How do I retrofit a digital temperature controller like the STC-1000 into a manual refrigerator?

Retrofitting a digital controller like the STC-1000 into a manual refrigerator bypasses the mechanical capillary thermostat, giving you exact degree control and tighter temperature swings.

Wiring Schema & Logic

The STC-1000 acts as a temperature-controlled single-pole switch for your cooling system.

• Terminals 1 & 2: Power supply to the STC-1000 unit (110V or 220V AC depending on model).
• Terminals 3 & 4: NTC Temperature Probe connections.
• Terminals 5 & 6: Heating Relay (used for fermentation chambers, keezers, or defrost heaters; leave disconnected for simple fridge cooling).
• Terminals 7 & 8: Cooling Relay (dry contacts wired in series with the compressor power line).

Step-by-Step Retrofit Guide

1

Disconnect Power & Locate Wiring

Safety prerequisite – electrical shock risk

Unplug the refrigerator. Remove the thermostat cover inside the fresh food compartment to access the old mechanical thermostat wires.

2

Identify Live, Neutral & Switched Wires

Identify the main incoming Live (Phase) wire, Switched Live wire going down to the compressor relay, and Neutral.

Disconnect the old mechanical thermostat completely.

3

Route NTC Probe into Fridge

Run the STC-1000 NTC probe inside the cabinet through the drain hole at the back or along the door seal liner. Position the probe tip in the middle of the cabinet suspended in air, away from walls or evaporator coils.

4

Wire Controller Power & Cooling Loop

Connect incoming Live and Neutral to Terminals 1 and 2.

Bridge a jumper wire from Live (Terminal 1) to Terminal 7 (Cooling Relay input). Connect the Switched Live wire going to the compressor to Terminal 8 (Cooling Relay output).

5

Mount Unit & Program Parameters

Mount the STC-1000 in a project box or custom cutout on the exterior wall. Plug the fridge back in and configure settings.

Essential STC-1000 Programming Settings

Hold the “S” button for 3 seconds to access the configuration menu: