Bosch Appliances 100 Combi Boiler manual Boiler pump capacity in single zone systems, Gpm

Applications Manual Bosch Greenstar 11

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 floor, 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 flow rate of 4.0 gpm. This allows sufficient 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 flow 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'

MBH output per 100’ at shown Medium Water Temperature

and 65°F Room Temperature

GPM

4

feet of head

4.375

110°F

16

120°F

12

130°F

26

140°F

32

150°F

38

160°F

46

170°F

54

180°F

61

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 flow 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. Data subject to change