Furnaces – Unit Heaters
Industrial facilities, which generally require only winter-time heat, often employ unit heaters to provide a direct supply of warm air where needed. Unit heaters are also found in box stores, showrooms, warehouses, stairways, and entryways.
The units are often suspended from the ceiling but many models can be mounted on a wall as well. Unit heaters operate as forced-air heating devices by pushing air over gas burners or tubular electric heating elements and blowing it directly into the space to be heated. Gas models which offer efficiencies up to 93% can be gravity vented or power vented and come with either single or two-stage gas valves for high and low firing. At least one manufacturer offers an indirect fired unit with one to three heat sections.
Many models allow for blower or fan only operation to help clear stagnant air and provide some cooling during warmer weather. Some units incorporate technology that senses heat build-up near the ceiling and turns the fan on to push the heat back down to floor level. Although gas models are not recommended for use in flammable areas, at least one manufacturer offers an “explosion proof” electric model for use around flammable gases, vapors and dust.
How It Works
Air flow enters the unit and warms as it travels across the heat exchangers. Heated air is blown out of the unit directly into the area to be warmed. Simultaneously, combustion air travels across the burner, through primary and secondary heat exchangers and out the exhaust vent.
Natural gas 25,000 to 400,000 Btu/h
Electric 208V to 600V, 1 or 3 phase