Direct Gas-Fired Make-Up Air Units
Direct gas-fired make-up air units operate at 92-100% thermal efficiency. Lower fuel consumption per CFM of heated supply air reduces annual gas costs, and that advantage compounds with system size and operating hours.
Configurations range from 600 CFM commercial kitchen units to 92,000 CFM for industrial applications. Options include 100% outside air, 80/20 recirculation, DX cooling sections, and VFD-equipped fans.
RWA Ventilation Solutions distributes direct gas-fired MUA units from various US-based manufacturers. We recommend units that fit your application, not a single manufacturer’s product catalog.
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Direct Gas-Fired Make-up Air Unit Diagram
Direct Gas-Fired Make-Up Air Unit Lines We Distribute
Each manufacturer line targets a different capacity range and application type. Most ship with modulating burners rated up to 30:1 turndown, with optional DX cooling, variable air volume packages, and BMS integration.
| Manufacturer | Series | CFM Range | BTU/hr Range | OA Config |
|---|---|---|---|---|
| AbsolutAire | AA-Series | 800 – 54,000 | 200,000 – 6,000,000 | 100% OA, 80/20 |
| AbsolutAire | V-Series | 800 – 13,000 | 155,000 – 1,125,000 | 100% OA |
| FloAire | F76 Compact | 600 – 1,400 | — | 100% OA |
| FloAire | F-D Modular | 1,000 – 21,000 | 250,000 – 2,500,000 | 100% OA, Recirc |
| FloAire | FAH/FAV Industrial | 5,000 – 92,000 | — | 100% OA, 80/20 |
| Hartzell | Series 78V/78H | 7,100 – 23,500 | 950,000 – 2,900,000 | 100% OA |
We are the authorized distributors for the leading American manufacturers of makeup air units. We’ll be pleased to provide the ideal make up air unit for your application as authorized representatives.
For a fast quote or if you have inquiries about commercial or industrial MUA, get in touch with us.
Applications and Typical CFM Ranges
Total exhaust output determines your make-up air requirement. Kitchen hoods, process fans, paint booths, dock doors, and general exhaust all contribute to that number. Undersized supply air creates negative building pressure and backdrafting risk. Oversized units waste heating capacity and short-cycle the burner.
| Application | Typical CFM Range | Notes |
|---|---|---|
| Small commercial kitchen / QSR | 600 – 2,500 | Single wall canopy hood |
| Full-service restaurant kitchen | 2,500 – 6,000 | Multiple hood runs, Type I and Type II |
| Auto body shop / spray booth | 4,000 – 12,000+ | Must match booth exhaust precisely |
| Loading dock / dock leveler zone | 2,000 – 5,000 | Intermittent door cycles drive sizing |
| Warehouse under 50,000 sq ft | 5,000 – 15,000 | Forklift exhaust, dock door infiltration |
| Distribution center 100,000+ sq ft | 15,000 – 50,000+ | Multiple units typical, VFD-equipped |
| Manufacturing / process facility | 5,000 – 100,000+ | Determined entirely by process exhaust |
For exact BTU and CFM calculations, use our make-up air unit sizing calculator.
Common DFMUA Configurations and Options
| Category | Standard | Available Options |
|---|---|---|
| Construction | G90 galvanized steel, 1″ insulation, hinged access doors | Roof curbs, hanging cradles |
| Burner and ignition | Stainless steel burner, cast aluminum manifolds, electronic flame modulation, redundant gas valves, direct spark ignition | — |
| Safety and controls | High-temp limit, airflow proving, pre-wired/pre-piped, 120V transformer, motor starter | Remote panel, BMS/DDC (BACnet, Modbus, LonWorks), freeze stat, gas pressure gauges |
| Fuel | Natural gas | Propane |
| Airflow | Indoor/outdoor, horizontal or down discharge | VFD/VAV packages, motorized intake dampers, discharge diffusers |
| Filtration | Standard intake | MERV upgrades, V-bank filter sections |
| Cooling | — | DX coils, evaporative media, chilled water coils |
| Certification | ETL listed, ANSI Z83.4 / CSA 3.7 | 80/20 recirculation (ANSI Z83.18) |
Why Work With a Distributor
Buying direct from a manufacturer limits you to one product catalog. If the best unit for your application sits in a different catalog, you never see it.
We represent multiple US manufacturers. Our engineers review your exhaust requirements, temperature rise, fuel availability, and facility constraints before recommending a specific unit.
Every unit ships US-made and backed by the manufacturer’s warranty.
Call 847-262-3457 ext. 23 or request a quote to start the spec review.
FAQ
What is the thermal efficiency of a direct gas-fired make-up air unit?
92-100% thermal efficiency, with approximately 92% sensible. The remaining 8% goes to latent heat in water vapor formed during combustion. No heat exchanger and no flue stack eliminate the efficiency losses found in other heating configurations.
Does a direct-fired unit add moisture to the air?
Yes. Combustion of natural gas produces approximately 1 lb of water vapor per 1,000 BTU. In dry climates and winter heating, this added humidity is a benefit. In paint booths, food processing, or humidity-sensitive environments, it may require additional dehumidification equipment.
What turndown ratio should I look for?
30:1 is the current standard on most commercial and industrial lines. High turndown prevents short cycling at part load and allows precise discharge temperature control across a wide operating range. Units with lower turndown ratios cycle on and off more frequently, increasing burner wear.
Can a direct gas-fired unit include cooling?
Yes. DX cooling coil sections, evaporative cooling media, and chilled water coils can be factory-integrated into most product lines. A single unit handles heating and cooling without requiring a separate system for summer operation.
Scott Williamson
Scott Williamson is an engineer specializing in industrial ventilation, including make-up air units.
His expertise has been recognized by leading business publications like HubSpot and Tech Bullion. Scott helps business owners find high-performance solutions that balance energy savings with daily operational needs.