4 wire smoke connection with ELK M1 gold


Active Member
Hello All,
It has been a while and I revisiting another new install of M1 gold in my new residential area. I know it is best advisable that all smoke detector (2W or 4W) shold be daisy chain wired. where I got confused now is where do I put the EOL relay and EOL resistor in my diagram. So this is what am trying to accomplish. 
1. Daisy chain wire my smoke detectors (4W)
2. Instead of using the power from ELK M1 gold panel, I will be using my ALTRONIX PDU8 external panel
3. whatever I do, I want the EOL relay inside my panel box.
4. Does ELK recognize the smoke detector connected to it as the "first" or "last" or it doesn't matter? I'm asking this cos I know the EOL relay and resistor needs to be on the last smoke detector. 
I need experts to chime in please. 


  • elk.png
    152.6 KB · Views: 13
I am not an expert but I will mention a few obvious things:
The end of line relay needs to be at the farthest detector in the chain. The only way to have the EOL relay in the panel is if you run another 2 pair of wires from the farthest detector back to the panel to make a big loop. The relay has to monitor all of the wiring from the panel out to the end of the line (hence the name) so either the last detector or run a loop back to the panel so that is now the very end of the wire run.
The end of line resistor needs to be connected to the end of line relay so that any break in the power feed will cause the relay to open and remove the end of line resistor from the detection loop to trigger a trouble.
And of course your auxiliary power is wired through a relay that the Elk panel will use to interrupt the auxilillary supply when you do a smoke reset on the M1.
The Elk panel does not know or care how many detectors you have or in what order you number them. The zone only wants to see the EOL resistor for normal state, an open circuit for trouble, or a short for alarm.
Not an expert. But, any particular reason you need 4 wire smokes? Much of what I read suggests it’s extra headache without much benefit for typical residential installs. Also the diagram appears to show 2 wire.

I’m using a System Sensor COSMOD2W with COSMO2W CO and smoke detectors. The setup is pretty straight forward and allows for CO, smoke and trouble signals to be sent to different Elk input zones.

I installed in existing construction here and a direct daisy chain wasn’t feasible so with 4 wire fire cable run to each sensor I could in effect daisy chain them back at the panel.

Sent from my iPhone using Tapatalk
The biggest reasons for using 4-wire (for me) are:
1 Current draw. 2-wire smoke loops are usually limited in max detector count because of current draw. This problem is compounded if you have a panel that only supports 1 zone/loop of 2-wire smokes.
2 I want to break my smokes into zones so I get an indication of where the fire is. I don't want to have to go running around checking thirty some smoke detectors over 4 floors in an emergency situation. 
I agree 2-wire are easier for small installations but they just don't scale well unless you get into the digital stuff where each device has a unique address and those just aren't practical for residential situations.