RS485 Wiring Video Guide
HPzenAi Relay Controller — RS485 Bus Wiring to Gateway
Video coming soon
Walkthrough video will be added here
Tools Required
RS485 wiring uses low-voltage signal cable. No specialist tools are required beyond standard wiring tools.
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.
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- 1RS485 A (+) — positive differential signal line; connect to gateway RS485 A.
- 2RS485 B (−) — negative differential signal line; connect to gateway RS485 B.
- 3Swapped A/B is the single most common installation error — verify polarity before powering on.
- 4The 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.
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- 1Run a twisted-pair shielded cable from the gateway RS485 terminal to the relay controller RS485 terminal.
- 2Connect the yellow wire (or A-labelled core) to RS485 A on both the gateway and the controller.
- 3Connect the green wire (or B-labelled core) to RS485 B on both the gateway and the controller.
- 4If 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.
- 5Tighten all terminal screws firmly.
- 6For 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.
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- 1Connect the gateway RS485 A and B terminals to the first device on the bus.
- 2From the first device's RS485 A terminal, run a cable to the RS485 A terminal of the second device.
- 3Repeat for RS485 B — all A terminals daisy-chained together, all B terminals daisy-chained together.
- 4Continue the daisy-chain to each additional device in sequence.
- 5Do not create star or branch connections — all devices must be in a single chain from gateway to last device.
- 6Assign each device a unique RS485 address (1–32) — devices sharing an address will conflict and neither will be detected.
- 7Fit a 120 Ω termination resistor between the A and B terminals of the last device on the bus.
- 8Maximum 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.
- 1The factory default RS485 address is 1.
- 2For the first controller, leave the address at 1 if it is the only device on the bus.
- 3For additional controllers, set each to a unique address — 1, 2, 3, etc.
- 4To 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.
- 5To 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.
- 6After 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.
- 1Ensure the relay controller is powered on and the RS485 cable is connected to the gateway.
- 2Open the HPzenAi app → Main Menu → Gateway → select your gateway.
- 3Tap RS485 Scan.
- 4Wait 30–60 seconds for the scan to complete.
- 5The relay controller will appear in the detected devices list.
- 6Tap Link to add the controller to your gateway and account.
- 7If 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
- 1RS485 A connected to A and RS485 B connected to B at all devices — not swapped.
- 2Daisy-chain topology used — no star or branch connections.
- 3Each relay controller has a unique address (no duplicates).
- 4120 Ω termination resistor fitted between A and B at the last device on the bus.
- 5Cable shield connected to ground at the gateway end only.
- 6RS485 cable routed separately from 230V mains power cables.
- 7All terminal screws firmly tightened.
- 8RS485 scan completed from the app — all controllers detected and linked.
Important RS485 Wiring Notes
- 1RS485 cables must not share conduit or trunking with 230V AC mains cables — route them separately to avoid electromagnetic interference.
- 2Maximum RS485 bus length is 1,200 m at 9600 baud — longer runs require a lower baud rate or RS485 repeater.
- 3Use shielded twisted-pair cable for all RS485 runs — unshielded cable is susceptible to interference, especially near inverters or variable-frequency drives.
- 4A missing or incorrectly placed termination resistor is a common cause of bus instability when multiple devices are connected.