heat alarms in garages con unit question 17th ed

[bobby101]

hi all i have recently done an new installation on a garage a very very large double garage to be more precise anyways my question is this i had to install two heat alarms,1 alarm for each car bay if you catch my drift.
my question is this, does the same building regulation apply to the installation of heat alarms in 17th ed boards or does it change i assume its the same but i would like to have a definitive answer. ta

 

[Des 56]

Are you asking about supply of the alarms,rcd etc

I was under the impression,heat alarms are not supposed to be fitted independantly of smokes
I may be wrong,but its the first thought I had when reading the post

 

[bobby101]

yes i wasnt sure if they had to have an independant supply or if being fed of a rcd fed busbar with other cb,s on said busbar was suffice to be acceptable

 

[bobby101]

i shall ask my post diffrently how do you install a heat alarm in a 17ed db to ensure full compliance with building regs all replies greatly appreciated ....... job being inspected on friday need to know asap so as to ensure i have done it ok

 

[Des 56]

When I said independant of smokes,I didn't mean the supply,I am almost sure I have read in the past, in the literature, that heat alarms can only be used within a system where there is at least one smoke alarm.as I said, I may be wrong on that

The supply question has been a hot poatoe on this forum a few times

My view of the regulations and adhering to common sense as well

The system will be fed off a regularly used local lighting circuit,in the event of loss of lighting the client is likely to reset an mcb
Others use a dedicated circuit where the mcb could be off, and the client never getting to know of it,with all the danger that could become,the supposed advantages of that,I cant even guess at

The brb says a system should have its own independant supply not interfered with by other circuit faults,this is with non domestic type alarms in mind,others use this reg to justify a dedicated circuit
In the brb it gives exclusions to that advise by advising that a system with a standby battery should be off a regularly used light circuit

 

[IQ Electrical]

My view of the regulations and adhering to common sense as well

The system will be fed off a regularly used local lighting circuit,in the event of loss of lighting the client is likely to reset an mcb
Others use a dedicated circuit where the mcb could be off, and the client never getting to know of it,with all the danger that could become

My view too.

 

[Des 56]

Further to my post
This is the information I saw on the aico site (my underlining )

Heat alarms are less likely to cause false alarm
problems as they are not responsive to any type
of smoke or fumes, only heat. Because of the
potential for a slower response than smoke
alarms, they should only be used in a fire alarm
system that also includes smoke alarms, and all of
the alarms must be interconnected.

Yet on the same site I saw fixed rate alarms that were stand alone units

 

[Deleted member 9648]

If the alarm circuit is fed from a frequently used lighting circuit the alarm circuit must have an independant means of isolation.

 

[robd]

Would agree with the idea of having the smokes on a lighting circuit, for the mentioned reasons. Have had various discussions with other people, some saying they should be on their own dedicated circuit due to ''segregation of safety circuits''. I'd tend to lean towards the practicality of having them on a lighting circuit so it would be noticed if the breaker was knocked off.

Just one point though, in terms of wiring the circuit would there be a preferred method, i.e. pick up the 1st smoke after the last light so the smokes are the end of the circuit, or wire the smokes as per normal and have two circuits going out the top of your MCB? Just a thought as I've seen it done both ways.

 

[accordfire]

Would agree with the idea of having the smokes on a lighting circuit, for the mentioned reasons. Have had various discussions with other people, some saying they should be on their own dedicated circuit due to ''segregation of safety circuits''. I'd tend to lean towards the practicality of having them on a lighting circuit so it would be noticed if the breaker was knocked off.

Just one point though, in terms of wiring the circuit would there be a preferred method, i.e. pick up the 1st smoke after the last light so the smokes are the end of the circuit, or wire the smokes as per normal and have two circuits going out the top of your MCB? Just a thought as I've seen it done both ways.

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).

 

[accordfire]

hi all i have recently done an new installation on a garage a very very large double garage to be more precise anyways my question is this i had to install two heat alarms,1 alarm for each car bay if you catch my drift.
my question is this, does the same building regulation apply to the installation of heat alarms in 17th ed boards or does it change i assume its the same but i would like to have a definitive answer. ta

The "building regs" would apply in terms of the age of the building - so if it is a new build, then yes, it will require fire prevention measures to be implemented. Whether that runs to the need to install automatic fire detection at all, depends upon the scope and nature of the building, proximity to living quarters, construction, storage of flammable materials etc.

