RCBO on but no power out

[TomSparkman]

Hi everyone.

I have come across a problem on a job that ive been on today.
Ive installed an additional C.U which supplies the new extension on this house, therefore i have had to split the tails and put new tails in to the old and the additional CU. Therefore ive had all mcb/rcbo turned off whilst doing this.

The only existing circuit i have worked on is the lighting which i have added an extra light switch.
All new circuits tested, all switched back on everything perfect.
Customer rings me to tell me lights and cooker arent working. So i go back around and the rcbo's in the existing CU which feed the lights and the cooker are both in ON position but there is no power coming out. The test button doesnt even make it flick to the OFF position.

Everything is fine with the new switch i have put on, IR done, Zs done. Everything was fine when i left ( unsure if cooker was on).

Why are the RCBO's not letting the power through?? I havent even worked on the cooker circuit

 

[freddo]

Busbar clamps in front of busbar touching before but now not after movement from installing new tails?

 

[TomSparkman]

Busbar clamps in front of busbar touching before but now not after movement from installing new tails?

Worth a try freddo...

 

[shaun1]

Since splitting the supply and adding new tails, have you measured the voltage at the main switch of the existing db. Have you checked this again since returning? Have you checked the voltage at the incoming side of the RCD. It sounds like something between the incoming supply and RCDs is open circuit. Does the new consumer unit work correctly?

 

[Richard Burns]

If the RCBO switches are moving freely and they do not trip on the test button it can only be that there is no power to the RCBO (though a fault could stop the RCBO tripping this is unlikely on both circuits at once).
Worth asking if they were working before you started work!
I would agree with Freddo a loose busbar connection assuming all other circuits are working OK.

 

[TomSparkman]

Since splitting the supply and adding new tails, have you measured the voltage at the main switch of the existing db. Have you checked this again since returning? Have you checked the voltage at the incoming side of the RCD. It sounds like something between the incoming supply and RCDs is open circuit. Does the new consumer unit work correctly?

Correct voltage at the supply to both DB. Correct voltage on busbar, correct voltage to bottom of both of the culprit rcbo, but now voltage out. No main RCD in existing CU.
New CU is working perfectly

 

[TomSparkman]

If the RCBO switches are moving freely and they do not trip on the test button it can only be that there is no power to the RCBO (though a fault could stop the RCBO tripping this is unlikely on both circuits at once).
Worth asking if they were working before you started work!
I would agree with Freddo a loose busbar connection assuming all other circuits are working OK.

The lighting circuit waa definitely working as ive added a switch to it (two way to intermediate) and ive tested it and checked lights worked.
The cooker circuit was definitely working yesterday but isnt now. I didnt have any reason to check this as all ive done is switch the rcbo off and back on whilst carrying out alterations to tails.

What such fault could occur causing the rcbo's to act in this way?

 

[Octopus]

If the test button on the RCBO isn't working, this would suggest there is no supply to the RCBO......

Maybe your new tails are not tightened up properly .......

 

[buzzlightyear]

the possibility ,is the rcbos tighten and the rcbos not dropped in stop any current getting through.

 

[WillWX]

Can you swap one with a known working from another way in the CU, to confirm fault with RCBO?

My first check would be busbar has clamped corrrectly or cables are properly clamped in terminals but if you haven't had them out at all etc then I suppose the chance of this is slim.

 

[telectrix]

check if the RCBOs are the type that you need to press fully down before resetting. this foxed me for a few minutes, once, years ago.

 

[Richard Burns]

If you have voltage at the bottom of the RCBO but not on the top and the RCBO is switched on then the RCBO is broken. This does not seem likely unless you switched them back on with a hammer.
It is possible that the test current on pressing the test button can be diverted partially through a fault and prevent the RCBO tripping, but it would still supply power.
The only other thing would be if the neutral were disconnected then there would be power at the RCBO but the circuit would not work, however the top of the RCBO would show no potential difference line to neutral but 230V to earth.

 

[happysteve]

If the neutral's not there (disturbed, perhaps), it would also give you the same symptoms you have described.

 

[westward10]

This is probably a simple problem, take them out and refit them because they may have always had casual contact with the busbar and by you fitting new tails you have disturbed them.

 

[westward10]

check if the RCBOs are the type that you need to press fully down before resetting. this foxed me for a few minutes, once, years ago.

Square D QOE?