Ferroli Domina F 24-30 E, Ferella F 24-30 MEL, MILOS Air Compact E Technical Manual

Supplied By www.heating spares.co Tel. [phone]



Wall-Mounting Gas Boiler



Airtight Chamber,
for Hot Water
and Heating

TECHNICAL

DOMINA F 24-30 E

FERELLA F 24-30 MEL

MILOS AIR COMPACT E

MANUAL

EDITION

092002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

1. Technical characteristics and data ......................................................... 3

1.1 Introduction ............................................................................................................3

1.2 Dimensions and connections .................................................................................. 4

1.3 General view and main components ...................................................................... 8

1.4 Technical data table .............................................................................................. 10

2. Product framework and internal components..................................... 11

2.1 Hydraulic circuit - heating..................................................................................... 11

2.2 Hydraulic circuit - tap water ................................................................................. 15

2.3 Gas circuit .............................................................................................................17

2.4 Burner unit ............................................................................................................21

2.5 Fume circuit .......................................................................................................... 23

2.6 Electrical circuit..................................................................................................... 27

3. Operation ............................................................................................ 30

3.1 Operating principle .............................................................................................. 30

3.2 Operating diagram ...............................................................................................31

3.3 Control panel ........................................................................................................ 32

3.4 Adjustments.......................................................................................................... 32

3.5 Setting operating parameters .............................................................................. 33

4. Troubleshooting .................................................................................. 34

2

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

1. TECHNICAL CHARACTERISTICS AND DATA
GENERAL

1.1 Introduction

Our appliance is a high-efficiency heat generator for central heating and hot-water production running
on natural gas or LPG (configurable at the time of installation).

The boiler shell consists of a copper laminar exchanger whose particular shape guarantees high exchange
efficiency under all operating conditions and an open-flue burner equipped with electronic ignition and
ionization flame control.

The boiler is totally sealed off from the installation room: the air needed for combustion is drawn from
outside and the flue gases are expelled by a fan. The boiler outfit moreover includes a variable speed
circulator, expansion tank, flow meter, safety valve, filler cock, air pressure switch, water pressure switch,
temperature sensors and a safety thermostat.

Thanks to the control and adjustment system, unit operation is for the most part automatic. The power
for heating is automatically governed by the control system according to the indoor characteristics, the
characteristics of the building and of its location. The power for hot water is automatically and continually
governed to ensure a fast delivery and comfort under all operating conditions.

There are 5 LEDs on the control panel providing information on the unit's operating status.

General Warnings

 Installation and maintenance must be carried out by professionally qualified personnel,

according to current regulations and the manufacturer's instructions.

 Incorrect installation or poor maintenance can cause damage or physical injury. The

manufacturer declines any responsibility for damage caused by errors in installation and use
or by failure to follow the manufacturer's instructions given in the instructions manual.

 Before carrying out any cleaning or maintenance operation, disconnect the unit from the

electrical power supply using the switch and/or the special cut-off devices.

Certification

The CE marking demonstrates that Ferroli gas units conform to the requirements contained in
the applicable European directives.
In particular, this unit complies with the following EU directives:

 Gas Appliance Directive 90/396 assimilated with Italian Presidential Decree DPR 15.11.96 no. 661
 Efficiency Directive 92/42 assimilated with Italian Presidential Decree DPR 15.11.96 no. 660
 Low Voltage Directive 73/23 (amended by 93/68)
 Electromagnetic Compatibility Directive 89/336 (amended by 93/68) assimilated with Italian

