RCD Pump Prob ?

I am having problems with the RCD socket that supplies my pebble pool pump tripping. I fitted the pump and electrics about 7 years ago and replaced the 240v Hozelock 1500 pump last year.
Over the last month the RCD started to trip - moisture in the outside connector I thought . Anyway I replaced the waterproof connector and inspected the outside IP65 junction box and all other connections . I have not yet cleaned the pump as its quite a task to get to it . The RCD still trips at intervals of 2 minutes too 2 hours !
The diagram below show the simplified circuit :-
Consumer unit - RCD socket - Pond Pump
My question is , do I need the RCD socket for my outside electrics ? Will the consumer unit protect the circuits with its RCDs and MCBs ? I am thinking the RCD socket may be playing up , and could I fit a standard twin switched socket .
Any ideas anyone.

 

The RCD will only trip if it detects current between live and earth or neutral and earth, as that usually means somebody is being electrocuted.

I'd check the quality of the earth connections at both ends (ie close to the pump and at the other end, presumably at the junction in the house at the start of the cable that runs into the garden).

Have you been able to rule out all possibility of damage or decay to the cable itself that could be allowing current leakage through damaged insulation? An electrician with one of those mega meter thingies will be able to test for such current leakage.

 

Dave I have checked , all the connections at the 3 junction points and the cables where possible.
The problem is on Sunday the pump ran for 4 hours and 6 hours with no problems , yesterday it ran for 15 minutes ! I suspect that the RDC socket is faulting.
My main question is if all the circuits are protected from the consumer unit , do I need another RDC socket unit to protect the outside static electrics ? So I have a pump protected by a socket RDC and then by a consumer unit RDC ?

 

If you just have the consumer to protect and it trips wouldn't that swich off the elec to your house, having the socket you have double protection and that shuts down first, some RCD sockets do get weak after a time (i think, I'm not a sparky) un les the pump is packing up

 

Depends on the age of the consumer unit. Older ones and ones that don't meet current current new build regs will only offer 'over-current' protection. That means they're nothing more than a modernised fuse box, using circuit breakers instead of fuses. If someone was being electrocuted to death (around 100 mA current if I remember right, might be less), they would not trip a conventional circuit breaker as there would be no over-current. An RCD is something different entirely. There should be no current flow at all between live and earth or neutral and earth. If there is, then either there's damaged cable/connection, or someone is getting zapped, so the RCD cuts the power.

So the short answer is, your consumer unit may or may not protect you, depending on whether it is new enough to have RCD functionality built in.

 

Think your right there Dave , the house is an early 80's build . So I presume it is the same consumer unit fitted . It is better to rely on a dedicated RCD for protection . I do have a spare RCD socket so I will change it this weekend , as Jiffy thinks they can get weak after while ,and see where we go from there . ( We all know its going to be the most expensive item in the circuit that is faulty , a new pump £45 and removing 50 kg off slate pieces ! )

 

Put the new RCD on this morning . When I was removing the original unit I found the live connection was loose ! Hopefully problem solved , just testing now

 

Some times it's something simple