High airflow for large northern Minnesota jobs
A make-up air heater brings in outdoor air, heats it and supplies it to a building to replace air leaving through exhaust or planned openings. BCI Rentals offers direct fired LP/NG make-up air heaters in 550K, 1.5M and 2.5M BTU catalog sizes, with listed airflow from 4,400 to 14,000 CFM.
Start with your airflow requirement, temperature rise and available fuel and power. Call to size the system and check availability, including the 550K option.
Large construction enclosures and industrial spaces can lose heat quickly when exhaust systems or open work areas move air out of the building. A temporary make-up air heater supplies tempered outdoor air as part of a planned supply and exhaust balance. That is a different job from simply recirculating and reheating the air already inside.
BCI's units use 100% outdoor air and direct firing. The burner heats the airstream directly, so combustion products and water vapor enter the supply air. Proper installation, combustion setup, outside-air intake and a suitable exhaust or relief path are essential.
Make-up air can support construction heating, large building shells, warehouses and temporary enclosures when the unit and ventilation plan suit the use. Call with the exhaust requirement and the work being done, especially if it involves coatings, fumes or materials with specific ventilation requirements.
| Unit | Capacity | Airflow | Approx. full-fire temperature rise | Listed power | Fuel |
|---|---|---|---|---|---|
| 1.5M make-up air heater | 1,500,000 BTU/hr | 9,500 CFM | About 145°F | 208/230V, 1-phase, 30A | LP or NG |
| 2.5M make-up air heater | 2,500,000 BTU/hr | 14,000 CFM | About 165°F | 208/230V, 1-phase 50A or 3-phase 30A | LP or NG |
| 550K make-up air heater Ask about availability | 550,000 BTU/hr | 4,400 CFM | About 115°F | 115V, 20A | LP or NG |
Temperature rise is an approximate standard-air calculation using listed BTU/hr ÷ (1.08 × CFM). It is the estimated increase above inlet temperature at full fire, not a guaranteed outlet temperature. Burner settings, controls, airflow and site conditions affect actual performance. Confirm power and capacity for the assigned unit; call to size your job.
These are airflow-based systems, so a blanket square-foot claim is not useful. A smaller building with heavy exhaust can require more make-up air than a larger building with limited air exchange. The 550K unit is listed in the catalog, but availability needs a phone check.
CFM means cubic feet per minute. Start with the amount of air the building exhausts or the air changes the project requires. When a project specifies air changes per hour, airflow in CFM ≈ building volume in cubic feet × air changes per hour ÷ 60.
For example, a 120,000 cubic foot space requiring four air changes per hour needs about 8,000 CFM. Four air changes is an illustration, not a recommendation for your building. The required rate depends on the process, occupancy and ventilation design.
Next, consider how much warmer the supply needs to be than the outdoor air. At standard air conditions, BTU/hr ≈ 1.08 × CFM × temperature rise in °F. Heating 8,000 CFM from 0°F to 60°F takes about 518,400 BTU/hr for that air alone. Building heat loss and control requirements still need to be considered in the full plan.
Have an HVAC professional establish the ventilation requirements when the process calls for it. We can then discuss which rental size fits the specified airflow, temperature and utilities.
Propane can suit a site without permanent gas service, but high-output heaters need a properly sized fuel supply. Tank capacity, cold-weather vaporization, regulator capacity, hose and inlet pressure all matter. Review these details with the fuel supplier and BCI before choosing the heater.
A gas connection must have adequate available pressure and flow for the heater along with the site's other loads. Connection size and supply-line length can affect the plan. Have the gas provider or qualified installer confirm the supply, then match the rental unit and its fuel setup.
Confirm electrical service separately. A 1.5M or 2.5M unit is not a standard household plug-in heater. Voltage, phase, amperage and connections must match the assigned equipment.
Bringing in cold outdoor air and exhausting moist indoor air can help carry water vapor out while materials dry. The result depends on outdoor conditions, moisture released by the work and the actual supply and exhaust balance.
Direct fired make-up air also adds combustion moisture. It should not be described as moisture-free heat or as a dehumidifier. For moisture-sensitive work, compare indirect fired heat and dehumidification with the project's requirements.
Schaefer fans can help distribute supplied heat through a large space, but air circulation does not replace the required outdoor-air and exhaust path. Use our direct vs. indirect heater guide to compare the systems.
No. Make-up air describes the job of replacing air leaving a building. BCI's make-up air units are direct fired and heat outdoor air. An indirect heater uses a heat exchanger to separate burner exhaust from supply air and may support a compatible return-air arrangement.
Yes. Fuel combustion adds water vapor to the airstream. Fresh-air supply with suitable exhaust can still remove net moisture from the building, especially in cold conditions, but the outcome depends on the job. Use humidity measurements and the materials' requirements to guide drying.
Floor area is only a starting point. Ceiling height, required air changes, exhaust volume, outdoor temperature and the target supply temperature drive selection. Call with those details so the unit is sized by airflow and heat requirement.
The three listings are LP/NG units. The assigned heater must be configured for the chosen fuel, with a correctly sized and regulated supply. Confirm connections and fuel capacity before making the site plan.
BCI is based in Backus and serves projects throughout the Brainerd Lakes area and north-central Minnesota, including Bemidji, Walker, Park Rapids and Grand Rapids. Call with the location and dates to discuss availability and delivery and pickup options.
Call (218) 947-3353 for a rate and availability. Bring the CFM requirement or building dimensions, temperature target, fuel supply and available power.