On 23/03/2019 14:24, wrote:
On Saturday, 23 March 2019 09:23:54 UTC, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2 hours
to swap a CU!

1. Charge up your cordless drills.

2. Start early and give yourself plenty of time.

3. Mark off the live cables with a sharpie pen well before you start,
ideally the day before. I use a series of dashes to identify the circuit
numbers. Write down a schedule of what dashes represent which circuit.
Take a photo.

4. Prep up the new CU as early as you can. Forgot the knockouts that
come with metal clad CUs and get out the jigsaw and make your own. Its
much easier to have a slot instead of a series of holes. If possible do
this the day before and superglue on some grommet strip.

5. Have a supply of spare cable and crimps ready to extend the cables.
If you are running out of time use strip connector and finish off with
crimps another day in your own time without rushing. Or use WAGO.

6. After removing the old CU you should, if required and it is possible,
reorganise the layout of the cables and the tails to suit the layout of
your new CU.

So if fitting a split load CU you would put the upstairs sockets next to
the downstairs lights etc. Prepare your preferred layout to match the
markings you have made on the cables the day before so you can write it
down.

This does not apply to an all RCBO setup (other than the two cables of a
ring might need to be placed next to each other).

In particular to the OPs setup I would not be surprised if all the
cables drop down from the ceiling and could not all be freed up and
organised in any layout he wanted.

7. After organising the layout of the cables tape the ends of each
circuit together ie LNE of upstairs lights or if a ring tape them as a
pair. Labelling the tape also helps as the tape will probably be over
the cable markings.

This will help you get get the cables into the new CU and stop neutral
mix ups

8. Think about the exact positioning of the new CU. If the OPs existing
CU was mounted right up to the ceiling then the front cover would not
fit. Hence it is 5mm below the ceiling. The same might apply to your new
CU. BTDTGTT.

9. If going all RCBO take out an insurance policy when buying the CU. ie
buy a 6A and 32A MCB when you buy the CU. Use them instead of RCBOs if
you have a nuisance trip and it will give you time sort out the cause of
the fault in your own time. If fitting a split load CU you have to leave
a non RCD space available to do this (not all split load CUs have a non
RCD side)

10. The wiki covers the second fix of the CU. However I usually put the
tails, earth and bonding earths in first followed by all the circuits
earths.

11. Go back a week later and recheck the tightness on all the terminals.

And test your ciruits beforehand, so you don't end up with a partly nonfunctional system for a while.


It's certainly worth checking what each MCB currently does.
A couple of months ago I found an incorrectly wired immersion and ring.
One of the legs of the ring went to the 16A immersion MCB and the other
leg and the immersion went to the 32A upstairs sockets MCB.

This would have easily been identified by turning the MCBs off one at a
time.


--
Adam

On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.



--
Adam

On Sunday, 24 March 2019 09:52:09 UTC, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.

Wylex RCBOs don't like to grip 2x 2.5mm cables unless they're twisted together. That can catch people out.


NT

On 24/03/2019 09:52, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki
article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.



Possibly - for us (or at least this one) slow coaches what take a /lot/
longer - fill a flask and cook the bacon before you start?

I suppose there'd need to be a new category of "only if you are
terminally slow" to mention that if you happen to have an isolating
switch after the meter, spare tails, a Henley block and space to
relocate the old CU with one or two circuits temporarily it's possible
to work with the comforts of home - and of course the frisson of
managing 2 sets of tails, 2 main switches, ....


--
Robin
reply-to address is (intended to be) valid

In message ,
writes
On Sunday, 24 March 2019 09:52:09 UTC, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.

Wylex RCBOs don't like to grip 2x 2.5mm cables unless they're twisted
together. That can catch people out.

Hmmm.. recent fiddling with ceiling roses (electrician fitted during the
last 12 months) indicates that twisted earth wires may loosen over time.
This version has a large brass post with ample space for three twisted
earth wires. Of the 5 sets 3 were very slack. I suppose the driver
needed for tightening the other shrouded terminals would be inadequate
for the bigger earth screw. Or possibly that twisted solid cores can
migrate?


