smoke detection/rcbo yes or no

[electrosparks]

HI SPARKYS
JUST A QUICK BIT OF ADVICE REQUIRED.
HAVE RECENTLY BEEN TO PRICE A DB CHANGE OF THE DUAL SPLIT LOAD VARIETY.and noticed the instal has a dedicated smoke detection circuit .Now i have also noticed that this circuit is buried in plaster (through a safe zone) and in fact all circuits are buried in plaster as the feeds drop down the wall from ceiling to db level. In no way could I claim that cables are 50 mm back from surface or would be in earthed steel containment
Now due to the circumstances I feel obliged to put smoke detectors on rcd protective device but realize safety services are not required to have additional protection.

Would it be better to put smokes on a rcbo as cables are not 50mm back
Or would it be right to leave circuit without additional protection.

Just for the record I fully believe in the use of 30ma rcd/rcbo and have done for the last 25 years or so as as I believe electrical safety takes precedent over nuisance. I also realize that sometimes incorrect selection of rcds can cause problems to some equipment including fridges and computers etc, and grouping circuits protected by rcds can have a negative impact with some equipment .
So if I put circuit on rcbo and in the future an earth fault was to occur the device was to trip indicating earth fault wouldn't that be better than if left unprotected and the same fault was to occur the protective device may not trip and potentially dangerous leakage currents may be present but smoke detectors still function, whats the point a safety service that can kill you.
I think in this case circuit should be rcbo protected but I have been wrong before.
Anyway sparks what is right db config or if any one wants to get it off their chest what should it be?:shocked:

 

[telectrix]

if you want the smokes RCD protected, trhen you must use a RCBO so that a fault in another circuit can't take the smokes out. at the end of the day, it's your call.

 

[Geordie Spark]

if you want the smokes RCD protected, trhen you must use a RCBO so that a fault in another circuit can't take the smokes out. at the end of the day, it's your call.

Thank God for that ...... it looks like I've finally done something right !!!

 

[MDJ]

I would avoid at all costs installing a smoke on a RCD, however if the method of installation means it needs to be protected via this method then 100% agree with tel.

 

[driverman]

Many sparky's say put smokes on a RCD / RCBO lighting circuit.....reason being client will take action if said light circuit not working thus ensuring supply to smokes. The other school of thought is, if on a dedicated RCBO and it operates for whatever reason, Client may not be aware that supply to smokes has been interrupted. Having said that, mine at home are on a dedicated RCBO.

 

[brucelee]

RCBO dedicated circuit or a regulary used lighting circuit protected by RCD either way is acceptable

 

[tazz]

This is were both regs come together, all wiring must meet IEE, so if an RBO or RCD is required, then it needs fitting....The BS5839 fire alarm euipment must indicate the loss of power. Personally I would fit an mcb on the non rcd side.

 

[Stroppy]

If the alarms have a built-in non-removable battery they will beep when power is lost, satisfying the 'indicate the loss of power' requirement, otherwise power them from a circuit with frequently used lights on.

 

[Outspoken]

RCD/RCBO on a life safety system...Pathetic. Next we will all need to wear Hi Vis jackets to walk on the public street FFS.

 

[telectrix]

i quite agree but reg. 522.6.101,102 and 103 say otherwise.

 

[Outspoken]

i quite agree but reg. 522.6.101,102 and 103 say otherwise.

Not having a Regs book to hand at the moment I cannot look up the exact wording, but I would point out the the 17th Ed states the following in respect of the use of RCDs;

Basic Protection: These may only be used as additional protection and must have an operating current of 30mA or less and an operating time of 40mS or less at 5xIΔn

Fault protection: Used where the loop impedance requirements cannot be met for for protecting socket outlets supplying portable equipment used out doors.

Now a dedicated circuit for a smoke detector does not fall under either of those because by placing the circuit on a suitably rated MCB you would meet the needs of the regulations in terms of protection against fault conditions.

