External supply and location of CU

[avinalarf]

Went to look at a job this morning. Client wants sockets & lighting to Summerhouse (glorified shed!) which is approx. 18m from CU. Nothing out of the ordinary will be used - power tools, lawnmower etc.

Have read a few previous threads and opinions differ. I've done some calcs and have come up with the following:

Fit 20A RCBO at dwelling CU

Fit 4-way CU in shed with 16A mcb for sockets and 6A mcb for lighting.

Use 4mm 3-core SWA

Chose 4-way CU as client may possibly want a supply to another shed going further down the garden.

I'm sure the setup is TN-S - photos taken will enable someone to confirm this I hope Pray. I'm not sure if I still need RCD protection at the shed CU or a main switch Blushing. I didn't think so as I was covered with the RCBO in the dwelling. Can someone confirm this theory.

I took some pics of CU and will post when I find cable to link my cell to the pc! The CU is located in a cupboard within the kitchen, in the most awkward position you can imagine! For me to access it comfortably, the cooker will have to be removed and the side panel of a unit

I know 17th isn't retro but can the CU remain in this position? To me, it just seems ridiculous to have to practically lie down to get your arm in there :_| I informed the client that I would make enquiries as to whether or not it would need re-locating. Not sure she'll go ahead with job if it does need moving as it will cost too much.

Thanks for any replies.

Nat

One other thing...Elecsa told me that the meter seal can not be broken without the distributor knowing. Is this just a simple case of a call to notify them of work being carried out?

 

[M107]

I'm not sure if I still need RCD protection at the shed CU

Not if you are using the rcbo at the supply end.

I know 17th isn't retro but can the CU remain in this position? To me, it just seems ridiculous to have to practically lie down to get your arm in there I informed the client that I would make enquiries as to whether or not it would need re-locating. Not sure she'll go ahead with job if it does need moving as it will cost too much.

Leave it where it is would be my option, if customer isnt wanting to pay out more for the job, remember you'll need to test & rectify any faults on all circuits if you shift the cu.

Where is the meter in relation to the cu? you might be able to fit a small enclosure in the meter cab (not supposed to but I've never had any come back) & split the tails.

One other thing...Elecsa told me that the meter seal can not be broken without the distributor knowing. Is this just a simple case of a call to notify them of work being carried out?

Yes you are supposed to get the DNO out to remove the seal & cutout (if it's not one of them new AMPEY meters with the nice iso switch), but like most things it'll cost........so I just ring the DNO say I'm removing the seal due to safety upgrade of the cu, they say fine note is made on customers details held by dDNO that a reseal is required at next visit.

By the way I'd put 2 core 10mm swa in, use the armour as the cpc, & terminate into an insulated enclosure at the shed, then TT the shed.

 

[Andy™]

Went to look at a job this morning. Client wants sockets & lighting to Summerhouse (glorified shed!) which is approx. 18m from CU. Nothing out of the ordinary will be used - power tools, lawnmower etc.Have read a few previous threads and opinions differ. I've done some calcs and have come up with the following:

Fit 20A RCBO at dwelling CU

Fit 4-way CU in shed with 16A mcb for sockets and 6A mcb for lighting.

Use 4mm 3-core SWA

Chose 4-way CU as client may possibly want a supply to another shed going further down the garden. in which case you should wire new supply in 6 or 10 to so it can be used as a feed to another shed (your VD may comply there, but it probably wont further down the garden)

I'm sure the setup is TN-S - photos taken will enable someone to confirm this I hope Pray. I'm not sure if I still need RCD protection at the shed CU or a main switch Blushing. I didn't think so as I was covered with the RCBO in the dwelling. Can someone confirm this theory.only needs one RCD - so if its RCD'd at house, then no further RCD req'd. or if run is in SWA, you could hae no RCD for SWA, and RCD at shed

I took some pics of CU and will post when I find cable to link my cell to the pc! The CU is located in a cupboard within the kitchen, in the most awkward position you can imagine! For me to access it comfortably, the cooker will have to be removed and the side panel of a unit

Welcome to the real world...

I know 17th isn't retro but can the CU remain in this position? To me, it just seems ridiculous to have to practically lie down to get your arm in there :_| I informed the client that I would make enquiries as to whether or not it would need re-locating. Not sure she'll go ahead with job if it does need moving as it will cost too much.just dont make it any more inaccessible. but it could be argued that your new work doesnt comply because of (bad) access

Thanks for any replies.