Presidential Decree DPR 15.11.96 no. 615

Version - 09.2002

3

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

1.2 Dimensions and connections

Domina F 24 E version

Top view

Key

1 System delivery
2 Tap water outlet
3 Gas inlet
4 Tap water inlet
5 System return

4

Bottom view

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Ferella F 24 MEL version

& Milos Air Compact E version

Top view

Key

1 System delivery
2 Tap water outlet
3 Gas inlet
4 Tap water inlet
5 System return

Version - 09.2002

Bottom view

5

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Domina F 30 E version

Top view

Key

1 System delivery
2 Tap water outlet
3 Gas inlet
4 Tap water inlet
5 System return

6

Bottom view

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Ferella F 30 MEL version

Top view

Key

1 System delivery
2 Tap water outlet
3 Gas inlet
4 Tap water inlet
5 System return

Version - 09.2002

Bottom view

7

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

1.3 General view and main components
F 24 E/MEL version

Key

5 Airtight chamber
7 Gas inlet
8 Tap water outlet

9 Tap water inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
19 Combustion chamber
20 Burner unit
21 Main nozzle
22 Burner
26 Combustion chamber insulation
27 Copper exchanger for heating and tap

28 Fume manifold
29 Fume outlet manifold
32 Heating circulator
34 Heating temp. sensor
36 Automatic air vent
42 Tap water temperature sensor
43 Air pressure switch
44 Gas valve
49 Safety thermostat
50 Heating thermostat
56 Expansion tank
63 Heating temperature setting
73 Antifreeze thermostat (optional)

R1-R2-R3-R4 Antifreeze heating elements

74 Heating system cock
81 Ignition electrode
82 Detection electrode
84 1st gas valve operator
85 2nd gas valve operator
90 Fume detection point
91 Air detection point
98 Off-On-Reset switch

114 Water pressure switch
132 Fume deflector
136 Flow meter
145 Water gauge
157 Tap water temperature setting
187 Fume diaphragm

water

(optional)

Version DOMINA - FERELLA - MILOS

8

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

F 30 E/MEL version

5 Airtight chamber
7 Gas inlet
8 Tap water outlet

9 Tap water inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
19 Combustion chamber
20 Burner unit
21 Main nozzle
22 Burner
26 Combustion chamber insulation
27 Copper exchanger for heating and tap

water

28 Fume manifold
29 Fume outlet manifold
32 Heating circulator
34 Heating temp. sensor
36 Automatic air vent
42 Tap water temperature sensor
43 Air pressure switch
44 Gas valve
49 Safety thermostat
50 Heating thermostat
56 Expansion tank
63 Heating temperature setting
73 Antifreeze thermostat (optional)

R1-R2-R3-R4 Antifreeze heating elements

(optional)

74 Heating system cock
81 Ignition electrode
82 Detection electrode
84 1st gas valve operator
85 2nd gas valve operator
90 Fume detection point
91 Air detection point
98 Off-On-Reset switch

114 Water pressure switch
132 Fume deflector
136 Flow meter
145 Water gauge
157 Tap water temperature setting
187 Fume diaphragm

Version DOMINA - FERELLA

Version - 09.2002

9

Supplied By www.heating spares.co Tel. [phone]

1.4 Technical data table

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

10

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

2. PRODUCT FRAMEWORK AND INTERNAL
COMPONENTS

2.1 Hydraulic circuit  heating

Hydraulic diagram for heating

When there is a call for heat, the room thermostat or control system make the burners ignite and the
circulation pump come into operation. The heat contained in the products of combustion is transferred
to the water by the system via the exchanger. For more details on the operating logic, refer to chap.3.

29-187

16

49

27

82

20

42
34

114

14
74

-

+

5

43

50

56

81

44

32
136

Key

5 Airtight chamber
7 Gas inlet
8 Tap water outlet

9 Tap water inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
20 Burner unit
27 Heat exchanger
29 Fume outlet collar
32 Heating circulator
34 Heating temperature sensor
42 Tap water temperature

sensor

43 Air pressure switch
44 Gas valve
49 Safety thermostat
50 Heating thermostat
56 Expansion tank
74 Heating system cock
81 Ignition electrode
82 Detection electrode

114 Water pressure switch
136 Flow meter
187 Fume diaphragm

10

Version - 09.2002

8

7

9

11

11

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Circulator (230v/50Hz)

Located on the heating circuit return, it is connected directly to the exchanger
via special forks and connected to the system via a threaded brass section.
It has three delivery/head levels (see diagram). Changing the delivery/head
changes the speed of the water flowing through the boiler exchanger and as
a result the temperature difference ( T) between heating delivery and
return. Clearly, increasing the delivery of the circulator decreases T and vice
versa. If it is not used for a long time, the impeller might jam due to debris
in the water. With the front screw it is possible to access the impeller, which
can be freed with the aid of a screwdriver. The connection to the expansion
tank and the air separator is installed on the pump casing.

