RCD Tripping

[mf1970]

Just moved in to our new house and everything was ok until the RCD "tripped". We have a boiler and oven on the same side of the RCD. The boiler is OK, so we removed the cable from the oven. Even without the oven connected and the switch "on", the RCD trips - not immediately, but after a few hours. My next step is to remove the spur cable from the "cooker switch" which feed the oven. If this also trips, have I isolated the problem to the cable from the CU to the switch (the cable is old type). The CU looks fairly new. Is the only next course of action to call an electrician. Will he be able to tell me if it's the cable by doing some tests ??????

 

[flameport]

If the oven isn't connected, it's either the boiler/pump etc. or possibly a damaged cable. Either way, it won't be easy or quick to locate this fault yourself.

Any electrician should be able to test the cables etc. to locate the fault.

 

[mf1970]

Thank you for your speedy response. I have tried to understand why this is happening and read somewhere on the internet that the CU is measuring how much current flows down the live and returns back through the neutral (sorry if this is incorrect or simplistic !!!), and when it trips it is because there is an inconsistency between the "flow" and "return" - does it make sense to you that, with nothing connected (except the boiler) and the cooker switch "on" that I have a problem, but with the boiler on and the cooker switch "off" everything is fine. Might it also be the CU - or is this unlikely or impossible - it appears fairly new? Is it right that it takes a few hours to manifest and trip? Does it make sense to disconnect the "spur" cable from the switch before calling the electrician to eliminate it?

It might seem that he will have to replace the cable and this seems like it will be a big pain, not least because of the kitchen tiles - ahhhhh

 

[User]

Admit I'm no expert but had similar problems, if there's no trip with the cooker switched off then must be the cooker itself, unless you're saying the cooker has a separate switch at the CU, in my experience it's almost never the CU or the cable but the appliance itself, disconnect the appliance then you'll know then get cooker fixed or new one

 

[User]

Even without the oven connected and the switch "on", the RCD trips

with the boiler on and the cooker switch "off" everything is fine

isn't that contradictory maybe I've missed something probaly

 

[mf1970]

We have CU -> Cable -> Cooker Switch -> Cable -> Spur -> Oven

Oven has been removed.

Cooker "switch" is off (no oven connected) , boiler on = everything OK.
Cooker "switch" is on (no oven connected) , boiler on = trips after a few hours.

Plan to disconnect cable from cooker switch to spur above, just leaving:

CU -> Cable -> Cooker Switch

to see what happens.

Suppose I could repeat with boiler off also.

But this is a real pain for me - i am sure that I will have to get someone to replace the cable.

 

[Aragorn84]

if theres no trip with the cooker switch off, the problem likely resides after the switch and the boiler is fine.

 

[User]

I'd say you've answered your own question. I would guess it's more likely a fault in the cooker switch or spur than the cable check it out (unless you can see some nail or something where the cable to the spur is)

 

[mf1970]

Thanks for the help everyone. Will do some tesing tomorrow.

 

[kevrevv]

Thanks for the help everyone. Will do some tesing tomorrow.

rcd is tripping do to a residual current leak. you will need to do an insulation resistance test on the cable. that will tell you if that cable is the problem. doubt it will be the switch nor spur unless u have moisure, grease etc allowing suface curent to flow across it?

 

[kevrevv]

Thanks for the help everyone. Will do some tesing tomorrow.

rcd is tripping do to a residual current leak. you will need to do an insulation resistance test on the cable. that will tell you if that cable is the problem. doubt it will be the switch nor spur unless u have moisure, grease etc allowing suface curent to flow across it?

rcds work on the principle of what goes out in the line, comes back in the nuetral if there is an imbalance, i.e. 30milli amps then it will trip.

 

[1john]

you havent got any wires touching anything or themselves from when you disconnected your oven?

 

[TicklyT]

Just a thought..... The OP said

.....We have a boiler and oven on the same side of the RCD....

Is that the protected side of the RCD, along with socket circuits etc. etc., or the unprotected side?

As both are usually fixed, hard wired appliances, some would argue there's little need for RCD protection for those two circuits.

What other circuits are connected in the CU, and where?

 

[mf1970]

Just an update and request for further information.

My set up was :

1. CU -> 2. Cable to -> 3. Cooker switch -> 4. Spur Cable to 5. Oven Outlet Connector -> 6. Cable to -> 7. Oven

I removed item 4. from the Cooker switch, and turned the switch on. I have not had any "tripping of the rcd" in 24 hours. I am therefore beginning to think that it is either the connection of the spur cable to the cooker switch, the connection of the spur cable to the oven outlet connector, or the cable between the two.

I have previously elminated 5,6, and 7 because I had previously disconnected these.

My test is either to have the cooker switch ON or OFF. Previously, with the cooker switch ON, I would get the tripping and with it OFF, I don't get the tripping. By simply removing the spur cable, with the cooker switch ON or OFF I don't get the tripping. Or at least as long as it last another 24 hours, I will be pretty sure this is the case. So it appears that I have the have the cable replaced.

Can I replace the cable myself? It is currently behind the kitchen tiles and behind some plaster (behind the base units). Will I have to keep it behind the plaster or can I surface mount it (it won't be seen as it is behind the units) If I remove the plaster, I hope to be able to "feed" the cable behind existing tiles to the cooker switch.

Also, someone on the boards mentioned that he thought it would be the spur cable because the fault only happened when I put the switch "ON", and with the cooker switch "OFF" no tripping happened. I don't really understand this, because even if the switch is ON or OFF, without an Oven connected how would the RCD know there was a fault? Does current flow and is it detected when the switch is ON even if nothing is connected?

 

[securespark]

If it is damaged by fire, flood rodent or impact, then yes, you can replace it without notifying.