don't use rcbos for TT

[mrloy99]

Manufactors instruction leaflet states {on schneider electric rcbo)
Do not use on installations that require double pole switching eg IT or TT.

 

[D Skelton]

Double pole isolation or switching on a TT system would be achieved by the main switch.

There is nothing wrong with installing single pole RCBOs on TT systems however if there was an s-type up front, you would need to install double pole RCBOs if RCBOs were specced for the job.

 

[spark 68]

Double pole isolation or switching on a TT system would be achieved by the main switch.

There is nothing wrong with installing single pole RCBOs on TT systems however if there was an s-type up front, you would need to install double pole RCBOs if RCBOs were specced for the job.

Why D ?

Most upfront S-types are DP/Multi-pole anyway, I have seen these double up as the Isolator too, in fact on the model forms there are boxes to fill in where the RCD is used as a mains switch.

Just curious to your reasoning as to why you would need DP RCBOs in the above scenario where an upfront DP or multipole S-type RCD is used.

 

[D Skelton]

Why D ?

Most upfront S-types are DP/Multi-pole anyway, I have seen these double up as the Isolator too, in fact on the model forms there are boxes to fill in where the RCD is used as a mains switch.

Just curious to your reasoning as to why you would need DP RCBOs in the above scenario where an upfront DP or multipole S-type RCD is used.

N-E fault on the single pole RCBO protected circuit will take out the upstream type-s too. So much for minimising inconvenience in the event of a fault! lol

 

[spark 68]

N-E fault on the single pole RCBO protected circuit will take out the upstream type-s too. So much for minimising inconvenience in the event of a fault! lol

Ah! Ok, good point, I have made the same case a few times on here myself about all SP RCBO boards as opposed to dual RCD boards, where they (SP RCBO's) won't isolate a N-E fault, no matter what the earthing system is, not just TT.

 

[spark 68]

It is about time more RCBOs were DP IMO.

 

[D Skelton]

Do you know of any manufacturers that make single module double pole RCBO's?

 

[spark 68]

I think you can get them (at a price!) from the usual big three, ABB, Schneider and Siemens et al, along with a couple of others, but Wylex and other typical domestic types seem to be nearly all SP, or at least from the typical wholsalers off the shelf, the DP types you probably have to order.

I don't really see why it should be the case though, if I recall the DP ones did take up two modules width, but I am sure I saw an advert somewhere the newer DP ones were single module width (it may have been at the Elex show).

Edit: a quick Google shows some MK DP single module ones, also some Proteus ones.

Here is a Link to some ECD ones http://www.electricalcomponentsdirect.co.uk/acatalog/Compact_Mini_RCBO_Circuit_Breakers.html

 

[Engineer54]

Think you'll find those RCBO's may well be SP+N rather than douple pole in the true sense of the meaning...

 

[MDJ]

Manufactors instruction leaflet states {on schneider electric rcbo)
Do not use on installations that require double pole switching eg IT or TT.

What they are trying to say is RCBOs are single pole and should not be used where double pole is required, They are not saying do not use on tt, why would they?

 

[SPARTYKUS]

They are prevalent in motor home CUs. Müller I think is the make. They do yoghurts too.

 

[Andy78]

Think you'll find those RCBO's may well be SP+N rather than douple pole in the true sense of the meaning...

The description in the link states disconnection of both line and neutral upon tripping.
Never heard of this brand before. Interesting price too ! I might bear them in mind for the future.

 

[SJD]

The price seems too cheap, not sure if there is some catch, or it is a direct import from Asia without lots of markups. I'm almost tempted to buy one and test it, would be good to hear if anyone has actually used these.

 

[Plonker 3]

They are similar price too Demans RCBOs for their Steeple range, although they are on SP. Only down side yo the ones linked is the supply needs wiring independently to it rather than just Busbar mount.

 

[SPARTYKUS]

Ive used ECD RCBOs. They work fine & still do (regularly check the 30 odd I installed.) the test results for each RCBO were also "fine". There were a couple of out of the box non workers- new ones were sent immediately no questions asked.

But Ive had that with every make.

 

[Knobhead]

Beats me why SP RCBO’s were ever made in the first place. Where’s the logic in sensing a N→E fault and breaking the L only?

 

[Engineer54]

The description in the link states disconnection of both line and neutral upon tripping.
Never heard of this brand before. Interesting price too ! I might bear them in mind for the future.

