By Chad Wiswall, Owner & Lead HVAC Technician, Alabama HVAC License #92244
Most restaurant HVAC failures in Montgomery do not happen because the equipment is bad. They happen because the system was sized for a generic building, not a kitchen that burns 600,000 BTU an hour from line cooking plus a dining room that is suddenly 80 percent full at 7 PM. Commercial HVAC for a restaurant is its own discipline, and the difference between a system designed right and one that was guessed at shows up in the food cost, the labor cost, and the Yelp reviews. This guide is part of our complete guide to HVAC in Central Alabama.
This guide is what I tell restaurant owners in Central Alabama when they call us after their second compressor failure in three years. Chad's AC Direct has been in business since 1993, and we have walked into more than a few kitchens where the original installer treated the building like a strip-mall retail bay. Here is what should have been done.
Kitchen Exhaust and Makeup Air: The Math That Gets Ignored
Every commercial kitchen in Montgomery operates under the International Mechanical Code and Alabama Department of Public Health restaurant regulations. The exhaust hood over a cooking line is sized in CFM based on the appliance lineup beneath it. A 10-foot Type I hood over a 6-burner range, a charbroiler, and a fryer typically pulls 2,400 to 3,200 CFM. That air has to come from somewhere.
If you do not install makeup air to replace what the hood is exhausting, three things happen:
First, the kitchen goes into negative pressure. Doors get hard to open, the dining room HVAC starts pulling air backward through the building, and gas appliances can backdraft. That last one is a carbon monoxide risk, and the Health Department will close you for it.
Second, the dining room air-conditioned air gets sucked into the kitchen and out the hood. You are paying to cool air that is leaving through the roof at the rate of 2,800 CFM. On a Montgomery August day, that is roughly $40 to $80 an hour in wasted energy, every hour the line is running.
Third, the kitchen staff cooks in a hotter, more humid, more uncomfortable environment. Turnover goes up. Productivity goes down.
The fix is a dedicated makeup air unit, usually a direct-fired gas heater for winter and an evaporative cooler or tempered DX unit for summer. In Central Alabama, untempered makeup air works for about 4 months of the year. The other 8 months, you want the makeup air conditioned or at least tempered, or you are dumping 95-degree, 75-percent-humidity air into a kitchen that is already 105 degrees on the line.
A correctly designed makeup-air system delivers 90 to 95 percent of the exhaust CFM (the kitchen should run very slightly negative so cooking smells do not migrate to the dining room). Anything less than 80 percent and you are still creating the negative-pressure problems above.
Dining Room Cooling: Why Manual N Beats a Rule of Thumb
The shorthand rule of thumb you hear is "one ton per 250 square feet for a restaurant." That number is wrong often enough that it has cost Montgomery restaurant owners hundreds of thousands of dollars in oversized and undersized equipment.
The right calculation for any commercial space is an ACCA Manual N (or for very large spaces, Manual Q). Manual N accounts for:
- Occupant heat load. Each adult diner adds roughly 250 BTU/hr sensible heat plus 200 BTU/hr latent (moisture). A 100-seat dining room at full capacity is adding 45,000 BTU/hr just from bodies. A rule-of-thumb sizing misses this.
- Lighting load. Restaurant dining rooms typically run 2-4 watts per square foot of lighting, which converts to roughly 7 to 14 BTU/hr per square foot of internal heat gain.
- Kitchen radiant heat bleeding into the dining room. Open kitchens, pizza ovens visible to diners, and pass-through windows all leak heat into the dining HVAC zone. A correctly designed system accounts for this and either creates a thermal break (a vestibule, a chase wall) or adds dining-zone tonnage to compensate.
- Solar load on glass. West-facing windows on a Montgomery restaurant pick up 200 BTU/hr per square foot of glass in late afternoon. East-facing windows get hit in the morning. Manual N runs the calculation hour by hour.
- Make-up air load on the dining HVAC. If the kitchen makeup air pulls from a return that crosses the dining zone, the dining HVAC has to condition that volume too.
