Options for Moving a CU

[SparkieMarky]

Hi Folks,

Be gentle with me it's my first post! And I can't stress highly enough this is purely a hypothetical question as I am genuinely interested in how others would approach this example. You have been asked to move a domestic CU from its current location to a new position. The CU contains the usual mix of final circuits, 2 x lighting (1.5mm), 3 x ring circuits (2.5mm), 1 x immersion heater (2.5mm), 1 x cooker (10mm), 1 x hob (10mm) etc...

Obviously the current cabling will not magically stretch to a new location so a number of circuits will need to be either extended or have new cabling run from the new CU position. This is assuming that there is enough head room in the installation design to allow the cables to be extended.

So my question is what would be your preferred go to method for addressing this type of job (appreciate all jobs are different but this is purely hypothetical) and we are assuming that the installation is in good order, there are no bodges etc.?

Personally I have done them in the past where I have replaced the cabling back to the first leg on each circuit and often complete circuits (once you start down the rabbit hole and uncover some of the crap that's out there you can't just leave it - well I can't .

The supplementary follow up question is what would be your preference if you had to move the CU but couldn't mount an enclosure in the position of the old CU. Thinking of the CU high on the wall in a room and the householder doesn't want to have anything there anymore as it spoils the ascetics in their newly decorated room...

 

[JAWS]

deleted

 

[Midwest]

Yep of course possible, just extend or reroute the existing final circuits to the new CU position, and factor in extending meter tails or run a new distribution circuit.

 

[buzzlightyear]

Thinking of the CU high on the wall in a room and the householder doesn't want to have anything there anymore as it spoils the ascetics in their newly decorated room...

tell them to move to next F88KING DOOR when you move the c/u.

 

[buzzlightyear]

how far are you moving the branch to the new consumer.

 

[buzzlightyear]

deleted

did I miss some thing massive one .

 

[JAWS]

did I miss some thing massive one .

I deleted it mate as I wasn't 100% sure I was giving out the correct advice and me being a trainee I believe this sort of advice is left to qualified electricians like yourself and others

 

[SparkieMarky]

Lets say we need to move it 3m in this case (so everything will need extending) and we will assume that running a new set of tails to the new positon isn't an issue - the world of make believe is a wonderful place . So what would be your prefed method for extending the exising cabling to the new location? And what are peopels thoughts on the various options open?

I am struggling to think of a really neat solution that would use just a single enclosure that would rated for 100A to house all the connnections in for the extensions. Din rail enclosure came to mind but looking at a lot on manufactures data sheets they don't mention the current carrying capacity of those connections. Concious that you could use a series on enclosures but looking at ones such as Wago if you are extending a ring you would need to use two (one for each leg) unless using their XL one. So lots to take into account as always to ensure that your design is safe.

Obvosiuly don't even want to get into the deabate about crimping solid T&E cable or soldering etc. But if using uninsulated through crimps on 10mm was an option what are the thoughts on the use heatshrink and issues around applied insulation?

 

[Octopus]

if the move means the CU will be more than 3 meters from the DNO head and meter you will need a switch fuse ....

What ever you do, just make sure that ALL the connections are readily accessible for inspection at a later date ..... so an enclosure where the old CU is may be the only option.

just saying

 

[SparkieMarky]

if the move means the CU will be more than 3 meters from the DNO head and meter you will need a switch fuse ....

What ever you do, just make sure that ALL the connections are readily accessible for inspection at a later date ..... so an enclosure where the old CU is may be the only option.

just saying

This is purley a hyperthetical one and really just intrested to see what options people had used in the past or would consider for extending the exsting circuits on mass. Wasn't to worried about the supply side as in my make believe land the DNO was moving the supply free of charge or it was going to be within 3m... Depending on the level of damage this could equally apply where a CU was being changed due to distress and cables needed to be shortened.

 

[Gavin John Hyde]

If possible I would go for an enclosure with Din Rail terminals, keeps it nice and neat, if done well the customers goes oooh and aaah and thinks you are the bees knees when they see it looking all pretty inside.
I have seen a recessed enclosure before that had din rails terminals in, looked really good, cables fed up into ceiling and to new CU position.
Given the din rail terminals would not be taking 100Amps then the rating isn't an issue as they are more than suited for typical domestic use, each brand has different specs.
At end of day if a customer wants something moved then they have to understand there are limits to what you can do within the regs.

 

[SparkieMarky]

If possible I would go for an enclosure with Din Rail terminals, keeps it nice and neat, if done well the customers goes oooh and aaah and thinks you are the bees knees when they see it looking all pretty inside.
I have seen a recessed enclosure before that had din rails terminals in, looked really good, cables fed up into ceiling and to new CU position.
Given the din rail terminals would not be taking 100Amps then the rating isn't an issue as they are more than suited for typical domestic use, each brand has different specs.
At end of day if a customer wants something moved then they have to understand there are limits to what you can do within the regs.

Yep fully agree with the limits of what can be done and I am sure most of us have walked away from jobs where there has been difficulty getting a customer to accept those limitations.

