PROBLEM TO BE SOLVED: To provide a control method of hot air heater for protected horticulture in which combustion operation control corresponding to a size of heating load in a greenhouse is performed.SOLUTION: There is provided a control method of a hot air heater for protected horticulture which is installed in a greenhouse for protected horticulture, which generates hot air by heat exchange between combustion gas generated by a combustion operation of a burner and air in the greenhouse and heats inside the greenhouse, in which a temperature difference between inside/outside the greenhouse for protected horticulture or solar radiation heat quantity to the greenhouse for protected horticulture is measured, greenhouse heating load is determined to any one of high load, middle load, and low load based on a measured value, and a preset temperature or an operation time period of an on/off control in a combustion operation of the burner is changed corresponding to the determined load. The preset temperatures for the middle load and the low load are set lower in steps than the preset temperature for the high load, and the operation time periods for the middle load and the low load are set shorter in steps than the operation time period for the high load.SELECTED DRAWING: Figure 6【課題】ハウス内の暖房負荷の大きさに応じた燃焼運転制御を行う施設園芸用温風暖房機の制御方法を提供する。【解決手段】施設園芸用ハウス内に設置され、バーナの燃焼運転により生じた燃焼ガスとハウス内空気との熱交換により温風を生成してハウス内を暖房する施設園芸用温風暖房機の制御方法であって、施設園芸用ハウスの内外温度差または施設園芸用ハウスに対する太陽輻射熱量を測定し、測定値によってハウス暖房負荷を高負荷、中負荷、低負荷のいずれかに判定し、判定された負荷に応じて前記バーナの燃焼運転におけるオン・オフ制御の設定温度または運転時間を変更する。中負荷時および低負荷時の設定温度を、高負荷時の設定温度よりもそれぞれ段階的に低く設定するか、中負荷時および低負荷時の運転時間を、それぞれ高負荷における運転時間よりも段階的に短く設定する。【選択図】図６