A properly Manual-N-sized restaurant typically lands between 1 ton per 150 square feet (high-occupancy, open kitchen, big west glass) and 1 ton per 350 square feet (low occupancy, closed kitchen, north-facing). The rule of thumb is right about 30 percent of the time, low about 40 percent, and high about 30 percent.
We have replaced 6-ton package units that were doing the work of a 10-ton system because the original installer sized for a retail bay. We have also pulled out 25-ton systems on 3,200 square foot dining rooms that short-cycled themselves into compressor failure because the load was 18 tons.
If you are building or remodeling a Montgomery restaurant, demand a written Manual N calculation from your HVAC contractor before equipment is ordered. It costs a few hundred dollars. It saves five-figure equipment replacement.
Walk-In Cooler and Freezer Refrigeration Loads
Restaurant refrigeration is a separate system from the building HVAC, but the two interact in ways that surprise owners.
Every BTU of heat the walk-in cooler removes from food and outside-air infiltration has to go somewhere. In most Central Alabama restaurants, the condenser dumps that heat into the kitchen ceiling space or into the dining room. A 6 by 8 walk-in cooler running in a Montgomery kitchen rejects roughly 12,000 to 18,000 BTU/hr of heat into the building. A walk-in freezer can reject 20,000 to 30,000 BTU/hr.
The fix, on new construction or major remodels, is a remote condenser mounted outside or on the roof so the heat is rejected outdoors instead of inside the conditioned space. This is a 10 to 15 percent capital cost increase on the refrigeration but typically pays back in 3 to 5 years through reduced HVAC load and longer compressor life on the building system.
On existing installations, at least make sure the condenser space (usually above the walk-in) has dedicated exhaust ventilation to the outdoors. Otherwise the kitchen HVAC ends up paying to cool the refrigeration condenser, which is fighting itself.
Alabama Health Department Compliance
The Alabama Department of Public Health requires kitchens to maintain temperatures that allow safe food handling. The relevant compliance points where HVAC matters:
- Walk-in cooler temperatures must stay at or below 41°F. If your HVAC is dumping heat into the cooler space (poor isolation, undersized condensing unit, dirty coil), inspectors will catch it on a routine visit. Repeated violations affect your health score, which is posted publicly.
- Hand-washing stations require hot water and a sanitary environment. A kitchen running over 90°F sustained ambient (which happens fast with hood imbalance) gets flagged for staff hygiene and food safety risks.
- Ventilation must move smoke, grease, and odors out without contaminating dining areas. A failed or undersized exhaust system that is allowing visible smoke into the dining room is a violation.
- Restrooms must have mechanical exhaust ventilation. This is a code requirement separate from the kitchen exhaust, and it must be on its own fan, not shared with the kitchen system.
Most of these issues are correctable, but they are easier to design in from the start than to retrofit after a Health Department violation.
Repair vs. Replace: When the Commercial RTU Has to Go
Rooftop units (RTUs) on restaurants typically last 12 to 18 years in the Montgomery climate, depending on maintenance. The decision to replace versus repair comes down to a few specific signals.
Replace when you see:
- The unit is over 12 years old AND the compressor is failing. A new compressor on a 12+ year RTU is $4,500 to $7,000 installed; a new RTU is $9,000 to $18,000 depending on tonnage. The replacement is usually closer to break-even than owners expect once you factor in efficiency gains.
- R-22 refrigerant. R-22 production ended in 2020 and reclaimed R-22 now costs $200 to $400 per pound. A leaking R-22 system can cost more in refrigerant alone than a new R-410A system would cost to operate.
- The unit short-cycles even after thermostat and control checks. Oversizing is rarely fixable without replacement.
- Repeated capacitor, contactor, or board failures within 24 months. The control board on a commercial RTU is $400 to $1,200 just for the part. Three failures and you have bought the new unit anyway.
- SEER rating below 11. Modern commercial RTUs run 14 to 18 SEER. The operating-cost difference on a 10-ton unit running 4,000 hours a year in Montgomery is $1,800 to $2,800 annually.
Repair when:
- The unit is under 10 years old and the failure is a discrete component (contactor, capacitor, fan motor, leaking valve).
- The refrigerant is R-410A and the leak is isolatable (line set or coil section, not the compressor body).
