if a RCD trips and needs resetting, is there always a fault/reason why it trips? or can the rcd itself just become faulty?
Thanks for your help again
Thanks for your help again
RCD question
- Thread starter reneel
- Start date
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It is possible that the RCD is faulty, however the most likely cause is a fault with the wiring or an appliance.
oh i see, thanks for your help.
i know fuses can blow due to surges and not always because of a wiring/appliance fault - rcd's then only trip if a fault...
to test an rcd you push the hutton in and it must pop out, is that correct?
i know fuses can blow due to surges and not always because of a wiring/appliance fault - rcd's then only trip if a fault...
to test an rcd you push the hutton in and it must pop out, is that correct?
Yes, pressing the test button should result in the RCD switching off.
However this only tests the mechanism, and won't reveal faults such as not tripping quickly enough or at the correct current.
The fact you don't have main equipotential bonding to the gas supply suggests that a proper inspection and test of the installation is long overdue.
However this only tests the mechanism, and won't reveal faults such as not tripping quickly enough or at the correct current.
The fact you don't have main equipotential bonding to the gas supply suggests that a proper inspection and test of the installation is long overdue.
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sorry I don't have a problem with the rcd tripping i was just enquiring as have read some bits about them and wondered why they tripped etc in general
is it true they trip due to a difference between live and neutral? what exactly does that mean! or due to an earth leakage? again, what exactly is that in laymans?
is it true they trip due to a difference between live and neutral? what exactly does that mean! or due to an earth leakage? again, what exactly is that in laymans?
thnaks that's good information
you know when a fuse blows - you can test an appliance or cable to see if there's a short circuit or can remove that appliance, replace fuse and if doesn't blow again you find the faulty appliance, how do you check for a faulty appliance if it causes a RCD to trip?
you know when a fuse blows - you can test an appliance or cable to see if there's a short circuit or can remove that appliance, replace fuse and if doesn't blow again you find the faulty appliance, how do you check for a faulty appliance if it causes a RCD to trip?
That can be quite tricky if the fault is intermittant. Even if its a constant fault down to earth it could be tricky if its in a washing machine element thats only in circuit for part of the cycle (the same would be true of it was taking out the MCB with a direct short)
Process of elimination, suspecting appliances which use water or have heating elements and sensible use of insulation resisatnce tests
And complicated by the fact that a fault ( neutral to earth ) will trip the RCD when an appliance on any circuit other than the one with the fault but protected by the RCD is switched on.
ok thanks for your help
what exactly is an insulation resistance test? i have heard of polarity, eart continuity and short circuit tests but not insulation resistance.
what exactly is an insulation resistance test? i have heard of polarity, eart continuity and short circuit tests but not insulation resistance.
The resistance of the insulation between two conductors which must not touch each other.
If it is too low too much current flows where no current should flow.
An insulation resistance test (AKA Megger) is basically a test of the insulation strength between conductors. The tester puts a voltage down the cable, usually 500vDC and uses this to determine the insulation resistance.
ok thanks - i understand, so basicaly you test between live and neutral, live and earth, neutral and earth and want a very low ohms reading?
NO you want a very HIGH ohms reading. HIGH ohms high resistance = low current.
Also you need to test at mains voltage or higher as defective insulation can measure OK at low voltages used my a multimeter as the insulation does not break at low voltage but will break at mains voltage.
This may help you.
http://www.tlc-direct.co.uk/Book/8.5.1.htm
Its a little out of date, but the principles are correct.
http://www.tlc-direct.co.uk/Book/8.5.1.htm
Its a little out of date, but the principles are correct.
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