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Topic starter
October 10, 2025 4:54 pm
I'm planning an installation based on a gridboss, flexboss21, and 2 indoor wallmount batteries, installed in my garage in California.
I'm planning to install a heat alarm above the batteries as required by code, and I saw someone's idea that it could be connected to the rapid shutdown switch, which seems like a good idea to me. But as I understand it, the rapid shutdown on the gridboss will open all the relays, cutting my home off from grid power entirely. That sounds good for a manual activation by a firefighter if my house is actually on fire, but I'm hesitant to make that automatic when the heat alarm goes off.
Is there a way I can connect the heat alarm to just trigger shutdown of the inverter/batteries, without opening the MID relay in the GridBoss? Maybe if I just wire it to the RSD port in the FlexBoss21, but not to the one in the GridBoss?
Topic starter
November 18, 2025 7:03 pm
The heat alarm I'm using is the First Alert/BRK HD6135FB, with the First Alert/BRK RM4 smart relay to convert the proprietary alarm interconnect signal to standard NO and NC dry contacts.
I saw someone post on diysolarforum that even without the RSD wires connected between the gridboss and flexboss (just the serial communication cable), triggering RSD on the flexboss caused the gridboss to shut down and open the grid relay, which is disappointing if true. Because the alarm interconnect works both ways, this means that if I set up automatic RSD, any time the smoke detectors in my house go off, I will immediately lose all power.
Can anyone from EG4 comment on whether this is/could be supported?
November 18, 2025 9:10 pm
@mbbush I thought the First Alert/BRK HD6135FB would need to be connected into the home Fire notification wiring as well. On its own it could help with rapid shutdown. Would be great if AHJs would consider it sufficient for Building code.
Topic starter
November 18, 2025 9:13 pm
@powerup Yes, it does require interconnection with the home smoke alarms. That's the reason for my concern that a nuisance smoke alarm inside the house would shut off all the power.
The only other workaround I can think of would be getting two heat alarms, putting them next to each other, and wiring one to the RSD, and the other to the home smoke alarms. But I'd really rather not do that, and I don't know what the inspector would say about it.
