Understanding the difference between direct and indirect fired heaters is crucial when choosing which heating system works for your job. Learn more about each unit here:
Direct Fired Heaters
Direct fired heaters are similar to a gas barbecue grill or your gas stovetop. With propane or natural gas heating, units force air directly through the flame to heat the air.
Benefits to using direct fired heaters include:
- Efficiency – Direct fired heaters convert 100% of the fuel being used to direct heat which lowers fuel consumption and operating costs
- Easy to Transport – Direct fired heaters are fairly simple pieces of equipment that can be moved to where heat is needed
- Powerful – High amounts of heat (BTU’s) are produced in smaller units when compared to indirect fire heaters
- Some units do not require electricity
- Lower rental costs – Direct Fired Heaters are less expensive
- Lower Maintenance Costs – Easier to maintain
- Built-in thermostat – On most models, a thermostat is used to control the temperature
- Safe for unsupervised use – Multiple redundant safety features allow direct fire heaters to stay running without supervision. Our heaters are CSA and UL rated.
Some drawbacks to using direct fired heaters are:
- Ventilation Required – The room must have some level of air exchange. Direct fired heaters cannot be used in a tightly sealed structure unless windows and doors can be opened for air exchange.
- Adds moisture and carbon monoxide into the air.
Direct Fired Heaters Applications
Generally, direct fired heaters are used on construction sites, outdoor applications, or warehouses. 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:
- Construction sites
- Warehouses
- Food industry
- Mining industry
- Petrochemical industry
Indirect Fired Heaters
Indirect fired heaters are just like your home oil or gas burning furnace with a chimney. With propane or natural gas heating units, the flame is contained in a burn chamber which heats a “heat exchanger”. The cooler air passes over and around the heat exchanger, thus heating the air. You can learn more about indirect heaters and watch us install one of our units.
Indirect fired heaters offer some positive points, like:
- 100% clean, dry air – The air being circulated never comes in direct contact with the flame.
- Built-in thermostats – Almost all indirect fired heaters use a thermostat
- Can operate in tightly sealed spaces – Indirect fired heaters do not release carbon dioxide into the space.
Some negative aspects of indirect fired heaters are:
- Higher Cost – The rental cost is nearly quadruple that of direct fired
- Lower Efficiency – Fuel efficiency is usually close to 80%
- Electricity Required – Indirect fired heaters always need an electrical outlet
- Requires exhaust ventilation – You must either vent the exhaust outside or duct the hot air inside. This makes installing and removing indirect heaters cumbersome because of the setup and tear down of ductwork.
- Hard to transport – Indirect fired heater units are much larger and less portable.
Indirect Fired Heaters Applications
Indirect fired heaters are perfect for a workspace that is tightly sealed and lacks a working heating system. Indirect fired heaters use a contained heating system that limits CO2 emissions, which makes these units a safe option for populated areas. Common applications include:
- Retail spaces
- Construction sites
- Hospitals & healthcare buildings
- Universities
- Chemical production industry
At Priority Rental, a Herc Rentals Business, we offer a broad variety of direct and indirect fired heaters for rent or purchase. For a more general overview of the heaters we offer, visit our portable heaters page.