After a New Consumer Unit, now I need EICR & 100A DP Isolation Switch

[i3_happy]

Trying to organise a CU replacement at home. It's a 1930s property. It's got a 10way CU but with no RCD protection.

Was after a larger unit with full RCBOs. Every Sparky I've spoken to has varied in their suggested plans.

1) Some say do an EICR first, others happy to just go straight with a new CU. EICR seems to add a big upfront cost.
2) Some mention DP RCBO, others don't.
3) One said for Building control notification, I've have to check the date on your smoke/heat & carbon monoxide alarm (?).
4) One said gas/water pipe bonding would be required and it's extra
5) One said, I'd have to get an isolator switch fitted by my supplier before the CU can be replaced. Currently there is only a mains fuse for isolation. The CU and mains fuse are both next to each other.

Prices vary for 1, 2, 3 significantly, I mean the most expensive quote is literally double the cheapest quote!

Any advice would be appreciated as this is driving me nuts!

 

[SJD]

Re (1), the testing for an EICR is pretty much the same testing you should do for a consumer unit change. So in theory you can have an EICR done, and the CU change costs should reflect that most of the testing has already been done. Many people would want to do the testing first on an old installation in case it throws up lots of unexpected and potentially costly issues.

Re (2), for a TT installation (earth rod rather than supplier earth), using DP RCBOs is essential, but the cost of them has come down now to not much more than single pole RCBOs that it might be simpler for someone to just stock the DP ones that suit all types of installation.

Re (3), that is nonsense, smoke or heat or CO alarms don't come into notifying a consumer unit change. You do need to make sure whoever does the work is registered and able to notify to BC via one of the schemes (NICEIC, ELECSA), otherwise it won't get done.

Re (4), the bonding must be checked and may need replacing or even adding if missing. That is likely obvious on a survey and can be included in a quote.

Re (5), some electricians would require this. Some DNOs are rather unhappy about a fuse being pulled, some are more enlightened.

 

[littlespark]

To answer some of those questions.

1) Before changing a CU, its good practice to at least perform a "mini" EICR, just to make sure there are no undetected faults which could trip a more sensitive RCBO. Borrowed neutrals on lighting circuits are a common thing. For a near 100 year old house, its wise to have one done, if its all original wiring, with possible DIY add-ons here, there and everywhere. It should be done as part of the board change price. There should be an installation certificate produced after the board change.

2) Manufacturers wouldn't make single pole RCBO's if they weren't permitted... so its down to the electrician... Some do, some don't specify double pole.

3) Its covered under Part P of building control.... but as i am Scottish, i dont have to worry about it, but one of my English colleagues will know more about it.
You can check the dates yourself.... Not the responsibility of the electrician... They can only advise.
Renewal of house insurance may be another matter though, if they are indeed out of date, or not enough of them.
You can contact building control yourself to see what is required.

4) Not necessarily. Many supply pipes and pipes within properties are plastic now, so it could be that earth bonding is only covering a metal stopcock and nothing else.

5) Yes. Electricians are not generally permitted to cut seals on supply fuses and pull them. (although some are)
An isolator fitted by the supplier allows anyone else to safely change the board by simple turning the isolator off.

 

[westward10]

Re (2), for a TT installation (earth rod rather than supplier earth), using DP RCBOs is essential, but the cost of them has come down now to not much more than single pole RCBOs that it might be simpler for someone to just stock the DP ones that suit all types of installation.

There is no requirement for a TT installation to have double pole circuit protection.

 

[DefyG]

2 replies and somewhat contradictory advice! the poor OP is no better off coming to this forum!

 

[littlespark]

3 replies, I counted. And the TT mention was just an example. There was no mention of it in OP.

Not really contradictory advice that I can see….
And if OP wants to save money, move out of London, because even changing a lightbulb down there costs an arm and a leg.

 

[nicebutdim]

2 replies and somewhat contradictory advice! the poor OP is no better off coming to this forum!

OP might do better to ask each electrician who quoted for reasoning behind their proposals.

Some proposals make sense, although not mandated by regulation, while others seem to be borne of myth. I'd be wary of any electrician who invents regulations, or who unquestioningly accepts information, as it would lead me to believe they know little of regulatatory requirements beyond what they've been told at one time or another.

As a caveat I would add that some regulations are open to differing interpretation, such as precisely what constitutes double pole isolation in specific circumstances, but plenty are very clear or even non-existent.

 

[DefyG]

Not really contradictory advice that I can see….

