High Integrety CU - Internal cabling

[SUNRAY]

They should have been removed from the regs when metal cases came in

More nonsense

Glad to see you agree with me.

What on earth could possibly let you think I agree with with such a stupid comment. There must be millions of them in use across the country, I'm sure their use for new or replacement work would have been curtailed if there was anyway they create the problems you seem to have with them.

 

[Harry Bloomfield]

They should have been removed from the regs when metal cases came in

Why? From a safety point of view a single RCB, is the equal of individual RCBO's, the only advantage is ease of fault finding and effect on fewer circuits, when faults occur. Faults are extremely rare indeed, so why the need to expend a great deal of money to make them easier to deal with, and especially in my own case - where I am on-site and well-equipped to easily isolate, to deal with them?

In the 40+ years I have lived here, there has never been a genuine fault. I have several times accidentally tripped the RCD in my workshop, when testing live equipment, but never under normal circumstances.

 

[SUNRAY]

Why? From a safety point of view a single RCB, is the equal of individual RCBO's, the only advantage is ease of fault finding and effect on fewer circuits, when faults occur. Faults are extremely rare indeed, so why the need to expend a great deal of money to make them easier to deal with, and especially in my own case - where I am on-site and well-equipped to easily isolate, to deal with them?

In the 40+ years I have lived here, there has never been a genuine fault. I have several times accidentally tripped the RCD in my workshop, when testing live equipment, but never under normal circumstances.

I can but agree with you.

In my case I've had 2 damaged cables; one was a chunk missing out of the insulation and sheath (No idea why and damaged before we moved in) in a cable under the kitchen units and a leaking washing machine hose soon highlighted it, second being rodent damage in loft on a Christmas eve.

Other than that; Extension lead damaged during gardening work, blown bulbs and faulty dishwasher mains filter.

That's all in 29½ years.

 

[plugwash]

The nightmare scenario with RCDs is that it trips every few days but you can't pin down the trigger, and tests come back with "no faults found", or alternatively that tests reveal a bunch of leakage but not localised to any one item.

The question is, how common is said scenario? I have certainly had unexplained RCD trips at my parents house, but never enough of them in a row to start formal fault finding. It would often trip a couple of times and then be fine for months on end.

I've had quite a few legitimate trips including

1. An electric shock.
2. Many times, accidental contact of neutral with earth during electrical work (MCB off but RCD on)
3. An old george foreman grill.
4. A screw through a conductor in a backbox (I think this took out both the RCD and the MCB but I don't remember for sure).

I also had an old monitor that would take out a plug in RCD if it shared one with the computer I had at the time (this was in a place that didn't have RCDs in the fixed wiring, but insisted I use plug in RCDs for all my stuff) but seemed fine if it had a plug in RCD to itself. I no longer have said computer or monitor.

 

[SUNRAY]

Yes it is different if there is regular tripping especially if it is intermittant. If that is the situation then I'd give due consideration to all RCBO's and chances are the 'fault' may simply disappear.

 

[Harry Bloomfield]

The question is, how common is said scenario? I have certainly had unexplained RCD trips at my parents house, but never enough of them in a row to start formal fault finding. It would often trip a couple of times and then be fine for months on end.

If that became a problem, then I be splashing out on a few RCBO's to try to localise the issue, down to one circuit.

An alternative, with a dual RCD board, is to simply move circuits, one at a time, to the second RCD.

 

[SUNRAY]

..An alternative, with a dual RCD board, is to simply move circuits, one at a time, to the second RCD.

The problem with that method is if the 'fault' is cumulative leakage.

 

[Harry Bloomfield]

The problem with that method is if the 'fault' is cumulative leakage.

Which can be measured anyway.

 

[securespark]

I have a similar story. When we moved in here a quarter of a century ago, we inherited a 1990s Hager board with an RCD incomer.

For one reason or another, we still have it.

We have only had a few RCD trips in that time. A flood under the floor that soaked a GF ring final junction box, a faulty tumble drier element, a spilt glass of water on an extension lead and another that escapes me, another faulty appliance, I think.

