Cooling a Commercial Kitchen in Phoenix
The hardest conditioned space in any Valley business, and the one where the HVAC problems are usually not the HVAC equipment.
Commercial kitchen comfort in Phoenix depends primarily on make-up air and exhaust balance rather than cooling capacity. Cooking equipment produces enormous heat, hoods remove large air volumes that must be replaced with tempered air, and building pressure problems make both the kitchen and the dining room uncomfortable.
Why kitchens are so hard
A commercial kitchen concentrates an extraordinary heat load in a small space: fryers, ranges, griddles, ovens, dish machines, and refrigeration equipment rejecting its own heat into the room.
Then a hood removes a very large volume of air continuously during service, and that air has to be replaced. In Phoenix, the replacement air is 110 degrees.
The result is that kitchen comfort is primarily a ventilation and make-up air problem, not a cooling capacity problem. Adding tonnage to a kitchen with an unbalanced air system does very little and costs a great deal.
Make-up air is the whole game
A make-up air unit supplies outside air to replace what the hood removes, delivered near the hood so it feeds the exhaust rather than crossing the kitchen.
When it is undersized, broken, not interlocked with the hood, or — very commonly — switched off by staff who find it drafty, the building goes negative. Outside air comes in through every available gap including the front door, the dining room stops holding temperature, and the hood loses its ability to capture smoke properly.
The tell is the front door. If it is hard to open or slams shut, the building is negative, and that single observation identifies the problem more reliably than any comfort complaint.
Tempering make-up air in Phoenix
In a temperate climate, untempered make-up air is often acceptable. Here it is not — bringing in 110-degree air untempered makes a kitchen unworkable.
Valley make-up air units therefore generally include evaporative or mechanical cooling. Evaporative works extremely well during our dry months and poorly during monsoon, which is why many restaurants have a make-up air system that performs beautifully in May and struggles in August.
That is a design reality rather than a malfunction, and knowing it prevents chasing a problem that is actually physics. Kitchens that need consistent performance through monsoon need mechanical cooling on the make-up air.
Where the heat is coming from
| Source | Consideration |
|---|---|
| Cooking equipment | The dominant load; hood capture is what controls it |
| Dish machine | Heat and humidity; needs its own exhaust |
| Refrigeration condensers | Reject heat into the kitchen unless remote-mounted |
| Lighting | Less than it used to be with LED |
| Staff | Meaningful in a busy kitchen |
| Infiltration from negative pressure | Often the largest fixable share |
Remote-mounting refrigeration condensers outside is worth mentioning specifically. Walk-in and reach-in condensers rejecting heat inside the kitchen add load to the space they are in, and relocating them outside is a meaningful improvement in a tight kitchen.
Practical improvements
- Verify hood exhaust and make-up air volumes are actually balanced, by measurement
- Confirm the make-up air interlock works with the hood
- Check whether staff have switched the make-up air off, and address why
- Add or repair dish machine exhaust
- Relocate refrigeration condensers outside where feasible
- Add spot cooling at specific stations rather than trying to cool the whole kitchen
- Ensure hood filters are cleaned on schedule — loaded filters reduce capture
- Keep condenser coils on rooftop units clean; kitchen grease loads them faster than normal
Spot cooling
Trying to hold an entire commercial kitchen at a comfortable temperature is usually impractical and always expensive. Spot cooling at work stations is a more realistic approach.
Directed air at the line, at the dish station, and at prep areas gives staff relief where they actually stand, at a fraction of the energy required to condition the whole room.
Ductless mini split heads, properly positioned, work well for this in some kitchens — though placement needs care around grease and cleaning requirements, and they need more frequent coil service in a kitchen environment.
The grease factor
Anything downstream of a commercial kitchen accumulates grease faster than equipment elsewhere. Rooftop unit condenser coils near a kitchen exhaust discharge load with an oily film that ordinary rinsing does not remove.
That film insulates the coil, raises head pressure, and cuts capacity — and it builds up far faster than dust alone.
Chemical coil cleaning on a shorter interval is warranted for units near kitchen exhaust. Quarterly is a reasonable baseline; some installations need it more often.
Frequently asked
Why is our restaurant kitchen so hot even with the A/C running?
Usually a make-up air problem rather than a cooling capacity problem. The hood removes a large volume of air that must be replaced with tempered outside air. When make-up air is undersized, broken, or switched off, 110-degree air infiltrates through every gap.
Why is our dining room uncomfortable when the kitchen is busy?
Negative building pressure. The hood is pulling more air out than the make-up air system is replacing, so outside air is drawn in through the front door and every other gap — directly into the dining room. A door that is hard to open confirms it.
How often do rooftop units near a kitchen exhaust need cleaning?
More often than standard units — quarterly chemical coil cleaning is a reasonable baseline. Grease from kitchen exhaust forms an insulating film that rinsing does not remove, which raises head pressure and cuts capacity.