I did say somewhat! The OP came here for some clarity on the situation but hasn't got it.
But we all know its not 'black and white' I've always thought if you get 6 or 10 sparks quoting for same job you will end up with 6 or 10 different ideas and prices but all could be compliant!!

 

[mainline]

Re (2), for a TT installation (earth rod rather than supplier earth), using DP RCBOs is essential

Can you elaborate please as to why it would be absolutely necessary


edit: Just noticed @westward10 post

 

[pc1966]

Can you elaborate please as to why it would be absolutely necessary

It only becomes necessary if there is an up-front delay RCD, then you need downstream ones to be DP switching or you have no selectivity on N-E faults. Typically that would be a more complicated TT set-up (e.g. main/sub-DB, armoured cable from cutout to CU so needs RCD protection for ADS, etc).

Given many of the cost-effective compact RCBO are now DP (e.g. Wylex/Crabtree, Fusebox) its not such a big deal.

 

[suffolkspark]

Trying to organise a CU replacement at home. It's a 1930s property. It's got a 10way CU but with no RCD protection.

Was after a larger unit with full RCBOs. Every Sparky I've spoken to has varied in their suggested plans.

1) Some say do an EICR first, others happy to just go straight with a new CU. EICR seems to add a big upfront cost.
2) Some mention DP RCBO, others don't.
3) One said for Building control notification, I've have to check the date on your smoke/heat & carbon monoxide alarm (?).
4) One said gas/water pipe bonding would be required and it's extra
5) One said, I'd have to get an isolator switch fitted by my supplier before the CU can be replaced. Currently there is only a mains fuse for isolation. The CU and mains fuse are both next to each other.

Prices vary for 1, 2, 3 significantly, I mean the most expensive quote is literally double the cheapest quote!

Any advice would be appreciated as this is driving me nuts!

1 yes on a property of that age i would 100% want to do an eicr first, it helps to manage cost expectations because there are most likely other areas which would benefit from upgrading, you may even have rubber cables, or at the least un earthed lighting circuits.

2 dp not required if its just a normal board and nothing to think about with selectivity on sub mains etc

3 yes a consumer unit change is notified to building control, usually by the electrician so make sure you get one thst can and is on the competant person register

4 gas and water does usually require bonding unless it enters the property as plastic, some qwerks here so electrician will advise during eicr

5 yes your supplier should come and fit you an isolator so the electrician can safely perform the consumer unit upgrade, but you can get the EICR done before this.

 

[mainline]

It only becomes necessary if there is an up-front delay RCD, then you need downstream ones to be DP switching or you have no selectivity on N-E faults. Typically that would be a more complicated TT set-up (e.g. main/sub-DB, armoured cable from cutout to CU so needs RCD protection for ADS, etc).

Given many of the cost-effective compact RCBO are now DP (e.g. Wylex/Crabtree, Fusebox) its not such a big deal.

An upstream s-type rcd can still trip in certain circumstances, so still doesn't give 100% selectivity.

The real point being that it's not a requirement to have DP rcbo.

 

[OLDBOY]

There is no requirement for a TT installation to have double pole circuit protection.

An upstream s-type rcd can still trip in certain circumstances, so still doesn't give 100% selectivity.

The real point being that it's not a requirement to have DP rcbo.

It is indirectly, there is a requirement for a single fault not to result in entire installation loss, therefore a tt installation with an upfront rcd would not be compliant where sp rcbo devices were used

 

[HappyHippyDad]

As you can see from the replies @i3_happy all of your electricians were right and all of them were wrong

 

[HappyHippyDad]

My thoughts for what they are worth..

1. Not always essential, but sometimes a good idea. Sometimes essential.
2. Not required as you will have a DP main switch.
3. Don't really understand this point. The electrician really needs to be registered and therefore they will notify the CU change to the building authorities. Smoke detectors are not involved here.
4. If there is no Main bonding in place then it is extremely likely you need it on the gas and 50/50 on the water (depending on if there is a blue plastic pipe entering the house from the ground).
5. I suppose so, but not many of us would insist on that. I can't argue with the electrician who said that though, as they are being professional and do not want to illegally remove the main fuse.

 

[i3_happy]

Thanks all for the advice and varying perpectives. So, bottom line is that none of this is really clearcut, but open to interpretation.

Given the various opinions and info, I've taken another look at all this....

1) EICR - seems the way to go, but a valid point that if a lot of testing is done upfront then the CU replacement costs shoiuld be lower.

