Need to verify Elk M1 kaypad and thermostat wiring


Active Member
I am building a new home and want to make sure I specify the correct wiring before I install an Elk M1 system.

From the installation manual it looks like the keypads require 4 wires, however elk recommends cat5.

Keypads have a removable wiring plug for connecting to the M1
4-wire data bus. CAT5 or CAT6 eight (8) conductor cable is recommended for all Data Bus cables. The extra wires provide
data return paths.

... whatever that means?

Also according to the ELK-M1XSP Serial Expander, Lighting/Thermostat Interface manual it looks like if I want to connect any thermostats I should be fine with 4 wires to each (for the supported thermostats (RS-232 or RS-485)?) however I am not 100% sure about this. Can anyone confirm this?

From the M1XSP Serial Port Expander to the Thermostat, RCS, Aprilaire, or HAI, I suggest you run CAT5. That way you are future proof. In reality you only need 4 wires: two for power and two for data.

If you have multiple thermostats and using a RS-485 data bus, you will need to wire the Thermostats in a daisy chain, thus needing two data conductors returning from a Thermostat run to go to the next Thermostat.

The M1 Installation Manual shows how to run RS-485 data buses. You can download the installation manuals from: ELK Manuals
You want to run more than what you think you would actually need. There are many good threads here about prewiring. In this specific case you could just get by with regular 4 conductor security cable, but what if you want to swap the keypad out later for a touchscreen? May want to consider cat 5's (maybe even 2)and power to keypad locations. Future proof yourself now while you easily can. The extra cost of the wire will easily make up for itself in less aggravation down the road.

I am intimate with my attic and drywall because I did not prewire 15 years ago.