RCD in consumer unit keeps popping, replaced with new one, still same issue

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AnthonyP

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Morning guys!

Over the weekend I noticed that the 80a RCD in my consumer unit kept tripping. The house doesn't have anything particularly power hungry - no air con, no DIY tools. It even trips in the  middle of the night sometimes (I know so because the house alarm has a little fit when it detects there is no longer any power and switches to the backup battery).

I am wondering what it might be? I replaced the RCD with a second hand one from eBay, seller has 100% feedback and stated it was tested. Is that my issues (I replaced a duff one with a duff one) or is there something else I should look for?

Here's the unit with the switch pointed out. I have a multimeter at the ready to test, just tell me what to target.

zezbHiA.jpg.266aa46e25711e7d5344f98016801566.jpg


a0kzlyd.jpg.09a3e65df5a9ac92d59b185ee64da5c0.jpg


Thanks in advance!

:)

 
The rcd is there to detect an earth leakage current. the fact it trips does NOT indicate that the RCD is faulty (as you have found out)

Instead it is showing that something somewhere in your house has an earth leakage fault. That might be a faulty appliance plugged in or it might be a fault with the fixed wiring wiring in the house.

Start by unplugging EVERYTHING and see if it still trips. If not plug things back in one at a time and see what makes it trip.  It can take a long time this trial and error method. Do you have an insulation tester? 

P.S I love the bodged "busbar" on the RCD side of the CU. The left hand busbar is not much better, what's with mcb's 7 and 8 that are from the RCD, a right mixed up bodge that CU

 
Last edited by a moderator:
Your consumer unit has been extensively and inappropriately modified, presumably at a time when new electrical work was being done.

I attach a diagram to show that a fault on certain circuits only may be causing the RCD to trip.

As identified above you can use trial and error over time to try to identify specifically on which circuit the fault is located but faults to neutral will not be found by the method of switching off individual circuits for a period.  Unplugging items connected to sockets or perhaps ensuring that the switch on what is probably an electric shower circuit may help.

Intermittent faults are hard to identify as the fault may not be present until the point of failure.

An electrician with an insulation resistance tester / earth leakage clamp meter may be able to narrow down the fault far more quickly.  This is your best method of approach.

Common causes of RCD tripping are water getting into a connection and cable damage from overheating.

The fault is often in an appliance rather than the circuit.

A leak of 30mA of current to earth will cause an RCD to trip.  This is to protect people from the chance of death by electric shock.

The RCD is performing its intended purpose correctly.

Bad CU1.jpg

 
Thanks for all the comments guys. I will do some trial and error testing and switch on / off some MCBs to see how the RCD reacts to it over the course of the next several days. Will report back anyhow. Oh and will get that busbar sorted!

 
AnthonyP said:
Thanks for all the comments guys. I will do some trial and error testing and switch on / off some MCBs to see how the RCD reacts to it over the course of the next several days. Will report back anyhow. Oh and will get that busbar sorted!
Click to expand...


Please leave that to a spark ............................

Ardet R said:
Your consumer unit has been extensively and inappropriately modified, presumably at a time when new electrical work was being done.

I attach a diagram to show that a fault on certain circuits only may be causing the RCD to trip.

As identified above you can use trial and error over time to try to identify specifically on which circuit the fault is located but faults to neutral will not be found by the method of switching off individual circuits for a period.  Unplugging items connected to sockets or perhaps ensuring that the switch on what is probably an electric shower circuit may help.

Intermittent faults are hard to identify as the fault may not be present until the point of failure.

An electrician with an insulation resistance tester / earth leakage clamp meter may be able to narrow down the fault far more quickly.  This is your best method of approach.

Common causes of RCD tripping are water getting into a connection and cable damage from overheating.

The fault is often in an appliance rather than the circuit.

A leak of 30mA of current to earth will cause an RCD to trip.  This is to protect people from the chance of death by electric shock.

The RCD is performing its intended purpose correctly.

View attachment 9445
Click to expand...




Not sure I agree with the arrows ........... could it be that the 2 MCB's to the left of the RCD are also downstream of the RCD? I think so

 
Murdoch said:
Please leave that to a spark ............................

Not sure I agree with the arrows ........... could it be that the 2 MCB's to the left of the RCD are also downstream of the RCD? I think so
Click to expand...
The arrows are just to say from this MCB to that MCB.  The white text box is meant to spread over the range of circuits covered.  The black bar is intended to indicate where the RCD protection stops.

