Page 1
Supplied by HeatingSpares247.com
Wall-Mounting Gas
Boiler
Airtight Chamber,
Heating
DOMITOP HF 24 - 30 E
FERELLA GOLD HF 24 - 30 MEL
TECHNICAL
MANUAL
EDITION
09ï2002
Page 2
DOMITOP HF 24 - 30 E
Supplied by HeatingSpares247.com
FERELLA GOLD HF 24 - 30 MEL
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 via external boiler...................................................... 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 Operating parameter adjustment .......................................................................... 33
4. Troubleshooting ................................................................................. 34
2
Version - 09.2002
Page 3
DOMITOP HF 24 - 30 E
Supplied by HeatingSpares247.com
FERELLA GOLD HF 24 - 30 MEL
1. TECHNICAL CHARACTERISTICS AND DATA
1.1 Introduction
Our appliance is a high-efficiency heat generator for central heating 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, safety valve, filler cock, air pressure switch, water pressure switch,
temperature sensor 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.
There are 5 LEDs on the control panel providing information on the units operating status.
General Warnings
Installation and maintenance must be carried out by professionally qualified personnel, according
to current regulations and the manufacturers 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 manufacturers 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
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DOMITOP HF 24 - 30 E
Supplied by HeatingSpares247.com
FERELLA GOLD HF 24 - 30 MEL
1.2 Dimensions and connections
Domitop HF 24 E version
Top view
12070 120 150
110
8480 80
460
725
272
249
CONNECTIONS AXIS
CONNECTIONS AXIS
100
760
160100 25 150 25
4
321
Key
1 System delivery
2 Gas inlet
3 System return
4 System filler inlet
4
98
15536 155
Bottom view
114
Version - 09.2002
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DOMITOP HF 24 - 30 E
Supplied by HeatingSpares247.com
FERELLA GOLD HF 24 - 30 MEL
Ferella Gold HF 24 MEL version
70 120 120 150
Top view
110
271
271
762
80
705
135
80
460
80
1602515025100
Top view
1 System delivery
2 Gas inlet
3 System return
4 System filler inlet
Version - 09.2002
15536 155 114
98
123
4
Bottom view
5
Page 6
DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
Domitop HF 30 E version
Top view
120 120
110
202
Ø80 Ø80 Ø80
460
15 430 15
110
692
363
760
36 215 54
155
1
23
77
189
Key
1 System delivery
2 Gas inlet
3 System return
4 System filler inlet
6
1
2
4
Bottom view
175
3
Version - 09.2002
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DOMITOP HF 24 - 30 E
Supplied by HeatingSpares247.com
FERELLA GOLD HF 24 - 30 MEL
Ferella Gold HF 30 MEL version
Top view
110 110120120
200
362
80 80 80
460
362
760
692
13 5
36 155 215 54
189
1543015
175
Key
1 System delivery
2 Gas inlet
3 System return
4 System filler inlet
Version - 09.2002
4
12 3
Bottom view
7
Page 8
DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
1.3 General view and main components
HF 24 E/MEL version
5
28
49
20
21
114
34
29 187 43
22 82 81
56
16
27
50
19
26
36
32
Key
5 Airtight chamber
7 Inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
19 Combustion chamber
20 Burner assembly
21 Main nozzle
22 Burner
26 Combustion chamber insulation
27 Copper exchanger
28 Fume manifold
29 Fume outlet manifold
32 Heating circulator
34 Heating temp. sensor
36 Automatic air vent
43 Air pressure switch
44 Gas valve
49 Safety thermostat
50 Heating thermostat
56 Expansion tank
63 Heating temperature adjustment
74 Heating system cock
81 Ignition electrode
82 Detection electrode
84 1st gas valve operator
85 2nd gas valve operator
98 Off-On-Reset switch
114 Water pressure switch
145 Water gauge
187 Fume diaphragm
117 4485841410
ON
RESET
OFF
°C
98 63 145
bar
3
4
2
1
5
0
6
DOMITOP - FERELLA GOLD version
8
Version - 09.2002
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DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
HF 30 E/MEL version
28
49
20
21
114
34
29 187
43
Key
5 Airtight chamber
7 Inlet
5
10 System delivery
11 System return
14 Safety valve
16
16 Fan
19 Combustion chamber
20 Burner assembly
21 Main nozzle
22 Burner
27
50
26 Combustion chamber insulation
27 Copper exchanger
28 Fume manifold
29 Fume outlet manifold
32 Heating circulator
34 Heating temp. sensor
36 Automatic air vent
43 Air pressure switch
22 82
19
26
81
44 Gas valve
56
49 Safety thermostat
50 Heating thermostat
56 Expansion tank
63 Heating temperature adjustment
74 Heating system cock
81 Ignition electrode
36
82 Detection electrode
84 1st gas valve operator
32
85 2nd gas valve operator
98 Off-On-Reset switch
114 Water pressure switch
145 Water gauge
187 Fume diaphragm
10
74
14 784 114485
ON
RESET
OFF
°C
98 63 145
bar
3
4
2
1
5
0
6
DOMITOP - FERELLA GOLD version
Version - 09.2002
