Relay Controllers
RS485 Wiring
Connecting relay controllers to the HPzenAi gateway over an RS485 bus.
RS485 Wiring Video Guide
Tools Required
RS485 wiring uses low-voltage signal cable. No specialist tools are required beyond standard wiring tools.
Tool Checklist
| Preview | Quantity | Item | Details |
|---|---|---|---|
| × 1 | Flat-Head Screwdriver (3 mm) | For tightening RS485 terminal block screws on the controller and gateway | |
| × 1 | Wire Strippers | To prepare twisted-pair cable ends before insertion into terminals | |
| As required | RS485 Shielded Twisted-Pair Cable | 1.0–1.5 mm² 2-core shielded cable — not included, sourced separately | |
| × 1 | 120 Ω Termination Resistor | For bus termination at the last device on runs longer than 10 m | |
| As required | Cable Labels / Markers | To label A and B terminals at each end of the cable run |
Flat-Head Screwdriver (3 mm)
For tightening RS485 terminal block screws on the controller and gateway
Wire Strippers
To prepare twisted-pair cable ends before insertion into terminals
RS485 Shielded Twisted-Pair Cable
1.0–1.5 mm² 2-core shielded cable — not included, sourced separately
120 Ω Termination Resistor
For bus termination at the last device on runs longer than 10 m
Cable Labels / Markers
To label A and B terminals at each end of the cable run
RS485 Terminal Identification
The relay controller has a 2-position RS485 terminal block labelled A and B on the controller PCB or enclosure label. RS485 A is the positive differential line (+); RS485 B is the negative differential line (−). The HPzenAi gateway has an equivalent A and B terminal block on its RS485 port.
Steps
- RS485 A (+) — positive differential signal line; connect to gateway RS485 A.
- RS485 B (−) — negative differential signal line; connect to gateway RS485 B.
- Swapped A/B is the single most common installation error — verify polarity before powering on.
- The RS485 bus carries communication signals only — it does not carry power. Each device requires a separate 12V DC supply.
Wiring a Single Relay Controller to the Gateway
For a single relay controller, wire directly from the gateway RS485 port to the controller RS485 terminal block using a twisted-pair cable.
Steps
- Run a twisted-pair shielded cable from the gateway RS485 terminal to the relay controller RS485 terminal.
- Connect the yellow wire (or A-labelled core) to RS485 A on both the gateway and the controller.
- Connect the green wire (or B-labelled core) to RS485 B on both the gateway and the controller.
- If the cable has a shield drain wire, connect it to the ground terminal at the gateway end only — do not connect the shield at the device end.
- Tighten all terminal screws firmly.
- For a single device on a short cable run (under 10 m), a termination resistor is optional but recommended.
Wiring Multiple Controllers on One RS485 Bus
Multiple relay controllers (and other RS485 devices) can share a single RS485 bus connected to the gateway. Wire them in a daisy-chain topology — avoid star or branch wiring configurations.
Steps
- Connect the gateway RS485 A and B terminals to the first device on the bus.
- From the first device's RS485 A terminal, run a cable to the RS485 A terminal of the second device.
- Repeat for RS485 B — all A terminals daisy-chained together, all B terminals daisy-chained together.
- Continue the daisy-chain to each additional device in sequence.
- Do not create star or branch connections — all devices must be in a single chain from gateway to last device.
- Assign each device a unique RS485 address (1–32) — devices sharing an address will conflict and neither will be detected.
- Fit a 120 Ω termination resistor between the A and B terminals of the last device on the bus.
- Maximum cable run: 1,200 m at 9600 baud with appropriate cable.
Setting the RS485 Device Address
Each relay controller on the RS485 bus must have a unique Modbus address. The address is set via the physical DIP switches or jumpers on the controller PCB, or via the app during commissioning.
Steps
- The factory default RS485 address is 1.
- For the first controller, leave the address at 1 if it is the only device on the bus.
- For additional controllers, set each to a unique address — 1, 2, 3, etc.
- To change the address via DIP switches: power off the controller, set the DIP switch combination for the desired address (refer to the address table printed inside the enclosure lid), then power on.
- To change the address via the app: go to Device Settings → RS485 → Device Address — this requires the controller to already be detected at its current address.
- After changing the address, perform an RS485 scan from the gateway to re-detect the device at its new address.
RS485 Scan and Device Discovery
After wiring, perform an RS485 scan from the HPzenAi app to detect the relay controller on the bus.
Steps
- Ensure the relay controller is powered on and the RS485 cable is connected to the gateway.
- Open the HPzenAi app → Main Menu → Gateway → select your gateway.
- Tap RS485 Scan.
- Wait 30–60 seconds for the scan to complete.
- The relay controller will appear in the detected devices list.
- Tap Link to add the controller to your gateway and account.
- If the controller does not appear, verify A/B polarity, confirm the controller has 12V power, and check for duplicate addresses.
Guided Help Center
Open the HPzenAi app.
RS485 Wiring Checklist
Steps
- RS485 A connected to A and RS485 B connected to B at all devices — not swapped.
- Daisy-chain topology used — no star or branch connections.
- Each relay controller has a unique address (no duplicates).
- 120 Ω termination resistor fitted between A and B at the last device on the bus.
- Cable shield connected to ground at the gateway end only.
- RS485 cable routed separately from 230V mains power cables.
- All terminal screws firmly tightened.
- RS485 scan completed from the app — all controllers detected and linked.
Important RS485 Wiring Notes
Steps
- RS485 cables must not share conduit or trunking with 230V AC mains cables — route them separately to avoid electromagnetic interference.
- Maximum RS485 bus length is 1,200 m at 9600 baud — longer runs require a lower baud rate or RS485 repeater.
- Use shielded twisted-pair cable for all RS485 runs — unshielded cable is susceptible to interference, especially near inverters or variable-frequency drives.
- A missing or incorrectly placed termination resistor is a common cause of bus instability when multiple devices are connected.