound_observation% |
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#20
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Dull thud, and all the lights dim momentarily.
Graham. wrote:
cartelist Are you a southerner? Bill |
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#21
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Dull thud, and all the lights dim momentarily.
On Fri, 07 Sep 2012 22:20:04 +0100, Nick Odell wrote:
Where's the refrigerator? Yeah, I was going to ask that, too :-) Old fridge and worn compressor mounts might produce a thump and flickering lights when the compressor starts. Our old one certainly did the flickering lights thing - sadly it kicked the bucket last week, but 35 years wasn't bad... cheers Jules |
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#22
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Dull thud, and all the lights dim momentarily.
On Sat, 08 Sep 2012 02:50:05 +0100, Bill Wright
wrote: Graham. wrote: cartelist Are you a southerner? Bill http://www.merriam-webster.com/dictionary/cartelist cartelist One that belongs to or favors (sic) a cartel. This word doesn't usually appear in our free dictionary, but the definition from our premium Unabridged Dictionary is offered here on a limited basis. Note that some information is displayed differently in the Unabridged. Words a commodity. Whatever next. -- Graham. %Profound_observation% |
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#23
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Dull thud, and all the lights dim momentarily.
On 08/09/2012 01:06, Graham. wrote:
On Sat, 08 Sep 2012 00:48:42 +0100, John Rumm wrote: On 08/09/2012 00:18, Graham. wrote: On Fri, 07 Sep 2012 23:51:05 +0100, wrote: On 7 Sep, Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? I see what you mean, and maybe Nick had this in mind too. It might account for the timing intervals, the inrush surge of the motor starting acting as the cartelist to set whatever it is off upstream. The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... I'd appreciate your view on what might be causing the thud John. Without hearing it, I am not sure I have one to be honest... A motor kicking in would be one option. Slightly percussive ignition of a boiler could also cause a thud (although that would not typically be associated with any electrical drop out). Big transformers at switch on can have similar effects. Automated systems like heating and cooling devices would obviously be prime candidates. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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#24
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Dull thud, and all the lights dim momentarily.
On Sat, 08 Sep 2012 04:49:56 +0100, John Rumm
wrote: On 08/09/2012 01:06, Graham. wrote: On Sat, 08 Sep 2012 00:48:42 +0100, John Rumm wrote: On 08/09/2012 00:18, Graham. wrote: On Fri, 07 Sep 2012 23:51:05 +0100, wrote: On 7 Sep, Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? I see what you mean, and maybe Nick had this in mind too. It might account for the timing intervals, the inrush surge of the motor starting acting as the cartelist to set whatever it is off upstream. The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... I'd appreciate your view on what might be causing the thud John. Without hearing it, I am not sure I have one to be honest... A motor kicking in would be one option. Slightly percussive ignition of a boiler could also cause a thud (although that would not typically be associated with any electrical drop out). Big transformers at switch on can have similar effects. Automated systems like heating and cooling devices would obviously be prime candidates. I've pretty much convinced myself it's something electrical blowing itself apart in a self resettable way. Maybe water gets into a joint and is instantly and explosively superheated, Do you think that could happen on a circuit protected by a 30 amp fuse, again and again without it blowing? I think the answer is yes if the loop impendence is high and the events are of short enough duration. I'm just afraid that it might be a cable protected by a fuse 10 times that value in a substation! Can't you sleep? -- Graham. %Profound_observation% |
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#25
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Dull thud, and all the lights dim momentarily.
Well does it affect other properties or not?
If not then as it could be pre meter, I'd suggest a call to the supplier who may be able to test for problems where you cannot. Brian -- Brian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: __________________________________________________ __________________________________________________ __________ "Graham." wrote in message ... I am trying to help some friends discover what is wrong with their electrics. The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. My friends had not attached any significance to these events until I called them catastrophic explosions, now they are worried. They hadn't noticed the lights flicker at all, they had heard the thuds but put it down to their neighbours door slamming, which isn't unreasonable having heard it. All the circuits are affected, lights and power. For the record, his consumer unit is an old MK type with rewireable fuses, one lighting cct has a retrofit 5 or 6 amp MCB, one of the later lever type. There is no history of any fuse blowing. The house is a semi, the meter and CU are in the hall cupboard far away from the party wall. The supply incomer, I imagine, enters from the street. The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. There is a conservatory with a solid floor at the back of the house. I thought water would be involved, and we have had torrential rain recently, however not a drop has fallen this week and I witnessed 3 of these events last night. I have an idea or two of diagnostic measures to try next time I visit, but what does the team say? -- Graham. %Profound_observation% |
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#26
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Dull thud, and all the lights dim momentarily.
