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3.5 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 connection. As an example, bi-
thermostats TR1 and TR2 can be adjusted so that there is a 10°C intervention difference between each
other (do not forget that knobs have a 43° to 85° regulation 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
3.5.1 REX DUAL/REX DUAL F CONTROL PANEL (Fig. 4)
The standard 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 43° to 85° and can be set by
the user by means of the front knob. The temperature differential of each bi-thermostat is fixed and approx.
7°C.
Safety thermostats (TS1 and TS2)
have a fixed setting of 100 (+0/-6)°C and can be manually reset in ac-
cordance 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. 4
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.
