Both RCDS Tripping

[Stephenge]

I have a problem with two separate rcds tripping, both are from the meter, one consumer unit in the house and one in the workshop 30m from the house. If the workshop rcd trips it also trips the house rcd. both consumer units are fed direct from the meter, the workshop having a 80a isolator. Cannot work out why the house rcd trips. Thanks in advance for any advice.

 

[James]

I would be starting by isolating the 2 boards and loop testing L to E and L to N
sounds like a N to E fault, possibly combined with a poor Earth.

 

[buzzlightyear]

If the workshop rcd trips it also trips the house rcd. both consumer units are fed direct from the meter

are both are on rcd same circuit?????

 

[Mikegh]

That wouldn't be a common fault one if the boards are independently wired

I'd prob be doing a quick examination of the boards and main supply point and earthing

Fault loop and IR readings

Rcd tests

 

[Mikegh]

Ime ^^ typo

 

[Stephenge]

are both are on rcd same circuit?????

No, separate supplies to each consumer unit from the meter

 

[UNG]

Has there been any recent work done or equipment installed that may affect the RCD's

 

[Stephenge]

Has there been any recent work done or equipment installed that may affect the RCD's

No, I don't think so, it's on my cousins farm, it seems to be a fault with a compressor, but cannot figure out why it trips the house RCD.

 

[buzzlightyear]

No, I don't think so, it's on my cousins farm, it seems to be a fault with a compressor, but cannot figure out why it trips the house RCD.

Can you put a pic up so that we can see the set up.

 

[Stephenge]

Can you put a pic up so that we can see the set up.

Will add a photo next time I go up the farm

 

[buzzlightyear]

Will add a photo next time I go up the farm

But have you asked him. Lol.

 

[Stephenge]

But have you asked him. Lol.

Yes, the wiring has not been altered in years, but the air compressor has started to trip the rcd both in the workshop and the house even though they are supplied from the meter box on separate supplies but from the same main fuse. I suspect a bad main earth, so will try an earth loop test.

 

[pc1966]

If you get a big dV/dt on the supply that can push an RCD over the trip threshold, so it might be the reason. however I would expect there to be some serious light dimming or other problems if that was the case!

It might be worth checking what the leakage normally is in the house to see if it is close to the RCD trip point.

Also in case there is a poor joint in the supply, try monitoring the volts and switching on a big load like cooker or similar (crude version of a PSSC test) and see if it is in line with a MFT's measurement of supply impedance.

 

[arashabb]

Hello everyone,
I am facing a similar problem in a bigger scale. we were told by a facility management in a building that (sometimes), 3 RCDs, on 3 different DBs trip at the same time! ( Normal ground floor DB, emergency DB in GF, Emergency DB in basement). then they switch them back on and everything works for another 2 weeks or so. ( normal DBs are fed through normal MDB and Emergency DBs through EMDB)

I am assuming there is a minor earth fault on one of the circuits in one of these panels and because of equipotential bonding throughout the whole installation via cable trays, GI trunkings and GI pipes, it somehow completes the circuit through other panels as well. can not explain it in any other way !

I guess the problem might be a minor loose connection on a connection terminal to equipment/socket or a slightly damaged wire somewhere in GI trunkings but not easy to do visual inspection on each circuit connection points either. (such as for the revolving door) and because it is not happening all the time, cant find it by a testing equipment either.

Any suggestion on why it is happening and how to find the solution?