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Domestic Hot Water Recirculation - Bosch Greentherm T9900 SE 160 Installation And Operating Instructions Manual

Indoor residential tankless water heaters, 160 000/199 000 btu- natural gas 160 000/199 000 btu - liquefied petroleum lp gas
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Installation instructions

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"
Total (Sum)
100 ft (30m) 100 ft (30m) 15
Table 18 Maximum pipe length
4.11.1 Start up procedure
Appliance damage!
▶ Ensure that the water circuit is fill before activate
recirculation mode.
▶ 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
House Recirculation
Compatible with dedicated return line and cross over mode
with thermal by-pass valve.
Dedicated mode
A dedicated return line is required in the installation.
90° Elbows
Fig. 30
Recirculation application
[1] Cold inlet supply
[2] Check valve field supplied
[3] Expansion tank field supplied
[4] Purge Valve recirculation circuit
[5] Shutoff valves field supplied
[6] Cold water inlet
[7] Gas supply
[8] Shutoff gas valve
[9] Hot water outlet
[10] 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)



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Greentherm t9900 se 199Greentherm t9900 se/i 199