SP/DP RCBO's for domestic .Do you have a preference ?

[LukeD]

Ive seen a few guys happy to fit both and a couple of others who only fit DP's . Do you have a preference ?

 

[stevethesparks]

Now available at a reasonable price DP all the way - cant see a reason not to.

 

[LukeD]

Now available at a reasonable price DP all the way - cant see a reason not to.

True....the drop in price is amazing .

 

[timhoward]

Preference will always be DP so
Neutral - earth faults are localised.

 

[davesparks]

I haven't done much domestic in years, is there now a readily available option for CUs that accept SPSN or DP devices?

My preference when I was doing more domestic was to use SPSN RCBO's when possible.

 

[nicebutdim]

I haven't done much domestic in years, is there now a readily available option for CUs that accept SPSN or DP devices?

My preference when I was doing more domestic was to use SPSN RCBO's when possible.

A number of manufacturers now offer SPSN RCBOs, with some doing so at very reasonable prices.

 

[timhoward]

I haven't done much domestic in years, is there now a readily available option for CUs that accept SPSN or DP devices?

Fusebox brand. It’s very good

 

[Mike Johnson]

Only option in Europe is DP we will eventually catch up.

Ohh do I dare say and use radials only and no loop in lighting.

 

[davesparks]

Only option in Europe is DP we will eventually catch up.

Ohh do I dare say and use radials only and no loop in lighting.

What do you mean by catch up? What in our electrical systems requires DP protection? Mainland Europe requires DP protection due to the differences in our systems.

 

[Mike Johnson]

Now how did I know it was going to be you that questioned my post.

 

[davesparks]

Now how did I know it was going to be you that questioned my post.

I don't know, but I am interested to know what exactly it is we need to 'catch up' with?

We have LV distribution which has a reliably earthed neutral so why would we need DP protection?

I fully support the use of SPSN residual current protection but I see no need for DP protection.

 

[LastManOnline]

What do you mean by catch up?

He is referring to the advantages of DP rcbo,s over single pole.

What in our electrical systems requires DP protection?

While it may not be a requirement ,it is always a benefit for final circuits to have DP isolation.

Mainland Europe requires DP protection due to the differences in our systems.

Mainland Europe uses the same electrical systems as the UK.

 

[davesparks]

He is referring to the advantages of DP rcbo,s over single pole.

While it may not be a requirement ,it is always a benefit for final circuits to have DP isolation.

Mainland Europe uses the same electrical systems as the UK.

DP rcbos don't have an advantage that is not also offered by SPSN RCBO's in the UK.

What is the benefit of DP protection in a system which had a reliably earthed neutral?

Mainland Europe does not have the same electrical system as the UK. For example their general purpose connector systems do not have polarity, whereas ours do.

As I have said may times one here I support the use of SPSN residual current protection, but I see no reson for DP protection generally.

I don't like this idea that 'DP is better than SP' without having a good supporting argument. Years ago in the UK DP protection was the standard because it was necessary, but we improved our electrical systems so that it is no longer required.

 

[timhoward]

As I have said may times one here I support the use of SPSN residual current protection, but I see no reson for DP protection generally.

i agree there is no need for over current protection on the Neutral unless it’s a specialist installation.
We also need to throw into the mix that several manufacturers call RCBOs double pole for ease when they are actually SPSN in reality.
There could therefore be terminology confusion here too.

 

[Mike Johnson]

I think its Double pole vs Double module that cause's the confusion.

 

[LastManOnline]

Welcome back by the way

DP rcbos don't have an advantage that is not also offered by SPSN RCBO's in the UK.

Iyou don't consider been able to isolate a neutral to earth fault on a final circuit a disadvantage ?
You don't consider been able to carry out an IR test on a final circuit without first having to disconnect a disadvantage ?
SPSN rcbo,s generally contain more electronics than their DOP equivalent.
I suspect that DP (and double module) rcbo,s dissipate heat better.
The single advantage I see SPSN having is the need for less space.Otherwise I see only disadvantages

What is the benefit of DP protection in a system which had a reliably earthed neutral?

See the above

Mainland Europe does not have the same electrical system as the UK.

Mainland Europe shares TNC-S and TT systems which are the two most widely used systems in the UK

I don't like this idea that 'DP is better than SP' without having a good supporting argument.

We are all entitled to personal opinion.But I can assure you that if you carried out more work in the domestic sector you would find DP rcbo,s make your life and the customers life considerably more convenient

Years ago in the UK DP protection was the standard because it was necessary, but we improved our electrical systems so that it is no longer required.

What are these "improvements" specifically?

