A geothermal furnace is a heat pump that uses water instead of air as a source of heat gain or loss. Water is pumped through a closed loop of pipes buried in the ground, or pumped from a well and discharged into another well or into a pond. The condenser and evaporator coil are enclosed in one cabinet. A backup electric heating element may be installed in the supply ductwork In heating mode, heat is extracted from water as it passes through the condenser, and released through the evaporator coil. In air conditioning mode, heat is extracted from the evaporator coil and released into water through the condenser. Accessories can include; an air filter, electronic air cleaner , high performance media filter, and a humidifier. The humidifier can be of the steam generating type, which will be line voltage powered, so caution must be taken to shut off power before servicing. Sometimes a condensate pump will be used to dispose of the water produce in the dehumidifying action of the air conditioning. If the system is zoned, a zone control panel and motor actuated dampers will be installed on the unit or in the ductwork. A filter or strainer may be installed in the supply side of the water feed to keep sediment out of the pump and condenser if drawn from a well. Routine maintenance includes replacing the air filter or washing the electronic air cleaner grids, cleaning the humidifier, and servicing the water filter or strainer. All maintenance should be done with the system shut down. Basic troubleshooting: Be certain that the thermostat is set higher than the actual room temperature and the selector switch to heat if in heating mode, or that the thermostat is set lower than room temperature and the selector switch is on cool if air conditioning is desired. If the thermostat is programmable, make sure it has fresh batteries. An easy test for power is to move the fan switch from "auto" to "on". If the blower runs there is power to the unit. If you are familiar with the fuse panel or circuit breaker panel, check for blown fuses or tripped breakers. Correct the problem once. If it repeats, call for service.
Check the water supply if fed from a well. A clogged filter or strainer may trip safety switches that will not allow the unit to run without water.
Because the controls are mounted internally and high voltage connections are exposed if the cabinet is opened, only a qualified technician should access them.