Unit heater

Definition - What does Unit heater mean?

Unit heaters are commonly used as forced air-heaters in greenhouses. These heaters are usually mounted overhead and receive heat from a boiler in the form of hot water or steam. Some unit heaters also contain fireboxes. These heaters are crucial for protecting plants and vegetables from the cold while maintaining an adequate temperature to boost plant development and growth.

MaximumYield explains Unit heater

A greenhouse unit heater may come in especially handy during the winter since it protects flowering plants from frost. In some cases, unit heaters can also protect vegetables and plants from various types of fungal diseases and mold.

Commercial planters normally choose between three different types of unit heaters:

  • Hydronic unit heaters: Because these are lightweight and compact, these are normally used for smaller greenhouses. Hydronic unit heaters generate heat through steam or hot water supplied through the greenhouse’s boilers. With these apparatuses, the supply piping can be attached either to the side, bottom or top of the unit.


  • High efficient condensing unit heater: Unlike hydronic heaters, these models do not use all the combustion heat. As a result, plenty of heat remains in the exhausted flue gases and these are extracted through a heat exchanger located inside the unit.


  • Power vented unit heater: These unit heaters can be vented horizontally or vertically. Ideal for greenhouse conditions, power vented heaters normally include heat exchangers and provide a thermal efficiency of 80%.
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