2 CU's At Once?

[clicon357]

I need to replace my CU currently an old metal Crabtree C50 board protected by a single RCD. All the house wiring needs replacing. What are the practicalities of fitting a new CU but KEEPING the old CU in place whilst I gradually replace the circuits. That might sound a bit mad but its not my day job and getting time is an issue. I do want to do it all myself though. Other than centre light fittings all switches and sockets would be changing position. Can't decide whether to just inform the LABC or join ELECSA. I wonder how much time you get with the LABC?

 

[robsparky1975]

Inform building control,as far as im awre there is no time limit

 

[Deleted member 19807]

no problem doing it this way if you have the space

 

[Guest112]

strange way of doing but do-able, you going to put some tails from existing db to new db temporarily untill your changeover of circuits is complete? then as you alter your circuits as you mentioned just transfer them to new db one by one untill you can ditch the old db and put tails into new db.

can you not alter the circuits and then change the db after youve moved your switches and sockets you mentioned? if your problem is because its your house and you want the power on at the end of every day you work on the job what are you gaining by putting the circuits in the new db? are you adding circuits and dont have the room in your existing c50 by any chance, im sure you have your reasons im just curious to why you would need two boards running at once when essentially you only have so many circuits to feed and aslong as they are correctly protected in the c50 you could then just take a couple of hours or so to change the board when your ready, or you could change the board first and then do your alterations etc

this would also save you extending circuits that you wouldnt necessarily need to on a db change if theres enough length left on them, but when moving circuits to new db youd probably have to extend each circuit, nothing wrong with through crimps but personally I like to avoid using them where i can,

 

[Geordie Spark]

I need to replace my CU currently an old metal Crabtree C50 board protected by a single RCD. All the house wiring needs replacing. What are the practicalities of fitting a new CU but KEEPING the old CU in place whilst I gradually replace the circuits. That might sound a bit mad but its not my day job and getting time is an issue. I do want to do it all myself though. Other than centre light fittings all switches and sockets would be changing position. Can't decide whether to just inform the LABC or join ELECSA. I wonder how much time you get with the LABC?

It's the way I've done it before & how I'm doing it right now in my own house. It makes perfect sense to me !!!

 

[Richard]

I need to replace my CU currently an old metal Crabtree C50 board protected by a single RCD. All the house wiring needs replacing. What are the practicalities of fitting a new CU but KEEPING the old CU in place whilst I gradually replace the circuits. That might sound a bit mad but its not my day job and getting time is an issue. I do want to do it all myself though. Other than centre light fittings all switches and sockets would be changing position. Can't decide whether to just inform the LABC or join ELECSA. I wonder how much time you get with the LABC?

We are forever re-wiring occupied council houses, and this is how we do it more often than not.

Rich

 

[clicon357]

Many thanks for all the replies. I was hoping the idea was a "goer" and it seems that it is. To try and answer some of the questions, well first off the whole thing is a mess - appreciate I need to elaborate there. Where to start is the thing:

- Current RCD "protects" the whole board - (see the next item). When it trips whole lot goes off.
- RCD is suspect as to tripping times - got a readings of 299ms on x1/0deg & on x5/0deg of simply in excess of 40ms (>40ms) on the meter last night so that's good enough for me to suspect it. I'll admit that the tester is NOT calibrated. A L-PE fault current of circa 50A suggests the RCD needs to be working properly to me!
- CU is metal clad - system is TT
- No equipotential bonding anywhere, (water, oil pipes)
- No cross bonding anywhere
- Generally copper pipes but with multiple plastic push fit connectors
- CU is in the porch, external and jammed against the ceiling. To work on it you need a short set of steps, the porch measures less than 1m x 1m so the porch light (bulb in a hanging pendant) burns the back of your head when looking in the CU.
- The house has multiple extensions added on over the years with power being taken off from "wherever was closest at the time. In the kitchen for instance 3 doubles on the "Kitchen Ring", 2 other doubles appear to be spurs off of the "Downstairs Ring"
- Multiple, hidden JBs
- Cable runs, clipping just a rats nest
- A real RAT problem as well
- Not enough circuits anyway for future "wants" (hot tub, freezer on separate, smokes, alarm)
- No smokes other than battery powered

I could go on. Couple it with the upstairs floorboards are the big T&G chipboard sheets glued together. Whole house is slowly (and I mean slowly) being remodelled. Seems only sensible to do the electrics. Thinking to move the CU to somewhere more accessible for a start. Run rat vulnerable circuits in steel conduit. Tempted by main incomer board and all RCBOs - yes I know ££££ but there are some deals around. Meteor appear to do the RCBO's for a little over a tenner and known makes only around the £25 mark now. So £250 for 10 circuits - a no brainer for peace of mind. As to a big new, decent board I was considering Eaton MEM - any thoughts?

