Installation Location: The First Threshold Determining Whether Make-Up Air Works
Choose the wrong location, and fresh air may be directly extracted by the exhaust hood, creating a "short circuit" — the make-up air volume may appear sufficient, but it never actually participates in kitchen air circulation. A reasonable installation location should follow the principle of "supply air path covering the work zone, avoiding short-circuiting with exhaust."
There are two common approaches: installing on an outdoor roof or exterior wall, delivering treated fresh air into the kitchen through ducts; or installing in an adjacent equipment room or corridor to shorten the supply path. Regardless of the method, supply outlets should be arranged in personnel activity zones or to the side and rear of stoves, creating airflow organization from clean zones to contaminated zones and from low-temperature zones to high-temperature zones. Avoid directing supply air straight at exhaust hoods, which causes airflow collision.
Special attention: make-up air outlets should not face gas stoves or open flame areas directly, to avoid airflow disturbance affecting combustion efficiency. Meanwhile, the fresh air unit's intake should be kept away from exhaust outlets and grease discharge points to prevent drawing in oil-laden air and causing secondary contamination.
Foundation and Mounting: Poor Vibration Damping Causes Endless Problems
Host unit installation is the skeleton of the entire system. For outdoor installation, concrete foundations or steel supports should be fabricated, with vibration damping and waterproofing treatments between the support and the roof. For wall mounting, expansion bolts are required, and the unit must be kept level to avoid additional vibration and noise during operation.
Rubber vibration pads or spring isolators should be installed at the unit base to reduce vibration transmission during fan operation. For large units installed on the ground, the concrete foundation should extend about 100mm beyond the unit base on each side, with surface flatness deviation controlled within 3mm per meter. After foundation curing, apply an anti-corrosion coating to extend service life.
For suspended installation, hanger rods must be anchored to cast-in-place concrete floor slabs — never to hollow-core slabs or lightweight steel keels. Hanger rod roots should use double nuts for fixation, and vibration-damping hangers must be installed with damping components in a free state, not pre-compressed.
Water Connections: Details Determine Whether the Unit Can Be Used
Water-cooled fresh air units require stable water supply and drainage conditions. The water system must ensure reasonable slopes for inlet pipes, overflow pipes, and drain pipes, with well-sealed joints to prevent leakage affecting kitchen hygiene.
Inlet pipes should be equipped with Y-type filters and ball valves for easy maintenance. In areas with hard water, a water purifier for filtration and softening is recommended to prevent impurities from clogging the water distribution system and scale from affecting heat exchange efficiency. Drain pipes need a certain slope to drain smoothly to floor drains, avoiding standing water and bacterial growth.
Condensate drain pipes must maintain a slope, typically no less than 1%, sloping toward the drainage point. Back-slope or "U" traps are strictly prohibited. A water seal should be installed at the condensate pan outlet, with seal height meeting the unit's negative pressure operating requirements to prevent condensate from being drawn into the fan or odors from escaping.
Winter freeze protection is easily overlooked. When ambient temperatures drop below 0°C, drain the water tank to prevent pipe cracking. For long-term shutdown, drain the coil and blow dry with compressed air.
Duct Connections: Short, Straight, and Sealed
The unit outlet connects to the kitchen interior through galvanized steel ducts or flexible hoses. Ducts should be as short and straight as possible, minimizing elbows to reduce resistance and ensure smooth air supply. If the supply distance is long, silencers can be added to the duct to control noise.
Flexible connectors must be installed at the junction between ducts and the fresh air unit, with a length of 150mm to 250mm, properly tensioned without twisting, and never used as load-bearing points — duct weight must not be borne by the equipment but by separate supports. Duct connections should be well sealed to prevent air leakage affecting supply performance.
Adjustable louver outlets are recommended for supply air, allowing airflow direction adjustment. If the kitchen has multiple partitions, multiple supply outlets can be installed to form organized make-up air flow.
Commissioning and Verification: Installation Is Not the Same as Being Ready to Use
Installation completion is not the end point — actual operation is needed to verify performance. During commissioning, first check whether the fan rotation direction is correct, whether the water pump supplies water normally, and whether the cooling pad or heat exchanger is evenly wetted. After operation, measure supply outlet air velocity and noise to confirm whether make-up air performance meets expectations.
The method for verifying negative pressure resolution is straightforward: close all doors and windows, turn on the exhaust system, and observe whether there is still obvious backdraft noise at door gaps. Light a cigarette or use a smoke generator to observe whether smoke is smoothly drawn into the exhaust hood. If door gap backdraft is obvious, make-up air volume is still insufficient — increase the fresh air unit's supply volume or add more supply outlets.
If conditions permit, the water-cooled fresh air unit can be interlocked with the exhaust fan, automatically supplying make-up air when exhaust is running, avoiding energy waste.
Common Issues and Maintenance
If the fresh air unit emits odors, it is usually caused by the water tank or cooling pad not being cleaned for a long time. Cleaning the cooling pad every two weeks and regularly replacing the water source is recommended. Excessive fan noise may be due to uneven installation or aged vibration pads.
Filters should be cleaned regularly. If airflow decreases, it is generally due to excessive dust accumulation in the filter. One month after operation, check whether suspension fastening bolts are loose. After two to three years of operation, conduct comprehensive maintenance: remove scale from heat exchanger tubes, clean fins, and lubricate fan motor bearings.
Installing a water-cooled fresh air unit is not as simple as "finding a wall opening and hanging it up." From location selection to mounting, from water connections to ductwork, every step affects the final result. Do the installation solidly, and the equipment can truly deliver the value of make-up air and cooling.