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[Brad Channing]

Involved in a new build installation where code is requiring that when the fire alarm is activated that the audio be cut to mains, monitors and a satellite classroom system.  The mains and monitors are to be powered speakers and the classroom is 70.7V.  I haven't had to deal with this before and thought I'd check in and see if anyone had some good suggestions.  I was looking into using Furman relay receptacles and the fire alarm voltage to cut AC to all the zones.  Is there a better solution?  Is it better to cut the audio signal to the speakers or the AC?  Any thoughts?  TIA

[Dave Sturzenbecher]

If you wish to cut audio to everything, then simply use an RDL piece on the output of your mixer. Check out the ST-SSR1.  With this you can either mute, or mute and select the fire alarm feed.

[Ivan Beaver]

Depending on the particular code-you might have to remove power from the amps.

We use Lowell RPC20 controllers for the AC and just interupt the closed contact and the amps will shut off.

But this can be a REAL pain.  Everytime there is even a minor alarm-the sound system will not work.

Be sure the customer knows this-but there is no way around the need for it-just make sure that you don't get blamed everytime the system won't turn on.

[Adam Kane]

Depending on what you're using (or will be using) for a DSP, many units can, via contact closure, be set to recall various presets...in turn muting or re-routing inputs/outputs in the event of a triggered alarm.

This only works if power doesn't have to be cut from the power amps, like Ivan stated.

[Brad Weber]

As already noted, check with the local officials.  I have had some allow muting at the DSP or via mute contacts on individual pieces of gear and others require actually breaking the power to the amps.

You might also want to find out if they are providing a dry contact closure or DC voltage from the life safety system and whether it is normally open/no voltage or normally closed/voltage present.

[Duane Massey]

Another option that I've used is to specify that the breakers feeding the amps be turned off by the fire system. The EC then becomes responsible for this, which makes my life as a small-time installer much simpler.

[Ivan Beaver]

Duane Massey wrote on Thu, 11 February 2010 19:47

Another option that I've used is to specify that the breakers feeding the amps be turned off by the fire system. The EC then becomes responsible for this, which makes my life as a small-time installer much simpler.

Except the cost to the customer just went way up.  But I guess you could argue that is not your concern-but "meeting fire code" is.

[Hal Bissinger/COMSYSTEC]

Except the cost to the customer just went way up.

Why would the cost go up? Shunt-trip breakers aren't that much more expensive than normal ones. After that the control is going to be the same. Actually it should cost less because no other equipment (like contactors) is needed. Matter of fact there may be other shunt-trip breakers in the panel to shut down fans and other HVAC stuff. The only downside is that they must be manually reset (just like a regular breaker that has tripped) after an event.

-Hal

[Brad Channing]

The main complication or PITA with this job is the powered speakers that were spec'd and whether to put the relay controlled receptacles at the speakers or have the power runs for the speakers run down to a common rack.  No matter how the fire alarm shuts off audio, the powered speakers needed to be powered down remotely and were getting run to controlled receptacles.  Now I'm thinking that flying conventional un-powered speakers with amps on the ground is going to make this simpler and more cost effective.

[Hal Bissinger/COMSYSTEC]

Now I'm thinking that flying conventional un-powered speakers with amps on the ground is going to make this simpler and more cost effective.

I think I agree with you there.

-Hal