Will your system work with a 24VAC thermostat?
Answer four questions about the wires on your old thermostat base. This page returns the OWON models that fit your system, tells you whether you need the SWB511 C-Wire Adapter, or explains why the system is not compatible.
1. Is this a high-voltage system?
Look at the back of your old thermostat. If you see 110V, 120V or 240V printed on it, or thick wires joined with wire nuts, the system is line voltage and is not compatible.
2. Is a wire connected to the C terminal?
The thermostat needs 24VAC power. Look for a wire on the terminal marked C, sometimes labelled COM.
3. Select every terminal that has a wire
Tick each label on your old thermostat base that has a wire attached. Leave the rest empty.
Select at least one terminal.
You will also need the SWB511 C-Wire Adapter. It powers the thermostat from Y/Y1, G and R (or Rc or Rh) and needs no new wires in the wall.
Send a photo of your old wiring to info@owon-iot.com and our engineers will confirm the model and the adapter requirement.
Decision logic follows the terminal rules in our Quick Start Guides. When the wiring does not match a known pattern, the check asks you to contact us instead of guessing.
Models this check can recommend
Depending on your wiring, the check returns one of these four thermostats. All of them run on 24VAC, support 2H/2C conventional and 4H/2C heat pump systems, and work with the SWB511 C-Wire Adapter when there is no C wire.
PCT533C-W-TY
4.3-inch 480x800 screen, no sensors, no humidity control
View PCT533C-W-TY →PCT5231-W-TY
9 remote sensors, dual fuel, LED segment display
View PCT5231-W-TY →PCT513
Up to 16 remote sensors, 4.3-inch touchscreen
View PCT513 →PCT533-W-TY
6 remote sensors, ACC1/ACC2 humidity control, 4.3-inch 480x800 screen
View PCT533-W-TY →What each result means
The check ends in one of five outcomes. This table is the same logic the tool runs, written out so you can follow it yourself.
| Outcome | When it happens |
|---|---|
| Compatible | You have R (or Rc/Rh), Y/Y1 and G, and a C wire or a valid adapter path. |
| Compatible with adapter | No C wire, but Y/Y1 and G are present, so the SWB511 can power the thermostat. |
| Humidity control | A Hum, Dehum or ACC wire is present. Only the PCT533-W-TY has ACC1 and ACC2 terminals, in 1-wire or 2-wire configuration. |
| Not compatible | Line voltage (110V/120V/240V or wire nuts), or wiring that uses water, multi-speed, 3-stage or other terminals this range does not support. |
| Needs a photo | The wiring is unusual - for example two conflicting O/B labels, three R wires, or an AUX wire combined with W. We confirm manually rather than guess. |
Systems this range does not support
- • 2-wire systems
- • Fan coil units
- • Multi-speed fans
- • ERV / HRV / VRV systems
- • Baseboard heaters
- • 3-stage conventional heating
- • Systems running at 120V or higher
- • Thick wires joined with wire nuts
Questions about the check
What does this compatibility check actually test?
It compares the wires on your old thermostat base with the terminals our thermostats need: R/Rc/Rh for power, C for common, Y/Y1 and Y2 for cooling, W/W1 and W2 for heating, G for the fan, and O/B for a heat pump changeover valve. If the wiring cannot supply power or cannot drive one of those functions, the system is not compatible.
Do I need a C wire?
The thermostat needs 24VAC power. With a C wire at the wall you connect it directly. Without one, you need the SWB511 C-Wire Adapter and at least Y/Y1, G and R (or Rc or Rh). If you also have W, the adapter keeps your second heating stage.
Why does a heat pump with auxiliary heat need an extra check?
A heat pump with auxiliary or emergency heat uses W2/E as a second heat stage. Some older systems label that wire AUX or E instead, and the mapping differs by model. When the check cannot confirm the mapping, it asks you to contact us rather than guess.
Which systems are never compatible?
Systems running at 120V or higher, systems with thick wires joined by wire nuts, 2-wire systems, fan coil units, multi-speed fans, ERV/HRV/VRV systems, baseboard heaters, 3-stage conventional heating, and thermostats wired with humidity, ACC or auxiliary terminals we do not support.
What happens after the check tells me which model fits?
Each recommended model links to its product page with the full terminal map and datasheet. If you send a photo of your old wiring, our engineers will confirm the model and the adapter requirement before you order.