- Maintenance has been current and the system has not had repeated failures.
Financing for Commercial Restaurant Owners
Commercial HVAC replacements run $9,000 for a small 5-ton unit to $40,000+ for multi-unit restaurant systems with makeup air. Most restaurant owners do not want to drop that out of operating cash, especially heading into a slow season.
Chad's AC Direct works with Wells Fargo Retail Services, Goodleap, Microf, and Alabama Power's commercial financing programs. For most commercial restaurant projects in our service area, financing structures available include:
- Same-as-cash 12-month or 18-month for smaller equipment swaps. No interest if paid in full by the deadline.
- 5 to 10 year fixed-rate installment with monthly payments, typical for full system replacements. Rates depend on credit but generally 7 to 12 percent APR for commercial.
- Section 179 deduction. Commercial HVAC equipment placed in service in 2026 qualifies for Section 179 expensing up to the annual limit. Talk to your tax preparer; the deduction can offset 25 to 35 percent of the equipment cost depending on your business tax bracket.
- Alabama Power commercial rebates. For qualifying high-efficiency equipment (16+ SEER for split systems, 14+ EER for commercial RTUs), Alabama Power offers rebates that typically range $50 to $200 per ton. These get applied on top of any financing.
We help structure financing so the monthly payment is close to or below the operating-cost savings on the new equipment. On most full-replacement projects in the Montgomery commercial restaurant segment, the new equipment pays for itself within 5 to 7 years through utility savings plus repair-cost avoidance.
Frequently Asked Questions
How often should a commercial restaurant HVAC system be serviced? Twice a year minimum: a spring tune-up before cooling season and a fall tune-up before heating season. Restaurant HVAC works harder than residential because of higher loads and longer run hours. Quarterly hood cleaning and exhaust fan inspection is also required by NFPA 96 and most insurers. Chad's AC Direct offers commercial maintenance agreements that bundle the HVAC and exhaust inspections into one schedule.
Can I use a residential HVAC contractor for my Montgomery restaurant? No, and here is why: commercial HVAC requires different sizing methodology (Manual N versus Manual J), different equipment categories (RTUs, makeup air units, exhaust hoods), and familiarity with the International Mechanical Code as it applies to commercial kitchens. Chad's AC Direct is licensed for both residential and commercial work in Alabama (license #92244). Most residential-only contractors are not.
What does a typical commercial HVAC replacement cost for a Montgomery restaurant? For a small restaurant (under 3,000 square feet) with a single 5 to 10-ton RTU plus exhaust hood and basic makeup air: $14,000 to $28,000. For a mid-size restaurant (3,000 to 6,000 square feet) with multi-unit HVAC plus makeup air: $30,000 to $65,000. Custom builds with full Manual N redesign, multi-zone systems, and high-efficiency equipment can exceed $80,000. We provide free written estimates after an on-site walk-through.
What is the difference between a Type I and Type II hood? Type I hoods handle grease-laden exhaust from cooking equipment (ranges, fryers, charbroilers, ovens). They require a UL 300 fire suppression system, daily cleaning, and quarterly professional cleaning. Type II hoods handle heat and moisture only (steam tables, dishwashers, coffee equipment) and have lighter regulatory requirements. Most Montgomery restaurants need at least one Type I hood and may need a Type II hood as well.
How quickly can Chad's AC Direct respond to a commercial HVAC failure during business hours? For our commercial maintenance agreement customers in the Montgomery service area, we target same-day response for any failure that affects operations. Our 24-hour emergency line (334-264-6464) is staffed for after-hours commercial emergencies as well. Restaurants cannot afford to close for an HVAC failure during a Friday dinner service, and we treat commercial calls accordingly.
Need commercial HVAC service for your Montgomery or Central Alabama restaurant? Call Chad's AC Direct at (334) 264-6464 (Montgomery) or (334) 478-1438 (Dadeville) to schedule a free in-home estimate or commercial walk-through. Alabama HVAC License #92244, BBB A+ Accredited since 1995, 1,247 5-star Google reviews from Central Alabama customers. Financing available through Wells Fargo, Goodleap, Microf, and Alabama Power.