Yes, but it'll be just switching the neutral, not DP in the true sense... Still serves the purpose though... DP RCBO's will have protection in both poles...

 

[Knobhead]

SP+N is better than SP alone.

 

[Engineer54]

SP+N is better than SP alone.

More, ...is always better!! lol!!

 

[Knobhead]

I’ve only got two RCBO’s in my flat, they’re coming out as soon as I get around to it.
I priced up Hager DP units, good job I was sat down when I saw the price. There’s bags of room in the board so a couple of MCB’s and a second RCD will be going in. It also means I can split the two rings between the two RCD’s. BTW it’s a 16[SUP]th[/SUP] board.

Before you ask, it’s how I found it when I moved in.

 

[Geordie Spark]

I’ve only got two RCBO’s in my flat, they’re coming out as soon as I get around to it.
I priced up Hager DP units, good job I was sat down when I saw the price. There’s bags of room in the board so a couple of MCB’s and a second RCD will be going in. It also means I can split the two rings between the two RCD’s. BTW it’s a 16[SUP]th[/SUP] board.

Before you ask, it’s how I found it when I moved in.

Are you sure you are competent to carry out this work??

 

[D Skelton]

Oh dear Tony! Carrying out electrical work in a house without being NICEIC registered! Don't be suprised when the Part P police come a'knocking! A cowboy now as well as a Yorkshireman, it just keeps on getting better and better!

 

[Geordie Spark]

Oh dear Tony! Carrying out electrical work in a house without being NICEIC registered! Don't be suprised when the Part P police come a'knocking! A cowboy now as well as a Yorkshireman, it just keeps on getting better and better!

Shall we flip a coin or spin a bottle of something to decide which of us is going to grass him up? :devil:

 

[GLENNSPARK]

Oh dear Tony! Carrying out electrical work in a house without being NICEIC registered! Don't be suprised when the Part P police come a'knocking! A cowboy now as well as a Yorkshireman, it just keeps on getting better and better!

but i am...and he rang me up asking if i`d do it for him....

which kind of blows geordie`s sly comment at #21 out of the water as well......:27:

 

[Geordie Spark]

but i am...and he rang me up asking if i`d do it for him....

which kind of blows geordie`s sly comment at #21 out of the water as well......:27:

More like Tony phoned your mother and she told you get round there and do it.

 

[GLENNSPARK]

More like Tony phoned your mother and she told you get round there and do it.

oh so he told you did he?...

only half the story as i was also told that if i didn`t i was to `get up them stairs without no tea`...

 

[Geordie Spark]

oh so he told you did he?...

only half the story as i was also told that if i didn`t i was to `get up them stairs without no tea`...

I like your mother ... she has style.

 

[telectrix]

didn't do a good job of passing it on though. :24::tank:

 

[GLENNSPARK]

I like your mother ... she has style.

yeah...she has.

 

[GLENNSPARK]

didn't do a good job of passing it on though. :24::tank:

my style comes across loud n clear in my posts & replies...

its a style all my own.....aften imitated...but never matched....

 

[telectrix]

can't match that. i only got a couple of zippos.

 

[GLENNSPARK]

can't match that. i only got a couple of zippos.

not much then against my..erm...5 i think ...at the last count...

 

[telectrix]

but i bet you not got a harley davidson one. that's worth 3 "ordinary" ones.

 

[GLENNSPARK]

but i bet you not got a harley davidson one. that's worth 3 "ordinary" ones.

well no...

see when i get them i dont plan on riding out for a week....

it just sort of....happens...

 

[not clever]

Do you know of any manufacturers that make single module double pole RCBO's?

I do & so do you, you'll have to visit the other forum to see & purchase them though.....................

 

[D Skelton]

I do & so do you, you'll have to visit the other forum to see & purchase them though.....................

You've lost me

 

[mrloy99]

What they are trying to say is RCBOs are single pole and should not be used where double pole is required, They are not saying do not use on tt, why would they?

I think they are......In a TT installation neutral is also classed as a line conductor,And as such if isolation to a particular circuit is required for maintenance or alteration we are supposed to be able to isolate both poles without having to knock the whole installation off via the mainswitch RCD. I am thinking that double pole CBs could be the answer(rather than dp rcbo's) I know that they are available,and you are still 30ma protected via main switch rcd. I'm a wee bit surprised mr Niceic hasn't made an issue about this before.

