fuse box in my shed upgrade

Macker

long story short , doing up my shed soon to be workshop ,this was a long time project but with the lock down I got a bit more time on my hands ,anyway the 20 year old wiring needed fixing , if I showed you my old wiring you'd have the fire safety officer around , well I changed all the sockets to 2.5 T&E and the lights , LED to 1.5 ,installed a new small fuse board in the shed even thought the shed has its own spot on the main house fuse board , my question is? the new fuse board has 6A , 16A and 32 A , i wired the lights into the 6A and the sockets into the 16A , left the 32 free , there are 6 double sockets ,one will run a freezer 24/7 one will run a TV couple of hours a day , same with a thread mill and the others a few power tools ,mostly chargers for my cordless tools , is my setup ok or should I use the 32A

2011

You could swap the 32A for a 16A so that the freezer could have a dedicated circuit (just a suggestion, not a requirement). This would reduce the chance of it ever tripping. However nothing wrong with using the 6 for lights and 16A for sockets. Both should have RCD protection of course as they are part of a domestic installation. Also as you may already know the "older type" of T & E is no longer permitted. Personally I would install an RCBO per circuit. For domestic installations I prefer to use over-current protection with a B type characteristic.

Needless to say the shed sub-distribution board should have a main isolation point. I would also link the earth bar in the main distribution board to the earth bar in the shed distribution board.

Other considerations:
What size cable is used to feed the sub-distribution board?
What protects this cable? 32A MCB?
What type of cable is used?
How long is the cable run between boards?

Risteard81

Macker wrote: »

long story short , doing up my shed soon to be workshop ,this was a long time project but with the lock down I got a bit more time on my hands ,anyway the 20 year old wiring needed fixing , if I showed you my old wiring you'd have the fire safety officer around , well I changed all the sockets to 2.5 T&E and the lights , LED to 1.5 ,installed a new small fuse board in the shed even thought the shed has its own spot on the main house fuse board , my question is? the new fuse board has 6A , 16A and 32 A , i wired the lights into the 6A and the sockets into the 16A , left the 32 free , there are 6 double sockets ,one will run a freezer 24/7 one will run a TV couple of hours a day , same with a thread mill and the others a few power tools ,mostly chargers for my cordless tools , is my setup ok or should I use the 32A

Are you a member of RECI?

Macker

Thanks for taking the time to reply , a lot to take in , no Not in the trade

2011

Macker wrote: »

Thanks for taking the time to reply , a lot to take in , no Not in the trade

For safety reasons this work should only be carried out by a qualified electrician. It is not really a DIY task.

From a legal perspective this work should only be carried out by a registered electrical contractor.
For more information please read the forum charter.

2011

Mod note: Please do not derail this thread. If you have a question about moderation feel free to PM me. Thank you.

Bruthal

Risteard81 wrote: »

Are you a member of RECI?

It is important to do what those in authority, or positions to advise, say alright.

Wearb

2011 wrote: »

You could swap the 32A for a 16A so that the freezer could have a dedicated circuit (just a suggestion, not a requirement). This would reduce the chance of it ever tripping. However nothing wrong with using the 6 for lights and 16A for sockets. Both should have RCD protection of course as they are part of a domestic installation. Also as you may already know the "older type" of T & E is no longer permitted. Personally I would install an RCBO per circuit. For domestic installations I prefer to use over-current protection with a B type characteristic.

Needless to say the shed sub-distribution board should have a main isolation point. I would also link the earth bar in the main distribution board to the earth bar in the shed distribution board.

Other considerations:
What size cable is used to feed the sub-distribution board?
What protects this cable? 32A MCB?
What type of cable is used?
How long is the cable run between boards?

I just picked up on this point and wondered about my own shed (a little similar to something we discussed recently); My tool shed (similar to what you see on motorway construction) has this label -see pic-. It was wired to my house some years ago by a reci mate that worked hand in glove with me in the past. It also has its own earth bar and the house earth isn't wired into the shed CU as far as I remember from when it was done, as I gave him a hand. We used 3 core swa. I don't remember how it was wired at my own CU.
Is it ok done this way?

Bruthal

The 3 core swa would be expected to include an earth core linking the house earth bar to the shed one.

Looks like the RCCB is being used as the main on off isolator as well. It probably switches everything in the shed off?

2011

Wearb wrote: »

It was wired to my house some years ago by a reci mate that worked hand in glove with me in the past. It also has its own earth bar and the house earth isn't wired into the shed CU as far as I remember from when it was done, as I gave him a hand. We used 3 core swa. I don't remember how it was wired at my own CU.