Now under 522.6.101 and 102 we have the requirement that cables buried less than 50mm into a wall without mech protection (lets ignore the comments about competent people) are required to be protected by an RCD, however as the smoke detector will be likely on a ceiling unless the cable is significantly in a wall likely to be drilled into then I do not see any need to install an RCD/RCBO on the circuit. Proper design/planning should actually eliminate the need for the RCD

 

[Darkwood]

It all comes down to class and category the building and residence situation falls under ... now the cable will need rcd protection but as for the separate rcbo it in most domestic situations is not necessary although as with others I will agree it is good design, a lot of people forget the detectors will have battery back-up and will be good for many months without mains power hence you can link a mains powered detector onto the local lighting circuit as any tripping of the circuit will be reset promptly if house is occupied and it doesn't effect the ability of the detector to operate.

 

[Darkwood]

Not having a Regs book to hand at the moment I cannot look up the exact wording, but I would point out the the 17th Ed states the following in respect of the use of RCDs;

Basic Protection: These may only be used as additional protection and must have an operating current of 30mA or less and an operating time of 40mS or less at 5xIΔn

Fault protection: Used where the loop impedance requirements cannot be met for for protecting socket outlets supplying portable equipment used out doors.

Now a dedicated circuit for a smoke detector does not fall under either of those because by placing the circuit on a suitably rated MCB you would meet the needs of the regulations in terms of protection against fault conditions.

Now under 522.6.101 and 102 we have the requirement that cables buried less than 50mm into a wall without mech protection (lets ignore the comments about competent people) are required to be protected by an RCD, however as the smoke detector will be likely on a ceiling unless the cable is significantly in a wall likely to be drilled into then I do not see any need to install an RCD/RCBO on the circuit. Proper design/planning should actually eliminate the need for the RCD

You will need to run the linking cables from floor to floor and in doing so in domestic usually will fall in a wall etc <50mm thus requiring rcd protection.

 

[Outspoken]

You will need to run the linking cables from floor to floor and in doing so in domestic usually will fall in a wall etc <50mm thus requiring rcd protection.

When I can I will look this up properly as I am at work at the moment. I do not do domestic work and haven't for years as I hate it with a passion, but I'll bet that there is a compliant work around.

 

[tazz]

With better technology in batteries are charging circuits, the BS suggested, in 2002 that most modern fire systems where capable of meeting standby conditions, exceeding 24hrs for L cat and 72 hours for P cat. And the days of coming straight off the bus bars were obsolete. Their aim was not to make the installed system the caurse of a potential risk. So it is now preferable to now come from a essential db (if fitted) or a non essential db via a dedicated mcb using enhanced cable. All modern fire alarm panels and part 6 detection must give and audio and visual indication of power loss.

 

[Darkwood]

Tazz we are talking requirements for domestic and only need grade f which is a battery only detector, the theme of the thread is when wiring a mains/battery detector and cables run <50mm that the cable needs rcd protection regardless of the circuits load if you don't have the necessary protection pointed out in 522.6.6, I see your point but you are complicating things here and your standard domestic doesn't require any panel and can even be piggy backed off a nearby lighting circuit.

 

[tazz]

Darkwood Understand what your saying, but both domestic Grade D mains and commercial Part 1 or Grade A domestic all follow the same principles, When powering any smoke detector or panel, iee regs must be followed as well as Bs5839. If a domestic smokes wiring requires rbo, under its 50mm rule, then it is advised to do so. The equipment must be able to indicate power failure by visual audio means.

Looking over my last posts, I maybe going to deep with regs, so I think the best statement to make her is 1. follow you IEE regs, if rbo, or rcd is required fit.
2. Any BS detector or panel is equiped to meet your decision

 

[Outspoken]

OK, I didn't finish until gone 22:00hrs last night hence no posts on this.

I have my Regs book here and can see an issue straight away, one I would not worry about as I do not do domestic works.

People have quoted Regs 522.6.101/2, however from what i have seen everyone has missed 522.6.103(vi) where is clearly states that for installations not intended to be under the supervision of a skilled or instructed person;

be provided with additional protection by means of an RCD having the characteristics specified in Reg 415.1.1

Now this regulation I find laughable, it states that effectively every circuit in a building where there is no access to a skilled or instructed person should have an RCD fitted, clearly aimed at domestic, but a reinterpretation would be that if the home has a skilled or instructed person in it then the requirement goes away so long as all other criteria are met.

