Earthing rod

[GLENNSPARK]

Tried that Mike. I've lost the will to live now though. I'd like someone to give me a valid reason for fitting a SP RCBO in any situation. The regulations are flawed, so don't try saying Reg. No. XXXX says so and so. The laws of physics don't change because the IET have bogged up writing the regulations by not taking N>E faults in to account.

i dont see the problem with split load configurations as well tony....
cheaper and RCDs are DP....

 

[MDJ]

Can't argue at all Tony, you have a very good point about RCBOs, I don't use them much, I do a lot of caravan site work and I use double pole RCDs not RCBOs, on a different note completely, I find it hard to make a dist board look neat with RCBOs in them, the silly neutral lead takes up a lot of space and makes the board look tatty haha

 

[Engineer54]

Personally, i can't see any problem using SP RCBO's on any TN installation. No different than the use of SP MCBs and fuses that we have been using for god knows how long. Any argument i can see against their use, would be on a TT installation.

 

[Knobhead]

Correct me if I'm wrong, isn't the idea of earth leakage protection to disconnect from the cause of the fault? Oh look there's a hefty fault flowing in the neutral, I'll turn the line off instead.

 

[Engineer54]

I'm not going to get into a war about the merits of TT and TNCS supplies, both have their advantages and disadvantages as we all know but out in the sticks where the supply authority provides no low impedance method of earthing there is still no alternative to an earth electrode, and if the ground is damp and its protected from mechanical damage it's fine. Same goes for the old voltage operated ELCB-in their day they were fine. I still come across domestic and agricultural installations that still have them in service, like anything else, if you test them regularly,they do the job they were designed to do.

Were they indeed?? So tell us, how do you regularly test those older VOELCB's, pushing the test button?? lol!! Those VOELCB's needed a tester that injected 50 volts into the system, so do you happen to own one?? I haven't seen one, for some 30 odd years now!!

 

[Engineer54]

Correct me if I'm wrong, isn't the idea of earth leakage protection to disconnect from the cause of the fault? Oh look there's a hefty fault flowing in the neutral, I'll turn the line off instead.

Well if you have an all RCBO CU, each unit will be only looking at the circuit it's protecting, so disconnecting the line to that circuit, will indeed stop the hefty return fault flowing in the neutral. I'm not saying i disagree with you in the principle of having the neutral switched/broken in a SP RCBO, and as i say, they are available now from one or two manufacturers.

 

[Knobhead]

If we follow the argument on. Why not have a SP RCD? Same difference.

 

[Engineer54]

If we follow the argument on. Why not have a SP RCD? Same difference.

Not really, because RCDs tend to be looking at several circuits rather than just one!!

 

[Knobhead]

One circuit or twenty circuits, there's a fault on one. Where is the difference?

 

[Engineer54]

Well unlike the RCBO's that only look at the circuit it's connected too and won't be affected by the other RCBO protected circuits, the RCD will, and why they are a pain to trace leakage faults. But they are DP, if SP the neutral fault problem you outlined above will be a problem.