NT

--
Tim Lamb

On 24/03/2019 10:07, wrote:
On Sunday, 24 March 2019 09:52:09 UTC, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.

Wylex RCBOs don't like to grip 2x 2.5mm cables unless they're twisted together. That can catch people out.




A lot of RCBO do the same.

Add to the list
Do a tug test.


--
Adam

On Sunday, 24 March 2019 10:42:58 UTC, ARW wrote:
On 24/03/2019 10:07, wrote:
On Sunday, 24 March 2019 09:52:09 UTC, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.

Wylex RCBOs don't like to grip 2x 2.5mm cables unless they're twisted together. That can catch people out.




A lot of RCBO do the same.

Add to the list
Do a tug test.


--
Adam

Adam (and everybody else) - thanks for the very helpful comments and suggestions which I will take on board. Good to have some affermitve feedback rather than a list of reasons why this job can't be DIY.

I'll post some feedback on how it goes, but it may not be for a few weeks.

Cheers - Kevin

On 24/03/2019 09:52, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki
article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

Make sure you have plenty of light, and try and find a way of getting
comfortable to work - be it suitable ladder or stool to stand / sit on,
and perhaps even some coats / cushions etc to prop against in those
horrible understairs cupboard working situations.

(for the latter, taking the cupboard door off its hinges can yield a bit
more wriggle room)

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.

Must admit I don't think I have ever timed doing it...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 24/03/2019 11:43, Kevin H wrote:
On Sunday, 24 March 2019 10:42:58 UTC, ARW wrote:
On 24/03/2019 10:07, wrote:
On Sunday, 24 March 2019 09:52:09 UTC, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW
wrote:

If you go ahead with it I'll post a few more tips than
the wiki article about real life CU swaps.

I'd be interested in that anyway if you have the time?
Would it be worth adding to the article?


John or NT usually add anything worthwhile I post to the
wiki.

So here are a couple of tips that would apply if I had more
than 2 hours to swap a CU!

OK I have woven some extra stuff into the existing article
based on these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to
test). It usually takes me 90 minutes to prep it up and mount
the board with the cables where I want them. The last 30
minutes is fitting the live, neutrals and MCBs or RCBOs.

Wylex RCBOs don't like to grip 2x 2.5mm cables unless they're
twisted together. That can catch people out.




A lot of RCBO do the same.

Add to the list Do a tug test.


-- Adam

Adam (and everybody else) - thanks for the very helpful comments and
suggestions which I will take on board. Good to have some affermitve
feedback rather than a list of reasons why this job can't be DIY.

You will usually find in this group, that the general assumption is
pretty much any job can be DIYed with the right mindset, research, and
practice.

(perhaps with a little caution introduced if it sounds like the poster
is about to qualify for a Darwin award!)

I'll post some feedback on how it goes, but it may not be for a few
weeks.

Cheers - Kevin



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sunday, 24 March 2019 10:39:12 UTC, Tim Lamb wrote:
In message ,
tabbypurr writes
On Sunday, 24 March 2019 09:52:09 UTC, ARW wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW wrote:

If you go ahead with it I'll post a few more tips than the wiki article
about real life CU swaps.

I'd be interested in that anyway if you have the time? Would it be
worth adding to the article?


John or NT usually add anything worthwhile I post to the wiki.

So here are a couple of tips that would apply if I had more than 2
hours to swap a CU!

OK I have woven some extra stuff into the existing article based on
these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to test). It
usually takes me 90 minutes to prep it up and mount the board with the
cables where I want them. The last 30 minutes is fitting the live,
neutrals and MCBs or RCBOs.

Wylex RCBOs don't like to grip 2x 2.5mm cables unless they're twisted
together. That can catch people out.

