4.11 Domestic hot water recirculation
The following drawings are provided to illustrate two possible
recirculation designs. These schematic is for illustration only
and must not be used for actual Installation without appropriate
engineering and technical advice from a properly licensed
professional in the locality where the installation is made.
In order to reduce the heat loss through the pipes, it's
recommended to insulate all the pipes in the recirculation
Maximum Pipe Length (Hot water supply and return lines)
Pipe Diameter ¾"
100 ft (30m) 100 ft (30m) 15
Table 18 Maximum pipe length
4.11.1 Start up procedure
▶ Ensure that the water circuit is fill before activate
▶ Open a hot water tap to fill the water circuit.
▶ Open the purge valve in the recirculation circuit (dedicated
mode) near the appliance water inlet.
▶ Turn on the appliance.
▶ Set the recirculation mode in HMI.
▶ Wait until there is no air in the recirculation circuit (a few
▶ Close water taps.
The recirculation system is operational.
4.11.2 Recirculation options
Compatible with dedicated return line and cross over mode
with thermal by-pass valve.
A dedicated return line is required in the installation.
 Cold inlet supply
 Check valve field supplied
 Expansion tank field supplied
 Purge Valve recirculation circuit
 Shutoff valves field supplied
 Cold water inlet
 Gas supply
 Shutoff gas valve
 Hot water outlet
 Pressure relief valve
Cross Over Mode
Cross over mode requires two (2) Grundfos thermal by-pass
Greentherm T9900 SE/i – 6 720 813 635 (2019/03)