Any preferences on din rail connectors brands? and definitely agree that they can look very neat especially when dressed well. I still look at some of our older stuff in our equipment rooms with beautifully dressed and laced cable tress and go "oooh and aaah"

 

[davesparks]

Ideally and wherever possible re-route or replace the first leg(s) of the circuits so that they reach the new CU without jointing cables.
If it’s not possible then a suitable joint and extension of the cable is the only option, if it’s multiple circuits then an adaptable box with din rail connectors is my preference.

 

[Gavin John Hyde]

Any preferences on din rail connectors brands? and definitely agree that they can look very neat especially when dressed well. I still look at some of our older stuff in our equipment rooms with beautifully dressed and laced cable tress and go "oooh and aaah"

I normally use Wieland Din Rail connectors. can normally pick them less than a quid each. so allow around £2.50 per circuit. but if buying in a pack or online can get them cheaper.

 

[Midwest]

I came close to the Wago's and Connexbox enclosure, but as I (and others) have suggested reroute cables or replace initial sections of finals. Probably remove over half the need for connections then.

 

[SparkieMarky]

I came close to the Wago's and Connexbox enclosure, but as I (and others) have suggested reroute cables or replace initial sections of finals. Probably remove over half the need for connections then.

Yep, this is typically what I have tended to do in the past as never been a huge fan of lots of connections but have used the odd wago box when necessary for a lighting circuit or the leg of a ring when it would be just that bit too disruptive.

This was one of those things I ended up mulling over as I have been off sick this last week or so and was intrested in others take on things (made a change from looking at the 18th ed or doing the odd online practice tests). So knowing that we often tend to stick to the way we do things it’s sometimes good to have a different perspective. After all it can get you out of a hole at a later date.

 

[Midwest]

ConnexBox sell an enclosure (plastic) or used to, which you can install Wago Top Job din rail mounted connectors. Bit expensive mind, about the price of a CU.

 

[SparkieMarky]

ConnexBox sell an enclosure (plastic) or used to, which you can install Wago Top Job din rail mounted connectors. Bit expensive mind, about the price of a CU.

I hadn't seen the ConnexBox enclosure although familiure with a lot of the other wago boxes. Its certainly a reasonable option if distrubption is not an option. Certainly gives to option for a neat job all though the knockouts look a bit large for my liking.

 

[BruceBanner]

In regards to the 3 meter rule dno's apply about switch fuse requirements if ccu over that from intake. Had to query wpd earlier in year about a job I had which simply would not accomote it. Advice was that they did not stipulate this, & as not part of their or supplier installation it was nothing to do with them & bs7671 applies. their only stipulation was that the meter had to be within 3 meters or their measures applied. Probably get shot for this but wanted to put it out there.

 

[Midwest]

I hadn't seen the ConnexBox enclosure although familiure with a lot of the other wago boxes. Its certainly a reasonable option if distrubption is not an option. Certainly gives to option for a neat job all though the knockouts look a bit large for my liking.

Yep does look a neat solution. They did used to post some photos of install in such a situation, but after A3 came into being they had been removed.

I queried the use of a plastic enclosure directly above a new A3 CU with my scheme (this will start the mud slinging!). Their guidance, was then (just after A3) was that the designer would have to consider reg 421.1.201, and whether it applied in such a case (yeah yeah, I know it applies to similar switchgear assemblies etc, etc).

I contacted Connexbox, who weren't impressed with that guidance. I did follow up the guidance from the scheme, but in the end didn't get the job. It was then I noted the pics removed from Connexbox site; wonder if they've been reinstated?

 

[SparkieMarky]

Yep does look a neat solution. They did used to post some photos of install in such a situation, but after A3 came into being they had been removed.

I queried the use of a plastic enclosure directly above a new A3 CU with my scheme (this will start the mud slinging!). Their guidance, was then (just after A3) was that the designer would have to consider reg 421.1.201, and whether it applied in such a case (yeah yeah, I know it applies to similar switchgear assemblies etc, etc).

I contacted Connexbox, who weren't impressed with that guidance. I did follow up the guidance from the scheme, but in the end didn't get the job. It was then I noted the pics removed from Connexbox site; wonder if they've been reinstated?

Not sure if they are the same pictures but they certainly have ones showing it installed directly above a CU altough not sure that its not a pre A3 plastic CU (but don’t use crabtree stuff much theses days myself). I had also been mulling over the issues around the material of the enclosure and A3

 

[Midwest]

Not sure if they are the same pictures but they certainly have ones showing it installed directly above a CU altough not sure that its not a pre A3 plastic CU (but don’t use crabtree stuff much theses days myself). I had also been mulling over the issues around the material of the enclosure and A3

Ahhh, they're back then. Certainly removed from their site once. Perhaps they've had a word!

Certainly doesn't seem to be covered by 421.1.201, but I always thought it wasn't within the 'spirit' of A3, especially directly above a A3 CU.

If your in a scheme, email them & seek guidance, if your concerned.