Hmmm.. recent fiddling with ceiling roses (electrician fitted during the
last 12 months) indicates that twisted earth wires may loosen over time.
This version has a large brass post with ample space for three twisted
earth wires. Of the 5 sets 3 were very slack. I suppose the driver
needed for tightening the other shrouded terminals would be inadequate
for the bigger earth screw. Or possibly that twisted solid cores can
migrate?

I don't think twisted cores are any more vulnerable to loosening, if anything they're less so, as you're less likely to end up with one weakly gripped. Screw connectors are known for coming loose, especially if not done up well to begin with.


NT

On 24/03/2019 21:54, wrote:

I don't think twisted cores are any more vulnerable to loosening, if
anything they're less so, as you're less likely to end up with one
weakly gripped. Screw connectors are known for coming loose,
especially if not done up well to begin with.


Crimp a ferrule on first.

On 24/03/2019 12:40, John Rumm wrote:
On 24/03/2019 11:43, Kevin H wrote:
On Sunday, 24 March 2019 10:42:58 UTC, ARWÂ* wrote:
On 24/03/2019 10:07, wrote:
On Sunday, 24 March 2019 09:52:09 UTC, ARWÂ* wrote:
On 24/03/2019 00:17, John Rumm wrote:
On 23/03/2019 09:23, ARW wrote:
On 22/03/2019 20:18, wrote:
On Thursday, March 21, 2019 at 11:29:13 PM UTC, ARW
wrote:

If you go ahead with it I'll post a few more tips than
the wiki article about real life CU swaps.

I'd be interested in that anyway if you have the time?
Would it be worth adding to the article?


John or NT usually add anything worthwhile I post to the
wiki.

So here are a couple of tips that would apply if I had more
than 2 hours to swap a CU!

OK I have woven some extra stuff into the existing article
based on these comments.



Anyone one else (including yourself) got any other tips?

I generally get a couple of hours to swap a CU (plus time to
test). It usually takes me 90 minutes to prep it up and mount
the board with the cables where I want them. The last 30
minutes is fitting the live, neutrals and MCBs or RCBOs.

Wylex RCBOs don't like to grip 2x 2.5mm cables unless they're
twisted together. That can catch people out.




A lot of RCBO do the same.

Add to the list Do a tug test.


-- Adam

Adam (and everybody else) - thanks for the very helpful comments and
suggestions which I will take on board. Good to have some affermitve
feedback rather than a list of reasons why this job can't be DIY.

You will usually find in this group, that the general assumption is
pretty much any job can be DIYed with the right mindset, research, and
practice.

(perhaps with a little caution introduced if it sounds like the poster
is about to qualify for a Darwin award!)


+1


Although I have one more tip

It's probably worth having a practice run of removing the main fuse
before you start. I have very occasionally found that they will not
move. Not very likely to happen in the OP's case as it is a newish house
but still worth checking.

The Main Switch of the CU must be in the OFF position when fitting and
removing the main fuse.


--
Adam

(perhaps with a little caution introduced if it sounds like the poster
is about to qualify for a Darwin award!)


+1


Although I have one more tip

It's probably worth having a practice run of removing the main fuse
before you start. I have very occasionally found that they will not
move. Not very likely to happen in the OP's case as it is a newish house
but still worth checking.

The Main Switch of the CU must be in the OFF position when fitting and
removing the main fuse.



Adam..


What's the latest on getting the distribution company putting a 100 amp
isolator switch in these days, do you still have to pay for it?..

--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

On 25/03/2019 20:09, tony sayer wrote:
(perhaps with a little caution introduced if it sounds like the poster
is about to qualify for a Darwin award!)


+1


Although I have one more tip

It's probably worth having a practice run of removing the main fuse
before you start. I have very occasionally found that they will not
move. Not very likely to happen in the OP's case as it is a newish house
but still worth checking.

The Main Switch of the CU must be in the OFF position when fitting and
removing the main fuse.



Adam..


What's the latest on getting the distribution company putting a 100 amp
isolator switch in these days, do you still have to pay for it?..


