Grundfos
World's Largest Circulator Pump Manufacturer — MAGNA3 Modbus Integration for KNX BMS
Grundfos (Bjerringbro, Denmark, founded 1945) is the world's largest circulator pump manufacturer with over 16,000 employees and production in 18 countries. The MAGNA3 intelligent circulator pump is the industry standard for HVAC hydronic systems — variable speed permanent magnet motor, built-in differential pressure sensor, and CIM 150 communication module (Modbus RTU/TCP or BACnet/IP) for BMS integration. KNX building automation systems integrate MAGNA3 pumps via Modbus to monitor pump speed, power consumption, and fault status in real time.
Role in our panels
How we use Grundfos
MAGNA3 pump technology: MAGNA3 (DN25–DN100, 0.25–1.5kW) features a permanent magnet ECM motor (IE5 efficiency class), integrated differential pressure control, and auto-adapt algorithm — automatically adjusts speed to match system demand without manual setpoint changes. The Grundfos EEI (Energy Efficiency Index) for MAGNA3: EEI < 0.20, meeting ErP 2015 Lot 11 requirements. Built-in display shows speed (RPM), power (W), differential pressure (kPa), and operating hours. The MAGNA3 has an RJ45 GENIbus port (Grundfos proprietary) and accepts the CIM 150 add-on module for Modbus TCP/RTU or BACnet/IP communication. CIM 150 Modbus integration: the CIM 150 module inserts into MAGNA3 GENIbus slot (no tools, slide-in). Modbus TCP: MAGNA3 IP address via DHCP or static (set via Grundfos GO app or Modbus register). Port 502. Key holding registers: 1 = pump speed reference (0–100%, write), 3 = actual speed RPM (read), 5 = motor power W (read), 7 = differential pressure kPa (read), 9 = pump head m (read), 11 = pump flow l/h (read, estimated from ΔP and speed curve), 100 = alarm word (bit 0 = motor fault, bit 1 = dry run, bit 2 = blocked rotor). KNX/Modbus gateway (Intesis or MDT): poll CIM 150 every 30 seconds → publish to KNX GAs for BMS visualisation and energy monitoring. Building automation integration: typical HVAC primary circuit: MAGNA3 pump on chiller/boiler primary circuit, CIM 150 Modbus TCP → IN701KNX gateway → KNX GAs: pump power (DPT 12.001, W), pump speed (DPT 5.001, 0–100%), pump fault (DPT 1.001). ETS6 logic: if pump fault GA = 1 → BMS alarm → send alert telegram to visualisation (Gira X1 homeserver). Energy reporting: daily energy Wh accumulator (MAGNA3 CIM 150 register 50 = energy kWh counter) → KNX energy metering cluster → BREEAM/ISO 50001 report. EN 15232-1 Class A: pump speed varies with actual system demand (AUTOADAPT mode) + KNX setpoint adjustment based on zone temperature deviations. Grundfos GO app and commissioning: the Grundfos GO app (iOS/Android, Bluetooth to pump display) allows commissioning engineers to: set operating mode (AUTOADAPT, constant pressure, constant curve), configure setpoints, view alarms, and set Modbus IP address without a laptop. For multi-pump systems (duty/standby, header pumps): Grundfos Multi-Pump Manager (built into MAGNA3 firmware) coordinates pump rotation without separate controller. KNX integration monitors the active/standby pump status via Modbus — which pump is running, hours since last rotation.
Modbus TCP integration via CIM 150 module — pump speed, power, differential pressure, flow, and fault status published to KNX group addresses for HVAC monitoring, energy reporting, and BMS alarm integration.
Used in these project types
Grundfos products
Key components we install
Grundfos MAGNA3 32-60 circulator
DN32 variable speed ECM pump for HVAC, AUTOADAPT pressure control, EEI<0.20
Grundfos CIM 150 Modbus/BACnet module
GENIbus plug-in module adding Modbus TCP/RTU or BACnet/IP to any MAGNA3 pump
Grundfos MAGNA3 25-40 N circulator
DN25 compact ECM pump for residential and small commercial heating circuits
Grundfos CMBE pressure booster
Variable speed domestic water pressure booster with built-in pressure sensor and Modbus option
Grundfos UPM3 circulator
Cost-effective ECM circulator for smaller heating systems, no BMS interface
Grundfos FAQ
Does MAGNA3 need a separate power supply for the CIM 150 Modbus module?
No — the CIM 150 module is powered by the MAGNA3 pump's internal 24V DC bus via the GENIbus connector. No external power supply is required. Simply slide the CIM 150 into the GENIbus slot on the pump head and connect the RJ45 Ethernet cable.
Can one Modbus TCP master poll multiple MAGNA3 pumps?
Yes — each MAGNA3 with CIM 150 has its own IP address on the building LAN. A Modbus TCP master (e.g., Intesis IN701KNX or MDT gateway) polls each pump by IP address separately. Ensure each pump has a unique static IP address configured via the Grundfos GO app or DHCP reservation.
What is AUTOADAPT mode and should it always be used?
AUTOADAPT is Grundfos's automatic differential pressure setpoint algorithm — the pump measures system flow and adjusts setpoint to maintain optimal efficiency without manual tuning. It is suitable for most variable-flow HVAC circuits. For constant-flow circuits (e.g., direct-return systems with fixed-flow pumps), use constant speed mode instead. EN 15232-1 Class A compliance requires variable speed control — AUTOADAPT qualifies.
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