hello all i may start some work this week can you take a look at photo`s of this new unit and my old unit i`m about to install this unit from screwfix also wanting to install a 63A MCB from this new unit to a garage unit with 16mm twin & earth cable i`m having a problem finding a garage unit which will accommodate 2 x 32A MCB and 1 x6A mcb reading up about RCBOs would it be better to use these in the garage unit thank you all
Looking at Screwfix website largest RCBO is 40 amp, type AC curve B 30 mA. I can't see any 63A RCBO's. And even with MCB largest is 50 amp. It says high integrity board, but would check on that, looking at British General CFDP16610 on other sellers web sites it does not say high integrity, what high integrity means is there are three neutral bars, so you have some MCB's on one RCD, some MCB's on other RCD, and also either MCB or RCBO which does not go through many RCD's so you can run steel wire armoured cable without RCD protection to a second consumer unit in your garage and that consumer unit will have the RCD for the garage.
One RCD could be removed in the main consumer unit, and RCBO's fitted in that side, but at £24 each that gets expensive, I paid £10 each for my RCBO's and still my consumer unit cost around £250 with surge protection and external isolator, a tad more expensive to the £68 you have paid. It was slightly bigger 18 module so with 2 for isolator and 2 for surge protection that left 14 RCBO's.
I made a mistake, I saw type B and thought the RCD built into the RCBO was type B but it referred to the tripping curve of the MCB portion of the RCBO and the RCD is type AC, not really what I wanted as I have some inverter powered equipment. Really needed type A.
So you could remove the RCD on one side and fit RCBO's maybe 3 RCBO's one for each ring final, and one MCB to feed garage, that's £72, then three RCBO's in garage another £72 plus the consumer unit, it starts to add up.
I went to local supplier (Link) and got a cheap CP (Electric) Limited board, as said £10 each for the RCBO's and they are available at 50 amp, I think price was before VAT can't remember exact price but under £250 and over £200 and included other bits like crimp pliers, cable, and external isolator.
The last house before we moved here had two RCD's feeding two fuse boxes, and from time to time they would trip for no apparent reason, it seemed to come as a batch with maybe two years between them, it was fitted late 90's so have had RCD protection for a long time, but over that time we have lost a few freezers full of food, so this time went all RCBO. One reason was lights split up/down and sockets split front/back so there is no way with just two RCD's that I could ensure lights and sockets in every room are on separate RCD's. And must have cost over £200 loosing two freezers full of food. Clearly did right thing as a roof leak did cause a RCBO to trip, but I could do without that circuit so no problem.
With the old dorman smith loadmaster I remember 70 amp MCB's, but not seen any over 50 amp with today's DIN rail mounted MCB's. As to if RCD in garage consumer unit or house consumer unit, both have plus and minus points, but with twin and earth not really any option, needs to be in house. Personally I would run SWA to garage unless integral.
paultoolbox wrote:hello all i may start some work this week can you take a look at photo`s of this new unit and my old unit i`m about to install
Often when doing a job like this it is best to get the electrician who is going to do the job first, not the other way round. That way he can test it all and issue a certificate, as without it can cause problems in the future.
thank you both for your kind reply's ericmark wow i like you already !!!! to think you had the time to write all that and explains things thank you ammmm would you have time to look at which main consumer box would be suitable for my needs and a garage cu my local wholesalers close to me are below ?
ericmark i`m a retired builder but still very active packed in building 30 years ago went into fitting kitchens and bathrooms i have re-run countless cables in the past so i know the dangers of electrics also replaced a few consumer units i have no worry s about replacing the old CU but the new CU if you agree would require a 63a MCB to the garage CU run with 16mm twin and earth ? i just need advice what to buy got SWA cable 1.5mm & 2.5mm all for the outside as i say looking into a good MAIN CU UNIT and a ( garage CU which i`m installing at rear of house ) as i want to control all lights from my house 8 fence lights 60w also a lamp post and a pillar light also 1x 100w flood light also a 4 outside outside sockets i have plenty off free time as i would like to carry out this work if needs be at end get someone to to test all ! thank you
The cost to DIY a new CU legally is prohibitive, in theory you can still do it, but in real terms the system would only work with an electrician working in his own home. The LABC inspector or in England a third party inspector has to satisfy themselves you have the skill. And the LABC in Wales don't know English charge £100 plus vat for the first £2000 worth of work, so doing a complete rewire may be worth DIY, but small jobs you pay the inspector more than it would cost to get a scheme member to do the job.
