heat alarms in garages con unit question 17th ed

[andekoch]

agreed bill

 

[Des 56]

Anything fire alarm should be fed from its own MCB wherever possible, for precisely the reason you mention, and the reason you give for "not".

If a lighting circuit goes, the back up batteries, often only alkaline, in a smoke alarm will be called into play. Once an alkaline battery is called into play, it will lose its charge fairly quickly. This in turn, may cause the detector NOT to operate when needed.

Besides --- If a lighting circuit trips, you can always tell......the lights don't work!

If a smoke detector circuit trips and the detectors aren't letting you know audibly there is no mains feed - CHANGE THEM NOW.

As for preferred methods, it is a BS5839 - 1 and 6 requirement that the supply is taken from an independent source. IMHO it should apply to ALL classes and categories of system. They should never be put on an RCD/RCBO protected circuit either.

It is NOT good practice to wire smoke detection into lighting circuits at all, frankly. If fire detection must share a source with lighting, then it should be at the MCB and nowhere else.

I am also of the humble opinion that ALL mains fed smoke or fire detection should be interconnected using fire resistant cable - most certainly where interlink functionality between one detector and another is required (unless wireless, obviously).

Guidance given by the IEE and a manufacturer, differs a little from your sensible approach to fire alarm supplies
Your opinion (which differs from Bs 5839-6) quote
It is NOT good practice to wire smoke detection into lighting circuits at all, frankly.

The prefered method of the IEE as in the on-site guide where all circuits are protected by rcds,"there is advantage to wire them off a regularly used local lighting circuit "
On site guide page 66 Note

We, as always, need to take care to be clear what is personal preference,so that the choices remain clear on these muddy issues

Another point which was used to assist the view of a seperate supply for these type of alarms was
quote
If a lighting circuit goes, the back up batteries, often only alkaline, in a smoke alarm will be called into play. Once an alkaline battery is called into play, it will lose its charge fairly quickly. This in turn, may cause the detector NOT to operate when needed.

This is the advise taken off the aico site in this regard
Battery life expectancy
quote
This will depend on a number of factors that will differ slightly
according to the type of alarm in use.
The 140 series alarms are supplied with an Alkaline battery which,
dependent on conditions, can provide up to 4 years standby supply,
up to 2 years without mains power.

The 150 series and the 160 series alarms are fitted with rechargeable
Lithium power cells which are continuously charged by the alarm
circuitry. They have a life expectancy greater than that of the Smoke
Alarm, i.e 10 years or more,which eliminates the need for
replacement.
That advise appears to contradict one of your personal reasons why a local lighting circuit should not be used
I make these comments as an electrican who has limited skills in alarm systems and installation
The comments I have made are based on guidances given to us where doubt may exist
I welcome your comments on the points made above
Regards Des

To the original post
here is a link to some useful information about househod smoke alarms
Aico Ltd

 

[accordfire]

Guidance given by the IEE and a manufacturer, differs a little from your sensible approach to fire alarm supplies
Your opinion (which differs from Bs 5839-6) quote
It is NOT good practice to wire smoke detection into lighting circuits at all, frankly.

The prefered method of the IEE as in the on-site guide where all circuits are protected by rcds,"there is advantage to wire them off a regularly used local lighting circuit "
On site guide page 66 Note

We, as always, need to take care to be clear what is personal preference,so that the choices remain clear on these muddy issues

Yes, however, the industry views this differently. Advice notes issued by FIA have contradicted the advice given by the IEE on site guidance previously too.

It is, as you say, muddy, hence why I pointed out my hope that the next amendment of BS 5839 would clarify, once and for all this issue.

There are a greater number of reasons why it is NOT advantageous to wire even smoke detection from a local lighting feed. Chief among those being that battery life is almost always quoted under "optimum" conditions, which often bear little relation to "real life" scenarios, and the more than chance possibility that a feed intended to supply a smoke detector directly will end up spurred into any other number of devices, or that lighting loads will change, as fittings do, possibly rendering the circuit faulty, or overloaded, increasing the risk to properly working detection.

Another point which was used to assist the view of a seperate supply for these type of alarms was
quote
If a lighting circuit goes, the back up batteries, often only alkaline, in a smoke alarm will be called into play. Once an alkaline battery is called into play, it will lose its charge fairly quickly. This in turn, may cause the detector NOT to operate when needed.