Yes in my area if it is a request and not a new supply.

It's probably easier and cheaper just to fit your own.

--
Adam

On Tuesday, 26 March 2019 19:46:41 UTC, ARW wrote:
On 25/03/2019 20:09, tony sayer wrote:
(perhaps with a little caution introduced if it sounds like the poster
is about to qualify for a Darwin award!)


+1


Although I have one more tip

It's probably worth having a practice run of removing the main fuse
before you start. I have very occasionally found that they will not
move. Not very likely to happen in the OP's case as it is a newish house
but still worth checking.

The Main Switch of the CU must be in the OFF position when fitting and
removing the main fuse.



Adam..


What's the latest on getting the distribution company putting a 100 amp
isolator switch in these days, do you still have to pay for it?..


Yes in my area if it is a request and not a new supply.

It's probably easier and cheaper just to fit your own.

--
Adam

Just following up on all the useful help and advice that was given in relation to swapping my CU.

I completed this task yesterday. Some notes and feedback which I hope may be useful for others considering doing this themselves.

In summary (to avoid reading back through the old posts), I am planning to fit an induction hob as part of a kitchen re-fit. This requires a 32A connection and there is no suitable connection available in the kitchen (I didn't want to extend/share the cooker connection which is on the other side of the kitchen). The CU is 25 years old, has no spare positions so a new CU was the way to go. Advice was (cost permitting) to go for RCBOs which I have done.

I bought a BG 10 way CU (just 100A isolator provided) and a set of RCBOs to match the current MCBs, plus some spare MCBs as advised (see later) to help with problem circuits. These were bought from TLC direct who delivered everything next working day (nearest store 20 miles away, and it was free delivery anyway). Total cost £205.

First observation (on receipt of the CU) - it is much smaller than it looks in the photos, and smaller than the current CU. Lesson #1: Check the measurements.

As advised, I marked up each cable with sharpie pen and backed this up with tape with the same information on each cable. The 3 ring circuits were individually paired. Took photos of the existing wiring. I have 3 separate lighting circuits and a mains smoke detector circuit. As part of previously turning off each circuit in turn, I have two lighting circuits on the ground floor which I planned to combine, and the upstairs lights would be combined with the smoke detector to both create 2 spare circuits in the CU (one being needed for the hob) and to make it obvious if there is a fault in the smoke detector circuit by having the lights not work.

I prepped the CU the day before - cutting slots in the top for some of the cables (and gluing in gromet strips) and fitting the RCBOs.

Saurday morning. Checked my meter was working by measuring the voltage in the CU. Then turned off each MCB before turning off at the outside isolator switch (no need to cut the seal and pull the fuse). Went back and checked that there was no voltage coming into the CU and then off it came. One thing I was surprised with (perhaps I shouldn't have been) was how loose some of the neutral and earth connections were. I've never checked the tightness of these connections in the 20 years we've been in this house. Perhaps that needs to be an annual check?

As part of the re-fit I checked there was continuity between the the two halves of the ring mains.

Given the smaller than expected size of the CU the cabling didn't go in as neatly as I was hoping. I could have shortended the length of some of the cables but decided at this stage the main job was to get power back on the house. A tidy up could wait for another day.

After a few issues with fitting the cables (see below) I had everything re-instated. Final check of tightness of every screw and a tug test on each cable then powered back up. All circuits came up apart from one of the combined lighting circuits which kept tripping. By trying each circuit in turn isolated the circuit with the fault and for now connected it to a 6A MCB to allow time for fault investigation. The lighting circuits were not on the RCB protected side of the old CU so this fault must have been present for some time. Will need to go around each of the lights to see if I can see where the problem is.

In total, with the fault investigation, it took 90 mins with a brief pause for a cold drink. I still need to fill any gaps with intumescent sealant which I'll do when I finally connect up the hob (cable has been run from the kitchen to the CU - what a chore that was - cutting holes in the ceiling at every joist which of course were perpendicular to the direction the cable needed to go). When I fit the cable next month I'll re-tighten all screws.

