RCD tripped by central heating which is on a separate circuit

[Dabbers]

Before I go any further can you tell me where the RCBO is in the DB is it next to the Main switch? i'm wondering if it has been positioned on the busbar which is controlled by the rcd the easiest way to determine this is the switch off the RCD and see if you still have power to the heating system. a picture speaks a thousand words? please let me know of your findings.

 

[Lucien Nunes]

This is a curious point.... It's so fundamental it would be easy to overlook. If the RCBO has been put on the RCD protected side by mistake, then a modest amount of leakage from the heating system would still tend to trip the RCD before the RCBO due to the additional leakage from the rest of the installation.

It seems unlikely that only the RCBO's neutral would be in the wrong busbar as mentioned earlier, because any heating system load should then cause an immediate trip.

 

[Dabbers]

This is a curious point.... It's so fundamental it would be easy to overlook. If the RCBO has been put on the RCD protected side by mistake, then a modest amount of leakage from the heating system would still tend to trip the RCD before the RCBO due to the additional leakage from the rest of the installation.

It seems unlikely that only the RCBO's neutral would be in the wrong busbar as mentioned earlier, because any heating system load should then cause an immediate trip.

My thoughts were the live on the wrong bus bar or neutral in the wrong bar could well be causing this issue I have seen this before the biggest trouble is that the load is very minimal on the heating system.

 

[Markyd]

This is why I asked for a pic 4 days ago

 

[L.F.]

Many apologies for not responding for several days but I've been diverted onto other domestic issues! The consumer unit is not very obvious to follow so I've drawn a schematic to show how it all fits together. It has been modified because originally it was thought that the central heating was causing the tripping problem, so it was put on an RCBO. That didn't cure the problem, so Sockets 2 was moved onto a separate RCD. By the way, MCBs on the Sockets 1 RCD include the fridge, cooker and freezer. The only other item on the Sockets 2 side is the Photovoltaic panels.

I am convinced the Sockets 2 RCD tripping is indirectly connected to the central heating. It trips every day now, between half an hour and an hour after the c/h comes on.

I'd be really grateful for any further suggestions I could discuss with the electrician when he comes later this week.