About 8 years ago I had a technical support rep at Bosch indicate to me that when this sort of thing is done, the panels need to be monitored via discrete input zones on an independently powered* transmitter (with its own backup batteries) regardless of how the fire alarm panels otherwise operationally interact, or the fire alarm panels require separate transmitters. This is done so that a catastrophic failure of one panel does not inhibit an alarm signal from a surviving panel to be transmitted.
*Can be on the same circuit breaker, but cannot be powered from one fire alarm panel's power supply.
Another issue worth mentioning is strobe synchronization.
So a independent 120V DACT?
Is that a UL thing?
I have to hear more about that, I recently was forced into a slightly similar situation, that the AHJ approved, with me stating on the record of completion that I couldn't confirm it was complaint and that he approved the design. I didn't turn it down because my new panel has an integrated DACT and was being treated as an independent system.
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He'll have to designate a 'master' and a 'slave' panel, assuming the AHJ only wants to reset one panel depending on the layout
This is the situation I had-
strip mall with 2hr fire walls between units
landlord controlled sprinkler system
A riser in common area serving two tenant spaces. (there are 6 risers 10+ tenant spaces)
One tenant space gets new addressable panel w/DACT "slave panel" Other tenant space served by this riser stays existing.
landlord controlled mall 'master' FACP- Conventional with no way to add an IDC
landlord 'master' FACP already monitored that waterflow, but could not trip the new tenant panel
Existing riser flow switch used to trip 4 devices off the DPDT contacts- 'master' panel, 'slave panel', other tenant space panel and waterflow bell.
The flow switch was connected within 3' to a relay j box to accomplish all that. It was explicit in all paperwork I would not/could not verify whatever was happening in that j box, and the other contractor would accept liability (yea like that would matter right?)
I had to make the waterflow input nonsilencable, autoresetting on the new addresable tenant panel. So when the WF switch alarmed, all the areas served by the riser would get notification, but the FD only had to reset the 'master panel'.
If a pull or smoke went off in that tenant space, then the FD would have to reset both panels, but somehow that was ok.
This is a simplification there was a lot more to it, it never sat well with me.