The CU has now been in for 24h. No nusance trips so far...

Some observations
1. The cable receptacles on the BG MCBs/RCBOs/Isolator switch are pretty shallow. I had to trim back every cable inc the tails down to 10mm
2. It is too easy to insert the cable behind the cable receptacle which meant the cable wasn't clamped. I had to remove 3 or 4 RCBOs to push back the clamp.
3. The CU case has a number of round "punch outs". These were recessed but there was no way (for me) that these were going to come out in any way other than by being cut out. Perhaps I needed a larger hammer and a more suitable drift?
4. Why are the neutral tails on the RCBOs so long? I didn't want to cut them (read somewhere that it was wasn't recommended to cut them). Perhaps if I had the appropriate crimps they could have been shortened but it was just a load of cable to tuck away behind the rail and which would make it much harder to replace a RCBO by having to unpick the neural wire.

Thanks again for the feedback and suggestions. My only regret is the cabling isn't neater. The only additional tools I purchased was a quality long nosed pilers and heavy duty cutters.

On 17/03/2019 09:22, Kevin H wrote:
New kitchen planning underway. Looks like we're going to replace a gas hob with an induction hob requiring a 32A connection back to the CU (photo he https://goo.gl/CGJfg3)

Not what you asked and i've not read the whole thread but there are 13A
'intelligent' induction hobs which will throttle zones where necessary.

I can't imagine this would be a problem at most times, I can't recall
ever caning all four zones simultaneously.

On 21/07/2019 12:11, Kevin H wrote:

Just following up on all the useful help and advice that was given in
relation to swapping my CU.

Thanks for the update Kevin.

I completed this task yesterday. Some notes and feedback which I hope
may be useful for others considering doing this themselves.

I bought a BG 10 way CU (just 100A isolator provided) and a set of
RCBOs to match the current MCBs, plus some spare MCBs as advised (see
later) to help with problem circuits. These were bought from TLC
direct who delivered everything next working day (nearest store 20
miles away, and it was free delivery anyway). Total cost £205.

There was a time a "normal" CU and MCBs could have costed that - so not
a bad deal.

Saurday morning. Checked my meter was working by measuring the
voltage in the CU. Then turned off each MCB before turning off at the
outside isolator switch (no need to cut the seal and pull the fuse).
Went back and checked that there was no voltage coming into the CU
and then off it came. One thing I was surprised with (perhaps I
shouldn't have been) was how loose some of the neutral and earth
connections were. I've never checked the tightness of these
connections in the 20 years we've been in this house. Perhaps that
needs to be an annual check?

Yup I have noticed that on old CUs a number of times. Hence the comments
last time to go back in a few weeks and tighten again after the copper
has had a chance to "relax".

As part of the re-fit I checked there was continuity between the the
two halves of the ring mains.

Given the smaller than expected size of the CU the cabling didn't go
in as neatly as I was hoping. I could have shortended the length of
some of the cables but decided at this stage the main job was to get
power back on the house. A tidy up could wait for another day.

Yup I said that to myself when I did the main one here ten years ago... :-)

(in reality I did need to do a bit of tidyup some time later as I wanted
to move the kitchen onto its own RCBO - and that forced a bit of cable
trimming to get it all fitted in there).

After a few issues with fitting the cables (see below) I had
everything re-instated. Final check of tightness of every screw and a
tug test on each cable then powered back up. All circuits came up
apart from one of the combined lighting circuits which kept tripping.
By trying each circuit in turn isolated the circuit with the fault
and for now connected it to a 6A MCB to allow time for fault
investigation. The lighting circuits were not on the RCB protected
side of the old CU so this fault must have been present for some
time. Will need to go around each of the lights to see if I can see
where the problem is.

Yup its a common issue - especially if the lighting circuits are old.
Good move having the 6A MCB to hand.

