2050 County 41 NW, Backus, Minnesota
Choose the system before the BTU rating
Direct fired heaters put combustion products into the heated airstream; indirect fired heaters use a heat exchanger to separate burner exhaust from the supply air. For a northern Minnesota jobsite, the right choice depends on ventilation, moisture, fuel, electrical service and whether you need air heat or heat applied directly to the ground.
BCI Rentals can help compare portable direct heat, indirect heat, make-up air and hydronic equipment for your project.
Make-up air is a ventilation function, not a separate combustion method. BCI's make-up air units are direct fired. Hydronic equipment carries heat in fluid, then transfers it through ground hoses or a compatible air heat exchanger.
| Consideration | Portable direct fired | Indirect fired | Direct fired make-up air | Hydronic |
|---|---|---|---|---|
| How heat reaches the job | Air passes through the burner airstream. | Air passes over a heat exchanger. | Outdoor air passes through the burner airstream. | Heated glycol circulates through hoses or a heat exchanger. |
| Combustion products | Enter the heated air. | Separate flue exhaust; excluded from supply air when properly set up. | Enter the supplied outdoor air. | Stay at the burner; heat travels in the fluid. |
| Combustion moisture at the work | Added to the airstream. | Not added to the supply air. | Added to the airstream; planned ventilation can still remove net building moisture. | Not added through ground hoses or the air exchanger. |
| Fresh-air requirement | Required ventilation must be maintained. | Building ventilation still applies; return air is possible on select units. | 100% outdoor air with a suitable exhaust or relief path. | Ventilation depends on the occupied space and work; burner stays appropriately located. |
| BCI fuel options | Propane / natural gas | Diesel or propane / natural gas, depending on unit | Propane / natural gas | Diesel in current Wacker listings; other options depend on unit |
| BCI catalog scale | 250K to 400K BTU class | 200K to 1M BTU classes; useful output varies | 550K, 1.5M and 2.5M BTU classes | Ground-thaw classes up to 2,500, 6,000 and 10,000 sq ft |
| Useful starting point for | Open or adequately ventilated construction work | Enclosed building heat and finish work | Large outdoor-air and exhaust replacement needs | Frozen ground, concrete heat and compatible hydronic air heat |
| Equipment examples | HeatStar forced air heater | Frost Fighter and Temporary Climate Solutions units | BCI's LP/NG make-up air fleet | Wacker Neuson E-Series; Heat King HK300 availability shown in its guide |
This is a selection guide. Follow the assigned unit's operating instructions and the project's ventilation, placement and clearance requirements. A dehumidifier or a fan does not replace required ventilation for combustion equipment.
Portable direct fired heat is a practical option when the work area and the manufacturer's ventilation requirements suit it. BCI's HeatStar unit uses propane or natural gas in the 250K to 400K BTU catalog class.
Because the heated air contains combustion products and water vapor, a tightly sealed finish-work space needs a different discussion from an open construction shell. Do not treat a high BTU rating as approval to use a heater in any enclosure. Tell BCI what the space is used for and how fresh air and exhaust will be maintained.
Choose an indirect heater when you want the burner exhaust kept out of the supply air. It is often the starting point for enclosed buildings, shops, drywall and painting work, and temporary spaces where combustion moisture would be undesirable.
Frost Fighter units in BCI's fleet include the IDH500QR, IDF500 and towable IDH1300. The catalog also includes a Temporary Climate Solutions HCI-600D. Choose by useful heat output, fuel, power and duct route rather than brand alone.
Heat alone does not remove water already in the building. You may need controlled ventilation or a dehumidifier as wet materials release moisture. Compare indirect heater sizes and ducting.
If the building exhausts large amounts of air, replacing that air is part of the heat load. BCI's direct fired make-up air units heat 100% outdoor air and supply it to the space, with listed sizes of 4,400, 9,500 and 14,000 CFM.
The outdoor supply can help carry indoor moisture out through the planned exhaust or relief path. The burner still adds water vapor. The combined effect depends on outdoor conditions, how much moisture the work releases and the supply and exhaust balance.
Size these units by airflow and temperature rise, with the full building heat requirement considered. See the make-up air size and power table.
A hydronic heater uses fluid to carry heat to the work. Lay glycol hoses over the thaw area and cover them with insulated blankets, or use the system according to the concrete curing plan. This puts heat at the surface rather than relying on warmed building air to reach frozen soil.
BCI carries Wacker Neuson E-Series ground heaters and Midwest Canvas blankets. A compatible HX200 heat exchanger can also transfer glycol heat to air. Combining air heat with ground work requires sizing for both loads.
Compare ground heater coverage or read about the Heat King HK300, including its availability status. BCI is a dealer for Wacker Neuson and Heat King; other heater brands listed here are part of the rental fleet.
Fans can improve circulation after heat enters the space. They help distribute air; they do not create heating capacity or remove water from a closed building by themselves.
No single type fits every job. Indirect heat keeps combustion exhaust out of the supply air, while direct fired make-up air can fit a large planned outdoor-air requirement. Hydronic heat addresses frozen ground and slab work directly. Choose around the actual heat and ventilation needs.
Yes. It adds water vapor from combustion to the supply air. Its outdoor-air supply and planned exhaust may still reduce indoor moisture overall. That is different from saying the heater adds no moisture.
No. A dehumidifier removes water from air; it does not remove the need for combustion ventilation or make an unsuitable heater appropriate for an enclosure. Follow the heater instructions and the site's ventilation requirements.
The HK300 is a hydronic glycol heater. It applies heat through hoses for ground or concrete work and can support compatible air heat exchangers. That differs from an indirect fired air heater that sends fan-driven air across a burner heat exchanger.
Confirm whether the rating is burner input or useful output, then consider building heat loss, required outdoor airflow, target temperature and the duct layout. Call (218) 947-3353 with the project details so we can help size the job.
BCI Rentals serves Backus, the Brainerd Lakes area, Bemidji, Walker, Park Rapids, Grand Rapids and surrounding northern Minnesota communities. Call (218) 947-3353 for a rate and availability.