The function of the recirculation pump is to ensure that hot water is always available as close to the consumption point as possible, in order to reduce water wastage and to increase comfort.
A recirculation pump can be sized for a given system using the following formulas:
Water flow qc= Φ/ΔT x 4200
qc = the circulating water flow [m3/s]
Φ = heat loss from the circulation system [kW]
ΔT = the water cooling, normally 5°C determined at the farthest consumption point [°C]
Normally uncontrolled pumps are used as the flow variation is relatively small. In large systems, however, it may be advantageous to use controlled pumps to enable adjustment of the flow when starting up the system and to be able to apply temperature control.