Sounder circuit interface

[Richard F]

I hope somebody out there can help with a question that has surfaced regarding using sounder circuits to operate external equipment via a relay, I can find no specific reference in BS5839, is it OK or just good practice to cable back to the panel, concerned primarily with conventional systems.

[Thebeardedyorkshireman]

Hi, I thought somebody would have picked this up for you but they must be all out on the razz!!
Sounder circuits are for sounders. Their integrity must never be compromised by the connection of any other equipment or cables. This is regarded as good practice. Any aux equipment that needs to be switched should be switched by the aux relays or outputs from the panel. In a Fire condition these outputs remain active even through the silence alarms stage untill the panel is reset. This act of 'Reset' signifies that the incident is over and that it is appropriate for items of plant, fire doors etc etc to return to their normal state.
The use of sounder circuits to switch external equipment precludes this unless you incorporate latching facilities with local reset. A good example is the switching of fire doors from sounder circuits (bad practice).
in a true fire the senior person may elect to silence sounders when the building is declared clear to improve communications. At this point any fire doors opened in the search will remain held back even though a fire condition technically exists. The same applies to a rapid action to silence sounders by untrained operators. There may be an actual fire condition in the building and all the doors are held back after being opened by evacuated occupants. The same applies to restarting mechanical air handling plant which could move smoke contaminated air into somebodys escape route.
I shall now get down from my soap box and start packing up for Christmas.
A merry Christmas to all the Gang on the forum.
Regards
Dave

The use of analogue systems makes things easier by the use of output units which can be programmed 'silenceable' or 'non silenceable for exactly the above reasons.

[Graeme]

i've been on the Raz for a week.

as Dave says....and Merry Xmas everyone too. hic!

[Wiz]

One example where the 'local' interface relay on sounder circuit method is perfectly suitable is where 240V AC high power alarm supplementary warning devices might need to be driven in areas of high ambient noise from, say, machinery.

Dave, it might be good practise to not use interface relays on sounder circuits in some circumstances, especially for some of the reasons your answer detailed, but does BS5839 say you can never do it?

Seasons Greetings to everyone from Wiz

[Thebeardedyorkshireman]

Wiz
I try to avoid getting the standard out of the cupboard but both me and the good Doctor can't remember anything in print due to a tricky blend of alcohol and altzimers. I will have a read and get back to you
Dave
ps
I agree with the mains siren, done it myself many times.

[AnthonyB]

How does the use of 240V AC high power alarm supplementary warning devices square with the requirement of the H&S (Safety Signs & signals) Regs requirement for auxiliary power supplies - are they supported by a generator or do you risk assess the liklihood of failure (although the power supply bit is an absolute duty IIRC)

[Thebeardedyorkshireman]

The sirens are supplementary to provide additional audibility to overcome background noise generated by mains operated machinery. If the mains fails,the noise stops. List it on the ticket, write it in the risk assessment.
Dave

[AnthonyB]

Aha - of course (d'oh!). Makes perfect sense, you'd still have the 24V sounders working & no machines!

[FireFly40]

What if you only had a local failure of power and other parts of factory still working (more possible than total power off) was given to me by fire officer. The factory was pretty well covered by big yodalarms but certain areas were still too noisy. The solution I used was take mains from offending machine supply to 240vac relay in box with mains siren. the sounder line runs through the NC contact with a big diode in parallel. When the mains fails you get sounder fault on panel (because you have one) If the fire alarm goes off big diode ensures no actual sounders stop working. If you use the relays with the clicky bit on top maintenance can frig the sounder fault when machine is off on purpose. One happy fire officer  GNV

[Martin Burford]

FireF
why not use flashing light alarms......it would avoid all that expense.
Conqueror

[FireFly40]

Your absolutely right never thought of that. Sometimes you can't see the forest for the trees. I was probably wallowing in the fact the old mains chloride 1500 fire alarms were still in the roof and cost nothing and cleaned up like new expensive ones. Surprised fire officer didnt say that though. It was about 15 years ago, younger less brain etc. I wont do that again!

[bolt]

Not every panel has an aux relay. Some cheap and plenty of old ones dont.  Sometimes there is no other choice but to use the sounder circuit to provide control to fire doors as a system upgrade it would prove very expensive to tell someone the FAP has to be scrapped just becuase it does not have an aux relay. The benifits of controlling fire doors  far out weigh any detrimental arguments regarding use of sounder circuits. I know of quite a few systems that bring the lift down to the ground floor, shut the gas off in the kitchens, start the staircase PPV system, shut down all the AC plant, flash lots of strobes as well as sounders, set the paging system off to alert of the alarm, undo all security magnetic door releases in the building, release all the fire doors, open the dampers, start the riser pumps and arm the FM200 systems and it all done off the sounder circuits via monitored slave relays.

I thought i add not everything resets automatically for obvious reasons.

[Graeme]

That's all very well until you get the usual member of staff who silences the alarm because it's making a noise.
The same member of staff who silences the alarm and then goes and investigates the zone in question.

All your interfaces that are not one shot are all reset.

[bolt]

Thats true which is why i said they dont all reset automatically. These are well run commercial buildings with strict protocol for bringing the building back to normal use following an alarm and the gas can only be restored manually. Fire door magnets do go live on silence but someone has to push them back open so in effect they are fail safe. The swipe card reset can only be done in the control room otherwise silencing the alarms could find fireman locked inside a fire area with major consequnces. The lift can be overrriden on silence or alarm via firemans switch. FM200 is always double knock or interlocked manual intervention. Dont go dumping that stuff without very good reason. Even the AirCon is sequentially restarted  per floor otherwise you bang on a reset with that amount of AC running in the summer it would probably trip out a few blocks of power. So the point is not every building is as simple as alarm silence reset.

[Wiz]

Some fire panel aux. relays reset on alarm silence. (this is because they sometimes share the same relay as a sounder circuit in the fire panel). So they don't all only reset on fire panel reset.
Therefore one should always carefully check how aux. relays actaually work in any panel before using them for any purpose.
Where aux. relays are not available in an old fire panel, but are required (other than controlled by a sounder circuit), it is sometimes possible to use any repeat panel zonal outputs available by connecting them all (via rectifier diodes) to a relay coil. These outputs follow the main panel zone indicators and should therefore only reset on main panel reset.
However, I agree that using a relay on a sounder circuit should not be a big 'No No'. The simnple fact is the fire panel should not be silenced until everybody at risk has been evacuated from the building and the next step of what should be done in the premises fire evacuation procedure should be under the control of a responsible person. Control panels have a controls key On/Off facility that means control functions should only be operated by a responsible person. If an idiot silences the alarm before it is safe to do so then there is something seriously wrong with the management function of the premises.
I would also use the argument that the idiot who silences the alarm when he shouldn't, is just as likely to try resetting it, with equally potentially serious consequences. Nothing can be made idiot- proof so why say that you can't wire control relays to sounder circuits when they would still provide the most important function i.e operate on a fire alarm condition. There are obviously any number of 'what if' scenarios but an equal number of 'what if' scenarios could be applied to an aux. relay within a panel (not least - 'what if it just did not work because of an 'open-circuit' coil)!