2) DP RCBO - actually the DP & SP are not too different in price, so why not go with DP, besides I have an electic car charger and would need a DP RCBO for that, I believe.

3) Smoke/Heat alarms - on the positive side it got me to check the dates on my alarms and just added a Heat alarm to the kitchen.

4) No earth bonding to Gas currently. The Water Supply pipe is the blue plastic for the incoming mains, so gathering that means no earth bonding required for the water.

5) For the iolator switch the DNO was not interested unless it was to be installed prior to the main fuse, however, British Gas surprised me by saying they could do it for £109 + tails cost extra. Will determine if the isolator will go between the fuse and meter or between the meter and CU. Given it's a smart meter probably the latter.

 

[HappyHippyDad]

Thanks all for the advice and varying perpectives. So, bottom line is that none of this is really clearcut, but open to interpretation.

Given the various opinions and info, I've taken another look at all this....

1) EICR - seems the way to go, but a valid point that if a lot of testing is done upfront then the CU replacement costs shoiuld be lower.

2) DP RCBO - actually the DP & SP are not too different in price, so why not go with DP, besides I have an electic car charger and would need a DP RCBO for that, I believe.

3) Smoke/Heat alarms - on the positive side it got me to check the dates on my alarms and just added a Heat alarm to the kitchen.

4) No earth bonding to Gas currently. The Water Supply pipe is the blue plastic for the incoming mains, so gathering that means no earth bonding required for the water.

5) For the iolator switch the DNO was not interested unless it was to be installed prior to the main fuse, however, British Gas surprised me by saying they could do it for £109 + tails cost extra. Will determine if the isolator will go between the fuse and meter or between the meter and CU. Given it's a smart meter probably the latter.

Excellent update, thanks. We like clear, well written updates

 

[mainline]

It is indirectly, there is a requirement for a single fault not to result in entire installation loss, therefore a tt installation with an upfront rcd would not be compliant where sp rcbo devices were used

My point is that using dp rcbos with upfront
s type rcd still wouldn’t give 100% selectivity.

 

[OLDBOY]

My point is that using dp rcbos with upfront
s type rcd still wouldn’t give 100% selectivity.

Agreed.
But people tend to look for a specfic regulation for a particular scenario. There is no specific regulation stating that a dp protective device is required for a tt with an upstream s type rcd. But nevertheless an sp device would not be compliant.

 

[davesparks]

My point is that using dp rcbos with upfront
s type rcd still wouldn’t give 100% selectivity.

Not 100% selectivity no, but better than with SP.
Also DP or SPSN RCBOs would allow the upstream RCD to be reset after it trips on a N-E fault whereas with SP RCBOs you could be stuck with the whole installation being off.

 

[mainline]

Not 100% selectivity no, but better than with SP.
Also DP or SPSN RCBOs would allow the upstream RCD to be reset after it trips on a N-E fault whereas with SP RCBOs you could be stuck with the whole installation being off.

Nobody is arguing that DP isn't a better option.

You could also have the whole installation off using DP rcbos, dependent on where the N to E fault was, I've seen N to E faults cause random rcbos to trip.

Also, regardless of whether Dp, Sp TT or Tn is used the fault will still remain.

Are DP rcbos a requirement ? NO

Are DP rcbos needed ? NO

 

[OLDBOY]

Nobody is arguing that DP isn't a better option.

You could also have the whole installation off using DP rcbos, dependent on where the N to E fault was, I've seen N to E faults cause random rcbos to trip.

Also, regardless of whether Dp, Sp TT or Tn is used the fault will still remain.

Are DP rcbos a requirement ? NO

Effectively they ARE a requirement where a 'back up' upstream S type RCD is employed on a TT system with final circuit rcbo protection as is general and good practice in the UK. It is not possible on such a system to completely design out all nuisance tripping of the up front RCD, but the only way to design out a known cause is to use dp rcbo's. To not do so would not be compliant.

 

[pc1966]

Thanks all for the advice and varying perspectives. So, bottom line is that none of this is really clear-cut, but open to interpretation.

Given the various opinions and info, I've taken another look at all this....

1) EICR - seems the way to go, but a valid point that if a lot of testing is done upfront then the CU replacement costs should be lower.

2) DP RCBO - actually the DP & SP are not too different in price, so why not go with DP, besides I have an electric car charger and would need a DP RCBO for that, I believe.

I think most folks will agree with you here.

3) Smoke/Heat alarms - on the positive side it got me to check the dates on my alarms and just added a Heat alarm to the kitchen.

