HI. First of all my electrical knowledge might not be that great so forgive me if I use a wrong term or anything. My house fuse box has 2 main circuit breaker(RCD ?) and a few smaller circuit breakers. Recently one of the RCDs trips like once or twice a week at a random time. When it has tripped I have not been using any iron,water heater, washing machine or dryer, and the only things that was on was the fridge and everything else was off(including lights). So when it tripped I tried to use the process of elimination, I turned everything off and then I restarted the RCD ( the test button works as it should btw) and then I turned every light and socket and appliance one at a time every 15 minutes, but it didnt trip. Since each time that it trips i'm not using many appliances i dont think it is due to overload. An electrician came and looked at it and he couldnt find any problem, but the RCD still trips randomly every few days. can it be the RCD is faulty? Any advice and help would be appreciated. thank you
My rcd trips every few days
- Thread starter darkrcd
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Hi
You have done most things to track down the fault.
You are left with the following.
Faulty RCD. Do you have a known good one to try in its place.
Intermittent Tripping is caused by several other things.
Two appliances with low level leakage. They will both run individually at less than 30mA levels. But both on together with go over the 30mA trip setting.
You mentioned the Fridge. It is a time related problem. After 15 min there may be moisture collecting inside the cabinate around some live terminals. Or at the rear where the refrigerant return line frosts up and can then drip onto a terminal box.
The other time related thing is, componants overheating in a partial burnout situation. The heat builds up and an insulation leak gets worse and is detected by the RCD.
Fridges Immersion heaters and Washing Machines are the candidates for dampness.
Regards
Mike
You have done most things to track down the fault.
You are left with the following.
Faulty RCD. Do you have a known good one to try in its place.
Intermittent Tripping is caused by several other things.
Two appliances with low level leakage. They will both run individually at less than 30mA levels. But both on together with go over the 30mA trip setting.
You mentioned the Fridge. It is a time related problem. After 15 min there may be moisture collecting inside the cabinate around some live terminals. Or at the rear where the refrigerant return line frosts up and can then drip onto a terminal box.
The other time related thing is, componants overheating in a partial burnout situation. The heat builds up and an insulation leak gets worse and is detected by the RCD.
Fridges Immersion heaters and Washing Machines are the candidates for dampness.
Regards
Mike
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There are two main scenarios.
1) Something with a timer is tripping the RCD.
2) Something external is tripping the RCD.
1) Items like freezers often have auto de-frost sometimes called frost free. At set intervals the freezer will heat an element clearing frost then return to cooling again. If the element is faulty it would be hard to find. In UK we are permitted sockets without RCD for fridge and freezer as long as marked only for use with them.
2) Spikes one the power lines can often trip RCD's in my house resetting one RCD will often trip the other one as everything is turned on together.
All RCD's are not equal. Some can reject spikes better than others. The X-Pole RCD has a monitor built in to show when a combination of items is bringing the system close to the point of tripping and trips at between 90% and 100% of designed leakage where most trip between 50% and 100%. There are even auto resetting RCD's however the price means one would only use them in places like remote pumping stations.
This old write up on the X-Pole may help you understand how this random tripping is quite normal with many RCD's.
This RCD in UK costs around £350 compared with £40 for a standard one. Not sure for a domestic I like the idea of auto reset. But just trying to show that although they may all say 30ma within 40 ms they are not all the same.
1) Something with a timer is tripping the RCD.
2) Something external is tripping the RCD.
1) Items like freezers often have auto de-frost sometimes called frost free. At set intervals the freezer will heat an element clearing frost then return to cooling again. If the element is faulty it would be hard to find. In UK we are permitted sockets without RCD for fridge and freezer as long as marked only for use with them.
2) Spikes one the power lines can often trip RCD's in my house resetting one RCD will often trip the other one as everything is turned on together.
All RCD's are not equal. Some can reject spikes better than others. The X-Pole RCD has a monitor built in to show when a combination of items is bringing the system close to the point of tripping and trips at between 90% and 100% of designed leakage where most trip between 50% and 100%. There are even auto resetting RCD's however the price means one would only use them in places like remote pumping stations.
This old write up on the X-Pole may help you understand how this random tripping is quite normal with many RCD's.
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If you have a spare RCD and you can get the pinout of the Integrated Circuit used in it, you can measure a voltage which shows how close the RCD is to tripping.
There might be various sources contributing to leakage current and this will be more useful than the go/no-go, trip or not trip you currently have.
If you do try a fix, from a statistical point of view and with failures once or twice a week, if you have no failures for 9 to 20 consecutive days, you have a high likelihood of the problem being gone.
I have at least one GFCI in the basement that I will do this modification on. You need two components to measure current imbalance: a toroidal transformer and an amplifier so you can measure the imbalance with a commonly available test meters. Fluke makes a meter for this but the cost is way up there.
There might be various sources contributing to leakage current and this will be more useful than the go/no-go, trip or not trip you currently have.
If you do try a fix, from a statistical point of view and with failures once or twice a week, if you have no failures for 9 to 20 consecutive days, you have a high likelihood of the problem being gone.
I have at least one GFCI in the basement that I will do this modification on. You need two components to measure current imbalance: a toroidal transformer and an amplifier so you can measure the imbalance with a commonly available test meters. Fluke makes a meter for this but the cost is way up there.
