How to wire a pull station to a horn/strobe

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How to wire a pull station to a horn/strobe

Postby Destin » Sat Feb 08, 2014 4:37 pm

So, you have a couple of fire alarm devices that you'd like to test out, but you don't have a panel. Not a problem. It's very easy to do, and this guide will get you started.

Items you will need:
- A pull station
- A notification appliance (horn, strobe, horn/strobe, bell, chime, light plate, etc - this does not include speakers)
- A power source
- The right wire
- The right tools

1. Determine the power requirements of your notification appliance(s)
Let's assume you have a horn/strobe. When you check the label on the back of your device, you should see something similar to "Operational Voltage Ranges: 16 - 33 volts". This means that any voltage within this range will effectively power the device. You may also just see "24VDC". Either way, 24VDC is the industry standard for modern fire alarm appliances. Chances are, most if not all of your horn/strobes will be the same. In that case, you'll need a 24VDC power supply. If your device has a different power rating such as 12VDC or 48VDC, find the appropriate power supply. If you see something like "25/70 VMRS", that is a speaker. Speakers need an audio source and amplifier, but we'll cover that in a separate thread which will come soon.

Many vintage notification appliances are AC. If you come across a device and don't see any mention of AC or DC on the label, 60Hz = AC. If you still aren't sure, test the device with DC first. If it's AC, you will just hear a clunk or nothing at all. But NEVER EVER power a DC device with AC - you might start a fire! If you have a device that's rated for 120VAC, that is the current running through your house. You can power it by stripping the end off of a lamp cord. If it's rated for something like 6VAC or 12VAC, you'll need an appropriate AC transformer.

Another factor to consider is current draw. For 24VDC notification appliances, you could buy this transformer which will support 1.5 amps of current draw. For the vast majority of notification appliances, that is more than enough. However, just to be sure, check the label on the back and you should see something similar to "24VDC, 0.063A". That rating is from a Wheelock 7002T, which would work fine with that transformer. If you have an older device such as a bell or light, the current draw may be much higher (such as 0.22A). Remember that if you want to power multiple notification appliances with one transformer, add up the current draw listed on each device and make sure that number NEVER exceeds the maximum draw listed on the transformer.

Finally, some horn/strobes may require a panel or sync module to activate at all. The only ones I can think of are Simplex's SmartSync or addressable TrueAlerts.

2. Make sure your pull station will work
A conventional pull station is similar to a lightswitch. It does not need any power to operate, but instead completes the circuit when it is pulled and allows power to flow to a horn/strobe. First, make sure your pull station is not addressable. If it is, you will see a module on the inside or the back containing a circuit board, rotary or DIP switches, and sometimes an LED. Addressable pull stations will only communicate with an addressable FACP, so to use it in your setup, you'll need to remove the two wires coming from the switch and only use those. If you have a coded pull station, just use the two normally-open contacts and it will work. If you're going to be switching AC current, check to make sure your pull station is rated for AC. DO NOT use it for this purpose if it is only rated for DC. And don't use a pull station in your house as a lightswitch.

3. Buy the power supply, wire, and tools
Now that you know the power requirements of your devices, buy the appropriate power supply. This one will be perfect for most applications, but if you want to power an oddball device or test AC alarms, make sure you find one with the right voltage rating and current capacity. If you're still unsure about what will work, feel free to ask a question on the forums.

DC devices can also be powered with batteries. Although I recommend buying a transformer, you can test a horn/strobe using two 12V batteries or three 9V batteries. To achieve the full voltage, these batteries would need to be connected in series. The diagram below shows how to do that.

Because the requirements for fire alarm wire in the "real world" are determined by very specific variables, there are many options available. However, for your setup, you'll want to find wire that is easy to work with, affordable, and most importantly, won't melt. 22 AWG non-shielded bell wire at the local hardware store is fine for small low-voltage DC setups. Choose solid over stranded if possible. If you're working with AC, I'd recommend 18 or 16 AWG to be safe. For setups with a large number of devices or anything that you're unsure about, consult an online wire gauge calculator or ask for a recommendation here.

The tools you'll need will vary depending on what you're doing. Everyone should at least have flat-head and phillips-head screwdrivers, wire cutters, and wire strippers. If you are wiring devices that have leads, get some wire nuts and electrical tape. A multimeter is also nice to have.

4. Make your connections and test it!

This diagram shows the basic wiring of two pull stations and two horn/strobes to a power supply:


For your setup, add or remove devices from this wiring method as necessary. Multiple pull stations are wired in series, while multiple notification appliances are wired in parallel. Polarity (+ and -) always matters on DC notification appliances. It does not, however, for pull stations or AC notification appliances. If your pull station or horn/strobe came with a resistor across the terminals, remove it before applying power. Notice the difference between a 2-wire and 4-wire horn/strobe. On a 4-wire device, the horn and strobe are powered separately. Simply jump one set of terminals to the other two power both at once. If your pull station has two switches or multiple sets of terminals, you only need to use one set of normally-open contacts.

If your setup isn't working properly, try powering your notification appliance directly from the transformer to ensure that it works. Double-check that all of your devices are compatible and go over your wiring. As always, if you're stuck, this forum is here to help. Good luck!

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