 

[nicebutdim]

SPSN rcbo,s generally contain more electronics than their DOP equivalent.
I suspect that DP (and double module) rcbo,s dissipate heat better.
The single advantage I see SPSN having is the need for less space.Otherwise I see only disadvantages

Dissipation of heat isn't generally an issue in domestic installations. It shouldn't be an issue at all if breakers are arranged in such a manner that circuits drawing high loads are kept separate from each other - eg. not placing shower and kitchen socket circuits next to each other, but that's good practice regardless of breaker size.

While there may be advantages to having double module breakers, in a domestic environment these are outweighed by constraints on space. In fact I generally see single module RCBOs in commercial and industrial environments, without any issues arising from heat.

I wonder if statistics exist to highlight different rates of failure between single and double module RCBOs., but I honestly wouldn't expect a higher rate of failure from single module units.

Is there any advantage to having double module DP as opposed to single module SPSN or would such a move be the equivalent to 'upgrading' to CRT televisions and 1980s sized cell phones?

 

[happysteve]

I suspect there's some confusion about RCBO terminology going on here.

I suspect some folk regard SPSN = single pole switched neutral.

I suspect some folk regard SPSN = single pole solid neutral.

I suspect some folk couldn't convincingly tell you the difference between single pole switched neutral, and double pole.

I suspect I'm in this category. If I had to hazard a guess, it would be that the RCD side of things doesn't care which is the line, and which is the neutral (as the device is measuring a difference between the two), but that overcurrent is determined by what flows through the line only. Whereas a double pole device could detect overcurrent in either line or neutral. But that's only a guess. Happy to be schooled, though

 

[nicebutdim]

I suspect there's some confusion about RCBO terminology going on here.

I suspect some folk regard SPSN = single pole switched neutral.

I suspect some folk regard SPSN = single pole solid neutral.

I suspect some folk couldn't convincingly tell you the difference between single pole switched neutral, and double pole.

I suspect I'm in this category. If I had to hazard a guess, it would be that the RCD side of things doesn't care which is the line, and which is the neutral (as the device is measuring a difference between the two), but that overcurrent is determined by what flows through the line only. Whereas a double pole device could detect overcurrent in either line or neutral. But that's only a guess. Happy to be schooled, though

As an apprentice I'm ready to be shot down but, as RCDs & the RCD element of RCBOs detect imbalance between line & neutral, it matters not which side current is leaking from. What matters is the detection of imbalance above a predetermined level.

DP isolates both poles, SP isolates line only and SPSN (single pole switched neutral) is a single pole device which also switches neutral - to all intents and purposes the latter isolates both poles, but it is the manner in which this happens that differentiates between DP & SPSN. I've read details on this forum about how the latter works, but can not recall sufficient detal to offer a concise explanation. I suspect @pc1966 might fill in the blanks.

 

[loz2754]

@happysteve is correct.

A single pole switched neutral RCBO does indeed switch both poles when operated (either by residual current detection, or by overcurrent).

The difference between a SPSN RCBO and a DP RCBO is that the SPSN only reacts to an overcurrent that occurs in the line, and not the neutral, whereas a DP RCBO reacts to an overcurrent in either the line or the neutral. The result is the same though, as both poles are isolated when the device operates.

With a single pole RCBO, the neutral is connected straight through, and will possibly cause upstream devices a headache in the event of a neutral to earth fault.

 

[Mike Johnson]

If I remember correctly its only the line that has the solenoid that trips, the neutral is just dragged along with the switch when tripping, obviously in a double pole double module RCBO or MCB the neutral is isolated when tripped, not so when its connected to all the other neutrals on the top rail. Fault finding on a full dual module dual pole board is so much easier and the boards are big enough to work on as well.

 

[LastManOnline]

With a single pole RCBO, the neutral is connected straight through, and will possibly cause upstream devices a headache in the event of a neutral to earth fault.

It's a simple choice really.

For the customer , SPSN rcbo,s means his installation is not protected against N to E faults in certain circuits.

For the electrician ,SPSN rcbo,s complicate what would otherwise be a relatively simple fault finding procedure.

 

[pc1966]

For the electrician ,SPSN rcbo,s complicate what would otherwise be a relatively simple fault finding procedure.

Surely you mean SP RCBOs?

With SPSN it allows the N path to be isolated making it simpler to IR test or stop an up-stream delay RCD tripping on a N-E fault.

 

[LastManOnline]

Surely you mean SP RCBOs?

Correct

 

[happysteve]

Thanks for the clarification.

I'm struggling to think of a circumstance where a fault (or combination of multiple faults) would be detected and cleared by a "true" double pole RCBO (one with overcurrent detection in N as well as L), where it wouldn't with a single pole switched neutral RCBO. Anyone?

 

[LastManOnline]

Thanks for the clarification.

