What do “NO” and “NC” mean on the relay module?
On the Snugr relay module, the terminals COM / NO / NC are a dry contact (a controlled “switch”) that Snugr opens or closes depending on the heating demand.
-
COM (Common): the common relay terminal.
-
NO (Normally Open): at rest the contact is open (COM and NO are not connected). It closes when Snugr calls for heat.
-
NC (Normally Closed): at rest the contact is closed (COM and NC are connected). It opens when Snugr stops the demand (or the opposite depending on usage).
The relay module is permanently powered by 230 VAC and receives from the Snugr gateway the command to open/close the relay according to regulation (heat / no heat).
Modules with 2 relays (R1 and R2)
Some modules (e.g., for a fan heater) may have 1 or 2 relays (R1 and R2).
If your module has 2 relays, they must be linked to the same room in Snugr and will be controlled at the same time.
How to choose between NO and NC
-
Connect one of the two control wires (dry-contact input / thermostat input of your device) to COM.
-
For the second wire, choose based on how your device behaves when the two wires are not bridged (not connected together):
Option A — Your device does not heat when the wires are not bridged
Use NO
-
At rest: COM–NO open → no heat
-
When Snugr calls for heat: COM–NO closes → heat
Option B — Your device heats when the wires are not bridged
Use NC
-
At rest: COM–NC closed → heat
-
When Snugr needs to stop heating: COM–NC opens → stop
Safety note
The module is powered by 230 VAC. Switch off power before wiring. If unsure, use a qualified installer/electrician.