Questions for smoke detector install

I'm working on getting everything installed and found many answers to most of my questions either in the install formal directions or in other forum topics, but I could use a little help on smoke detectors.  I have some old (yes past 10 years age) smoke detectors, but I want to get an understanding and handle on things before going and buying $130 worth of new ones. Plus, I have 10 yr battery powered smoke detectors in my house (1 on every level plus 1 in every bedroom) that are in lifetime range, so it's not a rush to get things up to spec...this is just going to be an added layer for notification if I'm not home.

So, what I have is System Sensor  model 2412TH detectors. SEE https://www.systemsensor.com/en-us/Documents/2412B_2412THB_2424_2424TH_Manual_I56-0286.pdf

In my original panel FBII XL-2, these were wired into I believe Zone 6.  The wiring from the panel went out on 4 wires to the basement detector which had the dining room detector daisy chained off of the basement.  The other one went straight to the 2nd floor hallway detector, which did not have any daisy chaining.

ALL of them I believe were wired in the same way which was based on terminal numbers:

1 - negative power - BLACK wire
2 - positive power - RED wire
7 - INIT CTK - YELLOW wire
8 - INIT CTK - GREEN wire

Per the linked PDF, 7 & 8 form a N/O circuit.

The "AUX" ports that are available are:
4 - N/C
5 - N/O
6 - Common

So far as I can tell there's no formal EOL relay anywhere in the walls and there wasn't in the old panel.  The were some resistors jumpered in between some of the ports and in line to wires (like other powered contacts in general, just some little light blue ones), but with all other things I've worked with so far on the install (like glass-break and motion etc.) that had them, they were no longer needed.

Do I just need to change SmartThings to think it's N/O instead of N/C and it will be happy/work?  Or do I need to modify the wiring to be using the AUX N/C (#4 terminal) or something else?  In the case of the upstairs, it doesn't daisy chain, so is that different vs. the ones that need to run in series?  I plan on the trigger to be to the sirens (which I found out I had speakers and not actual sirens so I ordered some $8 Honewells based on another question on the boards here), so I am not concerned with 1 detector knowing another (and I don't think they actually make noise).  If it make sense, I may just use the existing wire for floor 1 to fish a new cable run so it no longer daisy chains and then I can isolate the 3 floors to 3 separate zones so I would know where the fire was though if the way the circuit is triggered along a path could be smart enough to know if it was basement or 1st floor, then that wouldn't matter.

Thanks in advance for anyone that's knowledgeable on this that can explain it. I watched a ton of youtube videos and searched, but a lot of what I find didn't apply exactly to what I'm trying to figure out, so I am still confused.  :)

FWIW what I'll probably eventually buy is the DSC FSA-410BST's that are recommended here, but like I said, I want to understand the wiring/resistors and anything else I need before getting to that point, since i have the old ones that do work with power and seem to detect heat/smoke enough from my testing to light up individual "trigger" lights on them.

  • Update, last night I tried to do some more troubleshooting without success though then I later noticed that my board 2 was "unresponsive" in that the piezo chimes weren't working, so it is possible a combo I tried with the smoke alarms may have actually worked and there's no way I would've known.  What I found was on my Samsung SmartThings app that I was getting errors trying to view the device it would give the IP:port number of the board 2 and say the webpage wasn't reachable when I went into try and look at status (SmartThings, Automation, Konnected (Connect), Expansion board >, Device status IP:port) and there it just gave the Android error of webpage not available with I believe... a time out.


    So, when I got to work and was on my computer, I was thinking of ripping and rebuilding the Konnected/SmartThings integration from scratch based on something another person mentioned in another thread and I noticed when I went to my SmartApps in the SmartThings site, that it showed the konnected-io service manager as "unpublished" instead of published like it should be.  I told it to update/publish and then back on my phone (keep in mind I'm at work so the webpage looking for the LAN IP of my board wouldn't be able to load anyway), other things that were previously giving errors (like trying to remove a zone) etc. were once again working.  So, what I'll do is see if the door chime is working when I get home because that's technically currently the only thing on board 2 at the moment since I've removed the smoke detectors for right now so I can try again when I get home.

    Also, I went ahead and ordered the DSC FSA-410BST's.  If anyone can explain how best to do the wiring with the way I explained they're connected in my first post, that will still be helpful.  I will have the new ones on Friday.


    If my board is working as I hope when I get home... I may again play with the old smoke detectors just because I'm curious anyway.

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