In England you can have third party inspectors, but most the schemes simply will not allow it, and where it is allowed it is really an in-house thing so an electrician in a firm can sign off a plumbers work.
Also if the LABC inspector feels it is beyond his skill, he can appoint some one else to test it, and charge you his fee. This is what the LABC inspector wanted to do with my son and I when we took over a job in my mothers house. He would not accept my sons C&G2391 inspection and testing qualification, so my son said fair enough, but the guy you use must clearly be higher qualified than us, my dad has an electrical degree, only then did he back down and say we could do the whole job our selves.
When you sell or rent the house you will need a compliance or completion certificate, to be frank it's a tax, when I came to sell mothers house I could not find the certificates, so applied for replacements, I was told it would take 4 months, and it would cost how ever long it took them to find them, at so much per hour, clearly by that time house would be sold, it seems you can get insurance to cover any faults found when paperwork missing, but I then found the originals.
The paperwork was really useless, as it does not identify the installation certificate it refers to, so you could rewire a whole house and say the completion certificate related to that, when it only related to a kitchen socket. So it is all a trust thing anyway, however clearly doing that is fraud.
Changing a CU by the book is a problem even for electricians, we are officially not allowed to draw the main fuse, so it should be a case of fit an external isolator first, then get the DNO to wire it up, and then you can turn off power, how upset the DNO gets varies area to area, and in some areas they turn a blind eye to seals being broken when they see a new CU, technically I think the DNO should provide an isolator, but two wrongs don't make a right.
Problem with DIY is the DNO can think you have been stealing power, and with the new smart meters they are sent a message when power is lost, so they know you have drawn the fuse and for how long.
You want paperwork from a scheme member electrician that says they fitted the CU so you can show the DNO it wasn't me honest Sir.
If you use the LABC route, then they will insist it is done by the book, I could have simply said your not allowed to DIY fit a CU but technically that's not correct, but in real terms it's not easy.
Once you get an electrician who is a scheme member to do it, he will have a trade account with some whole sale outlet so can by it cheaper than you.
However you can clearly still fit the garage one, it would not be legal but unlikely to get caught, and you could always remove it before selling or renting house, and no one seems to worry anyway.
So now down to nitty gritty, how much power do you need in the garage? We will look at three stages. 1) 13A or less, all it needs is a fused connection unit FCU, no need for a CU. 2) 50A or less, depends on house CU what the largest MCB/RCBO is but it can come from the CU. 3) Over 50A in which case a henley block is used and wiring to shed has to be able to take the full 100A of the DNO fuse. A property under the control of an ordinary person should use type tested electrical equipment, which means although you can get a moulded breaker any size you want, you can't use them in the home as not type tested, well officially anyway. At around £95 without the enclosure the normally would be to fit a fuse like the one the DNO use.
Anyway you need to work out how much power you really need, if the electrician fits a 63 amp socket which you say is for a welder which needs a 45 amp supply and once he has gone you fit a blank and use it to terminate the SWA into then you have not made a new circuit, so in England have not broken the law. If you simply get him to fit a 45 amp RCBO ready great but I don't want to know your breaking the law, or anyone else on the forum, breaking the speed limit is something we all I am sure do, but posting a video on U Tube of you doing it is crazy, yet people do.
So really next is the cost of materials v chance of trip, I used an all RCBO board here, no way after last house do I want to lose a freezer full of food because some water gets into an outside light. My son is an electrician as well as me, so I was lucky he fitted it for me, but if he wasn't then I would have got a scheme member electrician to do it for me, so paper work all correct, at 69 year old at some time in the future it is likely either my wife or I will need home help, so health and safety at work comes into play, so all needs to be legal. Had same problem with mothers house, cost a fortune to get it rewired, but had to be legal so if mother went into a care home, we could rent out the house.
But when my son was going to fit a CU for me, I went into Link the local whole sale outlet and say what have you got, in hind sight I made an error as the RCBO are type AC and really should have been type A, but not really that worried, they still trip if some thing gets wet, I saw type B on the box and thought great, but it turned out it was tripping curve B the logo on the RCBO shows them to be type AC and there was nothing on the box or paperwork to say type AC just a small logo on the RCBO.
