An apparatus and system for efficiently and safely transferring heat from a masonry heater to an external heating device using coil pipes and a liquid circulation pump. Circulation of a heat transfer liquid in the apparatus and system is controlled based on the measured temperature of the heat transfer liquid in the coil pipe on a return side of the masonry heater. Two additional sensors near the external heating device are used to control the flow rate of the circulation of the heat transfer liquid in the apparatus and system, thereby controlling the amount of heat actually transferred to the external heating device.

An apparatus and system for efficiently and safely transferring heat from a masonry heater to an external heating device using coil pipes and a liquid circulation pump. Circulation of a heat transfer liquid in the apparatus and system is controlled based on the measured temperature of the heat transfer liquid in the coil pipe on a return side of the masonry heater. Two additional sensors near the external heating device are used to control the flow rate of the circulation of the heat transfer liquid in the apparatus and system, thereby controlling the amount of heat actually transferred to the external heating device.