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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Do circuit breakers die of old age?
I'm having intermittent problems with either the main breaker or the
ring main breaker tripping out. Main breaker is a Wylex 80/2 30m/a trip - the ring breaker is a 30A. A local spark has been around to carry out an hours worth of testing to ensure nothing silly had been done by the previous owners and other than saying that the ring breaker is normally 32A and that it's not such a good idea to have a RCD type main breaker all is as it should be. I work from home most days and have approximately 6 workstations in my home office, occasionally they are all on concurrently along with a number of associated small power supplies feeding printers etc - most of the time all is well however this morning turning on a single workstation tripped the ring breaker. Reset ring breaker then tried the workstation again and it tripped the main breaker, reset main breaker and tried another workstation and all was well - then turned on the first workstation again and again all was well. Sparky suggested having a dedicated ring installed just for my office so I could within reason have as many workstations on as I needed - but if the main breaker trips now with a very light load it will still trip even if I did have a separate ring. I've unplugged everything else that is connected to the ring such as TVs fridges etc and yet I can still - but only occasionally get the ring breaker or main breaker to trip when just turning on a signal workstation. The ring breaker has been changed for another 30A and it still tripped either itself or the main - the ring breaker has also been upped to a 40A and it still exhibits the same intermittent trip issue when different workstations are powered up. The only component not changed is the main breaker; do they have a life span of x years? - the board takes type 2 breakers which I have been told are like rocking horse droppings to find these days (seams to be plenty on ebay) - I'm tempted to get the whole board updated. |
#2
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Do circuit breakers die of old age?
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#3
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Do circuit breakers die of old age?
wrote in message oups.com... I'm having intermittent problems with either the main breaker or the ring main breaker tripping out. snip The ring breaker has been changed for another 30A and it still tripped either itself or the main - the ring breaker has also been upped to a 40A and it still exhibits the same intermittent trip issue when different workstations are powered up. The only component not changed is the main breaker; do they have a life span of x years? - the board takes type 2 breakers which I have been told are like rocking horse droppings to find these days (seams to be plenty on ebay) - I'm tempted to get the whole board updated. Lets get this right. You have an RCB which is the "main" incoming switch for your consumer unit and an MCB for the ring circuit. That on occasions either the MCB or the RCD will trip if you turn on a workstation. First of all when you say "turn on" a work station, is power already going to the PS and you're hitting the (soft) start button, or are you turning on the switch on the PS itself? Secondly does the MCB trip with just one or 2 workstations connected? Are all the workstations the same? I've had an RCDs trip when I've switched on at the PS which I assumed was due to suppression within the PS causing asymmetric current spikes on live and neutral. Hitting the soft start button on the front has never caused me any problems. Also, if needed, switching on at the wall helped because on mains socket outlets only the live is switched. For the MCB to trip it must be sensing some large current. The only thing I can think of is that some old power supplies had awful power factors, making the sensed current higher. |
#4
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Do circuit breakers die of old age?
What type (maker), and what tripping characteristic - Type 1, 2, 3, B, C or D? The MCB trips you're getting are puzzling. One of the following must apply: - you have a faulty piece of equipment with an intermittent short, etc., or a similar fault in the fixed wiring; The breakers are all Type 2 - i'm not aware what this signifies but it did cross my mind that they might be simillar to standard fuses insomuchas they can be slow blow, quick blow etc - at any one time i might have 10 workstations plugged in but not powered up - however i assume power is still going to their power supplies - i would imagine there to be a bit of a "peak inrush" (i forget the exact term) - demand if all of them had powered applied at the same time (this is what happens when i try to reset the trips) - maybe i need a slow blow type breaker? BTW changing the MCB to 40 A could be dangerous unless anyone's done some design calculations to show that it's OK. It makes the whole circuit non-standard and unlikely to comply with the wiring regs if the circuit's wired in 2.5 mm^2 twin & earth, as is usual. 40A breaker was swopped just as a test, it's back to the 30A now. Upgrade to a modern split-load board with a separate non-RCD protected socket circuit for your office. The sockets will need to be labelled as not suitable for portable equipment outdoors, and Section 607 high-integrity earthing should be applied. All other sockets in the house should be on the RCD protected side. (This assumes TN earthing. If it's a TT-earthed installation a 2-RCD set-up will be needed, or a supply upgrade to PME if available.) Do all new installations/upgrades include RCD main breakers ? |
#5
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Do circuit breakers die of old age?
Lets get this right. You have an RCB which is the "main" incoming switch for your consumer unit and an MCB for the ring circuit. Correct That on occasions either the MCB or the RCD will trip if you turn on a workstation. Correct First of all when you say "turn on" a work station, is power already going to the PS and you're hitting the (soft) start button, or are you turning on the switch on the PS itself? Secondly does the MCB trip with just one or 2 workstations connected? Are all the workstations the same? I have a number of workstations, any of them has been known to trip either breaker - they are less prone to trip if they are turned on via the wall socket and then via the soft start. All have 350 - 450W internal PSUs. |
#6
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Do circuit breakers die of old age?
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#8
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Do circuit breakers die of old age?
