STOKVIS ENERGY SYSTEMS REX F, Technical Manual

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3.7  REX DUAL/REX DUAL F OPERATING PRINCIPLES 

The boiler consists of 2 units of same capacity and  one only control panel for both units. Each  unit can work 

independently and the boiler can be operated partially. This  means that all panel controls (burner switches, 

thermostats and thermometers)  have been doubled. See paragraph 4.5 on c onnection. As an example, bi-

thermostats TR1 and TR2 can be adjusted so that t

here is a 10°C intervention difference between each 

other (do not forget that knobs have a 42° to 87° regul ation range with a 1/2 turn rotation about). Flow water 

temperature after 2 equal flows have been mixed corresponds to mean flow temperature of two units 

3.7.1  REX DUAL/REX DUAL F OPTIONAL CONTROL PANEL (Fig. 5) 

NOTE: for boilers with two different control panels, see Par. 3.4 

The optional control panel is made of plastic with IP40 protection degree and houses the regulation and 

safety instruments: 

The upper part of the control panel can be rotated  to gain access to the terminal board and uncoil the ther-

mostat and thermometer capillaries. A copy of the wiring diagram is contained inside the control panel. 

The regulation bi-thermostats (TR1 and TR2

) have an operating range from 42° to 87° and can be set by 

the user by means of the front k nob. The temperature differential of  each bi-thermostat is fixed and approx. 

7°C. 

Safety thermostats (TS1 and TS2) 

have a fixed setting of 110°C and can be  manually reset in accordance 

with Ministerial Decree 1/12/75 «R». 

Circulator consent thermostats (TM1 and TM2)

 have a fixed setting of 45°C with  a working range of 6°C: 

at start-up, with the heating system cold, this permits  higher boiler temperatures to be maintained thus re-

ducing the risk of flue gas condensation. 

For correct installation, refer to the boiler casing assembly instructions. 

Note:

 both hour meters start each time their own  burner starts. It is recommended that the numbers dis-

played by both hour meters are monitored . This helps guarantee that burners have almost the same number 

of working hours. 

Fig. 5 

KEY 

1 PANEL  LIVE 

2  BURNER SWITCH N. 1 

3  BURNER SWITCH N. 2 

4  HEATING PUMP SWITCH 

7 BOILER  THERMOMETER 

8  CONTROL THERMOSTAT N. 1 

9  SAFETY LIMIT THERMOSTAT N. 1 

11  CONTROL THERMOSTAT N. 2 

12  SAFETY LIMIT THERMOSTAT N. 2 

13  HOURS RUN METER BOILER N. 1 

14  HOURS RUN METER BOILER N. 2 

WIRING DIAGRAM 

Refer to the diagram supplied with the specific switchboard.