Difference between "Single pole with switched neutral" AND "Double Pole" ?

[runningpiglet]

Please clarify:

What event is an example where a '

Agree with Running Piglet. I'm not sure if things have changed but it used to be that an SP+N breaker will break last and make first the neutral and has no overload protection on the neutral pole. A 2-pole breaker obviously both poles feature mag and thermal overload and no particular order to the making and breaking of the poles. I only know for a fact in the old Heinemann MCB's the SP+N version had equally sized contacts on both poles but it wouldn't surprise me if modern versions had a smaller neutral contact in the interest of saving a tenth of a gram of brass.

Yeah, making the N contact smaller and slower doesn't just save brass it saves a lot of the arc blowout space too!

 

[mainline]

I don't think anyone would be jealous of the crap I have to deal with most days.

 

[poni]

Please clarify:

What event is an example where a 'double pole' device and a 'SP+N' device would act differently?

double pole MCB's are mainly used in industrial setting's for two phase supply's and single pole+ N are mainly use in domestic setting's, on a single phase supply they will do the same job, but so would a Three pole one, why would you use one? I don't think they make a 2 pole RCBO's, I am sure they only make only single pole +N ones, so not doing the same job ,i.e.. no earth leakage protection with a double pole MCB,

 

[poni]

I don't think anyone would be jealous of the crap I have to deal with most days.

nice

 

[runningpiglet]

would a Three pole one, why would you use one? I don't think they make a 2 pole RCBO's, I am sure they only make only single pole +N ones, so not

This one dates from 2001 so they did used to exist …

 

[runningpiglet]

This one dates from 2001 so they did used to exist …

Actually I see from my photo the diagram on the RCBO shows overcurrent trip only on in the phase line. So I guess that means it would be SP+N - or did you mean you did not know of 2 module width devices ?

 

[michael8554]

Here's the spec of a Fusebox RTAM Mini RCBO 1P + N.
To me it looks like "L In-Supply" and "N In Supply" both appear to be switched ?

 

[nicebutdim]

There are loads of single module RCBO options now switching both poles, including Fusebox RTAM range above, but these are considered SP+N as they don't have overcurrent protection on the neutral.

Ready to stand corrected, but I think the 2 module RCBOs used in many countries do have overcurrent protection on both poles.

 

[poni]

Actually I see from my photo the diagram on the RCBO shows overcurrent trip only on in the phase line. So I guess that means it would be SP+N - or did you mean you did not know of 2 module width devices ?

yes two pole not two module, I did know of the two module units , at a time that was all you could get, but I am glad that someone is watching me

 

[poni]

Here's the spec of a Fusebox RTAM Mini RCBO 1P + N.
To me it looks like "L In-Supply" and "N In Supply" both appear to be switched ?
View attachment 17658

that's what it says at the top of the page,

 

[poni]

There are loads of single module RCBO options now switching both poles, including Fusebox RTAM range above, but these are considered SP+N as they don't have overcurrent protection on the neutral.

Ready to stand corrected, but I think the 2 module RCBOs used in many countries do have overcurrent protection on both poles.

you could be right this one looks like its got O/L on both poles, I have must have seen them but really looked at them close

 

[nicebutdim]

you could be right this one looks like its got O/L on both poles, I have must have seen them but really looked at them close

It's not really the sort of thing I ever paid attention to, until I asked myself why RCBOs were being classed as SP+N as opposed to DP. Until then I'd called them all DP.

 

[mainline]

Until then I'd called them all DP.

Just like the vast majority of the sellers/manufactures do.

 

[runningpiglet]

It's not really the sort of thing I ever paid attention to, until I asked myself why RCBOs were being classed as SP+N as opposed to DP. Until then I'd called them all DP.

Yes, I wonder if it is an attempt to clarify and distinguish? A true 2 pole RCBO might be unable to fit into a single module width given the space needed for arc blowouts etc. And there was a time when some really nasty single pole one module width RCBOs were made which only opened the phase - the neutral passed through for residual current sensing but was not switched, meaning an NE fault tripped open the L but NE fault could persist! SP+N indicates that the N is switched too unlike those earlier SP horrors. I guess in most single phase cases true overcurrent sensing in N isn't needed because if the N fault current differs from the L current then the RCD portion will trip and if the N fault current balances the L current but is too high then the MCB portion will trip?

 

[nicebutdim]

Yes, I wonder if it is an attempt to clarify and distinguish? A true 2 pole RCBO might be unable to fit into a single module width given the space needed for arc blowouts etc. And there was a time when some really nasty single pole one module width RCBOs were made which only opened the phase - the neutral passed through for residual current sensing but was not switched, meaning an NE fault tripped open the L but NE fault could persist! SP+N indicates that the N is switched too unlike those earlier SP horrors. I guess in most single phase cases true overcurrent sensing in N isn't needed because if the N fault current differs from the L current then the RCD portion will trip and if the N fault current balances the L current but is too high then the MCB portion will trip?

There are still plenty of single pole RCBOs out there. It's odd that a majority of the SP+N come in a shorter form and the single pole devices, which in theory need less space, tend to be taller.

I like both poles switching for the reasons you state above, but never thought ill of SP devices as they are no different to MCBs in that regard. I suppose in more recent times we had an RCD upfront to be taken out by that NE fault, so perhaps I've been too kind to single pole RCBOs!