What is the difference between direct and indirect fired heaters

Since direct fired heaters have an exposed flame similar to a stovetop or grill, these units should be reserved for areas where there is plenty of ventilation and less foot traffic. Direct fired heaters are ideal because they are cost-effective, efficient, and easy to transport. Common applications include:.

Indirect fired heaters are just like your home oil or gas burning furnace with a chimney. Below is a diagram of a direct fired air heater. The air is heated when it passes over the heat exchanger and thus, the by-products of combustion remain inside the heat exchanger and do not come into direct contact with the process air.

Indirect fired air heaters are used for chemically sensitive products, foods, chemicals, pharmaceuticals, ect. Both types heat the air and work to keep the work area at a comfortable temperature.

However, each heater works best in different situations, and each has distinct benefits. Direct fired heaters are similar to a gas grill where the flame comes into direct contact with the air. These heaters provide heat by forcing air through a gas flame. The direct heat transfer is incredibly efficient and allows the device to heat a space quickly while using minimal amounts of fuel.

These portable heaters do produce CO2 emissions, so make sure to ventilate them properly. Direct fired heaters are completely self-contained.

This makes each unit relatively easy to move and adjust, saving you time and money in setup and installation procedures. Most of the direct fired heaters offered by On Site Companies are also dual fuel heaters.

This means they can be powered by either liquid propane or natural gas. Your heater can switch fuel sources by swapping out regulators, so you heater can adjust when you job site changes. The main benefit of direct fired heaters is that they are extremely efficient.

Since the heat is produced by the flame coming in direct contact with the fuel source, the heaters will convert almost all fuel into usable heat. Because of this, we recommend that you switch from convection heaters to standard direct fired heaters when your construction site obtains electricity. The design of direct fired heaters focuses on simplicity.

January 30, Direct Fired Heaters A natural gas or propane direct fired heater has an open flame that provides a safe way to heat industrial and commercial areas by maintaining a proper air-to-fuel ratio. Smaller Size — A direct fired burner can produce more heat in a smaller envelope compared to an indirect fired burner. This results in an overall smaller equipment footprint in most cases. Flexibility — Direct fired burners can be constructed to essentially any required size in order to achieve the required BTU rating, so you will not have to choose between either an undersized or oversized heater.

Additionally, direct fired heaters have much higher turndown ratios than indirect fired heaters, resulting in a greater ability to vary the heat output. Simplicity — As a heat exchanger and flue are not required, installation is made easier and maintenance costs will be decreased.

Equipment life expectancy is longer than indirect fired heaters. Temperature control is more precise compared to indirect fired heaters. Direct Fired Disadvantages Ventilation Requirements — Although these heaters operate within code prescribed safety limits, due to combustion products entering the airstream, proper ventilation is required to avoid buildup of gases such as carbon monoxide. Less Flexibility with Cooling Coils — If the refrigerant used in a DX direct expansion cooling coil leaks and then passes through an open flame, a toxic gas may be created.