Fire alarm amp muting

[c.cam108]

How important would you consider it to be to have a muting relay on large amp racks to kill the sound in case of the fire alarm?

 

Also what would be the best way of doing this. I was thinking of a small box with XLR ins and outs that switches off when power is applied/removed or when a panic button is pressed. What kind of signal should be used to activate the relay? A standard iec inlet?

 

Colin C

[Jivemaster]

With anything to do with fire alarms the first action is to read in detail the terms of the premises/entertainment licence. You should always consider that PA may be needed to order an effective evacuation. Only go to a separate "voice alarm" system if a/ you really need to, and b/ you can and will afford to install and maintain it to the appropriate BS. and c/ you will train all new staff in it's correct operation.

[KevinE]

Fire alarms give out 24VDC to bells and sounders, so you need a 24V interface relay off the alarm. Some alarms need terminators on their bells but if you have a relay in parallel with an existing bell, this will be present in that. You're probably best getting the alarm company to provide a feed (and possibly the relay too) to the amp room so that you don't negate any Fire Alarm approvals by a DIY job here (in case what you do affects the alarm..either physically or on paper!). Fire alarms are to BS and the installation as a whole must comply, not just the panel.

 

General practice is to use the N/C contact on this slave relay as a maintainer on a 240v or 415V contactor that feeds the amp or amps, so that in the event of the sounder actuating, the mains contactors are de-latched by even momentary activation of the fire slave relay. You can reset the amps by pressing the 'start' button on the contactor box once the fire alarm is muted or cleared.

 

The use of a contactor like this is required by many local authorities in clubs in particular where the internal sounders may be obliterated by music. It's common sense anyhow, and any venue owner who's into this risk-assessment thing will no doubt have considered it. I've worked in many venues that don't have it, and many that do..so I suppose it can't exactly be required by statute as such.

[Jivemaster]

If you have an installed PA then this can be muted in case of alarm with a priority paging nic for crowd control. If the power is cut then you have no way to address the assembled punters. If the power is cut then you must have a switch on sequencer installed or the alarm being turned off will ping most of your speakers.

 

Remember that in most venues the ratio of false alarms to real alarm situations will be in the order of 100:1 add in some (weekly?) alarm tests and a power off contactor is all too likely to be what costs you a complete set of speaker drivers at an inopportune time. A signal muting circuit will cause less damage.

 

The better method (IMO) is to mute or severely duck the music channels BUT have some mic channels stay live.

 

When I worked in a Leicester Square venue the procedure for a fire alarm was full evacuation as the punters were standing, -leave coats and bags behind. The procedure for a terror alert was for all punters to collect their coats and bags from the cloakroom and return to their seats. This was to reduce the number of coats and handbags to be searched as suspect packages and also because there was sometimes a two device threat where there may be a second device in the fire assembly area ready to attack the punters as they filed out of the premises.

 

There are risk assessments to make and they are best made with input from emergency services, who will be picking up whenever your alarm goes off during opening hours.

[Simon Lewis]

Colin,

 

Seems like a Formula Sound Guardian Mk2 is what you need. It will interface with your sound system (at line level) and yourf fire alarm system. When the alarm triggers, the programme level is reduced but a mic priority channel is provided.

 

As it's a commercial product, approvals, EMC, CE etc. are already in place.

 

Simon

[KevinE]

a power off contactor is all too likely to be what costs you a complete set of speaker drivers at an inopportune time.

Most nightclubs and pubs actually use power-off contactors with no ill effects.

[paulears]

I concur - our sound panel power is via a fire alarm maintained contactor and actuating it causes no panic noises, just a quick fade as the power supplys power down. resetting isn't a problem, as the surge on power up precludes anything other than a proper power up sequence - and involves a trip to reset the contactor. Our installation was not a discussion when it was fitted. We were told that it was a power off requirement. Input muting was not an option as it could be bypassed too easily and not noticed.

[Jivemaster]

Whatever you plan to fit -get it approved by your licensing authority. No approval, no licence.

