Stange fault on new installation

[Deleted member 26818]

Yes, no different to using a split load board, as found in thousands of installations.

 

[richy3333]

I have 12 years experience, have relevant courses and part p all done properly but im not here to justify that

i would have fitted a dual rccb board at scource but did this to reduce long runs, there are socket outlet and lighting curcuits on each board serving both floors so you dont loose all sockets on say ground floor because of 1 rcbo tripping. Same goes for lights Maybe i hadn't explained that well because the circuits are spread well accross the ccu's.

I was of the understandig that a type s 100ma rcd was required on swa on a tt installation but if i am wrong please tell me?

I will be checking leakage next week, untill then theres nothing more we can discuss really so thanks all for initial advice

Apologies, I wasn't asking you to justify your experience and qualifications, but wanted to glean what they were in relation to the description of your work and the assembled system. How much of those 12 years has been spent on TT systems I wonder (rhetorical question)?

Whatever is done now will only be fudging a sub-optimal install. In following years when he system trips out and the customer calls will you admit that the problem is a design fault?

I was of the understandig that a type s 100ma rcd was required on swa on a tt installation but if i am wrong please tell me? - How about you quote the relevant Reg to the forum if you think what you have said is correct? You could use it as a 'refresher' exercise?

I think we are done on debating the background to this strange fault and I'll look forward to reading what the fault is found to be and the corrective measures taken. Over to you...

 

[richy3333]

no, he is saying that each sub main and board are protected by a RCBO at source! So when the RCBO trips, the entire wing goes off

Murdoch, thats how I read it.

 

[Deleted member 26818]

Wasn't aware that the installation is TT.
As such the installation will either require a very low earth electrode resistance or RCD protection at source.
The OP has used RCBOs, which I doubt are time delayed.
The OP has split the installation across two RCBOs to ensure that if one trips, not all power and lighting is lost.
The OP has a fault which could be due to cumulative earth leakage.

Don't really understand why some members are slagging the OP off?
Yes the OP should have used 100mA s type RCDs up front, but construction methods require 30mA instead.

Note to OP, mechanical protection is not required to be earthed.

 

[Octopus]

Wasn't aware that the installation is TT.
As such the installation will either require a very low earth electrode resistance or RCD protection at source.
The OP has used RCBOs, which I doubt are time delayed.
The OP has split the installation across two RCBOs to ensure that if one trips, not all power and lighting is lost.
The OP has a fault which could be due to cumulative earth leakage.

Don't really understand why some members are slagging the OP off?
Yes the OP should have used 100mA s type RCDs up front, but construction methods require 30mA instead.

Note to OP, mechanical protection is not required to be earthed.

but my point is that the way it's been split is half and half, so down the middle, so an entire 1/2 can loose power when the RCBO trips, so sockets and lights in the same room!

 

[Simlec]

today i have a fault that is driving me crazy. new installation - barn conversion
end of overhead lines, transformer in garden serving 3 properties, this one has a new underground cable from pole to new cutout and has
been left on TT by dno (originally a temp supply)


i have a 2 way ccu with 2x rcbos, each serving a submain on 16mm t/e +10mmearth to a main switch / mcb board at each end of the barn (its huge!)


one end behaves perfectly
the other has a strange fault.
with everything on EXCEPT the hob and cooker isolators the installation has been running fine for weeks.
turn either of the above on and out goes the rcbo.. easy yes ?? dodgy new appliance??? NO
as with the rest of the installation off at each mcb, they run fine, flat out .then connect back in a lighting circuit that was otherwise fine (running for
3 weeks) and out goes rcbo :*( same if i connect in heating system, or insert a plug in socket tester!


rcbos test out fine
IR of entire installation is spot on, mostly clear, worst reading was 12mohm on said lighting circuit which rises to clear after a few secs
L-PEN at incomer is 0.18ohm (i put pme link in made no difference) current Ze as still TT is only 2ohm as it wet and transformer in the garden is only 10m away


whats going on!!!!!!

You need to remove the current single pole RCBO'S ASAP.
For every circuit.... The device must switch all live conductors in a TT system and all line conductors in a TN system.

 

[Deleted member 26818]

Yes not ideal, but no worse than many other configurations that I've seen or heard about.
For all we know the barn is open plan with just a separate bathroom?

No the device doesn't have to switch all conductors, there just needs to be a method of isolating all conductors.

 

[Simlec]

(b) for every circuit. Other than at the origin of the installation, every circuit or group of circuits that may have to be isolated without interrupting the supply to other circuits should be provided with its own isolating device. The device must switch all live conductors in a TT system and all line conductors in a TN system.

 

[Deleted member 26818]

Yep, isolation.

 

[Octopus]

(b) for every circuit. Other than at the origin of the installation, every circuit or group of circuits that may have to be isolated without interrupting the supply to other circuits should be provided with its own isolating device. The device must switch all live conductors in a TT system and all line conductors in a TN system.

which reg number is that?

 

[yellowvanman]

(b) for every circuit. Other than at the origin of the installation, every circuit or group of circuits that may have to be isolated without interrupting the supply to other circuits should be provided with its own isolating device. The device must switch all live conductors in a TT system and all line conductors in a TN system.

There is a difference between isolation and fault protection!

 

[Simlec]

537.2.1.1

There is a difference between isolation and fault protection!

Who said anything about faults !

 

[yellowvanman]

537.2.1.1


Who said anything about faults !

Doesn't say anything about individually being able to isolate a circuit, switching the main DP switch can isolate a circuit, OK it takes out the whole installation, but this relates to the quote:
'provision may be made for isolation of a group of circuits by a common means.'

Sinple pole RCBOs are for fault protection not isolation in TT systems.

 

[Deleted member 26818]

537.2.1.1
Who said anything about faults !

The RCBOs provide fault protection. They can be used for isolation, though in TT installations they would require to be double pole. Isolation however can be achieved by using the main switch which is required to be double pole.

 

[Simlec]

The RCBOs provide fault protection. They can be used for isolation, though in TT installations they would require to be double pole. Isolation however can be achieved by using the main switch which is required to be double pole.

So thats part (a) 537.1.4 sorted then at the origin.
Next up part (b) for every circuit. Other than at the origin........