As to how many electricians really look unless installing outlet for an electric vehicle I don't know? As said it was only after they were fitted I thought oh I have inverter drive washing machine, freezer and fridge freezer should have been type A not AC.
thank you ericmark i understand what your saying but i only want to install a better CU that is there now if you look at my cu i have a isolating switch under CU i would not need to draw the main fuse ideally i would love to get rid of all those card meters they are not needed any more i pay by direct debit can you take a look at my plan hope the image works i`ve taken out some sockets as perhaps are not needed would these work comfortable with no overloading from a garage CU as i would doubt that all sockets would not be used at the same time ? would you say that the 63A MCB at main CU is to big and perhaps a 50A MCB would work if the lighting to to big to work of 1 6A MCB i could install 2 6A MCB`S ? 1 for the fence lights the other for the flood light ?
i was going to run 2 x 2.5mm swa cable 1 direct to the shed just to add a light and a double socket i will not be drawing a lot of power from shed just the light and use sockets to charge phone or radio ( NO power tools ect,) cable 2 was to power water feature and other 4 sockets
i do not wish to nag you your final word i will have to accept what would be the point if connecting all the sockets outside and lighting and the garage CU then get an electrician in to replace the main CU would he then check my work oh be sarcastic i say i`m not checking that ! so i`ll be at no ends thank you again for your advice
Looking at your plan it would seem 32 amp would be ample, think some of the lamp sizes are OTT, you know as a builder without planning permission 150 watt tungsten is largest bulb permitted in the garden, I have not seen any change to lumen yet, but really should consider 35 watt LED as the limit. You don't want to upset anyone as you really I assume don't want to involve the council, so keep within sensible limits.
However maybe I am the last person to advise, I have just made a mistake with my own house, which will likely cost me money, still considering how to correct, I will tell you my error as you could easy make the same error.
On moving into this house, I found a fuse box and a consumer unit, the fuse box was between false ceiling and original ceiling so clear it needed moving, so off I went to local electrical whole sale outlet and got a metal consumer unit 18 module a surge protection device and isolator plus 14 RCBO's quick glance they said type B and at £10 each seemed good idea. I got my son to fit it for me, he is also an electrician. Thought jobs a good one.
But it seems the RCBO was not type B it was curve B, it was type AC, and the only marking to say type AC was the logo, nothing on the paperwork said anything about being type AC.
So I have a fridge/freezer, freezer, and washing machine all with inverter drives, so for front of house sockets the RCD part of the RCBO should be at least type A, a type A RCBO is £16 so swapping one for type A powering sockets at front of house not too bad, however what about the rest?
So we get a RCD as type AC, A, F, B etc. The type AC as the name suggests works A1 with a pure sine wave AC supply, however the core is made of iron, and this iron core can become saturated if DC is passed through it, so if any appliance has a half wave rectifier it can cause a DC component on the supply, in theory all should use a full wave rectifier, but a fault can cause half wave rectification, so where we have electronic equipment which rectifies the mains, we should use type A or better, this in the main raised its head with electric cars, where they use in the main type F RCD's, but it has turned the testing upside down, we in the past turned everything off to test, you would normally turn off computers before testing a supply when the test could cause the supply to trip, however it is the computer power supply which is likely to stop the RCD working, so maybe we should test with all switched on?
I am sure you can see a problem there, but as yet there does not seem to be a tester which simulates a DC component.
But with a MCB we don't test they trip at rated current, we just trust they will do as they say on the device, so we are told if there is any switch mode, inverters, or other equipment which rectifies the mains, it does not matter if rectified after a transformer, we should not use type AC RCD's. We don't test they will work with a DC component we just trust what the manufacturer says.
So what about LED lights, there is a clue in the name, D stands for diode, the device used to rectify with, they use in the main a full wave rectifier, but if one diode in the rectifier fails, they still work, maybe less light output, but still work.
So risk assessment in doors even if the lights RCD does not work, the risk is very low, so I am not changing the RCBO for lights, but that is my personal opinion, I have no facts to support that.