This is the advise taken off the aico site in this regard
Battery life expectancy
quote
This will depend on a number of factors that will differ slightly
according to the type of alarm in use.
The 140 series alarms are supplied with an Alkaline battery which,
dependent on conditions, can provide up to 4 years standby supply,
up to 2 years without mains power.

Indeed - Aico use Alkaline cells only in the 140 series detectors, and in standard bases. However, the "get out" is the key phrase "dependent upon conditions" - with experience, and having fitted well over a thousand Aico detectors of one sort or another, I can say with some conviction, that if anyone can show me a four year old alkaline battery, which has been used over that period, I will show you a smoke detector which has not (a) been tested, and (b) which in all probability does not work.

Quite contrary to what Aico claim, we, in common with many other companies in the industry, change alkaline batteries annually. The specific reason for this is that a proper test of this detection involves disconnection from the mains supply and testing on battery. Once that's done, battery is on the way out.

Characteristically, an alkaline cell will lose charge fairly quickly once current has been drawn from it. It is a primary reason why alkaline technology is only used rarely now, for low likelihood back up - in clock radios, for example, and in "cheap" smoke detectors....

FWIW, Aico, good as their products are, are still manufacturers, and not regulation writers.....and advice solely from one manufacturer's site should be taken, shall we say, carefully.

The 150 series and the 160 series alarms are fitted with rechargeable
Lithium power cells which are continuously charged by the alarm
circuitry. They have a life expectancy greater than that of the Smoke
Alarm, i.e 10 years or more,which eliminates the need for
replacement.

I mentioned alkaline cells or batteries as distinct from lithium batteries, which are designed to be integrated into circuits which are likely to require their use from time to time. It is, in fact, a key reason that Aico moved from using alkaline batteries in their detectors to lithium.

It is also worth mentioning that we won't fit 140 series detection, specifically because it uses alkaline back up rather than lithium.

That advise appears to contradict one of your personal reasons why a local lighting circuit should not be used
I make these comments as an electrican who has limited skills in alarm systems and installation
The comments I have made are based on guidances given to us where doubt may exist
I welcome your comments on the points made above
Regards Des

And valid your points are too, Des - it is ALWAYS good to pull up the advice you find and question everything. Whilst what you quote is indeed the case, and probably the advice many rely upon, I also speak, as I say, from experience of this kit every single day in life - and other fire detection kit too.

One of the points I tried to highlight, was the apparent conflict between BS 5839 and BS 7671 in places.

Safety, in terms of BS 7671, is "if it's an issue, shut it down. Fast". Which is sound advice in the main, as the risk from shock, or exposure to burns, etc. from electricity is very real, and very definite.

However, FIRE safety, is a different matter, and in this case, shutting the juice off as quickly as possible isn't always right, though electrical safety is also important (from the risk of ignition of fire as well as personnel safety).

As I mentioned earlier, the very best thing, potentially, would be to make it mandatory for fire safety circuits to be fed in isolation from any other supply, and clearly marked indelibly, in such a way as to be easily identified by eye.

I also maintain that twin and earth PVC cable should not be used for life safety circuits, whether supply, detection, or warning.

We are moving away from the era where smoke detectors were either mains only, or battery only, thankfully - but there is still a distance to travel here.

As far as it goes, the Onsite Guide is quite limited in the advice it gives in respect of fire detection - and the note you refer to, on P66, is unqualified advice - by which I mean, there is NO reason given as to WHY it is advantageous, in the note writer's opinion - it is a comment which has been challenged many, many times.

But that said, the whole "grading" of part 6 has been challenged many times too - why, for example, is there no need for fire resistant cable, or segregation at one level, yet there is at the next? Because your house is smaller, does it deserve a lesser level of protection? I don't think so.

You are right, however, that I offered advice based as much on experience, as on anything quoted by manufacturers, or admittedly, an unqualified comment in the OSG - at least, unqualified in the sense that no reasons are given for the note.

That, sadly, is still so much of the nature of both BS 5839 and BS 7671 - it is in many cases far too interpretive and subjective, rather than definite, and objective.

Different angles of approach perhaps - from fire safety, and from electrical compliance alone.

It remains, for now, I think, a question that will go on and on, all the time there is such differentiation between the lower three, and the higher three grades in part 6.