What is the trip current for the RCD? If 30mA then the RCD problem is
easy to explain. Computer power supplies tend to be of the switch-mode type rather than linear. Anyway the point is that switch-mode power supplies generally have a relatively high earth leakage current (typically 3-5mA). This means that it isn't at all surprising that you can trip the RCD occasionally as you must have 2 or 3 power supplies per workstation if you include printers, fax, monitors etc. To fix this you need not to have an RCD seeing the combined leakage current, i.e. get rid of the RCD incomer. Alternatively you may be able to swap it for an RCD with a higher trip current to avoid nuisance trips (100mA). Bear in mind that this will then mean none of your circuits is protected by a 30mA RCD and so additional RCD protection is required for any circuits where equipment may be used outside. This can be fixed by using RCBOs for other socket circuits. As to why the MCB trips, no obvious reason, should only be overcurrent. I'd either test all the power supplies or at least try to identify whether a particular psu is causing the problem by switching them one one at a time (with all the others disconnected). Testing is better. Fash |
#9
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Do circuit breakers die of old age?
The ring breaker has been changed for another 30A and it still tripped either itself or the main - the ring breaker has also been upped to a 40A Did you, or anyone else, calculate whether the wiring is suitable for this first? What calculation would that be ? - I've simply exchanged a suspect 32A breaker for a known good 40A one as part of a process of ellimination - the same issues were found so i changed it back. I have 4 TFTs - no CRTs - a small laser printer and couple of hub/routers + a max of 8 workstations. I normally use the soft start buttons to power up - therefore all of the internal PSUs are being fed from the ring but taking no real load - very often i have all workstations running without issue and can turn on/off via soft start without tripping yet at times even if i just have a couple connected to the ring it blows. Looks like a non RCD ring + indivdual on/off for each workstation is the way to go ? |
#10
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Do circuit breakers die of old age?
To fix this you need not to have an RCD seeing the combined leakage current, i.e. get rid of the RCD incomer. Alternatively you may be able to swap it for an RCD with a higher trip current to avoid nuisance trips (100mA). I did half come to this conclusion a few weeks ago but have managed to soldier on since - are 100ma RCDs commonly used/easy to obtain? - all i have found are 30ma versions. |
#11
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Do circuit breakers die of old age?
On 9 Nov 2006 10:38:46 -0800 someone who may be
wrote this:- Did you, or anyone else, calculate whether the wiring is suitable for this first? What calculation would that be ? The rather obvious cable sizing calculations. Had the wiring caught fire during this "process of elimination", which presumably lasted for some time, you might have been in a difficult position. I have 4 TFTs - no CRTs - a small laser printer and couple of hub/routers + a max of 8 workstations. Sounds like you need the specialist advice of an electrical designer. Looks like a non RCD ring + indivdual on/off for each workstation is the way to go ? Possibly. -- David Hansen, Edinburgh I will *always* explain revoked encryption keys, unless RIP prevents me http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54 |
#12
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Do circuit breakers die of old age?
David Hansen wrote: On 9 Nov 2006 10:38:46 -0800 someone who may be wrote this:- Did you, or anyone else, calculate whether the wiring is suitable for this first? What calculation would that be ? The rather obvious cable sizing calculations. Had the wiring caught fire during this "process of elimination", which presumably lasted for some time, you might have been in a difficult position. I have 4 TFTs - no CRTs - a small laser printer and couple of hub/routers + a max of 8 workstations. Sounds like you need the specialist advice of an electrical designer. Looks like a non RCD ring + indivdual on/off for each workstation is the way to go ? Possibly. The leakage current isn't affected by whether there is load or not from the power supply. And yes it is fairly easy to get hold of 100mA RCDs. Try http://www.tlc-direct.co.uk/Main_Ind...cds/index.html just don't expect screwfix to stock them. However screwfix do stock plenty of 1 module RCBOs which you could then use to protect your socket circuits that don't feed your office. Still worries me that the mcb was tripping. Fash |
#13
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Do circuit breakers die of old age?
"Fash" wrote in message ups.com... David Hansen wrote: On 9 Nov 2006 10:38:46 -0800 someone who may be wrote this:- Did you, or anyone else, calculate whether the wiring is suitable for this first? What calculation would that be ? The rather obvious cable sizing calculations. Had the wiring caught fire during this "process of elimination", which presumably lasted for some time, you might have been in a difficult position. I have 4 TFTs - no CRTs - a small laser printer and couple of hub/routers + a max of 8 workstations. Sounds like you need the specialist advice of an electrical designer. Looks like a non RCD ring + indivdual on/off for each workstation is the way to go ? Possibly. The leakage current isn't affected by whether there is load or not from the power supply. And yes it is fairly easy to get hold of 100mA RCDs. Try http://www.tlc-direct.co.uk/Main_Ind...cds/index.html just don't expect screwfix to stock them. However screwfix do stock plenty of 1 module RCBOs which you could then use to protect your socket circuits that don't feed your office. Still worries me that the mcb was tripping. It would concern me too. There is no reason why a PC power supply should trip a 30A breaker. I would like to know what these workstations are so I can avoid them. As for a solution either.. fix the PSUs in the workstations or use one or more UPS to power the workstations. |
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