Booster for signaling circuit FA

[JJWalecka]

Was told "We have to add a booster for one strobe because they can’t provide shop drawings for existing system".

Im unfamiliar with fire alarm systems.

Can someone point me in the right direction on what questions I should be asking

 

[Strathead]

Not sure what you are asking for about questions. I can tell you that the FA statement is reasonable. Per code, one must provide battery calculations for any additions. Without as-builts that would require a mapping of the entire system for battery calculations. For less than $1000 a power supply can be added. It will likely go in a room or near a power panel. Will require a dedicated 120 volt circuit or share the local fire alarm circuit if available, and if the system is in conduit a conduit to intercept the nearest fire alarm conduit. That is about it.

 

[gadfly56]

Was told "We have to add a booster for one strobe because they can’t provide shop drawings for existing system".

Im unfamiliar with fire alarm systems.

Can someone point me in the right direction on what questions I should be asking

This is frequently how jobs get quoted in our shop, for the reasons Strathead has mentioned. However, some semblance of common sense can be applied.

Each circuit on a booster power supply will be listed to 1.5, 2.5, or 3 amps (DC), typically. The power supply itself will have a max draw of 6, 8, or 10 amps (DC), typically. The power supply will have 4 or 5 output circuits, typically. As it happens, if you load up 3 or 4 of the circuits to their individual amp draw, you can't use the 4th or 5th circuit. So, if you look at the existing power supply, and it's using only 1 or 2 circuits, even if you assume they are maxed out, you can still add another circuit or even 2 as long as you keep the draw under the panel maximum. This all requires that whoever is quoting the work actually get out of the car and put their eyes on the inside of the booster panel, or have the customer send good pictures of the guts.

The other option is to meter the max amp draw on the installed circuits and go from there, although there is usually push-back from the building occupants about ringing the horn/strobes.

 

[JJWalecka]

Thanks for all that information. Appreciate it

 

[Strathead]

This is frequently how jobs get quoted in our shop, for the reasons Strathead has mentioned. However, some semblance of common sense can be applied.

Each circuit on a booster power supply will be listed to 1.5, 2.5, or 3 amps (DC), typically. The power supply itself will have a max draw of 6, 8, or 10 amps (DC), typically. The power supply will have 4 or 5 output circuits, typically. As it happens, if you load up 3 or 4 of the circuits to their individual amp draw, you can't use the 4th or 5th circuit. So, if you look at the existing power supply, and it's using only 1 or 2 circuits, even if you assume they are maxed out, you can still add another circuit or even 2 as long as you keep the draw under the panel maximum. This all requires that whoever is quoting the work actually get out of the car and put their eyes on the inside of the booster panel, or have the customer send good pictures of the guts.

The other option is to meter the max amp draw on the installed circuits and go from there, although there is usually push-back from the building occupants about ringing the horn/strobes.

Don't you find though that the Fire Marshals often don't have common sense either? Meter the circuits yes, but even with one device added, battery calcs are required. Using your first method, you would also need to figure the full panel amps for the battery calcs, which often the batteries aren't sized that large?

 

[gadfly56]

Don't you find though that the Fire Marshals often don't have common sense either? Meter the circuits yes, but even with one device added, battery calcs are required. Using your first method, you would also need to figure the full panel amps for the battery calcs, which often the batteries aren't sized that large?

I haven't run into a Fire Marshall I couldn't walk through it. And if you want, just set the existing panel circuits to their max value in the spreadsheet and go from there. I've had to do battery calcs for adding 2 devices using this method. Most AHJ's just want to see the calcs, they never verify them by hand. Which isn't to say you should fudge the numbers in your favor.

Using the first method you just assume the max circuit value for the circuits already in use and then calculate the real values for the circuit you are adding. The software does all the figuring. My personal experience is that you most often come up with surprisingly low values. Putting in two 12VDC x 12Ahr batteries is good for about 90% of cases. In the worst case, you have to add a battery box.