2-Way pump unit with 3-way mixing valve with compact energy meter M2 MIX3 Energy G21

2-Way unmixed pump unit with MID approved compact energy meter

The unit for 1” (180 mm) circulating pumps consists of:


  • Connection.
  • Mixing valve: 3-way..
  • Circulating pump with press-cable (for the models with it).
  • 3-way flanged ball valve supplied with in-handle thermometer (coded red, range 0°C-120°C). The third way M10x1 allows the dip fitting and the lead sealing of a ø5x45 mm sensor.


  • Flanged ball valve with non return valve 20 mbar (which can be excluded by rotating the handle by 45°) supplied with in-handle thermometer (coded blue; 0°C-120°C).
  • Distance piece made in plastic 3/4”x110 mm (DN15) or 1”x130 mm (DN20) that has to be removed, after having cleaned the installation, to fit the energy meter.
  • Flanged ball valve with T-handle.
  • Connection.

Energy meter G21, included into the packing, available in two versions:

  • DN15, Qn 1,5; 3/4”x110 mm; Kvs 3,0
  • DN20, Qn 2,5; 1”x130 mm; Kvs 5,0
Centre distance 125 mm. EPP insulation box (Measurements: 250x380x190 mm).
PN 10. Max Temperature 90°C (*).
External connections:  1” Female.


For power up to 50 kW (with Δt 20 K) and maximum flow 2150 l/h (*).
Kvs value: 8,0 (*).
Approximate data calculated with a 6 m nominal lifting power circulating pump.
For an accurate measuring or for higher flows, please refer to the curves shown in the technical section.
(*) The data are relevant to the pump unit without energy meter installed.

Available circulating pumps:                                                          Available energy meters:

Wilo Star RS 25/6 (W6)                                                                     G21 - DN15 - Qn 1,5 (1.5)
Grundfos UPSO 25-65 (G60)                                                           G21 - DN20 - Qn 2,5 (2.5)
Wilo Star RSG 25/8 (RSG8)
Wilo Stratos Pico 25/1-6 (P6)
We suggest you to install two isolating valves Art. 552 (see Correlated Articles) before the pump unit to allow an easy service or replacement of the components of the unit.
The pump units ModvlvS Energy are made to meter the energy in centralized heating and cooling installations. These pump units, thanks to two isolating valves on the return way, allow an easy mounting of the energy meter. The second temperature sensor is directly put into isolating valve of the supply way, without any adapter or pit. This special 3-way ball valve, placed after the circulating pump, allows the lead sealing of the sensor and also the replacement of it without draining the installation: it is enough to close the valve to isolate the sensor from the hydraulic circuit.
In this way the placement of the energy meter, after having cleaned and serviced the circuit or replaced it, is very easy.

Approximate data to select the appropriate meter

Model Energy meter Δt
Kvs of
the unit (*)
power and flow
of the installation
circulating pump
M2 G21 1,5 m3/h 20 K 2,8 18 kW  -  800 l/h Wilo Star RS 25/6 4,5 mH2O
M2 G21 2,5 m3/h 20 K 4,2 23 kW  -  1000 l/h Wilo Star RS 25/6 4,6 mH2O
M2 G21 2,5 m3/h 20 K 4,2 43 kW  -  1850 l/h Wilo Star RSG 25/8 4,6 mH2O
M2 MIX3 G21 1,5 m3/h 20 K 2,7 18 kW  -  800 l/h Wilo Star RS 25/6 4,5 mH2O
M2 MIX3 G21 2,5 m3/h 20 K 3,8 23 kW  -  1000 l/h Wilo Star RS 25/6 4,5 mH2O
M2 MIX3 G21 2,5 m3/h 20 K 3,8 43 kW  -  1850 l/h Wilo Star RSG 25/8 4,7 mH2O
(*) The indicated Kvs concerns the unit including the energy meter installed.
Code DN15: 203518-M3-1.5  -  with circ. pump: 203518-(W6/G60/RSG8/P6)-M3-1.5
Code DN20: 203518-M3-2.0  -  with circ. pump: 203518-(W6/G60/RSG8/P6)-M3-2.0
Note: The DN to which the identification codes of the units are referred are related to the nominal diameter of the energy counter.


  • Model: M2 MIX3 Energy G21