In total, with the fault investigation, it took 90 mins with a brief
pause for a cold drink. I still need to fill any gaps with
intumescent sealant which I'll do when I finally connect up the hob
(cable has been run from the kitchen to the CU - what a chore that
was - cutting holes in the ceiling at every joist which of course
were perpendicular to the direction the cable needed to go). When I
fit the cable next month I'll re-tighten all screws.

The CU has now been in for 24h. No nusance trips so far...

Some observations 1. The cable receptacles on the BG
MCBs/RCBOs/Isolator switch are pretty shallow. I had to trim back
every cable inc the tails down to 10mm 2. It is too easy to insert
the cable behind the cable receptacle which meant the cable wasn't
clamped. I had to remove 3 or 4 RCBOs to push back the clamp. 3. The

On many, just undoing the screw on the MCB "all the way" will force the
back of the cage to the back of the recess. Even if creating an opening
far wider than required for the wires in question, it is a way of
ensuring they all go in it, and not behind it.

CU case has a number of round "punch outs". These were recessed but
there was no way (for me) that these were going to come out in any
way other than by being cut out. Perhaps I needed a larger hammer and
a more suitable drift?

20mm hole saw is often easier.

4. Why are the neutral tails on the RCBOs so
long?

Not all CUs are small - so they have to give you enough slack to cope
with most situations. Its far less annoying to have to trim them down,
than needing to extend them. If trimming it makes sense to keep them
long enough that they can still fit in multiple positions in the CU - so
cut a bit longer than the "right" length in most cases.

I didn't want to cut them (read somewhere that it was wasn't
recommended to cut them). Perhaps if I had the appropriate crimps
they could have been shortened but it was just a load of cable to
tuck away behind the rail and which would make it much harder to
replace a RCBO by having to unpick the neural wire.

Thanks again for the feedback and suggestions. My only regret is the
cabling isn't neater. The only additional tools I purchased was a
quality long nosed pilers and heavy duty cutters.


--
Cheers,

John.

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This may add to the expense unless you can borrow one but using a screwdriver with a torque setting ensures you get all the terminal screws correctly tightened. As I was adding the last circuits to my garage CU I checked the ones I had done a couple of weeks before and they were still spot on. If you have to buy one Toolsatan do a Draper for £65 which is probably the cheapest around.

Whilst on the subject, I was tempted by the BG CU with the mini RCBOs until I read a review by an electrician that as he was torquing up the terminal screws the casing on the RCBOs were distorting and tending to split before he achieved the recommended torque even though his driver was recently calibrated.

Richard

Tricky Dicky wrote:

This may add to the expense unless you can borrow one but using a
screwdriver with a torque setting ensures you get all the terminal
screws correctly tightened. As I was adding the last circuits to my
garage CU I checked the ones I had done a couple of weeks before and
they were still spot on. If you have to buy one Toolsatan do a Draper
for £65 which is probably the cheapest around.

if you only need one or two torque settings, wiha sell adapters at
various ratings, about £25 each.

On Sunday, 21 July 2019 17:14:58 UTC+1, Tricky Dicky wrote:
This may add to the expense unless you can borrow one but using a screwdriver with a torque setting ensures you get all the terminal screws correctly tightened. As I was adding the last circuits to my garage CU I checked the ones I had done a couple of weeks before and they were still spot on. If you have to buy one Toolsatan do a Draper for £65 which is probably the cheapest around.

Whilst on the subject, I was tempted by the BG CU with the mini RCBOs until I read a review by an electrician that as he was torquing up the terminal screws the casing on the RCBOs were distorting and tending to split before he achieved the recommended torque even though his driver was recently calibrated.

Richard

I did see a couple of electricans on youtube using torque screwdrivers to finish off working on a CU. I did check the prices - around £65 as you say - but decided not to bother as I'm unlikely to need to do this again anytime soon.

I also noticed the body of the RCBOs flexing when I was doing the final tightening. There must be a reason these are nearly half the price of say the Hager RCBOs.