How do I wire the STC-1000 heating and cooling relays for a dual-stage temperature control chamber?

A dual-stage temperature control setup uses the STC-1000 to manage both a cooling source (refrigerator compressor) and a heating source (heat belt, heat lamp, or ceramic heater) to maintain an exact target temperature inside a chamber.

Terminal Layout Breakdown

The STC-1000 uses eight rear screw terminals:

• 1 & 2: Power Supply input (110V or 220V AC depending on unit rating).
• 3 & 4: NTC Temperature Sensor Probe (non-polarized).
• 5 & 6: Heating Relay output (normally open dry contact).
• 7 & 8: Cooling Relay output (normally open dry contact).

Wiring Logic & Schema

Because Terminals 5/6 and 7/8 are dry switches (unpowered contacts), they do not supply electricity on their own. You must feed incoming Live (Line) power into one side of each relay, then route the switched output from the other side to your respective heating and cooling loads.

                  ┌──────────────────────┐
                  │   STC-1000 REAR      │
                  │                      │
   [Line AC] ─────┤ (1) Power (L)        │
   [Neutral] ─────┤ (2) Power (N)        │
                  │                      │
    [Sensor] ─────┤ (3) Sensor           │
    [Sensor] ─────┤ (4) Sensor           │
                  │                      │
   [Line AC] ─────┤ (5) Heat Relay In    │
 [Heater L]  ─────┤ (6) Heat Relay Out   │
                  │                      │
   [Line AC] ─────┤ (7) Cool Relay In    │
  [Compress] ─────┤ (8) Cool Relay Out   │
                  └──────────────────────┘

  * Note: All Neutral wires (Power, Heater, Cooling Load) 
    are tied together on the main AC Neutral Line.

Step-by-Step Wiring Instructions

1

Connect Main Power Supply

Disconnect power source before handling mains voltage

Run main Live and Neutral wires from your mains supply line directly to Terminal 1 (Live) and Terminal 2 (Neutral) to power the STC-1000 display board.

2

Connect Temperature Probe

Attach the two wires of the NTC thermistor probe to Terminals 3 and 4. (Polarity does not matter for NTC sensors).

3

Create Live Jumper Bridge

Bridge a wire jumper from Terminal 1 (Live) to Terminal 5 (Heating Relay In) and another jumper to Terminal 7 (Cooling Relay In). This provides incoming line voltage to both relay switches.

4

Wire Heating & Cooling Outlets / Loads

• Connect Terminal 6 (Heating Relay Out) directly to the Live terminal of your heating device (or heating outlet socket).
• Connect Terminal 8 (Cooling Relay Out) directly to the Live terminal of your refrigerator compressor wire (or cooling outlet socket).

5

Tie All Neutrals Together

Connect the Neutral wires from both your heating load and cooling load back to the main incoming AC Neutral supply line (Terminal 2).

Recommended Dual-Stage Programming

Set the parameters so the heater and cooler do not fight each other:

• Cooling Trigger: Cooling turns ON when cabinet reaches F1+F2=21.0∘C, and shuts off when back at 20.0∘C.
• Heating Trigger: Heating turns ON when cabinet drops to F1−F2=19.0∘C, and shuts off when back at 20.0∘C.