 

[D Skelton]

I think they are......In a TT installation neutral is also classed as a line conductor,And as such if isolation to a particular circuit is required for maintenance or alteration we are supposed to be able to isolate both poles without having to knock the whole installation off via the mainswitch RCD. I am thinking that double pole CBs could be the answer(rather than dp rcbo's) I know that they are available,and you are still 30ma protected via main switch rcd. I'm a wee bit surprised mr Niceic hasn't made an issue about this before.

Because it isn't an issue. DP isolation is all that is required on a TT installation, it doesn't say where. Also, a neutral is never a line conductor.

 

[Knobhead]

Oh dear Tony! Carrying out electrical work in a house without being NICEIC registered! Don't be suprised when the Part P police come a'knocking! A cowboy now as well as a Yorkshireman, it just keeps on getting better and better!

There's a way around it. As I'm retired I'll get Glenn to do it for me

 

[Engineer54]

Originally Posted by mrloy99
. I am thinking that double pole CBs could be the answer(rather than dp rcbo's) I know that they are available,and you are still 30ma protected via main switch rcd. I'm a wee bit surprised mr Niceic hasn't made an issue about this before.

Far more sensible to have an all RCBO (SP+N) CU, than a couple of RCD's and a rack of DP MCB's, on a TT installation!!

Also have you considered the size that 10 circuit DP CU will be?? You'll be looking at providing at least a 26 way CU, including the DP isolation switch and 2 X RCD's, and that's not allowing for say a couple of spare ways for the future!! ...You won't be purchasing one of them for 50 odd quid!! lol!!

 

[Badged01]

There's a way around it. As I'm retired I'll get Glenn to do it for me

Theres a load of guys off here offering to do work for free ...... you just may have to put on your little tutu and pad out your chest some more

 

[not clever]

You've lost me

SBS supply trade only with true DP compact single mod rcbo's.
I thought you had seen them on the other forum, there's loads of photos of them in use.

 

[mrloy99]

Because it isn't an issue. DP isolation is all that is required on a TT installation, it doesn't say where. Also, a neutral is never a line conductor.

Sorry meant to say live..rather than line, neutral IS classed as a live conductor.
And without getting too ---- about the whole thing....We have to consider all possible scenarios.
We may wish to do work to a particular circuit without turning off the whole board.It is unlikely that all circuits have isolation after the board. eg lighting circuit with 2way switching
In TT situations neutral is not considered to have a RELIABLE connection to earth(unlike TN.where neutral and earth are joined at the service head)It is possible for the neutral to have a higher potential than earth .Removing the assumed neutral from the neutral bar is not recommended also due to a few possibilities,eg borrowed neutral or neutral in the wrong terminal in the neutral bar.
This voltage may only be a few volts and is unlikely to kill you but an unexpected tickle while working over the stairwell in a house could cause a fall.

 

[mrloy99]

Far more sensible to have an all RCBO (SP+N) CU, than a couple of RCD's and a rack of DP MCB's, on a TT installation!!

Also have you considered the size that 10 circuit DP CU will be?? You'll be looking at providing at least a 26 way CU, including the DP isolation switch and 2 X RCD's, and that's not allowing for say a couple of spare ways for the future!! ...You won't be purchasing one of them for 50 odd quid!! lol!!

Dunno about that!!!
The dp cb's I was using today(in an IT installation)were single module,same phisical size as normal cb's(general electric)

 

[Engineer54]

Dunno about that!!!
The dp cb's I was using today(in an IT installation)were single module,same phisical size as normal cb's(general electric)

That's true, but then most journeyman electricians don't know that they even exist.

I know that a guy is importing them from here (China) on another forum. How about giving us a link to these GE single module DP breakers, for everyone to see....

 

[mrloy99]

That's true, but then most journeyman electricians don't know that they even exist.

I know that a guy is importing them from here (China) on another forum. How about giving us a link to these GE single module DP breakers, for everyone to see....

i dont have a link but i could prob take a photo.They come inside these ips pre built bespoke panels made by a company called bender in uk.(I think they are german,but operate globally.)

 

[Richard Burns]

GE are a bit odd in that they appear to have a lot of good ideas but no kit available to purchase in the UK (and very expensive if it is available).
Having had a look GE do seem to make the Elfaplus Unibis but even their approved suppliers do not sell them!
View attachment ElfaPlus Unibis 1m 2P.pdf