Therefore a deviation from the Regs is possible so long as it was noted because they define a skilled person as;

A person with technical knowledge or sufficient experience to enable him/her to avoid dangers which electricity may create

And an Instructed person as

A person adequately advised or supervised by skilled persons to enable him/her to avoid dangers which electricity may create

Now those two scopes cover a lot of people and one must take it that we are to assume that anyone working or living in a building does not fit the above criteria because none of us have crystal balls (I just walk funny).

Clearly any installation must be compliant and we all need to make judgement calls on interpreting the above, we all accept that in commercial/industrial; buildings that any person undertaking any form of work on the infra-structure will either be skilled or under the instruction/control of a skilled person so it is reasonable to not apply to such installations, however we have to also look at domestic installations and also apply common sense.

Approved Doc B of The Building Regs (2000) encourages people to use domestic fire detection systems compliant with BS5839-6:2004 Grade D (System incorporating one or more interlinked mains powered smoke alarms {and heat alarms if required}, each with an integral stand-by supply. The interlink can be hardwired or radio-interlinked)

Now within the Regulations for Fire Alarms it clearly states that any interlinked cables should be readily distinguishable from those carrying power for other circuits, they should ideally be colour coded red but do not need to be fire resistant.

BS5839-6 gives various recommendations for installations in new dwellings and existing, it clearly indicates that smoke/heat detection systems should not be on an RCD unless you have a TT installation in which case they should be fed from the section protected by the 100mA Time delayed main switch RCD and not from circuits protected by 30mA RCD's, such as circuits feeding sockets and those outside of the installation.

Clause 15.4 in BS5839-6 states;

The normal supply for smoke alarms and any heat alarms in a Grade D system should be derived from the public electricity supply to the dwelling. The mains supply to the smoke alarms and heat alarms should take the form of either:
i) an independent circuit at the dwelling's main distribution board, in which case no other electrical equipment should be connected to this circuit (other than a dedicated monitoring device installed to indicate failure of the mains supply to the smoke alarms and any heat alarms); or
ii) a separately electrically protected, regularly used local lighting circuit.

I'll have a hunt in Wiring Matters when I get home again as I know that John Ware has written various articles on this very topic over the years.

Now as I see it if you have a split load board and the main switch is a time delayed RCD then there is no need to install an RCBO for the alarm circuit as the "monitoring" will be undertaken by the main RCD. I would not personally put the circuit on the lighting circuit if doing a new installation/rewire I would have a dedicated circuit with an appropriate MCB on the "general" side of the board and as far from 30mA protected circuits as possible.

 

[SPARTYKUS]

OK, I didn't finish until gone 22:00hrs last night hence no posts on this.

I have my Regs book here and can see an issue straight away, one I would not worry about as I do not do domestic works.

People have quoted Regs 522.6.101/2, however from what i have seen everyone has missed 522.6.103(vi) where is clearly states that for installations not intended to be under the supervision of a skilled or instructed person;

be provided with additional protection by means of an RCD having the characteristics specified in Reg 415.1.1

Now this regulation I find laughable, it states that effectively every circuit in a building where there is no access to a skilled or instructed person should have an RCD fitted, clearly aimed at domestic, but a reinterpretation would be that if the home has a skilled or instructed person in it then the requirement goes away so long as all other criteria are met.

Therefore a deviation from the Regs is possible so long as it was noted because they define a skilled person as;

A person with technical knowledge or sufficient experience to enable him/her to avoid dangers which electricity may create

And an Instructed person as

A person adequately advised or supervised by skilled persons to enable him/her to avoid dangers which electricity may create

Now those two scopes cover a lot of people and one must take it that we are to assume that anyone working or living in a building does not fit the above criteria because none of us have crystal balls (I just walk funny).

Clearly any installation must be compliant and we all need to make judgement calls on interpreting the above, we all accept that in commercial/industrial; buildings that any person undertaking any form of work on the infra-structure will either be skilled or under the instruction/control of a skilled person so it is reasonable to not apply to such installations, however we have to also look at domestic installations and also apply common sense.

Approved Doc B of The Building Regs (2000) encourages people to use domestic fire detection systems compliant with BS5839-6:2004 Grade D (System incorporating one or more interlinked mains powered smoke alarms {and heat alarms if required}, each with an integral stand-by supply. The interlink can be hardwired or radio-interlinked)

Now within the Regulations for Fire Alarms it clearly states that any interlinked cables should be readily distinguishable from those carrying power for other circuits, they should ideally be colour coded red but do not need to be fire resistant.