Nat

One other thing...Elecsa told me that the meter seal can not be broken without the distributor knowing. Is this just a simple case of a call to notify them of work being carried out?in an ideal world, DNO would install DP isolator. but that doesnt normally happen. could try calling DNO and asking them about it. If you do cut seals, be safe about it

my red

 

[Evans Electric]

If I were doing the job , I'd fit a 20a MCB at the house - 4mm X 3 core SWA to shed - metalclad 4 way C/U with RCD incomer. Wouldnt push it on moving the house C/U , sounds blooming awkward to me.

There is a previous thread on cutting meter seals, the upshot was that some areas will accept that you have removed them and will reseal others won't . In reality , we are not allowed to remove them. The correct way is to phone whoever supplies the power to that premises , who should turn up, remove tails and reseal, then make 2nd visit to connect your new tails, good is'nt it ? :|

Try phoning whoever fits the meters in your area, not the network, see what they say !

Deke

 

[avinalarf]

Leave it where it is would be my option, if customer isnt wanting to pay out more for the job, remember you'll need to test & rectify any faults on all circuits if you shift the cu.

But as I thought and Andy mentioned; "it could be argued that your new work doesnt comply because of (bad) access!" :_|

Where is the meter in relation to the cu? you might be able to fit a small enclosure in the meter cab (not supposed to but I've never had any come back) & split the tails.

Meter is right next to CU

Yes you are supposed to get the DNO out to remove the seal & cutout (if it's not one of them new AMPEY meters with the nice iso switch), but like most things it'll cost........so I just ring the DNO say I'm removing the seal due to safety upgrade of the cu, they say fine note is made on customers details held by dDNO that a reseal is required at next visit.

But what, if when they returned, they noticed that the CU hadn't been upgraded (or does this sort of thing just not happen!)

By the way I'd put 2 core 10mm swa in, use the armour as the cpc, & terminate into an insulated enclosure at the shed, then TT the shed.

Even if there aren't any extraneous bits there?

 

[Andy™]

But as I thought and Andy mentioned; "it could be argued that your new work doesnt comply because of (bad) access!" :_| i doubt anything would every be said

But what, if when they returned, they noticed that the CU hadn't been upgraded (or does this sort of thing just not happen!)

its probably obvious if a new CU is installed, expecially if its right next to meter

Even if there aren't any extraneous bits there?

It can be better (/easier) to TT it, but if main supply is TN-S i would normally export the earth. Your choice.

my red

 

[green-hornet]

I had the same problem about a year ago with the cu situated under the kitchen units, in a corner. When they had the kitchen fitted the corgi plumber suggested they move the gas meter because it would be hard to access after. They called the gas board who moved the gas meter no problem.

The electrician did his first and second fix in one go and left the cu in its original position.

The result was for any work to be done on that installation half the kitchen had to be removed.

Electricity at work act comes to mind when, as an electrician you have to work on an installation where ease of access and safe working could not be covered.

I asked to see the certificates the electrician had given them, "certificates? he did not give us anything but the bill".

To answer your other question follow andyc's advise if it is TN-S then export the earth, allow for the assumption that your installation mey be added to and please please make sure you only certificate for your work, number of points,r1+r2, end to end continuity, on rings, then you have proof that the work was added to at a later stage.

The NICEIC do a cu label that if removed shows as void, great for when you have done the work right and can prove the cu has been opened later by bob the builder.

 

[Andy™]

you can easily get small warranty void labels from just about anywhere. CPC sell them - or try ebay. i use them on alarm panels

 

[avinalarf]

Thanks everyone. Here are some pics of the setup - hope someone can confirm what it is.

http://i565.photobucket.com/albums/ss91/avinalarf/Image028.jpg

http://i565.photobucket.com/albums/ss91/avinalarf/Image030.jpg

 

[green-hornet]

I would have liked a photo head on, that is looking at the supply.

There appears to be two fuse holders with a link (u ).

Absence in the photo of any suppliers earthing would suggest a TT instalation, not clear on the photo's.Post some more pics if you can, the ones you have are a bit vague.

 

[avinalarf]

I would have liked a photo head on, that is looking at the supply.There appears to be two fuse holders with a link (u ).

Absence in the photo of any suppliers earthing would suggest a TT instalation, not clear on the photo's.Post some more pics if you can, the ones you have are a bit vague.

Sorry GH - I was crouched down, sticking my arm into the cupboard and just hoping for the best - hence why the pics aren't great! :_|

I'll try and price the job as best I can and if the client wants to go ahead, I'll get some more pics.

