Confused

[mort2376]

Evening peeps. How's everyone enjoying British summer ???

So apart from me scratching my head and declaring I'm going mad, has anyone else had this.......

New board all rcbos. Installed new 2 new circuits for new immersion tank.

1 for boost run on a push button timer switch, 1 for night time run on a digital timeclock.

So checking circuit as no tank installed yet. So 20a switches for tank connections turned off so zero load.

Boost timer works OK.

Time clock when you manually turn override on. The 6a lighting circuit trips.

The 16a immersion circuit stays on.
You can reset the 6a rcbo no problem.

Cycle through override from on to timed to off to on 6a rcbo trips.

Brand new 16a circuit. From board through loft clipped direct.

I'm scratching my head as circuits are not connected. 6a circuit only trips. 6a can be reset with the timer on.

I'm thinking if changing the 6a rcbo but has anyone else had a similar situation or caused this issue ?

 

[Andy™]

N-E fault on the lighting circuit most likely

 

[mort2376]

N-E fault on the lighting circuit most likely

But why only happening when the other circuit is on via the time clock and no electrical direct connection between the 2 ?????? Doing my tree in lol

 

[Geoff1946]

Check you haven't a neutral earth short in the immersion isolator switch.
Is the immersion feed clipped immediately against a lighting cable ? (Thinking maybe inductive coupling)

 

[mort2376]

Check you haven't a neutral earth short in the immersion isolator switch.
Is the immersion feed clipped immediately against a lighting cable ? (Thinking maybe inductive coupling)

I thought induction, but there is no load on the immersion yet. It goes from board to time clock then down to 20a dp isolator all new. Isolator is off as just coiled flex waiting for plumber to do his thing.

It's just weird.

 

[Andy™]

But why only happening when the other circuit is on via the time clock and no electrical direct connection between the 2 ?????? Doing my tree in lol

higher load, higher neutral voltage with reference to earth. more current flows N-E and trips the RCD/RCBO. see it more with higher loads like showers & electric cookers

 

[mort2376]

higher load, higher neutral voltage with reference to earth. more current flows N-E and trips the RCD/RCBO. see it more with higher loads like showers & electric cookers

But no current flow. Dp isolator is off as no immersion connected yet.

 

[SPECIAL LOCATION]

Have you ramp tested the 6A RCBO to see how sensitive it is?
i.e. to give you some idea of what sort of "apparent leakage" current you are looking for?

Are the two circuit RCBO's next to each other in the CU?
If yes can you move them further apart to see if the symptoms persist?

Could it be some sort of electromagnetic interference between devices in the CU?
They are all the correct manufactures devices in the CU aren't they?

Just guessing while taking a beer refuel before bed.

It will be interesting to see what you find out to resolve this!

 

[mort2376]

Will let you know. It's a new board so all same manufacturer. Picking up new rcbo this morning and heading back there.

 

[binky]

Will let you know. It's a new board so all same manufacturer. Picking up new rcbo this morning and heading back there.

It would be worth trying to identify a new RCBOs from a different batch date in case it's manufacturing fault.

 

[mort2376]

OK so found the issue. Tested circuits all fine in regards of ir tests.

Rcbo ramp test 24ma so that was fine.

Issue only happens when a light anywhere is turned on so it has to be as suggested a n-e fault.

Replaced rcbo as only other variable in the system. Now works fine.

Examined original rcbo and pic is below.

Not sure how something on the input side could cause thus issue especially only when another circuit is powered up.

Checked conductors on other circuits all fine.

Definitely a head scratcher, but it now works.

Quick brew and off to the next.

 

[kerching]

Was the N fly lead tucked behind the Din rail by any remote chance?
Where do you get Niglon RCBOs from in Preston?

 

[mort2376]

Yes it was tucked behind the din rail, CEF Leyland stock them. Better price than Fusebox just no 25a option yet.

 

[binky]

Anything weird id usually neutral fault

 

[Murdoch]

If I wasn't about to retire I'd remember that and look for it in the future