trouble with newly installed MK c/u

[jenions]

recently changed an old fuseboard to a new MK consumer unit with 2rcbo's and then RCD with 5 mcb's on it, now i IR all the circuits and all came out at <299Mohm but since day 1 the rcd has tripped whenever a high load is switched on? i tried the up and down ring and the fridge radial on 1 of the rcbo's (40A) and they worked fine but if i put them back on the rcd side they trip. anybody got any ideas? also the test button on the rcd isnt working, now this is the 2nd rcd ive tried as i changed the 1st 1 just incase that was faulty.

 

[topquark]

How can the main switchy go on the other side of the board, the L-N poles wouldn't allow you to do that....

Yep, absolute pain with MK boards!

 

[topquark]

Jenions the neutral link is present in the board so that you can put more circuits on one side of the CU and use the third unlinked neutral for another RCD. Because of the circuits design you have, you only need two circuits on the first neutral bar so there is no need to use the link. If the link is left in the current in the neutral can bypass the RCD so it sees a difference in current between line and neutral current and trips. Remove the copper link and this should solve the problem.

Well that's given the game away

 

[Knobhead]

He could use the link. There’s a neutral bar sat there doing nothing! The neutrals could be spread out to tally with the MCB’s then. And as for the 2[SUP]nd[/SUP] MCB from the RCD what’s coming out of that?

 

[topquark]

Gonna have to go and look at the piccy again now

 

[topquark]

Ah, that's just an RFC with a spur taken at the CU Tony, either that or whoever installed it was fresh out of MCBs

 

[richy3333]

annoying thing is, the rcd dont trip if you plug small loads in

Could it be a combined earth leakage issue as it only happens when sufficient load has been applied? Have you ramp tested the RCD and used an earth leakage meter to see? Possibly a certain appliance causing the issue - freezer maybe?

 

[richy3333]

annoying thing is, the rcd dont trip if you plug small loads in

Could it be a combined earth leakage issue as it only happens when sufficient load has been applied? Have you ramp tested the RCD and used an earth leakage meter to see? Possibly a certain appliance causing the issue - freezer maybe? That's what came to my mind when you mention the IR results were ok?

 

[Knobhead]

richy, Mafeking’s been relived!

 

[Risteard]

You can, as with MCBs, put more than one circuit into an RCBO but it's not good practice.

Not technically possible as it then becomes one circuit. So you could have multiple cores rather than multiple circuits in the protective device.

 

[topquark]

Not technically possible as it then becomes one circuit. So you could have multiple cores rather than multiple circuits in the protective device.

There's always one, and it ONLY becomes one circuit when you install THEM into the MCB so I stand by what I said