Checks

If the pump doesn't work:
 Check that the impeller is free to turn by turning the screw on the front

with a screwdriver.
 Check that both the card and the pump connection are powered.
 If there is no power supply, check the card.
 If there is power, change the pump.

Key

1 - 2 - 3 = Pump selector position

A = Losses of head 24kW version
B = Losses of head 30kW version

Air separator

This is used to expel the air in the heating circuit automatically. On boilers
with a twin heat exchanger, it is located on the pump casing. It is normally
accessible either via the fork or by simply unscrewing it from its seat.

12

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Expansion tank

It is connected to the pump casing via a pipe with a fork connection. On the 24kW version, it is located
above the pump, while on the 30kW version it is located behind the exchanger, inside the frame. The
expansion tank contains a diaphragm in contact, on one side, with the system water and, on the other side,
with the air under pressure (pre-loaded to 1 bar) inside the tank. By the expansion of the diaphragm and
ensuing compression of the air, the tank compensates for the thermal expansion of the water in the
heating system.

24kW 7-litre

version

30kW 10-litre

version

Twin Heat Exchanger

The exchanger is a copper laminar assembly. It comprises a thickly finned portion, three circular pipes
containing the heating water and, inside them, another three pipes in the form of a spiral containing the
tap water. The heating water exchanges directly with the burnt gases, while the tap water does not have
this kind of exchange, it receives heat indirectly from the water in the three heating pipes. In this way, the
surface of the coil does not reach very high temperatures so less scale gets formed. In addition, being very
small, it makes the water speed very high over its entire section, making mineral deposits of any kind
negligible. The typical omega shape of the finning ensures an even distribution of the heat over all the
finning, with consequent benefits in terms of exchange efficiency and the life of the exchanger. A special
surface treatment protects the exchanger against oxidation and corrosion.

Version - 09.2002

13

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Hydraulic unit

This is a single piece of brass to which the
exchanger delivery is connected for ease of
access. It accommodates a number of safety
and adjustment components.

The hydraulic unit includes:

- safety valve

- water pressure switch

- heating sensor

- filler cock

- tap water sensor

- tap water check valve

Water pressure switch

It ensures a minimum pressure for the system. It is normally open (NO) and
closes the contact when the pressure exceeds 0.5 bar. It works on low
voltage.

Safety valve

It opens if the pressure exceeds 3 bars, making boiler operation safer and
protecting it against overpressure. You are strongly recommended not to
use this valve to drain the system; once open, dirt could remain inside it,
preventing it from closing completely.

Check valve

This is necessary to ensure no water returns from the heating system to the
tap water circuit.

Filler cock

This is located between the heating delivery and the tap water outlet. It is not
fitted on the boiler for some markets such as the British and Belgian ones.

14

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

2.2 Hydraulic circuit  tap water

Hydraulic diagram for tap water

Key

5 Airtight chamber
7 Gas inlet
8 Tap water outlet

9 Tap water inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
20 Burner unit
27 Heat exchanger
29 Fume outlet collar
32 Heating circulator
34 Heating temperature sensor
42 Tap water temperature

sensor

43 Air pressure switch
44 Gas valve
49 Safety thermostat
50 Heating thermostat
56 Expansion tank
74 Heating system cock
81 Ignition electrode
82 Detection electrode

114 Water pressure switch
136 Flow meter
187 Fume diaphragm

When the card receives a signal from the flow meter indicating a tap-water draw of over 2.5 l/min, the
boiler starts working normally for tap water. If heating was in operation, or the pump was anyhow working,
the boiler will in any case give priority to the tap water, stopping the pump. The tap water does not
exchange directly with the products of combustion, but via the heating water in the exchanger, avoiding
sudden changes in temperature.

