Ferroli DOMINA N 80 DGT, Installation, Service And User Manual

DOMINA N 80 DGT

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8. FAULT FINDING

Before beginning any fault fi nding ensure that gas, water and electricity are available.

8.01 Operating Sequence

With the power established the boiler is in its stand-by  mode i. e. power on but no demand.  The operational 
sequence for C.H. and D.H.W. are as follows:

Central Heating Mode

External Call for Heat: 

The temperature regulator, built in or remote clock and room thermostat, if fi tted, must 

all call for heat. This will cause the pump to run.

Internal Call for Heat: 

C.H. fl ow temperature sensor, 88°C high limit and low water pressure switch all calling for 

heat. If both external and internal calls for heat are present the MF03 PCB will energise.

In demand the fan will go to high speed causing the air pressure switch to operate. If the overheat (100°C) stat is 
closed circuit the ignition will operate and the gas valve will be energised.

The burner will light at ignition burner pressure, automatically range rating itself up to the heating load, then 
modulating down when the boiler reaches the desired fl ow temperature. When the central heating is satisfi ed the 
burner will go off and the fan stops i.e. stand-by mode.

Note  - 

If the boiler thermostat is set to maximum than the burner pressure will go to maximum effectively 

bypassing the auto range rating facility

Domestic Hot Water Mode

External Call for D.H.W: 

Flow meter registers at least 2.5 litres/min fl ow to the hot water taps. 

Internal  Call  for  D.H.W: 

Hot water fl ow  temperature sensor 88°C high limit stat and low water pressure 

switch calling for heat.

If both internal and external calls are present the boiler follows the same sequence as for C.H. to light the burner. 
However, for D.H.W. the burner will go straight to maximum and then modulate once the water reaches the set 
temperature of the control thermostat. Turning the tap off will return the boiler to stand-by mode.

Note: 

Following shut down of the D.H.W. or C.H. the boiler will go into a three minute central heating delay.

8.02 Limit thermostats

  T/Stat            Location            Function                    Nominal                  Circuit                 Wiring
                                                                                  Operating                                          Colours
                                                                                  Temperature

  C.H. Limit

      Top RHS              Shuts downmain         88°C                         Low voltage         Blue

                         of Heat               burner if boiler                                            DC                        Brown
                         Exchanger          thermostat fails

  Frost

              Incorporated      Fires the boiler           7°C - 14°C                Low voltage         Red

                         in C.H.                and runs pump to                                        DC                        Red
                         Sensor                maintain minimum
                                                    water temperature

Overheat

       Top LHS              Protect boiler by        100°C                       240V AC               Brown

                         of Heat               stopping ignition                                                                      Blue
                         Exchanger          and cuts power
                                                    to gas valve

Note: 

Always check for suffi cient gas supply (20mbar inlet working  pressure for NG and 37mbar for LPG). 

Minimum of 22  mm diameter  pipework on C.H.  fl ow and return with adequate by-pass. A correctly installed 
fl ue system and a 3 amp fuse.