advice on changing my consumer unit please

[johnnyboy1950]

My First Post
My existing Consumer Unit has 8 MCBs and the main isolator is an RCD. Off of one of the MCBs is a circuit to the kitchen sockets and there is a spur off of the kitchen ring that goes to the garage. In the garage there is a CU unit with an RCD protecting the load. Along with the garage sockets and lights there is connected all my garden stuff, pond lights spot lights etc. At the moment I have a problem with something in the garden which is tripping not only the garage RCD but the house RCD so when the problem occurs in the garden the whole house goes off.
I know my first job is to change the main house isolator to an MCB and then protect the rest of the supply with dedicated RCDs. However all the CU units I've researched have a split system i.e.. a split unit with typically 2 RCDs protecting 4 MCBs each. If I connected my kitchen ring with the garage spur to one of these split units I would still have the situation where if I had a problem in the garden I would lose half my circuits. So my question is what do I need to do to protect my house with RCDs but protect the garage and garden the same way without losing supply to the house.

 

[UNG]

Your first job is to fix the fault in the garden rather than just reset the protection device

 

[Leesparkykent]

Changing the consumer unit will also be notifiable.

 

[johnnyboy1950]

To UNGs reply
Yes I know I need to fix the garden fault but in my current situation some the fault finding I do is going to result in the whole house going off. and in the future I want to be able to have a situation when anything in the garden which is a problem will not kill the house supply.

 

[johnnyboy1950]

I was hoping on this forum to get some good informed advice rather than a reminder of the red tape we are currently under. If nobody dares to give me any advice then I will have to work it out for myself.

 

[HandySparks]

My First Post
My existing Consumer Unit has 8 MCBs and the main isolator is an RCD. Off of one of the MCBs is a circuit to the kitchen sockets and there is a spur off of the kitchen ring that goes to the garage. In the garage there is a CU unit with an RCD protecting the load. Along with the garage sockets and lights there is connected all my garden stuff, pond lights spot lights etc. At the moment I have a problem with something in the garden which is tripping not only the garage RCD but the house RCD so when the problem occurs in the garden the whole house goes off.
I know my first job is to change the main house isolator to an MCB and then protect the rest of the supply with dedicated RCDs. However all the CU units I've researched have a split system i.e.. a split unit with typically 2 RCDs protecting 4 MCBs each. If I connected my kitchen ring with the garage spur to one of these split units I would still have the situation where if I had a problem in the garden I would lose half my circuits. So my question is what do I need to do to protect my house with RCDs but protect the garage and garden the same way without losing supply to the house.

Changing the main board to one containing RCBOs for each of the circuits would help limit the inconvenience. Or a 'high integrity' board containing a couple of RCDs for most of the circuits plus one RCBO for the circuit that the garage is supplied from.

Better, however, would be to supply the garage directly from its own RCBO (or MCB, depending on earthing arrangement and cable installation method) in the main board.

 

[Deleted member 9648]

I was hoping on this forum to get some good informed advice rather than a reminder of the red tape we are currently under. If nobody dares to give me any advice then I will have to work it out for myself.

Personally I would have thought an electrical engineer would be able to work it out for himself....I'm just an electrician and I could work it out.

 

[Pete999]

Fix the fault first and don't have two RCDs in series there won't be any discrimination,

 

[Octopus]

However all the CU units I've researched have a split system i.e.. a split unit with typically 2 RCDs protecting 4 MCBs each.

Best advice is to stop looking at the cheapest solutions.....

 

[telectrix]

first divert the feed to the outside to come from the main CU. rectify the fault before connecting, then consider a hi-integrity board or an all RCBO board as an upgrade.

 

[Spoon]

Personally I would have thought an electrical engineer would be able to work it out for himself....I'm just an electrician and I could work it out.

Doesn't it all depend on what job your are doing? I have learned a hell of a lot about domestic electrics from this forum. You should give the bloke some slack.

OP: This is a good forum mate. Most of the people give great advice. All the info you have been given so far is true.
If the only reason you want to change the house CU is due to a fault in the garage circuit then wouldn't it be better just to find the fault in the garage circuit? Or am I miss-reading your post.

 

[DPG]

I was hoping on this forum to get some good informed advice rather than a reminder of the red tape we are currently under. If nobody dares to give me any advice then I will have to work it out for myself.

I would have thought the advice of fixing the fault, and the work being notifiable was good advice. But if you're going to spit your dummy out then perhaps you will indeed have to work it out for yourself. Although if I were you I would employ someone who is competent to do this sort of work - otherwise you are putting you and your family at risk. Daz

 

[johnnyboy1950]

Thanks for the feedback people. I know what I need to do its just that I haven't found a piece of kit that will do it. Handysparks, the boards I have seen so far are typically split with RCD protection but don't have a spare slot for a single RCBO outside the control of the RCDs monitoring the split groups, so if you could point me to such a thing I would be grateful.
Also my point about the garden fault is surely that there is much more incidence of RCD trips in a garden environment (mowers, outdoor lights pond pumps etc.) that regardless of whether I have a fault now or not I would like any fault outside not to trip the house

 

[DPG]

I'd personally go the route that handy sparks suggested, ie. All RCBO devices. Daz

 

[johnnyboy1950]

AHA!
I have just looked on the screwfix site and High Integrity would seem to tick all the boxes, I didn't know that was the name for such a thing. I can pretty much carry on myself now. Of the choice of RCBO I have heard certain makes have failed testing. Which ones would you recommend please?

