How to Calculate Kitchen Makeup Air Fan Airflow? How to Disassemble a Water-Cooled Fresh Air Fan? One Article Explains Commercial Kitchen Cooling and Maintenance
Why Is Kitchen Makeup Air Fan Airflow Calculation the First Threshold for Commercial Kitchen Cooling?
Kitchen makeup air fan airflow calculation, in simple terms, is determining the volume flow rate of fresh air supplied into the kitchen based on the total exhaust volume of the kitchen exhaust system, the makeup air ratio, and the space ventilation requirements. In a commercial kitchen air conditioning system, the makeup air volume directly determines whether the kitchen can maintain a slight negative pressure, whether cooking fumes can be effectively exhausted, and whether chefs can achieve a comfortable perceived temperature. If the makeup air volume is insufficient, the exhaust fan will “fight for air,” causing cooking fumes to backflow, incomplete combustion, and even gas alarms; if the makeup air volume is too large, it will cause loss of cooling capacity and a surge in air conditioning energy consumption. Therefore, airflow calculation is not guesswork but a set of engineering algorithms that follow established rules.
There are three commonly used makeup air volume estimation methods in the industry: by the proportion of exhaust volume, by air changes per hour, and by fresh air volume per person. Typically, the makeup air volume for a commercial kitchen should be 70%–85% of the exhaust volume. This ensures both effective fume exhaust and a slight negative pressure in the kitchen, preventing cooking fumes from escaping into the dining area. For equipment such as water-cooled fresh air fans, airflow matching is especially important because their evaporative cooling effect is directly related to the intake air volume, water temperature, and wet-bulb temperature. If the makeup air volume calculation deviates by more than 15%, the supply air temperature of the water-cooled fresh air fan may rise by 3–5°C, greatly reducing the cooling effect.
Step-by-Step Guide to the Core Steps of Kitchen Makeup Air Fan Airflow Calculation
Step 1: Determine the Total Kitchen Exhaust Volume
The total exhaust volume mainly comes from local exhaust of heat source equipment such as stove exhaust hoods, ovens, and steam cabinets. You can estimate it using the length of the exhaust hood and the hood face velocity: Exhaust volume (m³/h) = Hood perimeter (m) × Distance from hood face to stove (m) × Cross-sectional velocity (m/s) × 3600. Generally, the cross-sectional velocity for Chinese wok ranges is 0.25–0.35 m/s, and for Western cooking ranges, 0.15–0.25 m/s. Add up the airflow of all exhaust hoods, then multiply by the simultaneous use coefficient (usually 0.8–0.9) to obtain the total kitchen exhaust volume.
Step 2: Select the Makeup Air Ratio
The makeup air ratio is not a fixed value. If the kitchen has air conditioning and high temperature requirements, the makeup air ratio can be 80%–85% of the exhaust volume; if the kitchen has no air conditioning and relies only on water-cooled fresh air fans for cooling, the makeup air ratio can be increased to 85%–90%, but care must be taken to maintain a slight negative pressure. Makeup air volume (m³/h) = Total exhaust volume (m³/h) × Makeup air ratio. This result is the makeup air fan airflow you need to select.
Step 3: Verify Air Changes per Hour and Fresh Air per Person
In addition to the exhaust ratio, verify using air changes per hour: Kitchen air changes are generally 30–50 times/hour, and makeup air volume (m³/h) = Kitchen volume (m³) × Air changes per hour. Also verify by fresh air volume per person: Makeup air volume (m³/h) = Number of people in kitchen × 30–40 m³/h. Take the maximum of the three to ensure both adequate exhaust and sufficient makeup air. Many commercial kitchen air conditioning manufacturers recommend a makeup air volume slightly greater than 75% of the exhaust volume but not exceeding 90%, which is particularly critical when selecting water-cooled fresh air fans.