Isolate the circuit to the conservatory for some hours to see if it stops,
but from the description, I have a nasty feeling its before the fuse boxes. Near here some houses reported similar issues some time back, then one day a cable blew a hole six feet wide in the pavement outside. It was due to a leaking sewer near a cable in the street and the sound of the minor problems was conducted by the cable to nearby properties, one must assume that eventually the partial short became a major one. Luckily nobody wa hurt but the power was off for several houses for a day or so while they fixed it. Brian -- Brian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: __________________________________________________ __________________________________________________ __________ "Graham." wrote in message ... On Fri, 07 Sep 2012 22:51:06 +0100 (BST), "Dave Liquorice" wrote: On Fri, 07 Sep 2012 22:17:50 +0100, The Natural Philosopher wrote: Might be a damaged incoming underground. Aye, I don't like the description of the sound as a "dull thud" that is too much like a muffled explosion for my likeing. Think I'd be getting onto the local REC, even on Saturday. If it is an underground cable fault it could make considerably more than a dull thud and a little flicker of the lights. This is my thinking too. 40 years ago I encountered something very similar the lights dimmed and there was a thud, but only after heavy rain. In that case the thud came from across the road under the pavement beneath a street light. My friends house is on an ordinary suburban street with underground distribution. Is it likely his incomer cable will enter from other than the front of the house? If it does enter at the front there is no chance the supply main runs where I can hear the noise, but it's still a worry. I am wondering about the power to the conservatory. If the cable(s) were undersized and the loop impendence high enough could you think of some momentary short circuit scenario that would cause these symptoms but not blow a 30A wire fuse? It could well be that the problem is next doors, I just cannot tell. -- Graham. %Profound_observation% |
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#27
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Dull thud, and all the lights dim momentarily.
Probably the design of the incoming cable makes bypassing the meter easier.
Brian -- Brian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: __________________________________________________ __________________________________________________ __________ "Graham." wrote in message ... On Sat, 08 Sep 2012 00:54:34 +0100, Grimly Curmudgeon wrote: On Fri, 07 Sep 2012 22:12:01 +0100, Graham. wrote: The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. She would say that. What she's not telling you is the basement and attic are full of dope plants and the thud-flicker are when the contactor for the lights cuts in and out via a timer. Actually all the plant nursery's the police have raided in the last few years are on my road. -- Graham. %Profound_observation% |
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#28
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Dull thud, and all the lights dim momentarily.
Big transformers at switch on can have similar effects.
Automated systems like heating and cooling devices would obviously be prime candidates. I've pretty much convinced myself it's something electrical blowing itself apart in a self resettable way. Maybe water gets into a joint and is instantly and explosively superheated, Do you think that could happen on a circuit protected by a 30 amp fuse, again and again without it blowing? I think the answer is yes if the loop impendence is high and the events are of short enough duration. I'm just afraid that it might be a cable protected by a fuse 10 times that value in a substation! Personally I would isolate *every* non used appliance for a few hours, fridge, freezer, any heating etc and then reduce the fuse capacity to 15a and switch a circuit on one by one individually to see if it's house side of the CU. If the incoming main is damaged there is an immediate need to get the board in to investigate as shared runs for water, leccy and gas often result it a far larger problem when any two coincide during a failure :-( A scan with a CAT device might be used to determine where any incoming supply issues might be. A local "engineer" for the high power supply bods round here who is one of my customers used to check for blown cables underground at streetlamp circuit problems by shoving a 6" nail in the last known live feed at a pole and watching where the ground erupted nearby so he knew where to dig and repair .... dodgy but it worked. Can't imagine where he got the nickname dodgy digger from...... |
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#29
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Dull thud, and all the lights dim momentarily.