BS5839-6 gives various recommendations for installations in new dwellings and existing, it clearly indicates that smoke/heat detection systems should not be on an RCD unless you have a TT installation in which case they should be fed from the section protected by the 100mA Time delayed main switch RCD and not from circuits protected by 30mA RCD's, such as circuits feeding sockets and those outside of the installation.

Clause 15.4 in BS5839-6 states;

The normal supply for smoke alarms and any heat alarms in a Grade D system should be derived from the public electricity supply to the dwelling. The mains supply to the smoke alarms and heat alarms should take the form of either:
i) an independent circuit at the dwelling's main distribution board, in which case no other electrical equipment should be connected to this circuit (other than a dedicated monitoring device installed to indicate failure of the mains supply to the smoke alarms and any heat alarms); or
ii) a separately electrically protected, regularly used local lighting circuit.

I'll have a hunt in Wiring Matters when I get home again as I know that John Ware has written various articles on this very topic over the years.

Now as I see it if you have a split load board and the main switch is a time delayed RCD then there is no need to install an RCBO for the alarm circuit as the "monitoring" will be undertaken by the main RCD. I would not personally put the circuit on the lighting circuit if doing a new installation/rewire I would have a dedicated circuit with an appropriate MCB on the "general" side of the board and as far from 30mA protected circuits as possible.

disagree.

Would always put smoke alarms in domestic properties on a lighting circuit. Its perfectly acceptable and makes sense, as said already there's little chance of not noticing the lights don't work. More chance not noticing the smoke alarm circuit tripped 3 weeks ago and the batteries are flat....

also the skilled/ instructed thing is a red herring & wasnt meant for domestic stuff, i think this has been cleared up in the latest release

 

[Outspoken]

disagree.

Would always put smoke alarms in domestic properties on a lighting circuit. Its perfectly acceptable and makes sense, as said already there's little chance of not noticing the lights don't work. More chance not noticing the smoke alarm circuit tripped 3 weeks ago and the batteries are flat....

also the skilled/ instructed thing is a red herring & wasnt meant for domestic stuff, i think this has been cleared up in the latest release

Your last comment is not correct, I have taken the comments from the latest edition of BS7671 that was only bought from the IET about a month ago and the definition does not appear to have changed.

The issue with the lighting circuit should really be determined by the size of the bathroom because if the ceiling height is less than 2.25m or the bottom of the luminaire is below 2.25m then Reg 701.411.3.3 must be adhered to that requires the lighting circuit to be RCD protected in accordance with Reg 415.1 which requires the RCD to have a 30mA rating.

Now as BS5839-6 clearly indicates that smoke/heat detectors should not be on an RCD rated at 30mA such a circuit should not be used.

The problem this introduces is that many domestic bathrooms in the UK do not have ceilings that allow for the bottom of the lights to be greater than 2.25m (7ft 4") from the floor. Clearly many do, but you would need to be sure first to ensure full compliance with both sets of regulations. My personal thought, and clearly others will see it as they wish and that is fine, that to ensure full compliance regardless if the snoke/heats are on their own circuit then you are on safe ground.

 

[richy3333]

Your last comment is not correct, I have taken the comments from the latest edition of BS7671 that was only bought from the IET about a month ago and the definition does not appear to have changed.

The issue with the lighting circuit should really be determined by the size of the bathroom because if the ceiling height is less than 2.25m or the bottom of the luminaire is below 2.25m then Reg 701.411.3.3 must be adhered to that requires the lighting circuit to be RCD protected in accordance with Reg 415.1 which requires the RCD to have a 30mA rating.

Now as BS5839-6 clearly indicates that smoke/heat detectors should not be on an RCD rated at 30mA such a circuit should not be used.

The problem this introduces is that many domestic bathrooms in the UK do not have ceilings that allow for the bottom of the lights to be greater than 2.25m (7ft 4") from the floor. Clearly many do, but you would need to be sure first to ensure full compliance with both sets of regulations. My personal thought, and clearly others will see it as they wish and that is fine, that to ensure full compliance regardless if the snoke/heats are on their own circuit then you are on safe ground.