For the record, my "personal" opinion - remains - all fire detection devices should be wired using fire resistant cable, in a segregated, or easily identified manner, and fed separately, preferably from as direct a feed as possible (i.e. no RCD or RCBO)- precisely for reasons of integrity of the system. In all honesty, I would far rather see a system in place for fire systems of all grades and categories which limited the provision and distance of low voltage in the system at all - e.g. some kind of transformer local to the main supply, and the entire system running on extra low voltage at all points - 24VDC being the most common.

Thanks, though for your input - it is good, I feel to have discussion and alternative views on these matters.


To the original post
here is a link to some useful information about househod smoke alarms
Aico Ltd[/QUOTE]

 

[Des 56]

Thanks very much Bill
That was a very interesting read and I do appreciate that experience and knowlege sometimes well outwiegh standard advise given by the "Rulemakers"

The points you made are driven by first hand experience and I will certainly take on board those views

Most on this forum who are involved in other sectors have little choice,other than to trawl the guidances, and take whats in them as the best information to be followed
As an electrician I sometimes cringe at opinions of new starters etc who blindly follow and dot every I and cross every T with total adhesion to what may be in appropriate working practices etc
Sometimes whats in a book reflects little on whats found in the real world,so in that sense I feel in the position of the new starter and will have an open mind on the questions

Its good know that we have experience and knowlege like yours available on this forum

 

[jpmiff]

Hi

very interesting read,

many thanks to Des 56 and accordfire, excellent

 

[accordfire]

Thanks very much Bill
That was a very interesting read and I do appreciate that experience and knowlege sometimes well outwiegh standard advise given by the "Rulemakers"

The points you made are driven by first hand experience and I will certainly take on board those views

Most on this forum who are involved in other sectors have little choice,other than to trawl the guidances, and take whats in them as the best information to be followed
As an electrician I sometimes cringe at opinions of new starters etc who blindly follow and dot every I and cross every T with total adhesion to what may be in appropriate working practices etc
Sometimes whats in a book reflects little on whats found in the real world,so in that sense I feel in the position of the new starter and will have an open mind on the questions

Its good know that we have experience and knowlege like yours available on this forum

Thank you Des.

You're dead right - and IMO it's a good thing we have a forum like this which allows us to ask others for their help and knowledge when needed, and IMO it only serves to make us all better, all a little more confident that we can do what we set out to.

One of the worst things any of us can do (in any aspect of life) I think, is close our minds to the ideas and opinions of others. Every one of us has lots to learn, every day.

Trust me - there's plenty I get out of being here too, and I know, even in the short time I've been here, I've learned lots.

Cheers!

Bill

 

[bobby101]

thanks guys for all your help only got one question though why when i purchesd a 17th ed board (wylex) was there no segergation or additional feed for supplying a seperate mcb since posting this i have noticed this issue is open to interpertation of the regs but could somebody please clarify why a smokie or heat detector cannot be put on a rcd protected i will reread all comments on this post the main reason for this post i have a select assement on wed an i wanted to show him this install now i am pappin it but on saying that the installation passed building control inspection

 

[accordfire]

Hey Bobby

I guess the simple answer is that CU manufacturers build their units for BS7671 and not BS5839.......

It isn't contra-BS7671 to install your smokes/heats on an RCD or RCBO circuit. They won't fail you for that.

If you've wired the detectors back to your CU either put them on a spare 6A or use the same way as the lighting.

It probably wasn't made that clear - it isn't a rule or regulation NOT to put fire safety on an RCD or RCBO, just good practice not to (IMO) - just make sure they have battery back up, and audible mains fail.

It does remind me of something else, actually - while on the subject of BS5839.

Compliance with British Standard 5839 - both parts 1 and 6, is dependent upon the "installation" receiving competent periodic maintenance.

How many of you (really, electricians, rather than fire/security bods) actually consider the added value to your business that offering an annual change of battery and test of the smoke(s) could offer you?

An hour's worth of time, and over time you've built up a residual value in your business, which is there year after year.....

Just a thought.

 

[bobby101]

i have just read the aico handbook (should have done that first) and it gives the following advice as recommendations....
option 1. install mains fed alarms with interconnection to a sole light fitting recommended ....
opttion 2. install mains fed alarm to a independant circuit at d.b also it states that they may be RCD protected if required as stated in BS 5839-6:2004
phew that will do me

 

[bobby101]

thanks bill iwas gettin worried nice one

 

[robd]

Interesting to hear things from different parts of the industry, doing mostly domestic work some of the things you've mentioned Bill are most interesting Good stuff fellas