What I described is the norm in ROI, it may not align perfectly with every single installation.

Question: So are only 2 cores of the SWA used (phase & neutral) ?

Is it ok done this way?

Maybe, maybe not.
It depends on the specifics of your installation.

If your installation is not neutralised then then either:
1) The earth fault loop impedance is very high
2) You have an enormous earth pit / lots of earth rods so as to ensure a low resistance connection to the general mass of earth.

In the ROI almost every installation is TNCS. In these instances the norm would be to link the earth bars. Other arrangements (in domestic installations) may differ but in Ireland they are few and far between.

Wearb

Bruthal wrote: »

The 3 core swa would be expected to include an earth core linking the house earth bar to the shed one.

Looks like the RCCB is being used as the main on off isolator as well. It probably switches everything in the shed off?

Rccb does switch off everything.

Whenever I get back of shed cleared up, I'll investigate if earths are linked outside.
I can't ask him because we fell out over him not getting the wiring of any of my children's houses. I didn't interfere with my childrens builder choices.

Bruthal

Wearb wrote: »

Rccb does switch off everything.

Whenever I get back of shed cleared up, I'll investigate if earths are linked outside.
I can't ask him because we fell out over him not getting the wiring of any of my children's houses.

Yes as 2011 mentioned, they should be linked (house DB earth bar to shed DB earth bar)

I didn't interfere with my childrens builder choices.

That sounds reasonable and realistic.

Wearb

2011 wrote: »

What I described is the norm in ROI, it may not align perfectly with every single installation.

Question: So are only 2 cores of the SWA used (phase & neutral) ?

I only know the shed side and only 2 cores used there. The earth to shed CU comes from shed earth rod.

It is possible that he broke the swa earth before it entered the shed and spliced it to the shed earth rod in the box at the back of the shed.


Maybe, maybe not.
It depends on the specifics of your installation.

If your installation is not neutralised then then either:

1) The earth fault loop impedance is very high

I don't know

2) You have an enormous earth pit / lots of earth rods so as to ensure a low resistance connection to the general mass of earth.

Just a single earth rod.

In the ROI almost every installation is TNCS. In these instances the norm would be to link the earth bars. Other arrangements (in domestic installations) may differ but in Ireland they are few and far between.

2 questions
1 What does "not use tncs supply" (on the yellow label in image) mean?
2 Is mine an unusual way of doing it. ... I understand that you haven't all the information that you need to fully answer this.

Risteard81

Wearb wrote: »

2 questions
1 What does "not use tncs supply" (on the yellow label in image) mean?
2 Is mine an unusual way of doing it. ... I understand that you haven't all the information that you need to fully answer this.

Presumably there is a TT system at this point. Whereabouts in Ireland are you?

Wearb

Bruthal wrote: »

Yes as 2011 mentioned, they should be linked (house DB earth bar to shed DB earth bar)


That sounds reasonable and realistic.

Ok. I'll open that denso (yuck) covered box at the back sometime when I can get in there through the junk. It might be linked there.

Wearb

Risteard81 wrote: »

Presumably there is a TT system at this point. Whereabouts in Ireland are you?

South east

Risteard81

Wearb wrote: »

South east

Fair enough. It just looks more like an installation in the Six Counties.

Wearb

BTW OP. Sorry if I seem to be taking over your thread, but I think it's pertinent to your issue also. If you have a problem with my posts, ask a mod to separate them into a new thread.

Wearb

Risteard81 wrote: »

Fair enough. It just looks more like an installation in the Six Counties.

AFAIK Shed was imported from UK.

Bruthal

Maybe the DB was in a temp construction setup with generators.

A photo of it with cover removed would be useful......

Wearb

Bruthal wrote: »

Maybe the DB was in a temp construction setup with generators.

A photo of it with cover removed would be useful......

I would guess the shed was on a construction site and supplied from a generator.



Sometime I'll clear the back out and have a look at that box.



DB?

Bruthal

Wearb wrote: »

DB?

Distribution board.

Risteard81

Bruthal wrote: »

Maybe the DB was in a temp construction setup with generators.

A photo of it with cover removed would be useful......

Removing the cover is illegal.

Wearb

Risteard81 wrote: »

Removing the cover is illegal.

If a tree falls in a forrest ........

Risteard81

Wearb wrote: »

If a tree falls in a forrest ........

