Technical Guide for Group Control Installation of DC FFU Fan Filter Unit

This is a professional and comprehensive technical guide for the installation of DC FFU fan filter unit group control. This guide will systematically explain the key technical points of the entire process from early planning to final debugging, aiming to ensure the successful installation and stable and efficient operation of a large-scale DC FFU group control system.
Technical Guide for Installation of DC FFU Group Control System

This stage is the cornerstone of success, determining the efficiency and quality of installation work.

•  On site survey and review
•  Ceiling Grid System: Accurately measure the flatness, levelness, strength, and size of the ceiling keel. Ensure that it can withstand the weight of all FFUs without deformation. The installation baseline must be accurate.
•  Plenum: Check the airtightness of the Plenum above the suspended ceiling. All wall panel joints and through wall holes must be strictly sealed with sealant to ensure no leakage, which is the key to ensuring room pressure difference and airflow organization.
•  Pipeline reservation: Confirm that the power cable tray and communication cable tray have been laid in place according to the design, the path is reasonable, and the reserved length is sufficient.
•  Preparation of technical documents
•  FFU point layout diagram: Clearly define the installation position of each FFU.
•  System wiring diagram: including strong current supply circuit diagram and weak current communication network topology diagram.
•  Address Planning Table: Each FFU is pre planned and assigned a unique address code (Address ID), usually compiled according to regional and row column rules for later management and positioning.
•  Control System IP Planning: If Ethernet communication is used, it is necessary to plan the IP addresses of the main control computer, gateway, and switch.
•  Material and tool preparation
•  FFU units: Enter the site in batches according to the installation progress and store in a clean and dry environment. It is strictly prohibited to remove the filter protective film.
•  Cables: Prepare sufficient power cords (RVVP), shielded twisted pair cables (commonly used for RS-485 bus) or Ethernet cables, power hoses, cable trays, etc.
• Special tools: multimeter, anemometer, differential pressure gauge, portable debugging terminal (if available), laptop (including debugging software).
•  Personnel training and technical briefing
•  Provide unified training to all installation and debugging personnel, clarifying the installation process, wiring standards, address setting methods, and precautions.
• Implementation of "Model Guide": Before formal installation, select a typical area (such as 4 FFUs) for sample installation, invite all parties to inspect and confirm the standards, and then proceed with large-scale construction based on this.

At this stage, it is necessary to strictly follow the procedures and pay attention to details and craftsmanship.

•  Installation of FFU body
• Handle with care: Avoid any collision or compression, especially the high-efficiency filter at the bottom.
• Positioning and sealing: Place the FFU smoothly into the ceiling grid, adjust the sealing strips or fixtures around it to ensure a tight and even fit with the ceiling frame, without gaps, and prevent air leakage. Check the direction of FF air outlet.
• Finished product protection: After installation, it can be covered with plastic film to prevent contamination during subsequent operations.
•  Electrical wiring, safety first: All wiring operations must be carried out in a power-off state.
• Strong current wiring: Connect the live wire (L), neutral wire (N), and ground wire (PE) correctly to the power terminal of the FFU according to the wiring diagram. It is recommended to use a hand in hand (Daisy Chain) power supply, which means that the main line is led out from the main power supply and multiple FFUs are connected in parallel to save wires and facilitate management. Note that the load of a single circuit should not exceed the capacity of the circuit breaker.
•  Weak current communication wiring: This is the core of group control. Shielded twisted pair cables (such as RVSP 2 1.0) must be used.
• Strictly distinguish polarity: The "A+" and "B -" (or "D+"/"D -") of the RS-485 bus must be unified throughout the entire line, and reversing them will result in communication failure. It is recommended to use uniformly colored lines throughout the entire line to distinguish between positive and negative.
•  Bus topology: Daisy Chain structure is used to connect all FFUs in series. Star or Tree connections are strictly prohibited, otherwise signal reflection may occur, leading to unstable communication.
• Terminal Resistance: On the communication terminals of the two FFUs at the farthest end of the entire RS-485 bus network, a 120 Ω terminal resistance needs to be enabled by dialing a code to eliminate signal reflection.
•  Shielding layer single point grounding: The shielding layer of the communication line should be grounded at a single point at the control system end to avoid the formation of a ground loop and the introduction of interference.
•  Address setting: According to the pre planned "Address Planning Table", use the dip switch or dedicated setting tool on the FFU controller to set a unique address code for each FFU. After setting, it is necessary to record the correspondence between its physical location and address.

This stage is crucial to ensure that the system operates according to its designed functionality.

•  Preliminary power on inspection: After a comprehensive inspection of the circuit, divide the power supply into zones/circuits. Manually start each FFU locally and confirm that the fan rotates correctly, runs smoothly, and has no abnormal noise or vibration.
•  Construction and testing of communication network, launch central control software, and scan the network. Check if each FFU can be successfully identified in the software. For unrecognized units, check their address, wiring, and terminal resistance settings, record the number of FFUs in the network to ensure consistency with the actual installation quantity.
• System function debugging
•  Single point control: Perform separate start stop and speed control operations on each FFU through software to confirm that the control command response is normal.
•  Group control: Group FFUs by region for group start stop and unified speed regulation.
•  Debugging of Automatic Control Strategy:
•  Constant air volume control: Set the target air volume value, and the system automatically adjusts the FFU speed to maintain a constant air volume.
• Fixed static pressure control: Connect the static pressure sensor, set the target static pressure value, and the system automatically adjusts the total air volume to maintain a constant static pressure.
•  Integration with BMS/BAS: Test whether the signal interaction between the system and the building management system (such as start stop signals, fault alarm signals) is normal.
•  Performance testing and acceptance
• Wind speed uniformity test: Use an anemometer to measure the wind speed of each FFU, and fine tune the system to make all FFU wind speeds reach the design value (such as
• 0.45m/s ± 0.1m/s) to ensure uniform wind speed throughout the entire area.
• Room pressure gradient adjustment: In conjunction with the fresh air unit (MAU), adjust the pressure gradient of each room to meet the design requirements.
•  Alarm function test: Simulate filter blockage, communication interruption, motor failure, etc., to confirm that the system can accurately trigger alarms such as sound, light, and text messages.
•  Document Handover: Provide a complete "FFU Address Correspondence Table", "Control System Operation Manual", "As Built Drawings", and "Debugging Report".

•  Planning stage: Detailed address planning and cable path planning to avoid address conflicts and difficulties in later search.
•  Wiring stage: The main reasons for communication failure or instability are consistent polarity of communication lines, correct bus topology, and enabled terminal resistance
•  Debugging phase: Verify each unit and debug the sequence from a single point to the system, ensuring no omissions and early detection of problems.
•  Full process: document records (address table, wiring changes), leaving the only basis for future maintenance.
• Finally, it should be emphasized that the installation of DC FFU group control is a system engineering that combines multiple specialties such as electricity, wind power, and control. Strict processes, unified standards, clear documentation, and a attention to detail attitude are the key to project success. It is recommended to have an experienced professional team implement it.