On 8 Sep, 05:10, Graham. wrote:
On Sat, 08 Sep 2012 04:49:56 +0100, John Rumm wrote: On 08/09/2012 01:06, Graham. wrote: On Sat, 08 Sep 2012 00:48:42 +0100, John Rumm wrote: On 08/09/2012 00:18, Graham. wrote: On Fri, 07 Sep 2012 23:51:05 +0100, wrote: On 7 Sep, * * * Graham. wrote: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. The freezer starting up? I see what you mean, and maybe Nick had this in mind too. It might account for the timing intervals, the inrush surge of the motor starting acting as the cartelist to set whatever it is off upstream. The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... I'd appreciate your view on what might be causing the thud John. Without hearing it, I am not sure I have one to be honest... A motor kicking in would be one option. Slightly percussive ignition of a boiler could also cause a thud (although that would not typically be associated with any electrical drop out). Big transformers at switch on can have similar effects. Automated systems like heating and cooling devices would obviously be prime candidates. I've pretty much convinced myself it's something electrical blowing itself apart in a self resettable way. Maybe water gets into a joint and is instantly and explosively superheated, Do you think that could happen on a circuit protected by a 30 amp fuse, again and again without it blowing? *I think the answer is yes if the loop impendence is high and the events are of short enough duration. I'm just afraid that it might be a cable protected by a fuse 10 times that value in a substation! Can't you sleep? -- Graham. %Profound_observation% The water in the cable theory was my first thought too. But can't the OP just turn the whole house off at the CU for an hour or so to determine whether the thump still occurs (or doesn't) even when the house is isolated. That would narrow the fault down a bit. |
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#30
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Dull thud, and all the lights dim momentarily.
On 07/09/2012 23:40, John Williamson wrote:
If his house is like mine (1930s ex-council), the incoming mains cable runs along the end of the 4 house terrace, then along the back wall, branching off to each hosue as it goes. That's typical for LA housing long before the Right To Buy legislation. Ofc, it causes all sorts of issues now, but at the time it seemed perfectly reasonable and economical. |
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#31
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Dull thud, and all the lights dim momentarily.
It happens that Graham. formulated :
I'm just afraid that it might be a cable protected by a fuse 10 times that value in a substation! Why not start by logging the events? My guess would be your mains supply cable, underground. Typically the duration of the event and its timing will vary depending upon the surrounding moisture in the ground. We had a similar problem between us and the sub-station. The brown out would last anywhere between a fraction of a second and several seconds and took months before it became a real issue. Eventually it blasted a large hole in the pavement. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
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#32
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Dull thud, and all the lights dim momentarily.
"Tim Streater" wrote in message ... In article , Graham. wrote: On Sat, 08 Sep 2012 02:50:05 +0100, Bill Wright wrote: Graham. wrote: cartelist Are you a southerner? Bill http://www.merriam-webster.com/dictionary/cartelist cartelist One that belongs to or favors (sic) a cartel. This word doesn't usually appear in our free dictionary, but the definition from our premium Unabridged Dictionary is offered here on a limited basis. Note that some information is displayed differently in the Unabridged. Words a commodity. Whatever next. No such word. 1) double clicks word 2) MT-Newswatcher - Services - Look up in Dictionary 3) Result: No entries found You should JFGI http://dictionary.reference.com/browse/cartelist |
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#33
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Dull thud, and all the lights dim momentarily.
A dull thud can be water hammer from a neighbour?
However that does not usually make the lights dim... if it IS the supply cable then the eventual bag can be quite destructive. It comes down to how fast a fault disconnects and how much moisture there is around - moisture flashes to steam and this can be particularly brutal under a concrete floor. 400A upstream fuse may need 4500A to blow 0.1sec which is 1 megawatt of energy shovelled into moisture which is going to become steam and expand in that 0.1sec. It sounds old enough to have a Paper Insulated Lead Covered (PILC) cable, which might have been bilked by a conservatory spade or simply a joint that is going high resistance, failing, moisture ingress etc. A high impedance supply will cause light dimming with high load, as will a stuffed joint box. Freezers require a fair whack to start which is enough of a load, and can bang if they do not start due to high impedance supply. So the two may be interconnected even if the fridge does not appear to be the fault. Defrost the fridge, switch the conservatory off, diary time. DNO may want them to do that before they come out. Steep sided crater in garden however will not be an asteroid, it will be a cable, wrong blast profile :-) ... could be a mole after Newcastle Brown Ale of course... but that is another matter. |
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#34
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Dull thud, and all the lights dim momentarily.
