RCD tripping.

[levvy]

Hi everyone. I am new to this forum, and I have a question. I have recently re-wired a house and fitted a new Consumer Unit. Checks were done and passed ok. 2 months later, owner phoned to say RCD was tripping. I checked it, and everytime he plugged in the microwave, it tripped the RCD. He used and extension cable to plug it to upstairs socket, and it worked fine. I checked earth connections, switched RCDs, it works for a short while and it trips again. My questions are:
1) Why start to trip after 2 months?
2) If the microwave is faulty, why does it work when its connected to upstairs ring?
3) Could it be a connection fault? ( I checked all)
Would a C rated mcb help?
Or is it something else?

Thanks for all answers in advance.

Lev

 

[martinxxxxxx]

I checked all)
Would a C rated mcb help?




Lev

How do feel it might help?

Martin

Have you PAT tested the extension lead (poor earth continuity) and the microwave (earth fault)

 

[Taylortwocities]

Is the upstairs ring on the same, or a different RCD to the usual one that the microwave is attached?
If they are different, there may be a level of earth leakage on that ring (from a number of leaky devices) and the microwave may be just enough to pust it over the threshold where the RCD trips.

The upstairs ring may not have as much standing earth leakage current on it.

As for

Would a C rated mcb help?

Why on eartn (excuse the pun) would that make any difference. Are you clear on the functional difference between an MCB and an RCD>?

 

[martinxxxxxx]

Bet the microwave is faulty and the extension lead dont have an earth connection

 

[sparkwright]

Does the microwave trip the RCD when plugged in any sockets downstairs?

 

[securespark]

What relationship have you with the person using the installation?

Who did the "checks"?

What were the results of the "checks"? Scanning and posting the EIC would be very helpful.

Has the "upstairs socket" got RCD protection at the CU?

What is the result of your IR testing?

What is the result of your RCD tests?

Why would a C curve MCB stop the RCD from tripping?

EDIT: Slooooooow poster...

 

[maltaron]

Could be the neutral shorting to earth in the socket the microwave to which the microwave is plugged. Possibly fixing screw penetrating neutral insulation.

 

[martinxxxxxx]

Could be the neutral shorting to earth in the socket the microwave to which the microwave is plugged. Possibly fixing screw penetrating neutral insulation.

Very interesting, not the 1st thing Id have thought of

 

[EFLImpudence]

Could be the neutral shorting to earth in the socket the microwave to which the microwave is plugged. Possibly fixing screw penetrating neutral insulation.

Wouldn't that trip the RCD with or without the microwave plugged in and even with the MCB turned off?

 

[viewer]

Bet Martin's right; only way to check is carry it upstairs and try there.

 

[EFLImpudence]

Bet Martin's right; only way to check is carry it upstairs and try there.

He used an extension cable to plug it to upstairs socket, and it worked fine.

There have been several cases of misreading in the last couple of days leading to lengthy discussions about the wrong end of the stick.

Edit- Whoops, sorry, just seen bit about no earth in lead.
Humble pie warming in oven.

 

[martinxxxxxx]

Bet Martin's right; only way to check is carry it upstairs and try there.

There other ways:-

A) test the extension lead with a PAT tester or Low resistance Ohmmeter on Low Ohms

B) Test the microwave with a PAT tester, see if it passes insulation and/or leakage current.

C) Call an electrician.

A short story - a mate of mine is a gp and he gets fed up with what he calls the "worried well" patients, one case he mentions come to mind. Super fit guy comes in and says after running 22 miles he gets a pain all down his right leg - Chas's answer; Stop running at 21 miles in future.

My answer throw said microwave and extension lead in the bin if you have not the wherwithall to test them.

Martin

Martin

 

[Electrifying]

Hi,

A good chance that you have a neutral/earth fault on one of the circuits connected to the RCD on the same side of the board as your downstairs ring final.

The microwave will be powerfull enough to raise the 'leakage' current to a level that trips the RCD.

Don't throw out the microwave or extension lead, yet - get an electrician to IR test neutral to earth on the board/circuits.

 

[martinxxxxxx]

I think the OP has long gone, so no more levity.