But all trips were explainable and the faults easily found.

And that's one RCD for a detached 5 bed house, over 25 years.

 

[SUNRAY]

We installed a pair of metal Wylex fuseboxes mid 70's in the house I grew up in and maybe 5 years later fitted a single RCD Basically as a junction to repair a damaged tail. No trips until well into noughties when the buried garage feed was damaged when a new fence installed. Garage feed was disconnected as that point. I imagine it's one of those just jobs to sort out as some time.

 

[ebee]

I do not know why a dual RCD board is referred to as "High Integrity" ! OK it`s better than one front end RCD but far worse the all RCBOs, there was a time when cost played a part and RCBOs were very expensive but those days are gone.
During that time I did install a few - reason being price but I would make the RCDs (RCCBs) each carry some power and some lighting (split sensibly to mitigate lose both power and lighting from one area) then RCBO a few circuits such as cooker (even new ones could be a bit leaky) and central heating (frost protection reasons) and perhaps a dedicated fridge/freezer circuit and maybe electric shower. giving a bit of resilience perhaps.
Nowadays all RCBOs for me (the only drawback being cumulative leakage on an installation as a whole (which never concerned us back in the days of all rewireable fuses, cartridge fuses or MCBc anyway, once an installation had left our control after testing).

Although, I myself, Have two "Front End" RCDs (Normal Domestic and Off Peak Storage Heaters) for very many years it has never been a problem, until this week, raining in via the old kitchen outbuilding chimley *used to be a gas fire there years ago) .
We were away Mon to Fri in a foreign country (Flamborough Head nr Bridlington) and Thurs morning My mobile rang and texted , power cut, I knew what had happened, 25hrs later on Friday morning Phone and text again Intruder alarm activation, the intruder alarm batter had discharged enough to cause activation .
Next door texted me a few mins later and I thanked her and informed her it would shut off after 20 mins.
About 4pm we returned home as planned (I didn`t want to cut the holiday short for three groups of our family and I had calculated that the alarm would hold off past the we small hours ) so just as bit of a mop up when we got home, fridge and freezer OK , freezer food was still frozen quite solid, RCD reset OK .
Now where is that builder I asked to repair the leak a couple of weeks ago?

So, to those stating that a front end RCD can cause problems I say yes you are absolutely right, they can.
Do that mean they often do so? I say no not often, usually, just the odd trip now and again from a, usually known, source. Of course my RCDs are AC type, they are tested, with a meter, regularly. Just the odd trip from a steam iron being over filled, a faulty kettle once and a leak from under the bath once in about 40 years-ish, maybe a bit less.
Would I install these days without an RCD? No.
Would I install :-
A front end RCD? No. a dual RCD board? No. All RCBOs? Yes (Type A)

 

[SUNRAY]

Only called high integrity as it followed on from the split load board which was half non RCD & half RCD.

 

[ebee]

Yes I know, in fact the older TT boards had Front end 100mA S type then a second RCD for 30mA Non delayed for power circuits . I just couldn`t get mee heed around the High Integrity saying when RCBOs were readily available and therefore Higher Integrity than that. my little joke really but I guess you knew that.
In fact, I wonder what these youngsters think we did before RCDs or ELCBs were available so freely?

 

[ebee]

I will not mention how we got electric to flow between buildings when wires and cables were so expensive and difficult to source so we used bits of wet string!

 

[SUNRAY]

Yes I know, in fact the older TT boards had Front end 100mA S type then a second RCD for 30mA Non delayed for power circuits . I just couldn`t get mee heed around the High Integrity saying when RCBOs were readily available and therefore Higher Integrity than that. my little joke really but I guess you knew that.

My early experience with TT systems always seemed to have a RCD before the fusebox (following on from the VOELCB).
AFAIA (I'm probably wrong and happy to be corrected) RCBO's were originally a standard 2P RCD and MCB joined together and taking up 3 spaces. Such arrangements are certainly still available today in some ranges.

In fact, I wonder what these youngsters think we did before RCDs or ELCBs were available so freely?

Ah that was before danger had been invented