New CU keeps tripping

[dx90]

Just had a new consumer unit installed to replace my ageing fused board and old type trip with a green button on it. The system is a TT, I think this is correct for over head mains that are feeding the house. The new CU has a 100mA RCD and a 30mA RCD with earth rod in the ground. I have never had the old trip, trip on me like this one for no apparent reason, but the new CU is tripping all the time, once every two days, some times every day and on one occasion twice in one day.
It will trip the 100mA RCD and when I reset, the electrics will come back on no problem.
Other times 100mA RCD will trip and when I try and reset, it will then trip the MCB for the down stairs sockets that are on a radial. Then I can reset the 100mA RCD and then reset the downstairs MCB and every thing ok then, well until the next time it gets tripped.
Sorry if I haven’t explained it to well, but I have done my best.

Anyone knows what could be causing this?

Thanks

 

[davy_owen_88]

Who fitted the new CU? What were the insulation resistance readings like? What circuits are being used when the RCD's trip? Is the 100mA RCD of the S-type variety (time delayed)? Are you sure the neutrals are in the correct neutral bar - all 30mA RCD protected circuits go in one bar, and the rest, plus the neutral from the 30mA RCD go into another...

 

[festa]

When a consumer unit is replaced by a competent person,it is up to that competent person to carry out a series of tests to ensure the existing installation is up to and meets the exsisting regulations.
Did you receive an Electrical Intallations certificate and inspection and tests sheets from the contractor you hired?

It `could` be a loose connection in the C.U or equipment in your dwelling that the contractor has moved to carry out his/her tests.

Your number one call should be to this contractor and have him back to check his/her work.

 

[dx90]

It is a qualified electrician that installed and done the tests. I have not been given the certificate yet as he has to find a reverse polarity fault on the lighting circuit but he did say that all other tests were within the specs and had passed all tests. All circuits were being used to some degree but nothing with to much load. The TV, washing machine, PC’s, no cooker, no dryer, just small stuff around the house really.
The RCD reads 80A-100mA WRM80/2 and the other RCD 80A 30mA WRS80/2 on the 100mA is the cooker NSB40, lights NSB06 and combi boiler NSB16 and on the other 30mA is sockets up NSB16 and down NSB16, kitchen sockets NSB32, shower NSB40 all are Wylex.
Before he came back to do his test we had no tripping on the new CU.

 

[RF Lighting]

The 100mA WRM80/2 RCD is not type S, so there is currently no discrimination between the 30mA and the 100mA RCD.

This means the fault could be anywhere on the installation.

The fault may not have been apperent previously as the old RCD will probably have been a voltage operated ELCB.

 

[dx90]

So could it be a peace of my equipment causing the tripping or is it almost certain to be a fault with the electric wiring etc?

I know that when the CU was put in there was a two week gap before coming back to do the testing and in that two weeks I did not have it trip. It only tripped after he did all his tests.

 

[securespark]

Did he reconnect this reverse polarity lighting circuit??

 

[dx90]

Yes

 

[nozspark]

Yeeeeeeeeeee Haaaaaaaaaaaaaaaa

 

[dx90]

Could it be my equipment causing the tripping or is a fault with the electric wiring etc?

 

[bernardgreen]

Could it be my equipment causing the tripping or is a fault with the electric wiring etc?

The mains filters in the power supplies of computer equipment have capacitors between live and earth and these create earth currents which appear to the RCD as a fault. The average filter creates about 2 to 3 milliamps of earth current so at about 10 filters the current is approaching that at which the RCD will trip.

 

[dx90]

It could be my pc in the living room that is causing the trip then. The power supply in my pc is a corsair 620.

Is there anything I can do to stop this happening?

Can I use my multi meter to check for this?

 

[Taylortwocities]

You'd need quite a few computers or similar pieces of equipment to create enough earth leakage to cause the RCD to trip. You need your sparky to resolve the reverse polarity issue and to carry out other tests (eg RCD ramp tests).

I guess he will be replacing the 100mA RCD with a Time Delayed (S Type)?
Hopefully u havent paid him yet?

 

[JohnD]

Is there anything I can do to stop this happening?

RCBOs would minimise the impact and localise the fault-finding (this is true)

I don't think a multimeter will help much, but a clamp meter will measure current flowing down a cable. You might need a more sensitive one than usual, though.

You could try switching off half the MCBs one day,and the other half another day. However this will not help if it is a neutral/earth fault.

You can also try unplugging all watery appliances (washing machines ,kettles, steam irons) and switching off the cooker, immersion heater and boiler (including supply to pump) with their DP isolators as these are common sources of leakage.

 

[Demonic]

I have 5 PCs on my downstairs RCD-protected ring and I have no problems whatsoever.