I wondered about the 2 fuse holders - why might it be like this? Does whether the installation is TN-S or TT make much difference to the overall cost of doing the work?

 

[avinalarf]

By the way I'd put 2 core 10mm swa in, use the armour as the cpc, & terminate into an insulated enclosure at the shed, then TT the shed.

I've been looking for junction boxes to join the tw&e with the swa inside. Any opinions on this one...

http://www.tlc-direct.co.uk/Products/LB9065.html

Doesn't say it takes 10mm though, so I'm guessing it's not appropriate. Any alternatives???

 

[Zeespark]

larf why not just buy a box like that (minus the cable terminals) and use a connector strip/wago's instead?

AndyGuiness Drink

 

[Evans Electric]

Nat, a PVC adaptable box will do your joint, get one without the connectors, they will be in the way of your SWA ,specially if you are going with the 10 mm ( too big IMO) size of box , 100 X 100 X 50 .

The incoming feed looks like a split -concentric which is usually PME , sorry TNC-S but I can't see the main earth connection on pics, C/U is a split load which makes you think its not TT .

You need to know about the supply , if its TT you may be quoting for an RCD and rod.

Two main fuses ? Is there a seperate nightstore meter hiding ? Is there a flat upstairs ? I have even known the second fuse to feed next door !!

Deke

 

[Andy™]

the second fuse could be for next door, or possibly communal lights. Feed looks like straight con (Evans - afaik, DNO dont use split con much), so either TNC-S or TT. if earth comes from top of neutral block (doesnt look like it), its TNC-S, otherwise looks like TT

Why do you need to join the SWA to T&E inside? can you not take the SWA direct to consumer unit? if the CU cant take a SWA, then an adaptable box to gland to then a hole straight into CU for cores. easier than joining in a box there

Cost wise between TT & TN-S isnt much. If the house doesnt already have a rod, then one will have to be installed.

 

[green-hornet]

I have seen a property where there are two main fuse holders and one was for next door.

There are quite a few like that where they loop the supply to serve two houses, normally the loop is internal and each house will have its own main fuse.

I agree with andyc on the swa take it to the cu, no messing about with joints.

 

[Evans Electric]

Just an additional thought on your SWA . I'd forgotten that we usually fit one of those PVC rotary switches ( yellow/black ones) serves as an isolator and also joints the SWA . You can't terminate the SWA at a Plastic C/U .

 

[green-hornet]

You can now, there are new products I will have a look and post the links

 

[avinalarf]

Ok guys - don't know what to start responding to as such a good response! Applaud Smiley And...I've been on the :Y so I may start blabbing .

EE - used a PVC box for my own 6mm SWA, but used a henley box inside it. Elecsa guy was impressed but I thought it was a bit overkill ?:| . 10mm overkill - what do you suggest, bearing in mind, client may want an additional shed with a supply further down the garden at a later date?

2nd fuse? Need to make additional enquiries. Is it not normal to have a split load CU on a TT system then? Why???

Andy & GH - I thought about the pain of requiring a joint inside, but was unsure if I could take the SWA straight to the CU. It's a Wylex board (not sure if that makes a difference).

EE - don't have a link to this isolating/jointing switch you fit do you?

GH - Would appreciate knowing which CU's I could terminate the SWA into as it would save having to join in the shed.

 

[Andy™]

Ok guys - don't know what to start responding to as such a good response! Applaud Smiley And...I've been on the :Y so I may start blabbing .EE - used a PVC box for my own 6mm SWA, but used a henley box inside it. Elecsa guy was impressed but I thought it was a bit overkill ?:| . 10mm overkill - what do you suggest, bearing in mind, client may want an additional shed with a supply further down the garden at a later date?

best use 10mm to take any additional load. could ask what they plan to use in the far shed if they do get it wired, then add a bit more and wire for that

2nd fuse? Need to make additional enquiries. Is it not normal to have a split load CU on a TT system then? Why???

for TT all circuit should have an RCD. in 16th, it would normally have been RCD TD incomer.

Andy & GH - I thought about the pain of requiring a joint inside, but was unsure if I could take the SWA straight to the CU. It's a Wylex board (not sure if that makes a difference).

that board will not take an SWA. but you could get an adaptable box with hole between this and CU, gland into box and take cores into RCBO. or use isolator as EE suggested (pic later)

EE - don't have a link to this isolating/jointing switch you fit do you?

i think this is what evans was referrings to

GH - Would appreciate knowing which CU's I could terminate the SWA into as it would save having to join in the shed.most IP rated CUs will have knockouts suitable for glands - so will most metal clad boards

my red