 

[DPG]

Have you checked the bonding is up to scratch? Also, what tests will you be performing? Daz

 

[telectrix]

hager, BG, wylex, schneider , crabtree --- all are top brands. there was a recall on wylex MCBs a few years ago, but that's all been sorted. i use BG. you can configure the board to have up to 3 ways direct from main switch.a split hi-integrity boare with the 2 RCDs covering the house and a RCBO for the outside is the cheapest option. if you want to comply with latest regs, it needs to be a steel enclosed CU. as for notifying to LABC, that's up to you. :17:

 

[Spoon]

Have you checked the bonding is up to scratch? Also, what tests will you be performing? Daz

And just to add to this. Do you have the correct equipment to test the install? I don't, that why I get someone in to do the jobs and test it for me. I also get the cert.

 

[Octopus]

Ask the sparky who is going to do the work?

 

[telectrix]

i can see a shared neutral rearing it's ugly head if OP has not got a MFT or similar.

 

[Octopus]

Yup. And even with one it's not easy. Trying to resolve one right now!

 

[telectrix]

Yup. And even with one it's not easy. Trying to resolve one right now!

get the snips out, man. :bucktooth:

 

[7029 dave]

Good advice given.

 

[rolyberkin]

I was hoping on this forum to get some good informed advice rather than a reminder of the red tape we are currently under. If nobody dares to give me any advice then I will have to work it out for myself.

Your 'well informed' advice was do not meddle with stuff you clearly know nothing about, like it or not it's not red tape it is the law. Is risking your own or your families life the cost of getting someone out who knows what they are doing, has the correct test equipment to find the fault, fix it and can put things right? You will probably spend more money doing work that doesn't actually need doing by having a go yourself. As and when you come to sell your house you will need a certificate for the new consumer unit and associated notifiable work.

 

[davesparks]

Thanks for the feedback people. I know what I need to do its just that I haven't found a piece of kit that will do it. Handysparks, the boards I have seen so far are typically split with RCD protection but don't have a spare slot for a single RCBO outside the control of the RCDs monitoring the split groups, so if you could point me to such a thing I would be grateful.
Also my point about the garden fault is surely that there is much more incidence of RCD trips in a garden environment (mowers, outdoor lights pond pumps etc.) that regardless of whether I have a fault now or not I would like any fault outside not to trip the house

What you need to do is have the wiring altered so that the external supply does not come from the kitchen circuit, but rather has its own circuit.
Nothing else will achieve a situation whereby faults on the external circuit do not cause a loss of power internally.

Having the CU replaced will possibly reduce the impact, but not necessarily eliminate it.

What is the reason for the RCD protecting the whole CU currently? Is it providing fault protection?


Sent from my iPad using Tapatalk

 

[johnnyboy1950]

I inherited the existing CU when I moved in. The main isolator is an RCD which is safe but inconvenient. I agree that supplying the outside directly from the CU is the best way but at the moment the garage and garden has an armoured cable underground from the inside kitchen wall behind the fitted cupboards. I would have to isolate that and run a new cable from the CU to the garage. Changing the main RCD to an MCB would involve pulling the sealed fuse anyway so I'm now thinking I'll just find the fault in the garden and leave everything else as it is.

 

[Spoon]

Can you not run a cable from the house CU to a metal junction box and wire the garage armoured cable to that? Use MF connectors if necessary.

 

[telectrix]

wot he just said. ^^^^^. but you'll still have the problem of a fault outside tripping the main RCD until and if you get a hi-integrity board fitted.

 

[Octopus]

I inherited the existing CU when I moved in. The main isolator is an RCD which is safe but inconvenient. I agree that supplying the outside directly from the CU is the best way but at the moment the garage and garden has an armoured cable underground from the inside kitchen wall behind the fitted cupboards. I would have to isolate that and run a new cable from the CU to the garage. Changing the main RCD to an MCB would involve pulling the sealed fuse anyway so I'm now thinking I'll just find the fault in the garden and leave everything else as it is.

How do you plan to fault find? Do you have an mft? And competence?

 

[Deleted member 9648]

How do you plan to fault find? Do you have an mft? And competence?

He's an electrical engineer.....considerably more competent than those advising him it would seem.

 

[Spoon]

I don't think competence is an issue here. It's just lack of knowledge on the domestic side. He is asking for info, that is all.
I am an Electrical Design Engineer but as I have said, before I joined this forum I knew hardly anything about domestic electrics. The only test equipment I have is a £10 digital mutimeter.....

 

[johnnyboy1950]

Thank you Wirepuller and Spoon
OK I was trying but it seems like I have to convince more than one or two people. My background since the late 70's has been CNC Machine Tools and in the last 10 years Gate Automation which is very much to do with electrical and electronics in the outside environment. I can easily diagnose the garden problem by a process of elimination. I think it is a garden light that is now smothered by a large shrub. It's quite straight forward to eliminate the supply from the infra red distribution box I have inside an IP66 box in the garden. All I wanted was a way of solving the inconvenience of the house going off when something happens in the garden/garage.
BTW this is the best site I've seen for a long time where people respond quickly even if its not the advice I want to hear.
Don't you guys have work to do during the day? LOL!

 

[Spoon]

See my post 27 mate. Wire the circuit to a RCBO (if the circuit requires it and if you can fit on in your house CU) . Then sort out the fault.