A humidifier having a field-replaceable water heating enclosure and a humidifier main unit configured to receive the field-replaceable water heating enclosure is provided. The field-replaceable water heating enclosure may include a water inlet, a water outlet, a water vapor outlet, and a resistive heating element. The humidifier main unit may be configured to provide water to the field-replaceable water heating enclosure via the water inlet when the field-replaceable water heating enclosure is received by the humidifier main unit. To facilitate this, the humidifier main unit may include a manifold structured to interface with the water inlet, the water outlet, and the water vapor outlet. The humidifier main unit also may be configured to provide electrical power to the resistive heating element of the field-replaceable water heating enclosure when the field-replaceable water heating enclosure is received by the humidifier main unit.