Go for Aico if you can, less trouble than other brands but slightly more expensive. Here in Scotland they now mandate a linked alarm system, but RF is fine for home use, and a great thing to get with Aico is the separate test/silence button for wall mounting.

Ei450 RadioLINK Alarm Controller | Aico

Ei450 RadioLINK Alarm Controller. The Ei450 is used to control all the alarms in a system from one place.

www.aico.co.uk

No more flapping towels or climbing on chairs to deal with a false alarm!

4) No earth bonding to Gas currently. The Water Supply pipe is the blue plastic for the incoming mains, so gathering that means no earth bonding required for the water.

The gas supply must be bonded if metallic pipe (almost always the case?) but if water main is plastic then not required as you say.

5) For the isolator switch the DNO was not interested unless it was to be installed prior to the main fuse, however, British Gas surprised me by saying they could do it for £109 + tails cost extra. Will determine if the isolator will go between the fuse and meter or between the meter and CU. Given it's a smart meter probably the latter.

They will always put an isolator switch between the meter and the CU. It makes tampering with the meter (and living) harder that way!

The quoted price looks reasonable enough to me.

 

[mainline]

The only way to design out a known cause is to use dp rcbo's. To not do so would not be compliant.

A dual CU with a pair of rcds and sp rcbos would be compliant.

The use of Dp rcbos is still not a requirement, you can't call it a requirement or say it's needed if there are other ways of doing things.

 

[mainline]

A dual CU with a pair of srcds and sp rcbos would be compliant.

The use of Dp rcbos is still not a requirement, you can't call it a requirement or say it's needed if there are other ways of doing things.

 

[nicebutdim]

A dual CU with a pair of rcds and sp rcbos would be compliant.

The use of Dp rcbos is still not a requirement, you can't call it a requirement or say it's needed if there are other ways of doing things.

There's a strong argument against this position from the perspective of potential nusiance tripping. It's one of those areas I'd raised where regs can be considered open to interpretation. I'd be happy to defend my position and I'm sure you'd be happy to do the same. Where our positions differ is that you'd likely be happy to install DP RCBOs at the insistance of a client, whereas I might refuse to install a dual RCD board if I felt there was good reason to do so.

 

[mainline]

There's a strong argument against this position from the perspective of potential nusiance tripping. It's one of those areas I'd raised where regs can be considered open to interpretation. I'd be happy to defend my position and I'm sure you'd be happy to do the same. Where our positions differ is that you'd likely be happy to install DP RCBOs at the insistance of a client, whereas I might refuse to install a dual RCD board if I felt there was good reason to do so.

I haven't fitted a dual rcd board for many years and am not likely to do so

I always fit dp rcbos
But I'm not required to do so

 

[nicebutdim]

I haven't fitted a dual rcd board for many years and am not likely to do so

I always fit dp rcbos
But I'm not required to do so

You're not required to do so in the circumstances in which you fit them or you believe there's no circumstance in which they need to be fitted?


My limited experience has already involved a couple of faults in which N-E issues caused subsequent problems on other circuits. I like the idea of knowing a future problem should be isolated with the circuit on which it occurred, thus further avoiding the possibility of nuisance tripping.

Most customers have the means to cover an additional few % on the overall job cost and also have the ability to understand a basic explanation for those costs. Customers who have to shave every penny from a job often aren't going to like my proposals anyway (and I'll seek to avoid them) and for customers who are of limited means I'll obviously aim to find a sensible accomodation that involves keeping costs low, while incorporating as much future convenience as possible.

No customer is ever going to thank me for the power not going off on more circuits than necessary, but I'm content knowing my ears won't burn too much if only one circuit goes off.

 

[OLDBOY]

As this is in danger of going round in circles I will finish up. The usual and preferred arrangement with a small tt installation is a 100ma or above S type rcd main switch and rcbo's. With this arrangement dp rcbo's are effectively a requirement IMO . Other arrangements may be devised,as above,in which dp rcbo's would not be a requirement. ( A dual rcd board AND rcbo's...).Remember....main bonding is a requirement....except when it isnt.

 

[mainline]

As this is in danger of going round in circles I will finish up. The usual and preferred arrangement with a small tt installation is a 100ma or above S type rcd main switch and rcbo's. With this arrangement dp rcbo's are effectively a requirement IMO . Other arrangements may be devised,as above,in which dp rcbo's would not be a requirement. ( A dual rcd board AND rcbo's...).Remember....main bonding is a requirement....except when it isnt.

Why would you have an rcd main switch with a full dp rcbo board ?