Just wondering Outspoken:

Why are you suddenly such an expert on domestics when by your own admittance you hate 'them' and don't do 'them'?

Why did you only buy the BGB last month when the Regs changed last year? I presume the update doesn't apply to you?

I don't understand why you are waffling on about bathrooms and smokes? What relevance is this to the discussion? How many smokes do you see in the bathrooms of average houses? I guess you must live in a mansion, being super-paid as an industrial spark

 

[stuartcourt]

Jesus ****ing wept Im going out

 

[Outspoken]

Just wondering Outspoken:

Why are you suddenly such an expert on domestics when by your own admittance you hate 'them' and don't do 'them'?

Why did you only buy the BGB last month when the Regs changed last year? I presume the update doesn't apply to you?

I don't understand why you are waffling on about bathrooms and smokes? What relevance is this to the discussion? How many smokes do you see in the bathrooms of average houses? I guess you must live in a mansion, being super-paid as an industrial spark

Bit touchy aren't you, Jesus Christ chap, you want to calm down or you'll have a heart attack. I bought a new regs book about a month ago because the last one was literally rained on when I left it on the roof of my car so I replaced it...is that acceptable to you ???

As for the experts on Domestic, I can bloody well read the regs book you know and have enough knowledge and experience to be able to understand what it and other regulations say.

Perhaps you might like to read the thread from the beginning and you will perhaps understand. No-one has said put a smoke in the bathroom so the waffle is from you as you have not bothered to read the posts correctly. The mention of bathrooms came from that comments regarding putting smokes on the lighting circuit...I suggest you reread what I wrote so you see the point I was making in the discussion with Sparktus.

 

[SPARTYKUS]

"ow as BS5839-6 clearly indicates that smoke/heat detectors should not be on an RCD rated at 30mA such a circuit should not be used."-tricky that bit, I'd say, one of those situations you might find yourself in with conflicting regulations.

I guess if you had smokes in a house with cabling buried in walls, that really needed to be on a 30mA RCD, another regulations conflicts with this, there must be a priority betwixt the regulations?

the technical/skilled thing I cannot back up, it was in reference to a post I vaguely remember on here so more digging required. :teeth_smile:

 

[Outspoken]

Spartykus, I think it demonstrates that that regulating bodies need to speak to each other when there is conflicting information being put out by their various publications. I believe we have all encountered examples over the years.

Clearly each and every installer should do what they personally feel is right for the installation they are dealing with, we can all sit in front of a computer and spout regulations but in reality the range of works that sparks are asked to undertake in the range of domestic properties is such that people simply need to apply bags of common sense so long as they clearly do not break any of the regulations under which you could be prosecuted or you are able to reasonably justify any deviation.

 

[Toonlad]

Just wondering Outspoken:

Why are you suddenly such an expert on domestics when by your own admittance you hate 'them' and don't do 'them'? Has never said he has never done them in the past.

Why did you only buy the BGB last month when the Regs changed last year? I presume the update doesn't apply to you? Maybe he bought a digital copy or a new replacement

I don't understand why you are waffling on about bathrooms and smokes? What relevance is this to the discussion? How many smokes do you see in the bathrooms of average houses? I guess you must live in a mansion, being super-paid as an industrial spark
nothing to do with how much you get paid, What relevance is this to this DISCUSSION

Let the lad have his say, he is being constructive and giving reason to his interpitation of the regs. If you had read his posts, yes he said he steers clear of them, But does not mean he hasnt got experiance of them. He said he would look into the regs when he got home, and he has done that, didnt need to but he has done none the less.

Lets just sit back and read what is said here, and if you or I have a different oppinion, then reply with support and reason as to why. This is how we learn, and this is why subjective regultions can be changed, as the clever people are not always that and miss the simple things.

Its a good thread, good discussion lets leave it to that please.