Version - 09.2002

15

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Flow meter

Located at the cold water inlet, its task is to provide the card with a signal
at a frequency (7 Hz per litre) in direct proportion to the tap-water flow rate.
It is composed of a body (stator) and a rotor inside it. There is a filter on its
inlet to prevent foreign bodies damaging it. It should be remembered that
to turn on the boiler for tap-water operation, the tap-water pressure must
be at least 0.25 bars and the draw flow rate must be greater than 2.5 l/min.

Check

To check it works properly, you need to make sure the flow rate is at least

2.5 l/min and then test the signal to the electric card with a frequency meter.
This makes it possible to understand whether the problem lies with the flow
meter, incorrect contacts, or the card.

Flow-rate restrictor

This is a diaphragm downstream from the flow meter. Its task is to limit the tap­water flow rate; the boiler modulates its capacity to keep the tap-water
temperature set by the user, but since the boiler capacity is limited to its rated
capacity, it is necessary to limit the tap-water flow rate to obtain high T.

16

In this case, above the flow­rate limit m, even though
the boiler is working at its
rated capacity, it is not able
to maintain the set tempe­rature of 50°C.

Version - 09.2002

*

Supplied By www.heating spares.co Tel. [phone]

2.3 Gas circuit

Gas circuit diagram

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Key

5 Airtight chamber
7 Gas inlet
8 Tap water outlet

9 Tap water inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
20 Burner unit
27 Heat exchanger
29 Fume outlet collar
32 Heating circulator
34 Heating temperature

sensor

42 Tap water temperature

sensor

43 Air pressure switch
44 Gas valve
49 Safety thermostat
50 Heating thermostat
56 Expansion tank
74 Heating system cock
81 Ignition electrode
82 Detection electrode

114 Water pressure switch
136 Flow meter
187 Fume diaphragm

Version - 09.2002

17

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Gas valve

It supplies gas to the nozzles between a minimum and maximum pressure.
For the valve to work correctly, it is necessary for the pressure upstream from
it to be stable and suited to the type of gas being used, while the valve will
supply a regular pressure to the nozzles. The gas valve contains two
operators. The function of the first one is to open or close, while the task of
the second one is to modulate the capacity according to the system's
requirements. The signal comes from the card (X6-1/2/3/4) and is in the form
of continuous voltage. The first operator receives fixed voltage that may be
between 80 and 110V DC, for the second operator the voltage will vary
between 25 and 54V DC according to the need of the main card.

Checks

If the valve doesn't work:
 Check there is gas, and that gas comes out of the valve by means of

screw B.

 If there is no gas, you must check there is voltage at the operators. This

makes it possible to understand whether the problem lies with the valve
(there is voltage at the operators) or with the card (there is no voltage
at the contacts X6-1/2/3/4).

Modulation

The control system governs its boiler capacity so as to keep the delivery temperature constant in
accordance with the settings on the control panel. The nozzle gas pressure is modulated by the valve and
specifically via the 2nd operator. The card provides a change in continuous voltage (between 25 and 54
V DC) according to the difference between the delivery temperature and the set point.

Checks

Modulation can be checked in three ways:
 Visually, by checking the flame.
 Using a pressure gauge to check the gas pressure downstream from the valve.
 Checking the voltage of the second operator on the card (X6, 1/2). This is the most effective method

in some situations. With this test, it is possible to understand whether the problem lies with the valve
or with the card.

Note that with very low pressure upstream from the valve, opening the valve may be slow and
the boiler could shut down due to failed ignition.

18

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Adjusting burner pressure

Since this unit has flame modulation, there are two fixed pressure settings: the minimum and maximum,
which must be as stated in the technical data chart according to the type of gas.

 Connect a suitable pressure gauge to pressure point "B"

downstream from the gas valve.
 Disconnect the pressure compensation tube "F".
 Take off the protective cap C.
 Set the potentiometer P3 (on the control card) to minimum

(clockwise).
 Run the boiler in heating mode.
 Adjust the minimum pressure with the screw D, clockwise

to decrease it and anticlockwise to increase it.
 Set the potentiometer P3 to maximum (anticlockwise).
 Turn on the TEST function by temporarily bridging X5.
 Adjust the maximum pressure with the screw E, clockwise

to increase it and anticlockwise to decrease it.
 Reconnect the pressure compensation tube F.
 Put the protection screw C back in.
 Disconnect the test jumper.