So should I really be advising you, when I get it all wrong in my own house?
hi ericmark thanks for posting read your post i have posted in another forum 2 guys replied whom you know of i`ve had no more response from them !
is it not better to ask than not ask you !
as you know more about what i want to do with the cu and my plans for example cu in screwfix the MX looks good but then again you would know which is best to use ! mcb`s or rcbo`s ? i have my 1.5m swa and my swa 2.05mm im going ahead with my plans i just hoping the these forum to help i enjoy doing electrics may it be small or big advice is better than non i would just like to tap your knowledge run 1 supply 2.5mm swa tee off to other sockets ? or 1 cable to shed ? than another cable to run other 4 sockets ? im running 1.5mm swa cables to fence lights but they have to run up the fence should i clad cables exposed to the elements ? another question is the 63mcb you said they wasn't one or not in screwfix ? is it feasible for a garage cu to have 2 X 32a mcb or rcbo if i need to run 2 x 2.5mm cables ? and 2 x 6a mcb or rcbo 1 for the fence lights the other for the flood light ? as i want to run them independently i`m very particular in my work if i do some thing it has to be done right hence my questions thanks ericmark hope to hear from you again help would be appreciated
Screwfix well Electrofix did give me discount, but no longer, there are some things I use Electrofix for like the LAP grid stuff, other things I use Link for which is my local whole sale outlet.
I think DIY is great, but there are safety issues, we have said on a few forums no point having the forum if we simply say get an electrician, however very few DIY people will have access to, or be able to safely use the test equipment to ensure the installation is safe.
Even in England the Part P law says CU fitting has to be registered, in Wales there is very little you can do officially.
OK on the odd time I may do 35 MPH in a 30 MPH limit, but I don't drive at 70 MPH in a 30 MPH limit, and the same applies to electrics, we all break the rules to a small extent, but you really have to consider how to ensure what you have done is safe.
A test set costs around £750 and I assume you would not buy one, so the other way is find some one who has got the equipment and get them to test.
The rub is of course they may tell you that's not acceptable and do nothing, so you need to follow the regulations as close as you can, so anyone inspecting is not going to blow a gasket.
So I would suggest you wait until the pubs open again and try and find a friendly electrician who will either test for you, or lend you a tester.
I have at work been asked questions, and given what I felt was good advice, then latter visited the guy, and realised he had not really related what he had, and as a result the installation was dangerous.
Even my dad's house, we had an electrician change a CU only to find he had not test gear and what he thought was an earth was an earth but was for the old party line phones, not the main electric supply, which had long since been made redundant.
Using a loop impedance tester it became clear there was no earth. But looking at the wires, it was not easy to realise the error.
What had happened I really don't know, there was an earth as when a lot younger I had made a mistake and blown a fuse with a line - earth fault, maybe there were iron water pipes which had been changed to plastic.
As said I went to whole sale outlet, asked for a all RCBO consumer unit with 14 outlets, and was sold what they had in stock and made an error with type of RCBO. If you look at the Screwfix site, as an example part number 3505X rather expensive but only using as an example, spec say 6 kA and curve B, but it does not say if type AC, A, B or F. This link https://www.electrium.co.uk/media/20200 ... CBO%20(Web).pdf shows it is a type A, but Screwfix are not alone in not actually saying what the type is. The cheaper BG RCBO part number CUCRB32 is type AC on the data sheet https://www.bgelectrical.uk/public/down ... _RCBOs.pdf but the logos say what type wavy line is type AC and wavy line with line with bumps on underneath is type A [attachment=0]Type A.png[/attachment] but not even sure if you need type A or not?
It seems with CP make type A are £16 so may be worth getting a CU which uses the cheaper options.
I think using the test button is likely good enough with a RCD or RCBO even if it takes 60 seconds instead of 40 mS in the main the RCD trips out before we touch some thing live, mainly due to water ingress. But the problem is the loop impedance, we need it for two reasons, one to show there is an earth, the other to see if 6 kA is enough, many actually read in amps called the prospective short circuit current, and ohms for the earth loop impedance.
It says in the regulations you can get it from enquiry, which means you can ask the DNO what it is at the head, then use a low ohm meter that uses at least 200 mA to calculate what it will be else where.
Why is it important, well the MCB is two devices in one, a thermal trip which is quite slow to act, and a magnetic trip which will work very fast, but with a B type MCB the magnetic part works on between 3 and 5 times the current of the thermal part, so for a B32 MCB the magnetic part needs 160 amp to flow, ohms law 230/160=144Ω add a 5% safety margin and 1.36Ω so with a ring final around centre we want 1.36Ω or less, with a 45A MCB want 0.97Ω or less.
So if the loop impedance is just a little high say 1.2Ω instead of 0.96Ω then with a short circuit it will take minutes to disconnect instead of a fraction of a second, this was not the case with the old fuse, it was only when we moved to the MCB this became a big problem, just a little over and tripping times are much increased.
