Tripswitch

DVardysShadow

stevemcol wrote: »

This is an educated guess so I'm happy to be contradicted. RCDs work on current differential (ie they compare what goes out on the live to what comes back on the neutral). Earth leakage to trip these devices is tiny. It's plausible, to me, that when the device is supplying a very small load, it may be slightly more sensitive than when saturated with heavier loads. If you appliance has earth leakage right on the threshold of the RCD, that might be an explanation.

You are on to it. Tripping occurs for 2 reasons

• On premises: Faulty appliance or wiring
• Off Premises: Voltage spikes and transients

I have successfully eliminated the off premises trips by permanently connecting a capacitor of about 4.7uF across Line and Neutral [Do not try this at home with a capacitor you have in a box or have bought from Maplins - you need one which is designed for this type of job]. All my trips since doing this I have been able to explain in terms of appliance issues.

Basically, off premises voltage spikes and transients contain frequencies much higher than the standard 50Hz mains and they find their return path through capacitance between Line and Earth in house wiring. This is registered by the earth leakage breaker as a fault. These spikes would happily go from Line to Neutral, but for the fact that the capacitance of this route in house wiring is much lower than to earth. By connecting a capacitor across Line and Neutral, most of the return current goes via Neutral and is not registered by the earth leakage breaker.

The problem is worse with low load in the house [and on the network generally], because the path from Line to Earth becomes preferentially better for the return current.

muckybutt

Good post there DVS :T

HoolyNI

stevemcol wrote: »

This is an educated guess so I'm happy to be contradicted. RCDs work on current differential (ie they compare what goes out on the live to what comes back on the neutral). Earth leakage to trip these devices is tiny. It's plausible, to me, that when the device is supplying a very small load, it may be slightly more sensitive than when saturated with heavier loads. If you appliance has earth leakage right on the threshold of the RCD, that might be an explanation.

Spot on. No trips last night.

Had the fuse box apart as well and tightened all connections but was no sign of any wear and tear in there thankfully.

stevemcol

DVardysShadow wrote: »

You are on to it. Tripping occurs for 2 reasons

• On premises: Faulty appliance or wiring
• Off Premises: Voltage spikes and transients

I have successfully eliminated the off premises trips by permanently connecting a capacitor of about 4.7uF across Line and Neutral [Do not try this at home with a capacitor you have in a box or have bought from Maplins - you need one which is designed for this type of job]. All my trips since doing this I have been able to explain in terms of appliance issues.

Basically, off premises voltage spikes and transients contain frequencies much higher than the standard 50Hz mains and they find their return path through capacitance between Line and Earth in house wiring. This is registered by the earth leakage breaker as a fault. These spikes would happily go from Line to Neutral, but for the fact that the capacitance of this route in house wiring is much lower than to earth. By connecting a capacitor across Line and Neutral, most of the return current goes via Neutral and is not registered by the earth leakage breaker.

The problem is worse with low load in the house [and on the network generally], because the path from Line to Earth becomes preferentially better for the return current.

Interesting. A 4.7uF cap would present a continous 85VA load but I guess that wouldn't cost you anything since your meter registers power and wouldn't 'see' the leading power factor load.