N.B. The test lasts 5 minutes. It is advisable to open 1 or 2 taps

to get rid of the excess capacity.

After checking or

adjusting the pres­sure, it is mandatory to seal
the adjustment screw with
paint or a specific seal.

Key

A Pressure point upstream

B Pressure point downstream
C Protection screw
D Minimum pressure adjustment

screw

E Maximum pressure adjustment

screw

F Pressure compensation tube

Version - 09.2002

19

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Gas supply conversion

The unit can function with either Natural Gas or LPG and is factory-set for use with one of the two gases,
as clearly shown on the packing and on the unit's dataplate. Whenever a different gas to that for which
the unit is preset has to be used, a conversion kit will be required, proceeding as follows:

1 Replace the nozzles at the main burner,

inserting the nozzles specified in the
technical data table, according to the type
of gas used.

2 Adjust the burner minimum and maximum

pressres, setting the values given in the
technical data chart for the type of gas
used.

3 Move the jumper JP02 on the card, as

shown in the diagram:

Natural gas operation

LPG operation

4 Apply the sticker, contained in the

conversion kit, near the dataplate as proof
of the conversion.

20

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

2.4 Burner unit

Operation

The burner unit comprises a manifold and 12/16 nozzles (depending on the capacity), the burner mount,
electrodes and the burner assembly.

Manifold - nozzles

The valve sends gas at a suitable pressure to the manifold, which
homogeneously distributes the gas to the single burner stages at the
nozzles. It is secured directly to the burner mount. Its positioning must be
exact since it affects the air/gas mixture. In addition, the threaded holes
forming the seat of the nozzles must be aligned with the respective Venturi
tube of the burner. If it were not so, the air/gas mixture would be wrong and
there would be poor combustion with an unstable flame. The nozzles are
made of brass and machined extremely precisely for their dimensions. There
is a seal between the nozzles and the manifold.

Ignition electrode

The ignition electrode is made of a metal alloy (Kanthal) that withstands high
temperatures and oxidation. Its base is composed of a ceramic composite
of glazed alumina whose purpose is to protect and electrically insulate it.
Once the ignition procedure begins, the card powers the electrode with a
pulsating voltage of a few kV, a series of electrical discharges is set off
between the electrode and the head of the burner (set at a distance of 3.5
mm). Clearly, these sparks are the trigger for the air-gas mixture. It is
important for the distance between the electrode and the burner head to be
3 - 4 mm and the discharge to be made at the centre.

Checks

If there is no discharge:
 Check whether the boiler shuts down, in which case check

the connection of the electrode to the card or whether it
discharges at other points; if necessary, check the safety
thermostat and the card.

 If the boiler does not shut down and the fan keeps on

working, check the air pressure switch.

 If there is a discharge, but no ignition and after 10 seconds

the boiler shuts down, check the gas valve and, if necessary,
the card.

 If there is a discharge and then a flame, but the boiler still

shuts down after 10 seconds, check the detection electrode
and its connection.

Version - 09.2002

21

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Detection electrode

Made of the same material as the ignition electrode, it is set 11 mm from
the burner head. Combustion causes the flame atmosphere to ionize,
making it conductive. Thanks to the mass of the burner, making a
suitable potential with the electrode produces a flow of direct current
on it. For our cards, it is necessary to have an ionizing current of at least

0.5 µA to detect a flame. A mean signal is normally obtained of
approximately 2 µA.

Burner assembly

The burner assembly is composed of 12 or 16 burner stages. Each stage is composed of two pressed steel
half bearings, with a suitably cut stainless steel head. Gas enters at the bottom of the stage. Thanks to
the special Venturi-tube shape of the bottom portion of the stage, the gas "injected" by the nozzle carries
with it the primary air needed for combustion. The air-gas mixture thus formed inside the stage is evenly
distributed on the burner head. Combustion takes place homogeneously over the entire length of the
single stages, with the contribution of the secondary air from the bottom of the burner mount and from
the combustion chamber itself. The set of stages in operation forms a single belt of flame, light blue in
colour, whose size varies according to the nozzle gas pressure, that is the boiler capacity modulation.