Should there be a need for automatic detection, it will likely be required to comply with BS 5839-6 at some level or another, in which case, it may very well also require interlinking with detection in the living area of the property too. A Fire Risk Assessment would identify the need, and level of detection required.

As for technical aspects, assuming automatic detection is required, then heat detection should NOT be installed as the sole means of fire detection. Combined detection is available, which can detect both heat and smoke, or if not, in the range of equipment in use, a smoke detector should be fitted in an appropriate area, or detectors in areas, as required, in addition to heat detection.

As to whether interlinking of the detection is required, this depends on the Grade of fire detection required.

However, a very, very large double garage, on its own, isn't the most descriptive of terms, in relation to why you say you had to fit them - why? Is it part of, or close to, living quarters? Or is it an insurance requirement due to the value of property within the garage?

Part of why I ask - it's going to be fairly pointless fitting any detection at all, if it is remote from a living area, and nobody can hear any sounders fitted.....you may as well just wait until the owner sees the flames.

If you can offer a bit more info as to why they were required, and the nature/location of the garage, I can provide a more definite answer for you.

As regards electrical connection, all that's really required for mains fed detectors is that they be connected via a non-RCD protected MCB, preferably dedicated to the detectors.

 

[robd]

Cheers Bill, interesting stuff. Why no to an RCBO though? preferable to being on an rcd with other circuits or not?

 

[accordfire]

Cheers Bill, interesting stuff. Why no to an RCBO though? preferable to being on an rcd with other circuits or not?

The idea behind it is that the supply to the detection should remain operational as long as possible, and if an RCBO (or RCD) was supplying the circuit, and for any reason tripped over a weekend, it could feasibly be up to 72 hours before anyone is on the premises again....by which time, the battery is flat, and no detection.

It was felt that maintaining the feed to the detection or system was more important than detection of earth faults - most "full" fire alarm systems will monitor the earth themselves anyway within the system, and most self contained/interlinkable smoke detectors are in any case Class 2, and do not use an earth themselves, though, clearly the cable should maintain a continous CPC for safety.

I appreciate fully, though, that an RCBO will offer different operating characteristics to and RCD, which is fault protection only, whereas an RCBO also offers over-current protection. I seem to recall that the no RCBO idea came down to something in the thinking that faults elsewhere on the overall electrical install could cause the circuit to trip, just as for RCDs though.

It also runs in my mind that an RCBO *could* still allow current to flow in certain fault conditions, even without an earth - as the neutral is common to other parts of the install too. I'm sure someone else can explain the technicalities of that better than I can, though - and I don't think it is relevant to why not to put detectors on an RCBO circuit in itself.

 

[andekoch]

the rcbo 'requirement' is to cover the cables burried less than 50mm or otherwise protected scenario.
i tend to put the smokes etc onto their own rcbo together with one light either hall or landing so that there is an obvious no power notification. I think aico recommend that one light is part of the smoke etc circuit as a visual power off indication.

 

[accordfire]

the rcbo 'requirement' is to cover the cables burried less than 50mm or otherwise protected scenario.
i tend to put the smokes etc onto their own rcbo together with one light either hall or landing so that there is an obvious no power notification. I think aico recommend that one light is part of the smoke etc circuit as a visual power off indication.

Hmm. Think I saw that too somewhere - I can understand one light fitting if used primarily as a mains fail warning device, but wouldn't be happy to see smokes fitted on a general lighting circuit.

For the reasons given previously, also wouldn't be happy to see smokes fed from an RCBO protected circuit - more so if the building is unoccupied for any length of time regularly.

Either way, there's no hard and fast RULE, just "best practice" at this point.

Personally, I'd be happy to see mandatory requirements for red sheathed cable (or red banded if carrying mains perhaps) to identify safety cabling by eye - especially at a CU or midway along its run (where it might get spurred).

I'd also be happier, overall, if building regs pushed through a move to get rid of Grades F, E, and D in domestic/HMO fire safety situations. They're only really there to provide some sort of minimum rather than none anyway.

It is something that the next amendment of part 6 should address, and the next amendment of part 1 will in all probability clarify fully the issue of main supply to the fire detection system.

I understand fully, however, that it is one of those areas, where BS 5839 can come into conflict with BS 7671 and vice versa - the requirement of one being to minimise any possible interruption to the supply to the FD&A, and the other insisting on the maximum safety for the supply cable. The two don't always agree.