Boiler Pump Capacity In Single Zone Systems - Bosch Greenstar 57 Manual

Applications Manual

Boiler pump capacity in single zone systems

When installing the boiler in a single zone application
without primary/secondary piping, it is critical not to
overload the pump. Use the Greenstar Heating or Combi
Boiler in this setup only in low pressure baseboard
applications. Radiant fl oor, panel radiator, or multi-zone
applications require primary/secondary piping. Do not
install zone valves with this system.
Recommended maximum: 70' (21 m) of 3/4" baseboard
at a 20°F delta T and a fl ow rate of 4.0 gpm. This allows
suffi cient reserves for the necessary supply and return
piping plus elbows.
Alternatively determine the system pressure drop on a case
by case basis to verify that the boiler pump is capable of
delivering the required fl ow rate. Table 2 provides as an
example the pressure drop of 100' of 3/4" baseboard and
its relevant heat output.
Water Flow Pressure Drop per 100'
GPM feet of head
4 4.375
Tab. 2 Pressure drop and heat output for ¾" baseboard
Add to that the pressure drop of supply and return piping
plus elbows and other devices like check valves.
Use the pump curves on the following page to verify that
the pump is capable of delivering the needed fl ow rate for
the given pressure drop of the system.
In order to save as much energy as possible and
keep water circulation noises to a minimum, select
the lowest possible pump speed.
If the working pressure cannot be met, use primary/
secondary piping.
Bosch Thermotechnology Corp.
MBH output per 100' at shown Medium Water Temperature
and 65°F Room Temperature
110°F 120°F 130°F
16 12 26
140°F 150°F 160°F
32 38 46
Bosch Greenstar | 11
170°F 180°F
54 61
Data subject to change