Thanks for reading.

 

[Octopus]

re the CU just make sure its an insulated type

 

[Rockingit]

I think you're answering most of your own questions! Good luck and have fun keeping the missus out of the way whilst you do it.

The only down-side of doing your own re-wire this way is that you have too much time to think and make improvements as you go and then you end up with a monster of an end result! I somehow managed to go from 6 ccts to 14 when I rewired my place, but I blamed it on too many mince pies eaten whilst doing it!!

 

[clicon357]

re the CU just make sure its an insulated type

I mentioned insulated CU's on a TT a while back in another post but cant find it at the mo. I'm sure one reply reckoned you don't have to have an insulated CU on a TT - I'm sure you do.

There's something in the OSG (not to hand at the moment) about enclosures for a TT being Class 2 or insulated - something to do with earth faults on the supply side?

My question then, on the back of that is what are the implications of bringing steel conduit into an insulated enclosure. I'm thinking on the lines of direct contact between the steel conduit and the supply side line. Not sure if I've put that over too well!

 

[Octopus]

I'd always put an insulated CU on a TT system.

Not sure about steel conduit into an insulated enclosure - out of interest why are you using steel conduit?

 

[supasparxs]

I need to replace my CU currently an old metal CrabHave a CPU (RCBO tree C50 board protected by a single RCD. All the house wiring needs replacing. What are the practicalities of fitting a new CU but KEEPING the old CU in place whilst I gradually replace the circuits.

I had (to be honest still have) an old Wylex rewirable CU and beside it, I have a CPU (RCBO only ) CU
as the new circuits are wired they went into the new board.

between the old board and the head I put a Isolator and then Henley blocks. The supply company wanted to change the meter a couple of months ago and now the Head, meter and MY ISOLATOR all have seals on them (should they have sealed my Isolator??????)

when the lounge is finish (if it's not including the decoration by the 25th I will be served 2 small morsals in a fleshy coloured bag for xmas dinner !!!)
the Wylex board will go into the scrap pile.

That might sound a bit mad but its not my day job and getting time is an issue. I do want to do it all myself though. Other than centre light fittings all switches and sockets would be changing position. Can't decide whether to just inform the LABC or join ELECSA. I wonder how much time you get with the LABC?

I am Napit, not Elesca, however whichever origination we all have joined there has always been an onsite assessment, that the inspector wants to see.
If your installation is incomplete you won't have one.

The membership cost of joining any of the part P registers is more than the cost of LABC.

please correct me if I am in error

 

[clicon357]

I had (to be honest still have) an old Wylex rewirable CU and beside it, I have a CPU (RCBO only ) CU
as the new circuits are wired they went into the new board.

between the old board and the head I put a Isolator and then Henley blocks. The supply company wanted to change the meter a couple of months ago and now the Head, meter and MY ISOLATOR all have seals on them (should they have sealed my Isolator??????)

when the lounge is finish (if it's not including the decoration by the 25th I will be served 2 small morsals in a fleshy coloured bag for xmas dinner !!!)
the Wylex board will go into the scrap pile.



I am Napit, not Elesca, however whichever origination we all have joined there has always been an onsite assessment, that the inspector wants to see.
If your installation is incomplete you won't have one.

The membership cost of joining any of the part P registers is more than the cost of LABC.

please correct me if I am in error

As least I'm on the right track. I dream of a nice new board and knowing its all good! A bit of a tricky call for me in terms of the length of time I'll take to install the new CU and ALL the circuits. I almost need to join ELECSA so I can make a "legal" start then call them in when I'M ready - which will be months away!. Or, I wonder just for this if I should just notify my LABC and start - as long as I do everything properly - which I will I can then take my time. I don't know if they have a time limit as such?

 

[clicon357]

I'd always put an insulated CU on a TT system.

Not sure about steel conduit into an insulated enclosure - out of interest why are you using steel conduit?

Rats & squirrels - or to use the technical term "fauna" - I'm paranoid about them. Old house which had a number of flat felted roofs. A new pitched roof has been put over the top with the old flat roofs still in place. Loads of inaccessible places where wires run etc.

 

[supasparxs]

I think Elecca want to see 2 installations, 1 minor works and another full scope (I'm sure someone will correct me if I'm wrong)

Napit only want to see 2 circuits preferably one of which a ring main

I don't know about LABC as I have never delt with them.

With my house, I did it "Illegally" I knew I had the qualifications, I had the experience, I had the test equipment and the correct level of insurances.
I was mainly doing CCTV work.

because electrical installation is a larger part of my works I am Napit

Richard