Step 4: Match the Water-Cooled Fresh Air Fan
The rated airflow of the water-cooled fresh air fan must cover the calculated makeup air volume and leave a 10%–15% margin. If the calculated makeup air volume is 10,000 m³/h, it is recommended to choose a water-cooled fresh air fan with a rated airflow of 11,000–11,500 m³/h. At the same time, verify whether the fan’s external static pressure is sufficient to overcome the resistance of ducts, elbows, and louvers. If the static pressure is insufficient, the actual airflow will decay by more than 20%, and the kitchen makeup air effect will drop significantly.
How to Disassemble a Water-Cooled Fresh Air Fan? Safety and Steps You Must Read Before Maintenance
How to disassemble a water-cooled fresh air fan is a headache for many kitchen equipment managers and maintenance personnel. This type of equipment integrates an evaporative cooling pad, water tank, water pump, fan, and frame. Improper disassembly can easily damage the cooling pad, tear water pipes, or even cause electrical short circuits. Below, taking the common LCCFAIR water-cooled fresh air fan as an example, we outline a safe disassembly process. Before starting, be sure to turn off the main power, close the water inlet valve, and wait for the water tank to drain. If the equipment is installed in a ceiling or at height, set up stable scaffolding and wear a safety helmet and non-slip gloves.
Disassembly Step 1: Power Off, Water Off, and Drain
First, disconnect the fan power switch and hang a “Do Not Close” warning tag on the distribution box. Close the water inlet valve, open the drain valve, and drain all standing water in the water tank and piping. If the ambient temperature is below 5°C, also blow out the water pipes with compressed air to prevent residual water from freezing and bursting the pipes. This step is the core safety prerequisite for how to disassemble a water-cooled fresh air fan and must never be skipped.
Disassembly Step 2: Remove the Air Inlet Louver and Filter Screen
Use a screwdriver to remove the fixing screws of the air inlet louver and gently take off the louver. Then pull out the primary filter screen. If the filter screen is heavily dusty, clean it with a vacuum cleaner first to prevent dust from falling onto the cooling pad during removal. Some models use a snap-on design, which can be removed by pressing the clips without tools. LCCFAIR water-cooled fresh air fans mostly use modular panels. When disassembling, note the screw positions to avoid confusion during reassembly.
Disassembly Step 3: Separate the Cooling Pad and Water Distribution System
The cooling pad is the core cooling component of a water-cooled fresh air fan and is usually fixed by a frame. First, remove the water distribution pipe above the cooling pad, handling it gently to avoid breaking the PVC pipe. Then loosen the pressure strips on both sides of the cooling pad and slowly pull the cooling pad out along the guide rails. If the cooling pad is stuck to the frame, gently pry it with a plastic scraper; never use metal tools to force it. After removal, stand the cooling pad upright and clean it with a soft brush and neutral detergent. Do not expose it to direct sunlight or squeeze it.
Disassembly Step 4: Remove the Fan and Motor
Disconnect the motor power wires and mark the wire numbers. Remove the connecting bolts between the fan volute and the frame, and move the fan out as a whole. If only the bearings or impeller need maintenance, you can remove only the motor and impeller assembly. Note that the impeller may be heavy and requires two people to work together. After disassembly, check whether the impeller is deformed and whether the bearings make abnormal noises, and clean dust inside the volute. During reassembly, ensure the fan rotation direction is correct; there is usually an arrow mark on the volute.
Disassembly Step 5: Check the Water Tank and Water Pump
The water tank is usually located at the bottom of the equipment. Remove the drain port cover for cleaning. If the water pump needs to be removed, first disconnect the power and water pipes, then unscrew the fixing screws. Check whether the pump impeller is entangled with debris and whether the float valve operates flexibly. How to disassemble a water-cooled fresh air fan ultimately comes down to “cut off the source first, then remove parts, handle gently, and mark clearly.” If you encounter complex models, it is recommended to contact the manufacturer or a professional maintenance team to avoid a small loss causing a big one.
