This blog aims to guide HVAC professionals which unit heater model is appropriate for a given application.
To recommend a heating solution to your customer that will deliver the result(s) desired, knowing the application is of utmost importance. Heating solution for a space being used as a warehouse (people walking) would be very different than space being used as an office (people sitting) or a church (noise levels from moving parts in the heating equipment).
Factors to consider when selecting a heating solution for an application
What is the space being used for?
Does the application involve ducting the unit heater(s)?
Is noise an issue?
Any contaminants in the space (chemicals, floating particles, etc.)?
How much heat loss needs to be replaced by the heating solution?
The layout of the space (including overall dimensions and ceiling height)?
Any bay doors in the space?
The above info helps determine whether blower unit heater is recommended or propeller, whether gas-fired unit heaters would be ideal or hydronic (steam/hot-water) or electric or infrared heaters, how many heaters, any accessories required for optimal and uniform heat flow/circulation in the space.
Different types of gas-fired unit heaters available
Blower vs Propeller
Power Vented vs Separated Combustion vs Condensing
Some applications where blower unit heaters are recommended are
Return Air Filter Rack Option (eg. flour processing plant)
Blower unit heater Model BDP
Power Vented vs. Separated Combustion vs. Condensing Unit Heaters
Power vented unit heaters use fresh combustion air from the space and use single-pipe vent system to exhaust flue gases outdoors. These are recommended for general warehouse, garage applications.
Separated combustion unit heaters use 2-pipe vent system – one vent pipe to bring in fresh combustion air from outdoors to the unit and another vent pipe to exhaust flue gases outside. These unit heaters also come with a power venter (or power exhauster) as power vented unit heaters above.
Condensing unit heaters are separated combustion unit heaters but with dual heat exchangers. Warmer flue gases come out of the primary heat exchanger and are then passed through secondary heat exchanger to draw out more heat from the flue gases. Since exhaust gases come out of the unit heater at much lower temperatures, these unit heaters can be vented using UL 686S PVC pipes. These are use 2-pipe vent system similar to separated combustion unit heaters.
Auto garage/workshop – power vented unit heaters with standard Al Steel heat exchanger
Welding shop – because of chemicals in the air and likely negative air space caused by exhaust fan(s), separated combustion is recommended
Car wash – because of chemicals and high humidity, separated combustion and stainless steel heat exchanger is recommended
Paint shop – because of chemical in the air, separated combustion is recommended
Wood workshop – because of wood dust, separated combustion is recommended
Chicken farm – infrared tube heaters (minimal noise from power venter motor)
Garbage room in high rise condos – separated combustion, Al Steel heat exchanger