Resi Sprinkler System Flow Switch Wiring

I have been working on a rewire of a remodel, and the fire sprinkler system was recently put in. The riser is outdoors. The only thing the sprinkler fitters did was install the flow switch, which is a System Sensor WFDTN. What is the preferred method to wire a bell to one? I would assume running thwn in sealtite from the flowswitch to a weatherproof single gang, sealtite inside the wall to the bell backbox, fed off of a dedicated circuit?

Pretty much. Come out of the flow switch (there should be two knock outs on the bottom - use one of them, don’t cut any new openings into the housing) with the seal tight and, if you are mounting the bell nearby, directly into the back box for the bell. There is no need for a junction box between. Feed your 120V directly into the bell backbox. Basically, the wiring to the waterflow switch is a “switch leg” to use an electrical term. This way you only need to feed three wires to the waterflow switch (two for the bell circuit, one ground) and you can do all your splicing at the bell. Wire up to the “NO” and “COM” terminals in the flow switch - one set of contacts only. This also reserves the other knock out and switch in case the homeowner wants to wire waterflow to a security panel.

You may want to test the switch after you have it wired up. There should be an inspectors test valve after the flow switch. Open up the valve and let the water flow. The bell should activate within 90 seconds. You don’t want it to activate immediately, in case there is a pressure surge in the water supply because that would make the bell false alarm. There is an adjustment dial on the waterflow switch, adjust it so the bell rings in about 60 seconds and that should be fine.

As far as a dedicated circuit for the bell, there are two schools of thoughts for residential. You local jurisdiction may require a dedicated and locked-out breaker. And not a bad idea - less on the circuit to cause an overload or fault. But there is also the idea of wiring the bell to a normal light and power circuit, like the circuit that powers the kitchen lights. This way if the breaker ever trips, the lights won’t work and the homeowner would turn the breaker back on.

For further information, here’s a link to the waterflow datasheet: https://www.systemsensor.com/en-us/Documents/WFDTN_Series_DataSheet_WFDS437.pdf

Does the system have a FACP? I know some places don’t require a FA system if the building is fully sprinklered (or old enough to be grandfathered in). If it does (and the system is addressable) you could use a monitor module to hook that switch to the panel, and set it to only output the sprinkler bell if tripped.

Edit: Just realized it’s a residential system. Yeah, you could run a bell off a dedicated circuit.

Standard practice is to use a 120v bell . The flow switch will be used to switch the HOTs only with the common and normally open contacts on one side of the switch . The other side will be reserved for a facp.