Collaborative Application Scenarios of Commercial Kitchen Air Conditioning and Water-Cooled Fresh Air Fans
In commercial kitchens, air conditioning and water-cooled fresh air fans are often not an either-or choice but work in coordination. Traditional commercial kitchen air conditioning is responsible for lowering indoor temperature, but if the makeup air problem is not solved, the cooling capacity of the air conditioner will be largely drawn away by the exhaust fan, resulting in “the air conditioner not cooling and cooking fumes backflowing.” Water-cooled fresh air fans precisely solve this contradiction: they send outdoor hot air into the kitchen after evaporative cooling through the cooling pad, both supplementing airflow and lowering the supply air temperature, usually 5–10°C lower than the outdoor temperature. This combination of “air conditioning + water-cooled fresh air” has become a standard solution for many restaurant chains and central kitchens.
In actual selection, top ten brand manufacturers will recommend first calculating the kitchen makeup air fan airflow, then choosing the water-cooled fresh air fan model based on the makeup air volume. If the kitchen already has commercial kitchen air conditioning, the makeup air volume can be appropriately reduced to 70%–75% of the exhaust volume to save cooling capacity; if the kitchen has no air conditioning, the makeup air volume should be increased to 85%–90%, and a water-cooled fresh air fan with large airflow and high static pressure should be selected. It is worth noting that the cooling effect of a water-cooled fresh air fan is greatly affected by the wet-bulb temperature. It is effective in dry regions, while in humid regions it needs to be used with dehumidification or air conditioning.
In addition, the installation position of the water-cooled fresh air fan also affects the makeup air effect. The air inlet should be far from exhaust outlets and pollution sources to avoid short-circuiting; the supply air duct should be as short and straight as possible to reduce elbows; if the kitchen ceiling height is limited, ceiling-mounted or wall-mounted models can be selected. Brands such as LCCFAIR provide multiple installation methods and can customize duct routing according to the kitchen layout. Regardless of which manufacturer you choose, airflow calculation should be the basis and maintenance convenience should be considered, so that the equipment can operate stably over the long term.
Common Problems and Pitfall Avoidance Guide
Many kitchens have stepped into pitfalls in makeup air systems: some selected a makeup air fan airflow that was too large, causing positive pressure in the kitchen, with cooking fumes escaping into the dining area through door and window gaps; some selected one that was too small, resulting in poor exhaust and chefs being choked by fumes so much they could not open their eyes. Some water-cooled fresh air fans had their cooling pads damaged after only half a year of use because the power was not cut off, the water was not drained, or a high-pressure water gun was used to directly flush the cooling pad during disassembly. The root of these problems is often not poor equipment quality but inaccurate airflow calculation in the early stage and incorrect maintenance methods later.
Pitfall avoidance rule one: Leave a margin in airflow calculation, but do not exceed 90% of the exhaust volume. Pitfall avoidance rule two: For how to disassemble a water-cooled fresh air fan, be sure to follow the sequence of “power off—water off—drain—remove panels—remove cooling pad—remove fan,” and never use brute force. Pitfall avoidance rule three: Choose brand manufacturers with after-sales support. Brands such as LCCFAIR that provide installation guidance and maintenance training can help you avoid detours. Pitfall avoidance rule four: Regularly clean the cooling pad and water tank. It is recommended to inspect every two weeks and perform deep cleaning quarterly; otherwise, scale and algae will clog the water distribution holes, and the cooling effect will drop sharply.
If you are planning a new kitchen or renovating an old one, you might first calculate the airflow clearly, then choose the right water-cooled fresh air fan, and finally post the disassembly and maintenance process on the wall of the equipment room. Only when the combination of commercial kitchen air conditioning and water-cooled fresh air fans is “calculated accurately, installed correctly, and disassembled steadily” can kitchen cooling, smooth exhaust, and controllable energy consumption truly be achieved.
To obtain more commercial kitchen air conditioning selection tips and water-cooled fresh air fan maintenance manuals, welcome to continue following our industry science column. You can also leave your kitchen area and number of stoves in the comments section, and we will help you make a preliminary estimate of the makeup air volume, so selection no longer relies on guessing.