So there are six circuits protected by the RCD the four to the right and the two to the left, extremely unconventional and pretty much wholly unnecessary.  busbars are not expensive and if someone was modifying socket circuits and adding a shower then they should have been prepared with the basics.  (Though I did have to dash out and get a busbar once when I was caught out by someone having cut the busbar short of the two empty spaces. :angry: )

 
AnthonyP said:
Morning guys!

Over the weekend I noticed that the 80a RCD in my consumer unit kept tripping. The house doesn't have anything particularly power hungry - no air con, no DIY tools. It even trips in the  middle of the night sometimes (I know so because the house alarm has a little fit when it detects there is no longer any power and switches to the backup battery).

I am wondering what it might be? I replaced the RCD with a second hand one from eBay, seller has 100% feedback and stated it was tested. Is that my issues (I replaced a duff one with a duff one) or is there something else I should look for?

Here's the unit with the switch pointed out. I have a multimeter at the ready to test, just tell me what to target.

Thanks in advance!

:)
Click to expand...


I would have started with testing the RCD to see if it is operating correctly first. For this you will need an RCD tested that includes ramp test. Then test the circuits, RCD's trip with miliamps, as they are designed to stop you being killed. (electricity will kill a healthy adult in under a second with far less than 1amp). The RCD is a 30ma NOT an 80A. 80A is the maximum load it can safely disconnect not the current that makes it trip. The logic of what you have tried so far to solve your problem is a waste of time and money.

Doc H.

 
so RCD randomly trips at any time of day, can you rest it immediately? If so I would bet on a dodgy fridge or freezer, they are the only appliances that run all day / night in most houses.

 
I was trying to figure out why there was a connection from the bottom of the RCD   ,,,off to the left  ....didn't realize it was connected  to two MCBs ....I thought it went up behind somewhere .       I've NEVER seen protected  MCBs  on BOTH sides of an RCD before .   :C :wacko:

I was about to comment that there were some rogue neutrals in the  RCD neutral bar  .  Four circuits but six neutrals .  

 
Last edited by a moderator:
Morning folks. I have been a recommended a good electrician but he is only able to come and see me next Thursday. :(

While I am waiting I would like to do more fault finding, because the issue is that as soon as the RCD trips, the house alarm goes ballistic because it thinks somebody is trying to bypass it. It went off once at 3am and today at 7am....I apologised to the neighbours by they were not happy (understandably).

Went to bed last night and before doing so, I switched off the 4 x MCBs to the right of the RCD:

1. Electric shower (we never use this, it does work, but we just don't use it)

2. Sockets first floor (on the image it is on, ignore, at the time of going to bed it was down / off)

3. Lights

4. Wall lights

So only the Ring Circuit 1st Floor and Ring Circuit Ground Floor was on. And at 7am, the RCD tripped.

yA5Nazh.jpg.4d854c334faab9e52404ad8e6611e95e.jpg


My plan is to repeat the above experiment again, but this time, in addition to having the 4 x MCBs to the right of the RCD in the off position, I shall disconnect anything plugged into the mains ion the 1st floor.

I am wondering if a lose wire is touching the back box or earth? We had some screwless sockets installed about 7 months ago, perhaps that is the cause?

 
You will be very lucky to find it without test gear.

About the only thing I would say worth a random check is if you have any outside lighting on the RCD make sure it's dry inside.

BTW, The kitchen sockets are the ones I would most want to be on the RCD.

 
Last edited by a moderator:
AnthonyP said:
Thanks for all the comments guys. I will do some trial and error testing and switch on / off some MCBs to see how the RCD reacts to it over the course of the next several days. Will report back anyhow. Oh and will get that busbar sorted!
Click to expand...


Oh dear. I can see this ending badly.

 
Tony S said:
Oh dear. I can see this ending badly.
Click to expand...
Why? Is it not a case of switching the unit off via the main switch (far left of CU), using a multi meter to see if voltage is flowing through anywhere I will be touching, then unscrewing the screws with an insulated screw driver and inserting correctly cut busbar in before tightening it back up? Is that not the correct way to do this? I changed the RCD in a similar way.

binky said:
so it isn't those 4 ccts (or unlikely) what you didn't do was isolate the other 2 ccts on the RCD - suggest you try those tonight .
Click to expand...
I will try the other two tonight, will see what happens. I also need to try the 4 on the right AND have everything out the sockets.

 

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