I'm struggling to think of a circumstance where a fault (or combination of multiple faults) would be detected and cleared by a "true" double pole RCBO (one with overcurrent detection in N as well as L), where it wouldn't with a single pole switched neutral RCBO. Anyone?

You are correct.The issue only arises with SP rcbo,s where the neutral is unswitched.These are the only ones I personally have worked with to date.

 

[pc1966]

Thanks for the clarification.

I'm struggling to think of a circumstance where a fault (or combination of multiple faults) would be detected and cleared by a "true" double pole RCBO (one with overcurrent detection in N as well as L), where it wouldn't with a single pole switched neutral RCBO. Anyone?

Historically some of the EU had both live connections off a three-phase supply (220V delta, not the 400V L-L seen now) so basically you needed fault protection on both lines.

In the UK the only likely situation is likes of 110V site transformers where again you have two line as 55V-0V-55V instead of line/neutral and a fault to earth needs over-current protection for both cases.

Yes, the RCD side of a SPSN RCBO should trip due to the imbalance but (a) I am not sure the 'SN' side is rated to break much as it probably assumes L opens first, and (b) the I2t let-though for a RCD is far higher as the trip times are typically several times longer than the 'instant' magnetic trip side of a MCB.

 

[pc1966]

Mainland Europe shares TNC-S and TT systems which are the two most widely used systems in the UK

That aspect is perfectly true, but historically they have not has the "strong polarity" assumption of the UK where we had polarised plugs and often line-only switching & OCPD due to N being very much definitely N by design & test.

 

[brianmoooore]

In the UK the only likely situation is likes of 110V site transformers where again you have two line as 55V-0V-55V instead of line/neutral and a fault to earth needs over-current protection for both cases.

And with the 230 - 0 - 230 volt supplies that are common in my area. I've fitted many DP MCBs over the years.

 

[brianmoooore]

@Mike Johnson or anyone else with knowledge of French electrics. Off topic, but is the polarity of sockets specified in France? Most of my encounters with French electrics are 16A sockets on camp sites, and, while most are wired neutral on the left when earth at the top, as in the UK, it's not at all unusual to encounter one with the live on the left.

 

[timhoward]

I suspect some folk regard SPSN = single pole switched neutral.

I suspect some folk regard SPSN = single pole solid neutral.

I'd assumed the former in my comments. The MEM catalogue says
"SPSN and TPSN indicate switched neutral. Neutral makes first and breaks last."

 

[Mike Johnson]

@Mike Johnson or anyone else with knowledge of French electrics. Off topic, but is the polarity of sockets specified in France? Most of my encounters with French electrics are 16A sockets on camp sites, and, while most are wired neutral on the left when earth at the top, as in the UK, it's not at all unusual to encounter one with the live on the left.

Most electricians in France would connect the neutral on the left, but and its a big but, in domestic installations anyone is allowed to work on the electrics, Francois down the local wine bar is just as prevalent as Dave down the pub, domestic sockets are restricted to eight on 1.5mm protected by 16amp MCB and twelve on 2.5mm protected by 20amp MCB, RCD's are restricted to eight circuits and all white goods on their own circuits, so the boards are bigger than we encounter in the UK and so much easier to work on, Oh yes all are dual pole, dual module.

Being dual pole dual module the polarity is not, in reality an issue as the plugs are not fused.

 

[brianmoooore]

I have a 13A s/socket with a neon near the door of the caravan, modified so that the neon is connected between live in and earth.
I would estimate that this neon lights when I plug in to around one in ten of the 16A sockets on French campsites. Not common, but a significant proportion.
I carry a 16A plug connected by a few inches of flex to a 16A line socket which is deliberately incorrectly cross connected to add in and correct things when this occurs.

 

[kropaske]

Had a chat about this with a spark that worked in Germany and Poland and 1P+N (spsn) rcbo are in fact allowed i assume it would be the same in France otherwise why would they be available to buy - commercial install perhaps.
Ring final circuits are also allowed there but very rarely used.
As for those huge boards circuits divisions are different and often houses are supplied with 3Ph instead 1Ph. There is no requirement to use double module Rcbo's however the requirement is to use rcbo that are voltage independent which means if N is lost rcbo will still operate unlike UK Rcbo's which won't. Majority of voltage independent Rcbo's are double module hence most install in EU will have those, but there are single module voltage independent 2P rcbo available as well.

 

[Mike Johnson]

Not the same in France, double pole double module only in domestic installations and definitely no rings, most rural properties are 3Ph and boards tend to be four row to split the phase's, the only real difference between Germany and France is that German boards are twelve modules wide, whereas French boards and thirteen modules wide, but I have insufficient knowledge on German installs to comment on single module voltage independent RCBO's?