what is the best way to change this over to a bell. This building has a wet and dry sprinkler system the wet system has a flow switch. The sprinkler guy installed a pressure switch in the dry system. Can we use the N.C contact on the flow switch to feed the common side of the pressure switch and then feed the bell. Any help on this will appreciated.
This is heavily AHJ dependent. Some will allow a single bell, some want multiple, some require it to be 120 vac in case the panel is dead water flow will at least be heard outside.
Some have a main flow switch before all risers to ring the bell and act as a redundant flow.
The proper way with one bell and an addressable panel is mapping a NAC for both flows.
With conventional you could use interposing relays, and even then it's not completely supervised.
Last time I had this, the bell was annunciating 3 risers, all 3 had pressure switches that we're wired in parallel. AHJ didn't care about supervision of the bell, as there was a supervised horn/Strobe next to it for general alarm, existing retrofit too.
Oh your idea: It would work as an unsupervised circuit. Unless its in conduit (not emt) within 20' in the same room, technically it's supposed to be supervised. Not everyone takes that into account.