Bruthal should not be allowed to publicly promote criminal acts. I have reported his post. Unfortunately he has a habit of trolling.

Wearb

Risteard81 wrote: »

Bruthal should not be allowed to publicly promote criminal acts. I have reported his post. Unfortunately he has a habit of trolling.

Well to be fair, he didn't suggest that I remove it

Bruthal

Risteard81 wrote: »

Removing the cover is illegal.

So I heard. Where does it say that though.

Just curious really.

2011

@Wearb:
If I were you:

1) First find out if your house is TNCS or not. It would be quite unusual if it wasn't. This can be established by looking inside the meter cabinet. If unsure you could post a photo here.

2) Next confirm whether the earth in the SWA is connected to the earth bar in the main distribution board.

3) Then confirm whether the earth in the SWA is connected to earth bar in the sub-distribution board.

As is pointed out at at nauseam on this forum from a legal perspective only a REC can work on a distribution board. Whether removing the cover and visually checking something can be defined as work is not an argument I have any interest in getting into. Either way there are risks associated with this so whoever does this needs to know what they are at.

Assuming (as is most likely) that the installation is TNCS I would ensure that the earth bars are linked.

To be honest in the event that you have a TT earthing system I am struggling to see why the earth bars should not be linked.
I must check this out properly when I have time.

Regarding the sticker on the board stating that it should not be fed from a TNCS supply, my guess is that this should not apply. However I wouldn't jump the gun on this without properly understanding how it is wired.

What you could do is measure the resistance between an earthed part in the shed (such as the outside of a metal socket) and something that is earthed in the house (like the metal enclosure of the cooker). A low reading would indicate that the earth bars are linked.

When you leave rules aside and consider what you are trying to achieve it is this:
A low resistance return path for a fault current. Why? Because we want the fault current to soar. Why? Because this will cause the upstream MCB to trip rapidly, thus safety disconnecting the faulty circuit.

Simply connecting an earth to a single earth rod will only provides a high resistance connection to earth, typically well over 100 Ohms. A really good connection to earth will require digging up most of your back garden to allow connection of multiple earth rods in parallel

However with a TNCS system your earth rod is essentially connected in parallel with all of the earth rods for the installations that are fed from the same transformer. There are other factors that help too.

So you should really check....

Bruthal

2011 wrote: »

To be honest in the event that you have a TT earthing system I am struggling to see why the earth bars should not be linked.

I would be checking the DB to ensure no links internally between N and E bars anyway.

Wearb

2011 wrote: »

@Wearb:
If I were you:

1) First find out if your house is TNCS or not. It would be quite unusual if it wasn't. This can be established by looking inside the meter cabinet. If unsure you could post a photo here.

2) Next confirm whether the earth in the SWA is connected to the earth bar in the main distribution board.

3) Then confirm whether the earth in the SWA is connected to earth bar in the sub-distribution board.

As is pointed out at at nauseam on this forum from a legal perspective only a REC can work on a distribution board. Whether removing the cover and visually checking something can be defined as work is not an argument I have any interest in getting into. Either way there are risks associated with this so whoever does this needs to know what they are at.

Assuming (as is most likely) that the installation is TNCS I would ensure that the earth bars are linked.

To be honest in the event that you have a TT earthing system I am struggling to see why the earth bars should not be linked.
I must check this out properly when I have time.

Regarding the sticker on the board stating that it should not be fed from a TNCS supply, my guess is that this should not apply. However I wouldn't jump the gun on this without properly understanding how it is wired.

What you could do is measure the resistance between an earthed part in the shed (such as the outside of a metal socket) and something that is earthed in the house (like the metal enclosure of the cooker). A low reading would indicate that the earth bars are linked.

When you leave rules aside and consider what you are trying to achieve it is this:
A low resistance return path for a fault current. Why? Because we want the fault current to soar. Why? Because this will cause the upstream MCB to trip rapidly, thus safety disconnecting the faulty circuit.

Simply connecting an earth to a single earth rod will only provides a high resistance connection to earth, typically well over 100 Ohms. A really good connection to earth will require digging up most of your back garden to allow connection of multiple earth rods in parallel

However with a TNCS system your earth rod is essentially connected in parallel with all of the earth rods for the installations that are fed from the same transformer. There are other factors that help too.

So you should really check....

Thanks for taking the time for such a detailed reply. I now understand the issues involved. Here is a pic of the meter box. I'll check the resistance later.

Bruthal

It is a TNCS by the look of that, as would be expected.