22

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

2.5 Fume circuit

Fume deflector and manifold

All forced-flow boilers have a fume deflector above the exchanger whose
main task is to make the secondary air crossing the burners uniform, making
the flame homogeneous and stable. The fumes then reach a fume manifold
whose job is to make them move on to the fan.

Airtight chamber

Its task is to isolate the products of combustion from the area surrounding
the boiler. The airtight chamber contains all the components involved in the
fume routing. The wires and pipes coming out of its lower portion are
insulated with silicone seals, while its upper portion is fitted for hooking up
with the flues. The cover is sealed off with a porous plate and is fitted with
two plugs for using a probe to analyse the fumes and combustion air.

Fan and pressure switch points

Powered at 230V/50Hz by the card (X6 - 7/8), the fan has
the job of expelling the products of combustion from the
fume chamber. A plate is normally placed above the
exchanger to act as a deflector, make the incoming air
from the bottom of the burner uniform, make the flame
stable and obtain the required air/gas ratio. In order to
make sure the fan works properly, there are two pressure
points inside it. The first one detects a static pressure
signal that is positive, the second one detects a dynamic
pressure signal via an appropriate Venturi tube, which
is negative. With the difference in pressure detected by
the two test points it is possible to check whether the
fumes are adequately evacuated.

Version - 09.2002

23

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Air pressure switch

This is used to check whether the fumes are adequately evacuated. The pressure switch compares the
static and dynamic signals coming from the pressure test points on the fan according to the figure. The
pressure switch is connected to the card and is normally open (see diagram). Before the card initiates the
ignition procedure (opening the valve, etc.), you must make sure that the fan works properly and that the
air pressure switch ensures this by closing its contacts. This happens if the difference in pressure is
165±15Pa. So the signal must be at least 180Pa. To open its contacts again, the difference in pressure must
drop under 150±13Pa. To perform checks on contact opening and closing, it is always recommended to
check directly on the card (X5 - 3/4).

Checks

It is necessary to check:
 Whether the electrical connections are correct.
 Whether the pressure test point pipes are clean and contain no condensation water.
 That the signal is open when the fan is not working.
 That the pressure is at least 180Pa and that above this pressure the pressure switch closes its

contacts.

 If the signal is low, it is necessary to check that the fume diaphragm is correct, the fan has 230V, the

pressure test points are properly inserted and the Venturi tube has no burrs of any kind. Lastly, check
that the ends of the pipes are not obstructed.

N.B. The pressure difference must be measured with the airtight chamber closed. The pressure gauge
connections can come out through the hole, which is closed by a silicone plug, on the front of the cover.

Key

NO = Normally open
NC = Closed
C = Common

24

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Fume ducts

The unit is type C with an airtight chamber and forced draught, the air inlet and fume outlet must be
connected to one of the following extraction/suction systems. With the aid of the tables and methods of
calculation indicated, before commencing installation, it is first necessary to check that the fume ducts do
not exceed the maximum permissible lengths. The current standards and local regulations must be
observed.

This C-type unit must be installed using the fume exhaust and suction ducts supplied by FERROLI
S.p.A. in accordance with UNI-CIG 7129/92. Failure to use them automatically forfeits all warranty
and liability of FERROLI S.p.A.

Diaphragms

Boiler operation requires fitting the diaphragms supplied with the unit as instructed in the following
tables. As the resistance of the fume ducts changes, the diaphragms make it possible to keep the
combustion parameters (CO2, etc.) within the optimum operating range. Note that with low-resistance
fume ducts, a high-resistance diaphragm (small hole diameter) is used and vice versa.

Choosing the diaphragm using coaxial
pipes

Changing the diaphragm

If inserting or changing a diaphragm, it is necessary to
remove the fan assembly, take out the fume coupling 1
and insert the required diaphragm 2.

