only 1 pole mains switch in my consumer unit??

Andy From Sligo

Why is only a 1pole Mains Switch (GE LT1 63a single pole switch with fuse) fitted in my consumer unit - when did them regs change from fitting a 2pole mains switch .. and reason for it? - and is that a change for the better? - when you turn off the mains in the consumer unit dont you want to kill both Live and Neutral?



Whats best single pole or double pole to isolate CU? - I would go with double pole switch myself

Tuco88

I don't remember a double pole ever being required, it's the E.S.B do not like Neutrals especially the main neutral being switched.

If it was a TN-S perfect. But on a TN-C-S it's another risk of failure, resulting in fun times on the earthing. IMO.

Andy From Sligo

I have only ever known DP main switches fitted to CU's - 25 years ago I used to work at a builders providers on a trade electrical counter and we used to sell the Wylex CU's and they had 100a DP Main switch - and all house I have rented in between , they have always had DP Main switch - this is the first time I have come across a consumer unit with just a single pole isolating switch - just seems weird to me to not see a DP Main switch.

Risteard81

Double Pole switches are used in the north and in Britain. They aren't used in the south and unlike their counterparts in the north (and Britain) they provide overcurrent protection.

Andy From Sligo

Risteard81 wrote: »

Double Pole switches are used in the north and in Britain. They aren't used in the south and unlike their counterparts in the north (and Britain) they provide overcurrent protection.

not doubting you but we have rented 3 houses in ROI and am pretty sure they were DP with a seperate 'bottle fuse' on the DIN rail unless my memory fails me

Risteard81

Andy From Sligo wrote: »

Risteard81 wrote: »

Double Pole switches are used in the north and in Britain. They aren't used in the south and unlike their counterparts in the north (and Britain) they provide overcurrent protection.

not doubting you but we have rented 3 houses in ROI and am pretty sure they were DP with a seperate 'bottle fuse' on the DIN rail unless my memory fails me

Are you sure it wasn't just a single pole isolator switch in series with a fuse instead of a single module switch fuse?

Andy From Sligo

Risteard81 wrote: »

Are you sure it wasn't just a single pole isolator switch in series with a fuse instead of a single module switch fuse?

maybe - although I think it would have jumped out at me that it was single pole .. just as how I have noticed in this box and therefore I would have remember it I should have thought.

Steve

2P isolation switches are fine, fusing the neutral here is against regs.

Andy From Sligo

the 62a fuse in the switch is a good idea , better that as well as the 80a fuse in the meter box - but I really cant see why the idea of no DP isolator unless I am missing something.

There are other switches in my house 20a and 13a fused spur that are double pole so you can kill both live and neutral to the appliance/device

Steve

The norm in Ireland is TN-C.

This means the neutral is earthed at or around the meter and so will be pretty much guaranteed to always be at earth potential.

There is, in theory, no safety need to isolate it in this case.

Fusing the neutral, on the other hand can cause you a world of trouble.

Risteard81

Steve wrote: »

The norm in Ireland is TN-C.

TN-C is not legal here.

TN-C-S is the norm in the south. Unlike TN-C this means that the PEN conductor terminates in the ESB cutout - there is no PEN conductor within the installation.

Steve

Risteard81 wrote: »

TN-C is not legal here.

TN-C-S is the norm in the south. Unlike TN-C this means that the PEN conductor terminates in the ESB cutout - there is no PEN conductor within the installation.

Sorry, yes, you are correct on that.

Doesn't change my advice to the OP.

Andy From Sligo

Strangely - looking up on GE website for my consumer board (GE Euroline) unless I have missed it they only seem to do a single pole isolator main switch (LT1) or a 3pole Isolator main switch (LT3) but no double pole

Andy From Sligo

so really if the system shares the neutral with the earth the last thing you want to do is cut the earth with a 2 pole switch if it has live and neutral going through it then so I suppose that does make sense then because even if you turn off the mains switch the neutral (/earth) is still connected , which is good because you dont want to be isolating the earth .... so really it makes you think that with all the other CU's I have come across then with DP main switch your effectively isolating earth as well when you throw the mains switch ... well presuming you havent got the earth going to an earth rod in the ground too

Risteard81

Andy From Sligo wrote: »

so really if the system shares the neutral with the earth the last thing you want to do is cut the earth with a 2 pole switch if it has live and neutral going through it then so I suppose that does make sense then because even if you turn off the mains switch the neutral (/earth) is still connected , which is good because you dont want to be isolating the earth .... so really it makes you think that with all the other CU's I have come across then with DP main switch your effectively isolating earth as well when you throw the mains switch ... well presuming you havent got the earth going to an earth rod in the ground too

No. You aren't correct.
A double pole switch would isolate both live conductors - it would NOT isolate the earthing conductor or the main protective conductor. These would be connected from the MET to the earth electrode and the ESB's PEN conductor in the cutout respectively. But that isn't the way it is done in the south of Ireland - only the phase conductor(s) are isolated.

Steve

No, isolating the neutral never isolates the earth. Even 2p ones don't.
3p isolators are for 3- phase , they don't isolate either neutral or earth.

Tuco88

No, If you install a double pole switch (replace the 63a S/F) you will still have an earth. The earth (neutralising link) is taken from the E.S.B pen conductor at the E.S.B meter so joint to the neutral there.

