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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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RCD tripping
One of the RCDs in the split consumer unit tripped yesterday. It was the
side I'd previously had a problem with concerning the lighting wiring. Not a good time for a wiring check... However, a quick check turning off and then on each MCB in turn on that side showed it wasn't the lighting wiring. I'd got out a 10" desk fan which hadn't been used since last summer, and that had been on an hour when it tripped the RCD. Resetting the RCD and turning on the fan had it tripping again in a few minutes. I've just dismantled the fan (not easy - many hidden plastic catches and unreachable circlips) and put it on in free air. After an hour the outside of the windings were at 87 deg C, and the laminations furthest from them were at 67 dec C. I assume that if left on the enamel on the wires would have reached a high enough temperature to fail and rubbed against the laminations (which are earthed), so tripping the RCD. Fortunately, I've always got a couple of spare fans and the tip is now open for electrical goods. -- Jeff |
#2
Posted to uk.d-i-y
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RCD tripping
On 29/05/2020 10:41, Jeff Layman wrote:
One of the RCDs in the split consumer unit tripped yesterday. It was the side I'd previously had a problem with concerning the lighting wiring. Not a good time for a wiring check... However, a quick check turning off and then on each MCB in turn on that side showed it wasn't the lighting wiring. I'd got out a 10" desk fan which hadn't been used since last summer, and that had been on an hour when it tripped the RCD. Resetting the RCD and turning on the fan had it tripping again in a few minutes. I've just dismantled the fan (not easy - many hidden plastic catches and unreachable circlips) and put it on in free air. After an hour the outside of the windings were at 87 deg C, and the laminations furthest from them were at 67 dec C. I assume that if left on the enamel on the wires would have reached a high enough temperature to fail and rubbed against the laminations (which are earthed), so tripping the RCD. Fortunately, I've always got a couple of spare fans and the tip is now open for electrical goods. My last and worst RCD tripper was an earth neutral short. Other culprit have been wet electrics due to weeping plumbing, a stove element whose insulation was breaking down, and a burned out washing machine motor that showed a 2k short to earth on the armature windings. Its easy enough to pop a meter across a disconnected fan switch it to 'on' and see if it has leakage -- There is nothing a fleet of dispatchable nuclear power plants cannot do that cannot be done worse and more expensively and with higher carbon emissions and more adverse environmental impact by adding intermittent renewable energy. |
#3
Posted to uk.d-i-y
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RCD tripping
On Fri, 29 May 2020 11:52:14 +0100, The Natural Philosopher wrote:
On 29/05/2020 10:41, Jeff Layman wrote: One of the RCDs in the split consumer unit tripped yesterday. It was the side I'd previously had a problem with concerning the lighting wiring. Not a good time for a wiring check... However, a quick check turning off and then on each MCB in turn on that side showed it wasn't the lighting wiring. I'd got out a 10" desk fan which hadn't been used since last summer, and that had been on an hour when it tripped the RCD. Resetting the RCD and turning on the fan had it tripping again in a few minutes. I've just dismantled the fan (not easy - many hidden plastic catches and unreachable circlips) and put it on in free air. After an hour the outside of the windings were at 87 deg C, and the laminations furthest from them were at 67 dec C. I assume that if left on the enamel on the wires would have reached a high enough temperature to fail and rubbed against the laminations (which are earthed), so tripping the RCD. Fortunately, I've always got a couple of spare fans and the tip is now open for electrical goods. My last and worst RCD tripper was an earth neutral short. Other culprit have been wet electrics due to weeping plumbing, a stove element whose insulation was breaking down, and a burned out washing machine motor that showed a 2k short to earth on the armature windings. Its easy enough to pop a meter across a disconnected fan switch it to 'on' and see if it has leakage Not so obvious when the unit is cold. |
#4
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RCD tripping
On 29/05/2020 12:23, Smolley wrote:
On Fri, 29 May 2020 11:52:14 +0100, The Natural Philosopher wrote: On 29/05/2020 10:41, Jeff Layman wrote: One of the RCDs in the split consumer unit tripped yesterday. It was the side I'd previously had a problem with concerning the lighting wiring. Not a good time for a wiring check... However, a quick check turning off and then on each MCB in turn on that side showed it wasn't the lighting wiring. I'd got out a 10" desk fan which hadn't been used since last summer, and that had been on an hour when it tripped the RCD. Resetting the RCD and turning on the fan had it tripping again in a few minutes. I've just dismantled the fan (not easy - many hidden plastic catches and unreachable circlips) and put it on in free air. After an hour the outside of the windings were at 87 deg C, and the laminations furthest from them were at 67 dec C. I assume that if left on the enamel on the wires would have reached a high enough temperature to fail and rubbed against the laminations (which are earthed), so tripping the RCD. Fortunately, I've always got a couple of spare fans and the tip is now open for electrical goods. My last and worst RCD tripper was an earth neutral short. Other culprit have been wet electrics due to weeping plumbing, a stove element whose insulation was breaking down, and a burned out washing machine motor that showed a 2k short to earth on the armature windings. Its easy enough to pop a meter across a disconnected fan switch it to 'on' and see if it has leakage Not so obvious when the unit is cold. I have yet to see a direct short to earth that vanished when cold as a failure mode on ANYTHING -- You can get much farther with a kind word and a gun than you can with a kind word alone. Al Capone |
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