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.