Proper weird fault

[RF Lighting]

That's what I figured.

I disconnected the ends of the ring and measured ~40V to earth with a high impedence meter on both line and neutral.


Now the bit I don't get.

If you switch the RCBO off with the lever it will reset as seen at the very start of the video, but it will not reset if it's been tripped with the test button or an RCD tester.

 

[flameport]

If you switch the RCBO off with the lever it will reset as seen at the very start of the video, but it will not reset if it's been tripped with the test button or an RCD tester.

Perhaps the electronics in the RCBO require that there is zero current before resetting.
Switching the lever manually doesn't activate the RCBO electronics, because it is just mechanically opening the contacts.

 

[SgtTrojan]

30 minutes of typing and pondering, watching again and again, deleted due to inebration inhebeation inebriation <<drunkenss

 

[SgtTrojan]

What are the electrical separation test results for 8L2 and 7L1 please?
Chatter in the staff room suggests:

1) A break down in insulation between (probably neutral) conductors in both circuits
2) A "borrowed" neutral or permanent line from the socket circuit for the permanent lines required for the PIR and/ or the emergency light.

An excellent video dude.

 

[bernardgreen]

Perhaps the electronics in the RCBO require that there is zero current before resetting.
Switching the lever manually doesn't activate the RCBO electronics, because it is just mechanically opening the contacts.

I think Flameport is right.

It is possible that the electronics reading the sensor will, once tripped, not permit reset until there is a balance in the live and neutral through the sensor. Currents induced in those leads by capacitive coupling from voltages in other cables running side by side may be enough to prevent the sensor and electronics from allowing a reset.

 

[aptsys]

There's no 'electronics' inside an RCBO, so there is nothing clever that will wait for the current imbalance to equal zero before it'll reset. If the imbalance is below the trip threshold, then it'll reset.

 

[bernardgreen]

There's no 'electronics' inside an RCBO

Some types do use a Hall effect sensor and a simple amplifier as this is cheaper to make than winding a secondary winding on the toriodal of the sensor. And that will have hysterysis, operate at 30mA but not release until a much lower current.

Purely electro-mechanical ones make well keep the trip lever in the tripped position on a very small amount of un-balance current. In a mechanical relay the current required to move the armature and contacts is many times the current required to keep it held in once the armature is touching the electromagnet. The same will apply in an RCD or RCBO, once the magnetic gap in the mechanism has been closed by the pull of 30mA it could be held by as low as 5 mA or less.

 

[bernardgreen]

There's no 'electronics' inside an RCBO

Some types do use a Hall effect sensor and a simple amplifier as this is cheaper to make than winding a secondary winding on the toriodal of the sensor. And that will have hysterysis, operate at 30mA but not release until a much lower current.

Purely electro-mechanical ones may well keep the trip lever in the tripped position on a very small amount of un-balance current. In a mechanical relay the current required to move the armature and contacts is many times the current required to keep it held in once the armature is touching the electromagnet. The same will apply in an RCD or RCBO, once the magnetic gap in the mechanism has been closed by the pull of 30mA it could be held by as low as 5 mA or less.

 

[ban-all-sheds]

Whenever my CU RCD trips it will never reset until every MCB downstream of it is turned off, and there have been lots of posts here from people reporting the same behaviour with theirs.

 

[SgtTrojan]

BUMP - Eager to know

 

[RF Lighting]

What are the electrical separation test results for 8L2 and 7L1 please?
Chatter in the staff room suggests:

1) A break down in insulation between (probably neutral) conductors in both circuits
2) A "borrowed" neutral or permanent line from the socket circuit for the permanent lines required for the PIR and/ or the emergency light.

An excellent video dude.

Unfortunately I haven't done any IR testing between the circuits yet, but both circuits on their own test out fine.

There is definately no borrowed neutrals or anything like that. It is a new install done by the company I work for. I have just inherited the job as the lad who was doing it has left the company.

I'll possibly be back there next week to do a bit, so I'll do some more testing if I'm there.

 

[securespark]

Whenever my CU RCD trips it will never reset until every MCB downstream of it is turned off, and there have been lots of posts here from people reporting the same behaviour with theirs.

This is true of earlier gen MEM boards.