How to Select the Right Gas-Fired Make-Up Air Heater for Your Industrial Facility
Exhaust fans protect your plant, but they can also waste heat, lower building pressure, and drive up energy bills. Installing a Hartzell gas-fired make-up air heater is the solution. These units bring in fresh, tempered air and maintain balanced pressure for safer, more efficient operations. A properly sized system delivers the warm airflow your facility needs, improving comfort, protecting equipment, and slashing unnecessary energy costs.
Why Make-Up Air Matters
Exhaust fans keep your plant safe, but without proper replacement air you’ll experience negative building pressure, slamming doors, dust infiltration, drafts, and overworked heating systems trying to warm cold infiltration air. The result: higher energy costs and uncomfortable working conditions.
The solution is 100% replacement of exhausted air with properly heated, tempered fresh air.
How Industrial Make-Up Air Heaters Work
An industrial gas-fired make-up air unit pulls in outdoor air, warms it using a natural gas or propane burner (either direct-fired or indirect-fired), and delivers it indoors. This maintains consistent building pressure, improves indoor air quality, and dramatically reduces energy bills—especially in colder climates.
Horizontal vs Vertical Gas-Fired Make-Up Air Units
Hartzell offers two primary configurations to fit different facility layouts and requirements.
| Configuration | Best For | Key Advantages |
|---|---|---|
| Horizontal (Series 78H) | Sidewall / through-wall installations | • Ideal when roof access is limited • Easier service access at ground level • Lower installation cost in many cases |
| Vertical (Series 78V) | Facilities where floor space is at a premium | • Frees 100% of indoor floor space • Quieter operation inside the plant • Better aesthetics and security |
Key Specifications to Evaluate
When choosing a gas-fired make-up air heater, focus on these critical metrics:
- CFM (Cubic Feet per Minute): Must match total exhaust rate 1:1 for proper pressure balance
- BTU/hr: Rough rule – 1 million BTU ≈ 20°F temperature rise at 10,000 CFM
- Drive Type: Direct-drive = less maintenance; belt-drive = adjustable airflow
- Noise Levels: Target ≤ 85 dBA in occupied areas
- Construction: G90 galvanized steel for corrosion resistance and durability
Improving Heating Efficiency & Cost Savings
Today’s units deliver outstanding efficiency and fast payback:
- High-Efficiency Burners: Up to 92% efficiency (direct-fired)
- Modulating Turndown: 25:1 ratio uses only the gas needed
- Typical ROI: 18–24 months
Installation & Maintenance Best Practices
Do:
- Size gas lines correctly for full-load operation
- Install vibration isolators for quieter performance
- Use Hartzell easy-access panels for 15-minute filter changes
Don’t:
- Cut corners on rooftop curbs or sidewall supports
- Skip annual burner inspections and cleaning
Application Examples
- Auto Shop: 15,000 CFM unit reduced heating costs by 25%
- Food Processing Plant: 20,000 CFM rooftop unit freed 400 sq ft of floor space
Schedule a Complimentary Audit
Stop losing heat and money through your exhaust fans. Let a Hartzell engineer evaluate your facility and recommend the perfect gas-fired make-up air solution.
Contact Hartzell Air Movement today to get started.
Frequently Asked Questions
What is an industrial make-up air heater?
It is a system that provides heated fresh air to replace air removed by exhaust fans, maintaining proper building pressure and comfort.
Should I choose a horizontal or vertical unit?
Horizontal units work best for sidewall installations; vertical (rooftop) units are ideal when indoor floor space is at a premium.
How much can I save on energy bills?
Modern modulating units typically reduce gas costs by 20–30% versus older, less efficient systems.
Direct-fired or indirect-fired?
Direct-fired units are more efficient and suitable for most general spaces. Choose indirect-fired when combustion byproducts must stay separated from the indoor air stream.
How do I correctly size a unit?
Match CFM to your total exhaust rate and calculate BTU/hr based on desired temperature rise. Hartzell provides free sizing audits.
How noisy are these units?
Indoor units operate at or below 85 dBA. Rooftop units are even quieter inside the building.
What maintenance is required?
Annual burner inspection, quick filter changes (as little as 15 minutes with Hartzell access panels), and periodic checks of gas lines and drives.