Fire Alarm

Status
Not open for further replies.
A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
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.
 
horsegoer said:
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.
Click to expand...

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.
 
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 said:
Are horn and speaker synonymous in this conversation, or am I missing something?
Click to expand...

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.
 
George Stolz said:
Are horn and speaker synonymous in this conversation, or am I missing something?
Click to expand...

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.
 
horsegoer said:
SPKR/STROBE OR HORN/STROBE.... same thing
Click to expand...

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.
 
gadfly56 said:
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.
Click to expand...

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.
 
MichaelGP3 said:
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.
Click to expand...

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.
 
Volta said:
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.
Click to expand...

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.
 
MichaelGP3 said:
... 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.
Click to expand...

'K, I agree.
 
Status
Not open for further replies.
Top