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#35
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Dull thud, and all the lights dim momentarily.
On Sat, 08 Sep 2012 00:56:09 +0100, The Natural Philosopher wrote:
The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... My bench saw does, 1.2kW induction motor IIRC. No soft start either so it makes quite a bang in itself as well as dipping the lights. Depends. When I had a 1947 vintage lump of iron up a pole to supply me the microwave would do that all on its own. Our "800W" microwave and the Dyson vac does that as well not as much as the bench saw though, though the Dyson is close. The pole transformer is quite small probably only rated at 100A. We do have some E7 heating but I suspect that when that was put in by one of the previous owners they didn't bother telling the REC... -- Cheers Dave. |
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#36
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Dull thud, and all the lights dim momentarily.
On Saturday, September 8, 2012 9:48:43 PM UTC+1, The Natural Philosopher wrote:
Is this one of those cases where the Board* will shove a monitor on the line? *or whichever bunch of charlatans does the same function these days There are online and offline monitors, they can "spike" the line to force a soft fault to become a hard fault. It is a yellow pelicase box, indeed there are a few re fault tracing on LV. The OP should report it at least rather than wait. |
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#37
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Dull thud, and all the lights dim momentarily.
Dave Liquorice wrote:
On Sat, 08 Sep 2012 00:56:09 +0100, The Natural Philosopher wrote: The inrush for an induction motor can be enough to dim the lights for the whole house just on its own... My bench saw does, 1.2kW induction motor IIRC. No soft start either so it makes quite a bang in itself as well as dipping the lights. Depends. When I had a 1947 vintage lump of iron up a pole to supply me the microwave would do that all on its own. Our "800W" microwave and the Dyson vac does that as well not as much as the bench saw though, though the Dyson is close. The pole transformer is quite small probably only rated at 100A. We do have some E7 heating but I suspect that when that was put in by one of the previous owners they didn't bother telling the REC... 100A? when I were a lad.....I don't think it looked like it would do 3KVA frankly... -- Ineptocracy (in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers. |
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#38
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Dull thud, and all the lights dim momentarily.
Graham. writes:
The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. .... The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. I thought water would be involved, and we have had torrential rain recently, however not a drop has fallen this week and I witnessed 3 of these events last night. .... I had exactly this problem 20 years ago soon after I moved in to a house I had just bought. The bangs seemed to be days/weeks apart, though Eventually diagnosed to a blocked underground watercourse running through the front garden, water coming in under the floorboards, and some plonker having left a dangling unterminated live mains cable lying on the rubble under the floor. The end of the cable was clearly split and blown apart. I still haven't worked out the exact mechanism: mains is A/C so electrolysis producing hydrogen shouldn't be the answer. -- Alan J. Wylie http://www.wylie.me.uk/ |
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#39
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Dull thud, and all the lights dim momentarily.
Alan J. Wylie wrote:
Graham. writes: The last 3 or 4 times I have visited them I have heard a thud, and the lights blink at the same moment. This happens maybe twice per hour, but not regularly enough to be able to predict the next event. ... The bangs however seem to emanate under the floor at the back of the house near to, or maybe even beyond the party wall. The elderly lady next door says she hasn't noticed anything. I thought water would be involved, and we have had torrential rain recently, however not a drop has fallen this week and I witnessed 3 of these events last night. ... I had exactly this problem 20 years ago soon after I moved in to a house I had just bought. The bangs seemed to be days/weeks apart, though Eventually diagnosed to a blocked underground watercourse running through the front garden, water coming in under the floorboards, and some plonker having left a dangling unterminated live mains cable lying on the rubble under the floor. The end of the cable was clearly split and blown apart. I still haven't worked out the exact mechanism: mains is A/C so electrolysis producing hydrogen shouldn't be the answer. whats AC got to do with it? -- Ineptocracy (in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers. |
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#40
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Dull thud, and all the lights dim momentarily.
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