| 摘要 |
This air heating device especially suited for low pressure air comprises an air duct in which an electric heating coil is located together with a thermistor which is part of an electronic thermostat to control the electric heating coil. The thermistor bead is so located as to see the heating coil and be exposed to the radiant heat of the latter. The thermistor is used as an airflow sensor so that the heating coil will gradually be decreasing its heating capability to eventually shut off according to the air velocity and temperature entering the duct; heating will be restored automatically once the airflow in the duct assembly has sufficiently cooled down the thermistor, therefore the thermistor acts as an airflow sensor to modulate the heating capacity according to the quantity of air flowing through the heating device to prevent overheating of the coil and consequently the activation of a thermal cut-out safety feature. The heating device can be used either in a fresh air intake for a central air furnace or for a heat pump or simply for baseboard heating with a duct fan, or as a unit incorporated into a larger forced air heating network system.
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