Choosing the diaphragm using sepa­rate pipes

.

1

Boilers are fitted as standard with the smallest
diaphragm in the series.
Before inserting the fume outlet pipe, it is therefore
necessary to check there is the right diaphragm
(when it is to be used) and that it is correctly
positioned.

Version - 09.2002

.

2

25

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Calculation example

Here we give an example of the calculation for a separate
fume outlet. We recommend inserting a condensate trap
on long vertical sections to prevent condensation getting
onto the burner and damaging it. If monitoring the con­densate trap is not guaranteed, it must be fitted with a
suitable drain pipe and air trap, which in its turn must be
appropriately connected to a suitable drain.

26

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

2.6 Electrical circuit

Electrical terminal board

Follow the instructions given in the figure to access the electrical connection terminal board.
The layout of the terminals for the various connections is given in the wiring diagram.

Wiring diagram

Key

16 Fan
32 Heating circulator
34 Heating temperature sensor
42 Tap water temperature sensor
43 Air pressure switch
49 Safety thermostat
50 Heating thermostat

N.B. Respect the phase and neutral connections

Version - 09.2002

72 Room thermostat (not supplied)
73 Antifreeze thermostat
81 Ignition electrode

82 Detection electrode
114 Water pressure switch
136 Flow meter

27

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Main electronic card

The electronic card is a Honeywell MF03: part of the card works on low
voltage (24V) and the remainder on 230V (see diagram) and it is fitted with
a fuse (2A). Part of the card is used to control ignition, so it is hooked up to
the detection and ignition electrodes and the safety thermostat. There are
loads and controls common to the card that have already been described,
such as:

 Pump.
 Fan.
 Gas valve.
 Air pressure switch.
There remain some components described hereunder.

Ignition + detection electrode, see chap. 2.4 Burner Unit

Safety thermostat

X6 - 5/6 has a thermostat with gold contacts that opens if the temperature
exceeds 100°C. Connected directly to the ignition and main card, when it
opens it cuts off the power supply to the valve directly, shutting down the
boiler. It is set on the left-hand side of the exchanger by a spring.

Limit thermostat

Connected on the main card X4 - 6/7, it is a thermostat with silver contacts
that opens if the temperature exceeds 88°C. It requires no manual resetting
and closes the contacts again if the temperature falls under 70°C. It is set on
the right-hand side of the exchanger by a spring.

28

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Heating and tap water temperature probe

These are NTC sensors that increase their resistance as the temperature
decreases and are connected directly to the main card X4 - 24V (heating 12­13, tap water 10-11). The heating sensor performs the antifreeze function
too.

Version - 09.2002

29

Supplied By www.heating spares.co Tel. [phone]

3. OPERATION

3.1 Operating principle

When there is a call for heating, the circulator and fan start working; then the air pressure switch enables
the control and safety unit to ignite the burner. Via the electronic flame modulation system, the boiler
capacity is gradually metered till it reaches the set delivery temperature. If the power needed for the
heating plant is lower than the minimum boiler power, when the delivery temperature exceeds the
setting of 6°C, the burner switches off and the electronic system enables re-ignition only after another
2 minutes. On reaching the set ambient temperature (room thermostat), the burner switches off and the
circulator keeps on working for another 6 minutes to enable better heat distribution throughout the
system. If hot tap water is drawn off during the heating phase, the electrical heating circuit automatically
turns off and the hot tap water production circuit switches on. Throughout this phase the heating system
circulator stops and the boiler delivers water at the set temperature.

The boiler keeps the tap water temperature constant by means of flame modulation, even when
different quantities are drawn off.

Test function

Bridging the terminals of connector X5 turns on Test operation. In this mode the boiler works as in
heating mode, but tap water operation, idle time and modulation are turned off. The test lasts 5 minutes.
We recommend opening 1 or 2 taps to get rid of the excess capacity.

Post-circulation

After the call for heating, the circulator performs "post-circulation" for approximately 6 minutes to
prevent thermal inertia and balance the system boiler temperature.

