Fire Alarm

[Alwayslearningelec]

I know the class of the system matters but out of curiousity does a speaker strobes usually get a one pair for the speaker and one pair for the strobe so essentially you can use one (2) pair wire two single pair wires? Would that be correct?

What governs how many devices can be put on a loop?

Thanks.

 

[gadfly56]

I know the class of the system matters but out of curiousity does a speaker strobes usually get a one pair for the speaker and one pair for the strobe so essentially you can use one (2) pair wire two single pair wires? Would that be correct?

What governs how many devices can be put on a loop?

Thanks.

Yes, speaker/strobe combination units have separate pairs for the speaker and the strobe. Whether or not you can use a 4-conductor cable or need (2) 2-conductor cables depends on what the manufacturer says. However, depending on the candela setting for the strobes, you might want to run separate cables anyway. A 16-2 and a 12-2 are going to be a lot cheaper than a 12-4, and easier to handle.

The voltage drop and current draw are going to limit how many strobes you can put on a circuit. Usually the manufacturer has their own limit, but it's typically much higher than what you can do in the field. They use a "best case" of all strobes set to 15/75.

For the speakers, it's voltage drop and wattage settings and what the amplifier can handle.

 

[George Stolz]

I need to get out more. I've never seen a horn strobe that took more than a pair of wires.

 

[Alwayslearningelec]

Would you ever use more then a 2 or 4 conductor cable for initiating/signaling devices? THanks.

 

[George Stolz]

I just wire according to the drawings. Isn't the system being designed by the fire alarm company? :?

 

[Alwayslearningelec]

I just wire according to the drawings. Isn't the system being designed by the fire alarm company? :?

Not looking at drawings for this. Just was curious about some FA stuff.

 

[MichaelGP3]

Typically, speaker wires are shielded, and incorporate a drain. I wouldn't recommend feeding both speakers and strobes from a single cable for several reasons that fall into 2 categories: cost of materials & cost of labor.

Use voltage drop calculations for strobe, horn/strobe, & horn circuits.

Use db loss calculations for audio (speaker) circuits.

 

[George Stolz]

Are horn and speaker synonymous in this conversation, or am I missing something?

 

[ron]

Are horn and speaker synonymous in this conversation, or am I missing something?

Horns just make ... well horn noises, and speakers allow delivery of voice evacuation messages when there are amplifiers and microphone.

 

[iwire]

Are horn and speaker synonymous in this conversation, or am I missing something?

Speaker strobes will make 'horn' noises but can also provide fire department directions via a mike at the fire panel (or wherever).

Usually found in taller or larger buildings.

One of the Lowes we did got voice evac due to the FD being PITAs.

 

[MichaelGP3]

Are horn and speaker synonymous in this conversation, or am I missing something?

George: Horns, like chimes, bells and strobes are driven by 12, or more typically, 24 volt DC power supplies (in a very small fire alarm panel, this power supply may be integrated into the common control).

Speakers (in the fire alarm business) are driven by 25 or 70.7 volt amplifiers, and are not interchangeable with horns, chimes, bells or strobes.

 

[Alwayslearningelec]

SPKR/STROBE OR HORN/STROBE.... same thing

 

[gadfly56]

SPKR/STROBE OR HORN/STROBE.... same thing

Ummm, NO!

Horn/strobes can be 4-wire or 2-wire and typically operate on 24VDC. They are activated by notification appliance circuits of the sort found in any fire alarm control panel.

Speaker/strobes are ALWAYS 4-wire devices. The strobe part is activated from a NAC, and the speaker is tied, in some manner, to an amplifier, operating on 25 or 70 VDC in the US. In Europe, they may also operate on 100VDC. The speaker portion is NEVER tied to a NAC.

 

[MichaelGP3]

Ummm, NO!

Horn/strobes can be 4-wire or 2-wire and typically operate on 24VDC. They are activated by notification appliance circuits of the sort found in any fire alarm control panel.

Speaker/strobes are ALWAYS 4-wire devices. The strobe part is activated from a NAC, and the speaker is tied, in some manner, to an amplifier, operating on 25 or 70 VDC in the US. In Europe, they may also operate on 100VDC. The speaker portion is NEVER tied to a NAC.

Pardon me, but if you're seeing 25, 70.7 or 100 volts DC at the amplifier's output terminals, you'll be able to smell the speakers as well as hear them.

 

[Volta]

Pardon me, but if you're seeing 25, 70.7 or 100 volts DC at the amplifier's output terminals, you'll be able to smell the speakers as well as hear them.

Why? Many sound systems use 70 volts. They don't drive regular 8 ohm cones, but rather a (usually multi-tap) winding integral to the speaker package.

 

[MichaelGP3]

Why? Many sound systems use 70 volts. They don't drive regular 8 ohm cones, but rather a (usually multi-tap) winding integral to the speaker package.

I think I may have been conflating DC appearing at an amplifier's output terminal (it shouldn't, this is a sign of filter capacitors in the amplifier's power supply going bad) with the oscillations that occur when an amp is clipping or attempting to replicate a square wave, seen when an amplifier is well on it's way to burning out it's output transistors.

Your point that 25 or 70.7 volt speakers, having different impedance characteristics than 8 or 4 ohm speakers, would tolerate this better than I suggested is well taken. But the adjustments made to calibrate 25 or 70.7 volt audio occur in the AC realm, performed with a true RMS AC meter or an oscilloscope. You shouldn't be seeing DC voltage coming out of an amplifier.

 

[Volta]

... Your point that 25 or 70.7 volt speakers, having different impedance characteristics than 8 or 4 ohm speakers, would tolerate this better than I suggested is well taken. But the adjustments made to calibrate 25 or 70.7 volt audio occur in the AC realm, performed with a true RMS AC meter or an oscilloscope. You shouldn't be seeing DC voltage coming out of an amplifier.

'K, I agree.