Heat pumps with fan coils
A fan coil pushes room air across a water coil. Because the fan does the work, a small unit delivers a lot of heat or cooling from moderate water temperatures, and the same terminal serves both seasons.
Heating and cooling water temperatures
Fan coils are usually selected for heating at 35–45 °C flow and cooling at around 7 °C flow with a 12 °C return. Renova's own RE series fan coils are rated with 45 °C water in heating and 7 °C in cooling. Lower heating water temperatures raise the heat pump's COP but reduce fan coil output; the selection balances the two.
Condensation and condensate drainage
Chilled water below the room's dew point dehumidifies the air, and that water must go somewhere. Every fan coil used for cooling needs a drain tray connected to a condensate line with a continuous fall, or a condensate pump. Pipes carrying chilled water need vapour-tight insulation, otherwise they drip.
Fan control and noise
Fan speed sets both output and noise. Units sized so they normally run at low or medium speed are quieter than small units running flat out. DC fan motors allow fine speed steps and low power draw.
Thermostats and two-pipe changeover
On a two-pipe system the whole circuit carries either warm or chilled water. Each fan coil's thermostat switches the fan and, where fitted, a valve; the heat pump decides the season mode. Where valves can close, protect the heat pump's minimum flow and system volume with a bypass or buffer tank.
Hydraulic balancing
Fan coils close to the heat pump see more pressure than those at the end of the run. Balancing valves set each unit's design flow so that distant rooms are not starved.
Related: Renova RE fan coils · Underfloor heating · RV series
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