Problem with split load CU

[DaveVector]

Hi Folks, I've had a strange and frustrating day today. Installed an MK split load Consumer unit to replace two rewireable fuse boards.
Earth system is TT 14.5 ohms PFC is 1.86 M ohms I've split the load over two 63A 30mA RCd's as follows (left to right from main switch):

1. Oven, Downstairs sockets, Spur sockets, Lights (they are all on one circuit!)
2. Shower, Kitchen sockets,Upstairs sockets, Spur sockets

Now here's the headache:banghead:...all circuits have been tested individually and, apart from a slightly low IR reading on the upstairs sockets (174M ohms), they all check out fine. But when everything is wired in and energised, using the microwave on the kitchen sockets or the upstairs sockets (all side'2') trips the RCD on the other side ('1') and sometimes side '2' !!
So I double checked that I had wired the board up correctly( no neutrals put to wrong neutral bar, RCD's wired as per manufactures instructions, no rings crossed...). Then tried just having the kitchen sockets on one side with the oven or the downstairs sockets or the spur sockets on their own. Still the wrong RCD trips!!
Ditto using upstairs sockets only.
Ditto using spur sockets on side 2
So then I took the lighting circuit out of the puzzle. Same result.

The only area I am uncertain of, is the cable from the main cut out. This runs as a single cable from the top of cut out to the meter. I presume this is in fact two-in-one which seperrate at the meter?

So can anybody shed some light please, before I spend another 3 hours scratching my head and cursing!!

 

[DaveVector]

you wont be able to SEE the fault... you need to test for it...!!! go to bed relax, start again tomorrow fresh and ready to go with a clear head..!

What! you mean get some sleep and have a fresh look tomorrow. Revolutionary idea, but might be worth a try

 

[ruston]

If the kitchen is the only obvious alteration I would start with that circuit to see if they have messed about with the N's. Take the tails out at the board and see if this helps.

 

[DurhamSparky]

Titanic was defo brand new!! i can see the add in Ship trader now!

New ship careful owner,only made one journey so low miles, left in hands of trustworthy officer who left his binoculars down below. slight damage to Port side although should T-Cut out, will throw in Wet and Dry Vac to winning bidder!

collection only (located 79k miles from DH1)

 

[telectrix]

but are we sure it was an iceberg that sank it? were'nt you training on torpedoes at the time?

 

[ipf]

You win the prize for spotting the (deliberate) mistake..should be 1.86K amps.

Bit high.. another deliberate?

- - - Updated - - -

 

[Guitarist]

Well, whenever I go to a customer who has been having problems with RCD's tripping on a consumer unit that their builder or plumber has fitted, it turns out to be a simple fix.... Take all the circuits off the RCD side and put them onto the main switch side.... See, you don't have to be an electrician to sort out a fault

Disclaimer : This is not actual advice

 

[telectrix]

or just replace the RCD with a 2 pole switch. can then charge another punter for the RCD, cleaned up and tested of course. (same disclaimer applies)

 

[DurhamSparky]

whats with the disclaimers...!!! thats exactly what i do...!!

(same disclaimer applies)

 

[alli]

Please don't take any offence as I am sure you wouldn't be a stupid as me, but I've only once left the solid neutral bar in the CU joining all the neutral bars together, It took me ages to work out why the RCD's werent holding, its sometimes the blindingly obvious you overlook. I called myself a prat for about a week after that, funny enough I haven't done it since.

 

[telectrix]

looking at the thread title, it's so negative. there are no problems, only solutions

 

[ipf]

Or remove all rcbo's and replace with mcb's

(same disclaimer applies)

That's what i found on a job last year. Nicked the rcbo's I'd installed....

 

[Guitarist]

looking at the thread title, it's so negative. there are no problems, only solutions

Or as I was told by the last company I worked for... "We don't have any problems in this Company...only opportunities to learn"

 

[trev]

Guys... save all the hassle, just bypass the RCD. No more nuisance trips, less crap to cart around etc etc.
Same Disclaimer Applies

 

[DurhamSparky]

hahahah thats shocking!!! i hope you told customer to ring police..!!!

mid you it probably was police trading as electricians!!

 

[Guitarist]

Or remove all rcbo's and replace with mcb's

(same disclaimer applies)

That's what i found on a job last year. Nicked the rcbo's I'd installed....

I wonder if you could find out who it was and change their wheels for bricks....