Every summer, restaurant owners call HVAC companies complaining their kitchen is too hot. The HVAC company checks the rooftop unit, maybe adds some refrigerant, and hands over a $500 bill. The kitchen is still hot.
The problem usually isn't the AC. It's the air balance between your exhaust hood and makeup air system.
Why Kitchens Get So Hot
Commercial kitchens generate massive amounts of heat — fryers at 375°F, ovens at 450°F, charbroilers over 600°F, steam tables, dishwashers. The exhaust hood is supposed to capture that heat and pull it out through the roof.
But the hood can only capture heat that rises into it. If the airflow pattern is disrupted — by a broken makeup air unit, an unbalanced supply, or turbulence from a poorly positioned air curtain — the heat escapes into the kitchen instead of going up the hood.
The Three Most Common Causes
1. Makeup Air Unit Blowing Directly at the Hood If the MAU supply air is aimed at the hood face or cooking surface, it disrupts the natural thermal plume rising from the cooking equipment. The hot air and smoke scatter instead of being captured. The heat stays in the kitchen.
Fix: Adjust MAU discharge direction, reduce velocity, or reposition supply diffusers.
2. Too Much Supply Air (Positive Pressure) When the MAU supplies more air than the exhaust removes, the kitchen goes positive. Hot kitchen air can't flow into the exhaust — it pushes outward into the dining room and recirculates in the kitchen. The hood captures less.
Fix: Reduce MAU fan speed or open exhaust dampers to restore proper 80% supply-to-exhaust ratio.
3. Exhaust Not Pulling Enough Air The exhaust fan may be running but not moving enough air — worn belts, dirty fan wheel, or dampers partially closed. The hood looks like it's working but it's only pulling 60-70% of design CFM.
Fix: Exhaust fan service — belt replacement, fan cleaning, damper adjustment. Then rebalance the system.
How to Tell If It's an Air Balance Problem
- The kitchen is hot but the dining room is comfortable (or smells like the kitchen)
- The hood is running but you can see heat haze or light smoke escaping
- The HVAC company says your AC is working fine
- Adding more AC doesn't help
- The problem is worse during peak cooking hours
- Staff standing directly under the hood are the hottest
The Solution Is a One-Time Air Balance
A qualified technician measures your exhaust CFM, supply CFM, face velocity at the hood, and runs a smoke capture test. Then adjusts dampers and fan speeds until the system is balanced. Takes 3-4 hours for a single hood system.
Once balanced, the hood captures the heat, the kitchen temperature drops, and the AC can actually keep up because it's not fighting thousands of CFM of misrouted hot air.
True Commercial Service provides kitchen air balancing for restaurants across Oklahoma City, OK. If your kitchen is too hot and your HVAC company can't fix it, the problem is probably on the roof — not the AC unit. One visit, one balance, problem solved.
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