RCD tripping... What other problem determination can I do?

[mikeyking]

Unfortunately my electrician is too busy installing EVs so I've kinda been left on my own for now! I have an issue where the RCD labelled #1 in the attached picture trips as soon as I attempt to turn the immersion heater on. I've had the immersion heater replaced (well, I couldn't get it out of the hot water tank and nor could my plumber so he replaced the tank and immersion heater) but it still trips.

I did have a MyEnergi Eddi installed to divert excess solar to the immersion heater, but I've now taken that out of the equation and the immersion heater is wired directly into the correct switch. The heating system will run fine, pump etc. off the same circuit but as soon as I turn the immersion switch on the RCD trips.

I've replaced the switch, checked all the connections and can't see any issue. Does this seem like a neutral leak somewhere? How can I find out where that is?

Any advice would be appreciated and not legally binding

 

[LastManOnline]

Unfortunately my electrician is too busy installing EVs so I've kinda been left on my own for now! I have an issue where the RCD labelled #1 in the attached picture trips as soon as I attempt to turn the immersion heater on. I've had the immersion heater replaced (well, I couldn't get it out of the hot water tank and nor could my plumber so he replaced the tank and immersion heater) but it still trips.

I did have a MyEnergi Eddi installed to divert excess solar to the immersion heater, but I've now taken that out of the equation and the immersion heater is wired directly into the correct switch. The heating system will run fine, pump etc. off the same circuit but as soon as I turn the immersion switch on the RCD trips.

I've replaced the switch, checked all the connections and can't see any issue. Does this seem like a neutral leak somewhere? How can I find out where that is?

Any advice would be appreciated and not legally binding

View attachment 97124

You,ve had the immersion heater replaced (and presumably it came with flex attached) and the immersion switch replaced .So in principle its a brand new system.Should all work fine.Unusual its not.Why is it tripping?

Three possibilities come to my mind..

First, you have ended up with some new but defective parts.

Second ,either you or the plumber have inadvertently connected something incorrectly and diverted current via the earth causing the rcd to trip

Third, there is possibly an N to E fault in another circuit .These faults normally only manifest themselves when a large load is switched on in a healthy circuit.

 

[mikeyking]

Third, there is possibly an N to E fault in another circuit .These faults normally only manifest themselves when a large load is switched on in a healthy circuit.

Thanks for the quick response - I think it's the third option unfortunately. Maybe a new defective immersion heater but that was the reason I replaced it because it was tripping previously. So the assumption was it was the immersion heater tripping. Now it's been replaced with new the same fault is there so looks like the heater wasn't the cause previously.

Unlikely to be number 2 as both the plumber and myself have rewired it. It's a new flex as well between the immersion and switch so not that.

So, looks like a N to E fault - do I need a sparky with specialist equipment to diagnose where that fault is?

 

[LastManOnline]

Thanks for the quick response - I think it's the third option unfortunately. Maybe a new defective immersion heater but that was the reason I replaced it because it was tripping previously. So the assumption was it was the immersion heater tripping. Now it's been replaced with new the same fault is there so looks like the heater wasn't the cause previously.

Unlikely to be number 2 as both the plumber and myself have rewired it. It's a new flex as well between the immersion and switch so not that.

So, looks like a N to E fault - do I need a sparky with specialist equipment to diagnose where that fault is?

I would have to say yes if its in the fixed wiring.They are among the most challenging faults to locate.However if the fault is in an appliance you should be able to find it by unplugging everything or if its a fixed applianced ,switch off the double pole Isolator.Try your immersion then and reverse the whole process until it trips again

 

[mikeyking]

I would have to say yes if its in the fixed wiring.They are among the most challenging faults to locate.However if the fault is in an appliance you should be able to find it by unplugging everything or if its a fixed applianced ,switch off the double pole Isolator.Try your immersion then and reverse the whole process until it trips again

So, electrician came over and was great. Traced it all through. In the end looks like an issue between the RCD and the switch so probably a fixed wiring issue. After we recreated the RCD tripping (i.e. supposedly isolated) there was still 18V draw on the wire so a N->E issue somewhere?

Anyhow, plan is to replace the wire between circuit board and immersion and put a small RCD in the airing cupboard... Thanks for your help!