So if an electrician fits a CU you will get an installation certificate, on that certificate it will show the PSCC and ELI at the consumer unit, so although a multi-meter will not measure using 200 mA it will be in the main good enough for you to test the impedance at any new installation, even simple measuring, we know you can have for example 106 meter of 2.5 mm cable in a ring final and still be within the volt drop limits.
I am not that good at maths, I make errors, so I built a java script program to work it out for me, so I could enter figures where I know the results to see if any errors in program, so reasonable sure now no errors so I can use it to plan an installation.
You get to know when your sailing close to the wind, so most times I install then test, only when I think it may fail do I calculate first, but so much easier now, always seemed to get decimal point wrong with the slide rule, it was OK if I knew answer should be around 1.5 if got 14 or 0.14 I knew I had missed adding or removing a 0, when the calculator came out it was so much easier. But electrical maths includes square roots and imaginary numbers, so needs a good calculator.
I have a copy on the PC of most of the regulations, but have misplaced the book, and so don't have the formula to hand, it was my poor maths which means I only have a foundation degree level 5 not an honours degree. And I will admit there was a lot of luck involved in my passing.
The more one knows, the more one realises how little one knows, my father-in-law had a sign on his desk, these people who think they know it all, are especially annoying to those of us that do.
He would claim light bulbs don't give out light, the suck in the dark, and so when full they go black. We know it is wrong, but try proving it.
Links don't really matter, what I was pointing out, is the problem with RCBO's finding out what you are buying, type AC or type A because for some reason the sellers don't seem to tell you, so you need to get manufacturers part number and look at data sheet to find out.
As to if there is really a problem using type AC I really don't know.
hello ericmark can you take a look at this i need some advice please completed my building work and now on stand by bored !!!!! why you ask i`ve taken all of your good advice so contacted 7 local electricians well over 2 weeks now not one reply !!!! OK lock down so as i`m now waiting on people WHO MAY NEVER TURN UP !!!! I WILL NOT BE TOUCHING THE MAIN CONSUMER UNIT !!!! so i`m asking for some help to assist a electrician if and when one turns up ! can i run all the cable outside already bought 1.5mm 3 core SWA and 2.5mm 3 core SWA i would like to do this work if i connect all the cables tees to daisy chain the lights leading to the lights then leaving all the tee joints exposed ( but sealed ) so if he wants can check my connections he can ? should i run one 2.5mm to shed or one cable for all 5 sockets and tee off from one socket to next ? also the garage unit which will be installed at back of house surely i can install this CU running all cable to the unit but not connecting them ? so when an electrician finally arrives hopefully his work will be less and i`m not hanging around doing nothing so please can you help in what materials to buy or best ones to buy for example this tee from screw fix
Hylec TEEBOX IP67 MINI T-JUNCTION WITH TERMINAL STRIP (72715)
any good or can you advise what one`s to buy which you all have more knowledge than I thank you Paul
hello all fed up had 4 sparks around one said job to large ! had a lot of good advice but sorry to say no way i would pay someone over £3,000 so i have come down from my ladder so now just wanting to run maybe 4 socket outside and 4 led lights can you advise on my new layout
my main CU unit is a crabtree 80A RCCB 30mA2 pole BS 4293 type SB6000 it has 2 spare slots I also have a spare 32amp mcb As I can’t seem to buy a larger fuse bigger than a 32 amp My question is can I run a 6mm SWA cable from this 32amp To this unit from the screw fix unit below
British general 5- module 3 way populated garage ( 1926G )
I'm now wanting to install this garage unit at rear of house inside ! Then run 4 outdoor garden sockets of the 32amp And run 4 led fence lights off the 6amp My other question is the 32amp mcb on my main CU Good enough to run 6mm SWA cable to the screw fix unit Been told to buy a 63amp for my CU but cannot buy any bigger than the 32 amp ! Thank you paul
What your asking I can't really answer, however my house has a 60 amp supply and the main fuse has never blown, it is likely you can run all you want from a 13A fuse.
In the main garage supply only needs a fused connection unit (FCU) in house and a switched FCU in garage with 3 amp fuse for lights. There is normally no need for garage consumer units, and the like unless your doing welding or running large machines.
Main thing is RCD protected and able to turn it off if anything goes wrong so can still use house electrics.
With my old house I actually plugged in all sheds so I could easy disconnect them.
Blagdon did a kit, designed to get around the Part P laws in Wales, now not as strict in England, so you can plug in all your garden using a pre-assembled system. I would have a look at it and decide if it will do what you want.
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