Why would you want to fit non protected MCB’s?
Practicing a Consumer Unit install
- Thread starter Jupiter01
- Start date
Sponsored Links
Them boards have been around years, even when it was NOT compulsory to rcd virtually everything, so non protected MCBs were often used, maybe freezer sockets or critical circuits possibly Alarms, lighting anything really that you would have preferred not going off.
Nowadays the End Neutral bar would likely more get used for Rcbos, again for things that you want to reduce likelyhood of going off due to non related faults on other circuits.
True high integrity boards now come prepared to fit Rcbos as far as I know, i am not sure how you intend connecting rcbos into that Dual rcb board you have.
Nowadays the End Neutral bar would likely more get used for Rcbos, again for things that you want to reduce likelyhood of going off due to non related faults on other circuits.
True high integrity boards now come prepared to fit Rcbos as far as I know, i am not sure how you intend connecting rcbos into that Dual rcb board you have.
Last edited:
Just slide the RCD's across to suit.
What about the Live supply, does the bus bar just bodge in with the two tri rated browns ?, will it fit ? if so not sure he has spare busbar without reducing the Rcd protected ways.
Then again if hes not using the board he may well intend cutting one short
Sponsored Links
Some surgery to (or changes of) busbars would probably then be required, wouldn't it?
Kind Regards, John
It all looks messy to me, Two 16mm ? browns plus a bus bar into 1 terminal just dont seem right.
These boards look more of a fire risk now than they have ever been
They seem quite typical of many makes to me and it's only one cable and one bussbar.
Is that not the same as the pic of your CU?
Last edited:
No more than the rest of it.
The safety or lack thereof of single pole isolation depends on the reliability of the upstream neutral connection. If the upstream neutral conductor breaks then the neutral conductor can be "dragged up" and become live.
Clearly the electrical industry considers single pole isolation in distribution boards to be a sufficiently safe working practice. Implicitly they consider the risk of the upstream neutral conductor failing during the works to be sufficiently small that it can be neglected.
While I can't put numbers on it, I would expect the neutral connection in a plug-fed piece of equipment to be less reliable that that at a typical fixed distribution board for several reasons.
1. A plug can be pulled partially out of the socket, it's essentially random which of live or neutral breaks first when this happens.
2. A flexible cord is far more likely to suffer from broken wires than undisturbed fixed wiring is.
3. Large conductors seem to be seen as more reliable than small ones generally (see for example the "high integrity earthing" rules).
4. The design of household wiring accessories require that the wiring be done before the accessory is pushed into place, I find it hard to trust the reliability of such connections and indeed I've seen several pop out over the years. This last point is somewhat mitigated by the use of ring final circuits, but not every socket is on a ring.
these boards come with a single length of bussbar which needs to be cut to length, which I'd hope is a standard system.What about the Live supply, does the bus bar just bodge in with the two tri rated browns ?, will it fit ? if so not sure he has spare busbar without reducing the Rcd protected ways.
Then again if hes not using the board he may well intend cutting one short
Having another look at the pic of you CU the only real difference I see is the flexes into the neutral bars may not be professionally terminated and it makes me wonder if thay are like that all the way through.
Fair enough - but, although I don't disagree with what you say about the theoretically increased risk of a broken neutral when the feed to the CU is via plug/socket/flex, I would personally say the the probability of such a failure arising "during the works" would also be "sufficiently small that it can be neglected".
Let's face it, in the vast majority of cases none of the theoretical neutral issues with plug/socket/flex which you mention are ever going to arise during decades in use/service, so the probability of such a problem arises during the few minutes or hours "of the work" must be incredibly small.
Kind Regards, John
- Joined
- 27 Jan 2008
- Messages
- 23,855
- Reaction score
- 2,699
- Location
- Llanfair Caereinion, Nr Welshpool
- Country
Yes earth where black circle.
Note they are type AC RCD's which are not really suitable for supplying multiple circuits, as a fault with one circuit allowing DC could stop the RCD tripping, with a second fault on another circuit.
The use a high integrity CU with RCBO's needs some careful thought, the main items you don't want to trip are lights and refrigeration, for a RCBO only to supply the fridge/freezer great, if it trips clearly a fault with fridge/freezer so you will loose food even if you are fully aware it has tripped, but where it feeds more, as with a kitchen ring final, then you want to know if some thing else causes it to trip.
I have a rechargeable torch plugged in so if the RCBO trips it lights which is likely to alert me rather fast to fact it has tripped, but simply loosing the light on a fridge/freezer you are likely to miss it, son had the house alarm on same circuit and it would beep with loss of power.