Question, A double pole MCB is the N pole an actual MCB does it provide overcurrent also? Or is it a dummy mcb...

aido79

Andy From Sligo wrote: »

so really if the system shares the neutral with the earth the last thing you want to do is cut the earth with a 2 pole switch if it has live and neutral going through it then so I suppose that does make sense then because even if you turn off the mains switch the neutral (/earth) is still connected , which is good because you dont want to be isolating the earth .... so really it makes you think that with all the other CU's I have come across then with DP main switch your effectively isolating earth as well when you throw the mains switch ... well presuming you havent got the earth going to an earth rod in the ground too

I think you might be out of your depth here if you are talking about isolating an earth.

Risteard81

Tuco88 wrote: »

Question, A double pole MCB is the N pole an actual MCB does it provide overcurrent also? Or is it a dummy mcb...

Depends whether it is a true double pole device or whether it is a single pole device with a switched neutral pole.

Andy From Sligo

bit confused now because if the earth shares the neutral wire on a TN-C-S and there is no earth rod at the premises if you did have a DP switch and turned it to off then the live and neutral to the breakers and rest of the earth wires for the rest of the house would be isolated as well? - unless the earth wires in the cables leading to 13a sockets and light switches are on the incoming side of the isolator?

on another side note if its TN-C-S earthing system and the neutral acts as an earth as well as a neutral - in theory (and I have never tried it) what happens if you attach the neutral and earth wire in say a socket - RCD wouldnt trip no? because RCD is detecting current difference between live and neutral? - similarly if you attached one pin of a light bulb to live and the other one to earth would it light or would it trip?

Andy From Sligo

aido79 wrote: »

I think you might be out of your depth here if you are talking about isolating an earth.

but say like on the UK system if that has double pole switch and you isolate the live and neutral then if neutral is acting as an earth on a TN-C-S system wont you be isolating the earth too?

Andy From Sligo

aido79 wrote: »

I think you might be out of your depth here if you are talking about isolating an earth.

heres a point about isolating the earth - say if there is lightening and you have an earth rod outside (or even if its TN-C-S using ESB neutral as earth) and you turned off mains switch that will only isolate live only (not earth, nor earth) and that lightening strike was strong could it hit earth rod in back garden (or ESB TN-C-S) and then come up full force through CU and onto all your earthed metal things inside your house? - if you had a 3 pole (L,N,E) in CU and it was lightening you could turn off main switch in CU and kill all 3 couldnt you? (presuming the force of the lightening wasnt so strong that it would jump the air gap of the isolator which I suppose it could)

Tuco88

Risteard81 wrote: »

Tuco88 wrote: »

Question, A double pole MCB is the N pole an actual MCB does it provide overcurrent also? Or is it a dummy mcb...

Depends whether it is a true double pole device or whether it is a single pole device with a switched neutral pole.

I take it both can be sourced so, it's just a thought from this topic.

aido79

Andy From Sligo wrote: »

but say like on the UK system if that has double pole switch and you isolate the live and neutral then if neutral is acting as an earth on a TN-C-S system wont you be isolating the earth too?

No.

aido79

Andy From Sligo wrote: »

heres a point about isolating the earth - say if there is lightening and you have an earth rod outside (or even if its TN-C-S using ESB neutral as earth) and you turned off mains switch that will only isolate live only (not earth, nor earth) and that lightening strike was strong could it hit earth rod in back garden (or ESB TN-C-S) and then come up full force through CU and onto all your earthed metal things inside your house? - if you had a 3 pole (L,N,E) in CU and it was lightening you could turn off main switch in CU and kill all 3 couldnt you? (presuming the force of the lightening wasnt so strong that it would jump the air gap of the isolator which I suppose it could)

A 3 pole isolator is used for isolating the 3 phases(L1, L2 and L3) in a 3 phase system. You would never use it to isolate L,N and E.

Lightning by nature is trying to get to earth so will take the path of least resistance. It is also far more likely to hit something like your tv aerial than an earth rod( especially since it is normally in a plastic box in the ground) so the chances of anything becoming live in your house would be extremely slim.

Andy From Sligo

aido79 wrote: »

I think you might be out of your depth here if you are talking about isolating an earth.

when I used to sell the residential CU Boxes in the UK they all had (think it was 80a) unfused double pole mains switch , the earth in them days (we were talking late 80's) got their earth from metal water pipes and earth rods at the premises - it wouldnt have been TN-C-S not in them days I am pretty sure, but then again all the pipes up through the mains water tap would have been metal/copper anyway - so when you threw the main switch it the CU it killed Live & Neutral but not earth , come to think of it if my memory serves me correct there were an options on the wylex boxes you could have one fitted with 80a main DP switch or we did configurations with a 30ma 80a ELCB as the main switch in the CU - never a CU with both DP switch and ELCB (RCD's were not out for CU's then I dont believe) only portable 13a RCD's for lawnmowers etc

Andy From Sligo

aido79 wrote: »

A 3 pole isolator is used for isolating the 3 phases(L1, L2 and L3) in a 3 phase system. You would never use it to isolate L,N and E.

Lightning by nature is trying to get to earth so will take the path of least resistance. It is also far more likely to hit something like your tv aerial than an earth rod( especially since it is normally in a plastic box in the ground) so the chances of anything becoming live in your house would be extremely slim.

thanks