[c.cam108]

Thanks for the replies guys. I should have said earlier but I was thinking more about temporary pa than a fixed install.

 

Obviously this gives less scope to modifying the alarm system, hence the panic button idea.

 

Colin C

[Jivemaster]

With multiple locations then you will likely have multiple licences, compliance with the licence terms is the important part. If the licence says PA to go off, or PA to stay on for announcements, in an emergency situation then that is what you must provide. Also ensure it cannot be tampered with.

[c.cam108]

Ok can I bring this down a bit to this scenario. In a school/hall/club/etc. The PA will be there for a night probably on a basic wet hire for a band night etc. Any integration with the existing fire alarm system will most likely be out of the question due to cost/hassle. What would you suggest? How about the operator just pulls down the master faders? Actually now I think about it, that seems the most sensible solution.

 

This ain't Hampden Park we're talking about, it's about a hundred folk coming to see a band at their local. Are the regulations so tight that even then I would have to bring in a fire engineer to hook me up and thoroughly test and risk assess the whole system?

 

Colin C

[mutley]

When I worked at a large national holiday resort (think 'Redcoats'), we used 'Allen & Grief' DR8 zoners, which connected to the fire alarm circuit via the 9-pin D-sub on the back of the unit. The fire alarm company installed and provided the 9-pin D-sub for us to connect to the appropriate equipment. And when the zoner goes faulty - which it often seemed to do! - you can simply unplug it , and plug the alarm mute plug into the replacement unit.

 

We once had some Ibiza DJs in for an adult weekend, and they were driving the system so hard that a brand new set of twin 18" cone 800W subs caught fire! The noise from the 3000 people was so loud that even once the fire alarm had been activated and the music was cut, it took a few minutes for the pi$$ed-up punters to realise!

 

Instead of using the zoners, if your sound desk has 'Master Inserts', you could (as a bit of a project) link these to a relay's NC contacts, so that they break the circuit upon activation, and you could include an 'Emergency Announcement Mic' wired to the relay's NO contacts... But as KevinE has mentioned, the whole fire alarm needs to comply with all relevant regs, (National, local and venue-specific), so you'd need to look into this properly, and almost certainly get your alarm company to install the relay unit at least...

[adam2]

Ok can I bring this down a bit to this scenario. In a school/hall/club/etc. The PA will be there for a night probably on a basic wet hire for a band night etc. Any integration with the existing fire alarm system will most likely be out of the question due to cost/hassle. What would you suggest? How about the operator just pulls down the master faders? Actually now I think about it, that seems the most sensible solution.

 

This ain't Hampden Park we're talking about, it's about a hundred folk coming to see a band at their local. Are the regulations so tight that even then I would have to bring in a fire engineer to hook me up and thoroughly test and risk assess the whole system?

 

Colin C

 

As others post, in a large nightclub or similar venue, a "power off contactor" operated via the fire alarm is often a requirement of the licence.

 

It would however be OTT to demand this in a small venue, especialy when the kit is hired or borrowed for each event.

What is sometimes instaled in smaller venues is a number of mains sockets (13 amp and/or 16 amp ceeform) these outlets are normaly live, but are isolated via a contactor if the fire alarm sounds. Any noise making equipment should of course be powered from these outlets.

If this is installed it should of course be used.

 

If no such is installed, then perhaps it should be considered, but that is for the owner of the venue to consider, not someone just useing it for a night or two.

 

If no automatic power off facility is available, then the PA operator should be vigilant for the sounding of the fire alarm, and promptly silence the music.

This should be adeqaute in small simple venues, such as refered to above.

[J Pearce]

A strober flasher could be placed near the likely FOH position for venues that regularly host temporary systems, as when a band or dj is mid set it can be hard to hear an alarm. (Been there done that, had to comms back to FOH that we really ought to evacuate the 600 drunk punters... fortunately it wasn't a fire just an artist having a fag in his dressing room)

[Alwal]

interesting thread.

I like the look of the guardian CX4 ... this could be an interesting concept to discuss with the post 16 production arts students!