MHI Hydrolution EZY R290 (RC-HY40-W / NIBE SMO 40)

Use cases

• Cloud monitoring of all key R290 sensors: outdoor, supply/return, DHW, flow, 3-phase currents, condenser-out temperature, and degree minutes.
• Daily / weekly SCOP and SPF reporting using the heat-meter split between hot water (44306) and heating (44308) divided by 3-phase electrical consumption.
• Real-time alerting on defrost-fail (alarm 28), high-pressure (154/162/163), and sensor faults (100/102) per outdoor unit.
• Smart-grid demand response by writing SG Ready function codes (48043) during PV surplus or low spot-price windows.
• Remote tuning of heating curve and offset (47007 / 47011 / 47012) per climate system without a site visit.
• Boost or block hot-water production (47041) on demand during a high-spot-price hour.
• Multi-site fleet rollout: same template covers all MHI Hydrolution units AND NIBE F-series, F1245, F1255, SMO 40, VVM 320 etc.

Installation

1. 1Procure the MODBUS40M accessory (Mitsubishi Heavy Industries part MODBUS40M, equivalent to NIBE part 067 144). List price €340 - 550 depending on market.
2. 2Power off the RC-HY40-W. Mount the MODBUS40M board inside the controller enclosure and wire X1 (12V / A / B / GND) to AA3-X4 pins 9 / 10 / 11 / 12 per the NIBE MODBUS 40 installer manual.
3. 3Power the unit back on, then in menu 5.2 "System settings" mark MODBUS 40 as ON. Verify in menu 3.1 that "Modbus 40 vX" is shown - vX should be 10 or higher.
4. 4Wire MODBUS40M-X2 (GND / B / A) to the RS-485 RTU port of the ModbusCloud gateway with a shielded twisted pair (ground the shield at the master side only).
5. 5Configure the ModbusCloud gateway: RTU 9600 baud, 8 data bits, no parity, 1 stop bit (8N1). Slave ID 1 (or whatever you set in menu 5.3.11 if firmware permits).
6. 6Set the master polling: inter-poll delay >= 1000 ms, response timeout 2100 ms. For high-frequency polling of up to 20 16-bit registers, create a LOG.SET file with NIBE ModbusManager and load via USB at menu 7.1.
7. 7Optional but recommended: verify word-swap consistency between pump menu 5.3.11 and gateway. This template uses CDAB (word-swap ON) for all 32-bit registers.
8. 8Import this template in the ModbusCloud portal, link to your gateway, and verify with a live read on register 43001 (software version) and register 40004 (outdoor temperature).

Things to watch for

01

Writes are accepted but the heat pump does not change behavior. Why?

Most likely you are using FC06 Write Single Register. The MODBUS40M does NOT support FC06 - it silently acknowledges but ignores the command. Switch your gateway to FC16 Write Multiple Registers with register count = 1 (or 2 for 32-bit). This is documented in NIBE FAQ MODBUS 40 (TIF 1321-2).

02

32-bit values (currents, energy meters, 32-bit degree minutes) read as absurdly large negative or positive numbers. What is wrong?

Word swap mismatch between controller and gateway. The MODBUS40M default (with word-swap on) places the high word in the low address (CDAB). If your gateway expects ABCD, toggle the controller in pump menu 5.3.11 or flip the gateway endianness. This template ships with byte_order=CDAB for all 32-bit registers; change to ABCD if your unit has word-swap disabled.

03

I want to change the slave address (multiple units on one RS-485 bus) but menu 5.3.11 is missing. Why?

Configurable slave address (1-247) requires MODBUS 40 accessory firmware version 10 or later AND heat-pump firmware version 5539 or later. Check menu 3.1 for the MODBUS 40 version. If older, slave stays fixed at 0x01 and you can only have one MODBUS40M per RS-485 segment.

04

I do not see any data even though the gateway connects. What is wrong?

Verify three things: (1) the MODBUS40M physical card is installed inside the RC-HY40-W and wired AA9-X1 to AA3-X4 pins 9-12; (2) it is activated in menu 5.2 System Settings (you should see "Modbus 40 vX" in menu 3.1); (3) timing - set master timeout to 2100 ms and inter-poll delay >= 1000 ms (only LOG.SET registers respond within 500 ms).

05

My RC-HY40-W has a touchscreen and Wi-Fi setup - is this template still right?

No. If your unit has a 4.3 inch colour touchscreen it is the newer SMO S40 (S-series), which uses native Modbus TCP on port 502 with a completely different register map (M12676EN). Use the dedicated NIBE S-Series template instead. The RC-HY40-W in current MHI Hydrolution EZY R290 shipments (as of 2026-05-20) has a monochrome LCD with jog wheel.

06

Heat-meter register 43230 reads 0 or nonsense. Why?

Register 43230 (combined heat meter) was deprecated in pump firmware v4798. Use the split registers 44306 (heat meter from HW compressor EP14) and 44308 (heat meter from heat compressor EP14) - they are in kWh with scale 0.1.

Registers (1000)

1000 read / 214 write