The more there is on a RCD the more likely to trip, theory is great, we should test the installation and if the leakage exceeds 9 mA on any RCD (Including RCBO's) we should split the circuit further, however I for one don't have a clamp-on ammeter that will measure 0.001 amp, so only way for me is to use the RCD tester with all MCB's on when doing the ½ test so if an extra 15 mA does not trip it likely less than 9 mA to earth.
To fit a CU or do any other wiring you need to inspect and test, I looked at the idea of rewiring my mothers house, I realised all my test gear was either faulty or out of calibration, and I would need to pay the LABC to notify them, so it would cost me around £300 over and above materials used to DIY, also there was a time problem, I would need to have mother in a home while re-wiring, so would cost around £600 per week, so getting some one in likely rewired in a week, DIY more like 3 weeks to a month. So to be worth doing I needed to consider getting some one in would save around £1500 and they would likely charge around £2000 for labour so was simply not worth doing DIY.
Many years ago I did my City & Guilds 2391 and this was a 12 week course on inspection and testing, at the end we had to fault find on a board which was designed to simulate a house wiring, it cost at the time around £60 for course 12 weeks, one night per week of around 3 hours, I would say a course like that would be good training even if you fail.
Same goes for PAT testing course, when I did it the 16th edition as it was then, PAT testing and inspection and testing ran one after the other, so 24 weeks in all. The 16th edition only teaches how to read a book, so that one not so important. Now of course 18th edition.
The published success rate for schools and collages messed things up, years ago before the tables it did not matter to collage if you passed or failed, but now it does, and so hard to take exam only, and the cost of courses has also gone up.
Full time was £10 but one course was £120 last time I went to collage (Did 'A' levels) so I did photography and chemistry so the maths course cost me £10. And when I looked at electricians courses they were clearly designed for school levers and other students did not even know gold was a conductor, so course started at a very low level, which was rather boring for me, so I did a degree in electrical engineering instead. I used the time I could not work due to an industrial accident.
Note they are type AC RCD's which are not really suitable for supplying multiple circuits, as a fault with one circuit allowing DC could stop the RCD tripping, with a second fault on another circuit.
The use a high integrity CU with RCBO's needs some careful thought, the main items you don't want to trip are lights and refrigeration, for a RCBO only to supply the fridge/freezer great, if it trips clearly a fault with fridge/freezer so you will loose food even if you are fully aware it has tripped, but where it feeds more, as with a kitchen ring final, then you want to know if some thing else causes it to trip.
I have a rechargeable torch plugged in so if the RCBO trips it lights which is likely to alert me rather fast to fact it has tripped, but simply loosing the light on a fridge/freezer you are likely to miss it, son had the house alarm on same circuit and it would beep with loss of power.
The more there is on a RCD the more likely to trip, theory is great, we should test the installation and if the leakage exceeds 9 mA on any RCD (Including RCBO's) we should split the circuit further, however I for one don't have a clamp-on ammeter that will measure 0.001 amp, so only way for me is to use the RCD tester with all MCB's on when doing the ½ test so if an extra 15 mA does not trip it likely less than 9 mA to earth.
To fit a CU or do any other wiring you need to inspect and test, I looked at the idea of rewiring my mothers house, I realised all my test gear was either faulty or out of calibration, and I would need to pay the LABC to notify them, so it would cost me around £300 over and above materials used to DIY, also there was a time problem, I would need to have mother in a home while re-wiring, so would cost around £600 per week, so getting some one in likely rewired in a week, DIY more like 3 weeks to a month. So to be worth doing I needed to consider getting some one in would save around £1500 and they would likely charge around £2000 for labour so was simply not worth doing DIY.
Many years ago I did my City & Guilds 2391 and this was a 12 week course on inspection and testing, at the end we had to fault find on a board which was designed to simulate a house wiring, it cost at the time around £60 for course 12 weeks, one night per week of around 3 hours, I would say a course like that would be good training even if you fail.
Same goes for PAT testing course, when I did it the 16th edition as it was then, PAT testing and inspection and testing ran one after the other, so 24 weeks in all. The 16th edition only teaches how to read a book, so that one not so important. Now of course 18th edition.
The published success rate for schools and collages messed things up, years ago before the tables it did not matter to collage if you passed or failed, but now it does, and so hard to take exam only, and the cost of courses has also gone up.
Full time was £10 but one course was £120 last time I went to collage (Did 'A' levels) so I did photography and chemistry so the maths course cost me £10. And when I looked at electricians courses they were clearly designed for school levers and other students did not even know gold was a conductor, so course started at a very low level, which was rather boring for me, so I did a degree in electrical engineering instead. I used the time I could not work due to an industrial accident.
The incoming supply’s earth connects to the earth terminal that you circled on the picture.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
