UL 731:2018 Oil-Fired Unit Heaters.
1.1 These requirements apply to oil-fired unit heaters as defined herein. Unit heaters designed to supply heated air through ducts are covered in the Standard for Oil-Fired Central Furnaces, UL 727.
1.2 The oil-burning equipment covered by these requiremetns are intended for installation in accordance
with the National Fire Protection Association Standard for the Installation of Oil Burning Equipment, NFPA
31, the International Mechanical Code and the Uniform Mechanical Code.
1.3 If a value for measurement is followed by a value in other units in parentheses, the second value may be only approximate. The first stated value is the requirement.
2.1 For the purpose of this standard, the following definitions apply.
2.2 AIR SHUTTER — An adjustable device for varying the size of the air inlet or inlets regulating primary or secondary air.
2.3 ANTIFLOODING DEVICE — A primary safety control which causes the fuel flow to be shut off upon
a rise in fuel level or upon receiving excess fuel, and which operates before the hazardous discharge of
fuel can occur.
2.4 APPLIANCE FLUE — The flue passages within the appliance.
2.5 AUTOMATICALLY LIGHTED APPLIANCE — An appliance in which fuel to the main burner is normally turned on and ignited automatically.
2.6 BAFFLE — An object placed in an appliance to direct the flow of air or flue gases.
2.7 BASE — The main supporting frame or structure of the furnace, exclusive of legs.
2.8 BURNER — A device for the final conveyance of fuel or a mixture of fuel and air to the combustion zone.
2.9 BURNER, AUTOMATICALLY LIGHTED — One where fuel to the main burner is normally turned on and ignited automatically.
2.10 BURNER, MANUALLY LIGHTED — One where fuel to the main burner is turned on only by hand and ignited under supervision.
2.11 BURNER, MECHANICAL-ATOMIZING TYPE — A power-operated burner which prepares and delivers the oil and all or part of the air by mechanical process in controllable quantities for combustion. Some examples are air atomizing, high and low pressure atomizing, horizontal rotary, vertical rotary atomizing, and vertical rotary wall-flame burners.UL 731 pdf download.