Regards
Toony

 

[Darkwood]

Posts 24 / 25 kinda hit the nail on the head ...you can't do right for doing wrong; Here we have conflicting regulations one that governing the safety/dangers of the cable <50mm and the other that's trying to maintain the function of a critical safety device but the way I see it as ive already pointed out that the mains linked detectors in houses will give light and sound audio warnings for many months after power failure and still operate so I cannot understand why covering a detector with a rcd is such a no no. As for the reg' that asks for a recognised difference in the cable colour again this doesn't happen in domestic, sparkies don't buy a full coil of alternative coloured sheath just to run a what would be a short in length circuit, they use the cable already in their kit. Im not discussing larger projects here like commercial industrial or multiple occupancy building here im just talking your average sized domestic install. I personally don't do domestic but do come across fire alarm installs on larger projects, im currently taking over a multiple occupancy building where each flat has its own independent fire alarm off the flats CU and all communal areas like entrances, hallways etc has a full monitored system independent of each flat.

 

[richy3333]

Bit touchy aren't you, Jesus Christ chap, you want to calm down or you'll have a heart attack. I bought a new regs book about a month ago because the last one was literally rained on when I left it on the roof of my car so I replaced it...is that acceptable to you ???

As for the experts on Domestic, I can bloody well read the regs book you know and have enough knowledge and experience to be able to understand what it and other regulations say.

Perhaps you might like to read the thread from the beginning and you will perhaps understand. No-one has said put a smoke in the bathroom so the waffle is from you as you have not bothered to read the posts correctly. The mention of bathrooms came from that comments regarding putting smokes on the lighting circuit...I suggest you reread what I wrote so you see the point I was making in the discussion with Sparktus.

Not touchy at all. My periods not due for a couple of weeks and I'm way to chilled to get angry
It's just that I've read other threads you've posted on many of which you appear to be in conflict with established forum members?

 

[Outspoken]

Not touchy at all. My periods not due for a couple of weeks and I'm way to chilled to get angry
It's just that I've read other threads you've posted on many of which you appear to be in conflict with established forum members?

With respect, just because someone is an established member does not mean their view is always right...not saying anyone is specifically wrong either, with the Regs a lot is down to interpreting what they are saying in their gobbldigook legalise and all who use them will read different bits differently, that is life.

However just because you think I had a conflict with someone doesn't really mean you should just jump in feet first unless you have read all the posts in a given thread because otherwise you end up in conflict potentially...I know that as I have done similar on a different forum (not electrical) and felt silly after..

 

[telectrix]

i would not, myself, install a fire alarm ( meaning a control panel with detectors, call points and sounders ) on a RCD. even if it meant surface wiring or earthed conduit for the drop down a wall. however, in a domestic situation with interlinked smoke detectors i would prefer to connect into a frequently used lighting circuit.

 

[tazz]

The important part missing here,is the fire alarm or mains smoke detector is there to protect life, dont make it the caurse of taking life. Personally and by the 5839, i would like to see supply taken from mcb, with no rcd protection, but if this means in domestic premises, increasing the risk of electic shock, then the wiring regs come first,
If all wiring is tested and fully compliant, there is no reason for an rcd or rbo to trip

 

[GLENNSPARK]

if you want the smokes RCD protected, trhen you must use a RCBO so that a fault in another circuit can't take the smokes out. at the end of the day, it's your call.

better them pulled of a lighting point (via FCU)....that way if you lose the power to the smokes/heats....the lighting will/should also be out......
the best way of giving smoke/heat alarm cables additional protection as well as having a clear indication of a loss of supply......

 

[tazz]

Would not disagree with that.....The be all and end all, you write your cert for the wiring making sure all is safe, and on the BS5839 p6 cert you write the variation that a rbo has been installed to comply with iee due to bathroom ceiling level, or any other Iee reg that applies.

 

[Darkwood]

I see all your sides here but one thing you all forget is if power is lost to a standard domestic mains detector with battery back-up it will still function for years .... consider a battery only detector and how many years it lasts before battery goes low.... so the whole argument about losing power is not relevant ....... im struggling to see some of your concerns here... so the danger of the detector losing power isn't a concern so the BS 7671 regarding cables <50mm takes a higher risk unless the occupants go on holidays for 3 yrs and in that time the mains trips and when they return they don't notice cos the battery is dead and that night they get killed in a house fire.....well I'll take the risk to stand my day in court if that occurs...

 

[tazz]

I see ll your sides here but one thing you all forget is if power is lost to a standard domestic mains detector with battery back-up it will still function for years .... consider a battery only detector and how many years it lasts before battery goes low.... so the whole argument about losing power is not relevant ....... im struggling to see some of you concerns here...

This was my comment earlier, and is very relevent