Circulator anti-locking

If not used for 24 h, the circulator is turned on for a few seconds to prevent it locking due to an extended
stoppage during summertime operation.

Gradual starting on heating (gradual increase in heating temperature)

The time to reach the maximum heating temperature is 5 minutes.

Limit thermostat

The 88°C limit thermostat coming on causes the burner to switch off momentarily via the ignition unit
and the heating circulator to start up.

Antifreeze protection

The antifreeze function is turned on by the heating temperature sensor when the temperature falls under
5°C. In this phase, both the burner and the circulator start working. When the temperature reaches 15°C,
the burner switches off while the circulator keeps on working for another 6 minutes.

Tap water circuit antifreeze protection (optional)

It is possible to ensure antifreeze protection for the tap water circuit with the antifreeze kit comprising
4 heating elements of 10W - 230V to be connected to terminal X2 of the control card.

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

30

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

3.2 Operating diagram

Version - 09.2002

31

Supplied By www.heating spares.co Tel. [phone]

3.3 Control panel

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

3.4 Adjustments

Room temperature adjustment (with room thermostat on)

Using the room thermostat or remote control, set the temperature desired in the rooms. Controlled by
the room thermostat, the boiler lights and heats the system water to the set system delivery setpoint
temperature. The generator turns off when the desired temperature in the rooms is reached.

If the room thermostat or the remote control are not installed the boiler will keep the system at the set
system delivery setpoint temperature.

System temperature adjustment

With knob B on the control panel we can set the required system temperature. To prevent localized
condensation on the fume circuit, we recommend a minimum temperature of 60°C.

Hot water temperature adjustment

With knob C on the control panel we can set the tap water temperature from 40°C to 55°C (62°C on
inserting jumper JP03).

Summer/Winter selection

Setting the adjustment potentiometer B to minimum (), the boiler works on Summer.

Adjusting the heating t by changing the circulator delivery-head

The temperature difference t (difference between the system delivery and return heating water
temperatures) must be under 20°C and is obtained by changing the circulator delivery-head with its
variable speed device (or switch).

32

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

3.5 Operating parameter adjustment

Boiler parameter adjustment

P1 Temperature adjustment potentiometer.

Controls the heating delivery temperature from 30°C to 85°C.
The minimum position selects Summer operation.

P2 Hot tap water adjustment potentiometer.

Controls the hot tap water temperature from 40°C to 55°C.

P3 Heating capacity adjustment potentiometer.

P4 Potentiometer to adjust the burner gas pressure in the ignition phase.

The maximum ignition time is 10 sec.
The ignition curve should be regulated taking account of the type of burner and fuel used

(natural gas or LPG).

P5 Minimum pressure adjustment potentiometer.

The potentiometer P5 is to be used if it is necessary to adjust the minimum current to the second
coil of the gas valve.

This adjustment makes it possible to increase the gas valve minimum opening pressure electrically.
The potentiometer P5 is used when the mechanical minimum of the gas valve does not enable
adequate adjustment.

Jumper operation

Version - 09.2002

33

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

4. Troubleshooting

Flow Diagram 1

Checking Electric Power Supply - System Pressure and Antifreeze Protection

34

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Flow Diagram 2

Checking Hot Water Operation

Flow Diagram 3

Checking Heating Operation

Version - 09.2002

35

Supplied By www.heating spares.co Tel. [phone]

Flow Diagram 4

Checking Fan/Fume Circuit

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

36

Version - 09.2002

Supplied By www.heating spares.co Tel. [phone]

Flow Diagram 5

Checking Ignition

DOMINA F 24 - 30 E

FERELLA F 24 - 30 MEL

MILOS AIR COMPACT E

Flow Diagram 6

Check the Modulation of the Hot Water and Heating

Version - 09.2002

37

Supplied By www.heating spares.co Tel. [phone]

Supplied By www.heating spares.co Tel. [phone]

Supplied By www.heating spares.co Tel. [phone]

37047 SAN BONIFACIO - VR - ITALY
tel. [phone] - tlx 480172
fax [phone]

cod. 354M002/0