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FERELLA GOLD HF 24 - 30 MEL
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1.4 Technical data table
DOMITOP HF 24 - 30 E
DOMITOP - FERELLA GOLD
Powers Pmax Pmin
Heating Power (Net Heat Value - Hi)
Heating Power (Gross Heat Value - Hi)
Useful heating power 80°C - 60°C
Gas supply Pmax Pmin
Natural Gas main nozzles (G20) mm 12 x 1.30
Natural Gas supply pressure (G20) mbar 20.0
Pressure at Natural Gas burner (G20) mbar 11.8 2.5
Natural Gas delivery (G20) nm
LPG main nozzles (G31) mm 12 x 0.77
LPG supply pressure (G31) mbar 37.0
Pressure at LPG burner (G31) mbar 36.0 7.0
LPG burner (G31) Kg/h 2.00 0.87
Heating
Maximum working temperature in heating °C 90
Maximum working pressure in heating bar 3
Safety valve bar 3
Minimum working pressure in heating bar 0.8
Expansion tank capacity litres 8
Expansion tank pre-filling pressure bar 1
Boiler water content litres 1.5
Dimensions, weights connections
Height mm 760
Width mm 460
Depth mm 272
Weight with packing kg 35
Gas system connection inches 1/2
Filling system connection 1/2
Heating system connection 3/4
Electrical power supply
Max electrical power absorbed W 125
Power voltage/frequency V/Hz 220/50
Electrical protection rating IP 44
kW 25.8 11.2
kcal/h 22,200 9,900
kW 28.7 12.4
kcal/h 24,700 10,700
kW 23.3 9.7
kcal/h 20,000 8,300
3
/h 2.73 1.19
inches
inches
24 KW
30 KW
Pmax Pmin
33.1 14.5
28,500 12,500
36.8 16.1
31,600 13,800
30.0 12.7
25,800 10,900
Pmax Pmin
16 x 1.25
20.0
11.8 2.5
3.50 1.53
16 x 0.75
37.0
35.5 7.0
2.57 1.13
90
3
3
0.8
10
1
1.7
760
460
363
45
1/2
1/2
3/4
125
220/50
44
10
Version - 09.2002
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DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
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
222
82
20
-
+
5
43
50
56
81
44
Key
5 Airtight chamber
7 Inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
20 Burner assembly
29 Fume outlet manifold
32 Heating circulator
34 Heating temp. 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
84 1st gas valve operator
114 Water pressure switch
187 Fume diaphragm
222 Copper exchanger
34
114
14
74
10
Version - 09.2002
7
11
32
11
Page 12
DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
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 doesnt 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
m
C.A.
6
5,5
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
3
2
1
0,6 0, 1 1, 1, 1, 1, 2 2, 2, 2,6
B = Losses of head 30kW version
A
B
2,8 3 3,2 3,4 3,6 3,8 40,40,20
Air separator
This is used to expel the air in the heating circuit automatically and is located
on the pump casing. It is normally accessible either via the fork or by simply
unscrewing it from its seat.
m3/h
12
Version - 09.2002
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DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
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
8-litre version
30kW
10-litre version
Exchanger
The exchanger is a copper laminar assembly. It comprises a thickly finned portion and four circular pipes
connected together in series. The water exchanges directly with the combustion gases and makes the
system safe via a safety thermostat (100°C) and the limit thermostat (88°C). Due to its shape and design,
the heat gets evenly distributed 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
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DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
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
- 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
It ensures the filling system flows only in one direction and remains airtight
along with the cock.
Filler cock
The boiler has a 1/2 connection on the right-hand side of the heating delivery
for filling the system. It is not fitted on the boiler for some markets such as the
British and Belgian ones.
14
Version - 09.2002
Page 15
DOMITOP HF 24 - 30 E
Supplied by HeatingSpares247.com
FERELLA GOLD HF 24 - 30 MEL
2.2 Hydraulic circuit - tap water via external boiler
Hydraulic diagram for tap water
The HF is a boiler for heating only. However, if required, the HF has a special kit for connecting the boiler
for tap water, too, via an external boiler. The solution shown in the hydraulic diagram has a three-way diverter
valve and a sensor for the external boiler. The kits also contain connection pipes that vary depending on the
model. The tap water temperature can be adjusted by inserting the knob (included in the kit) in the control
panel (D).
29-187
16
49
222
82
20
34
114
14
74
-
+
5
7
A
10
43
50
56
81
44
32
11
VD
C
D
E
B
F
Key
5 Airtight chamber
7 Inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
20 Burner assembly
29 Fume outlet manifold
32 Heating circulator
34 Heating temp. sensor
43 Air pressure switch
44 Gas valve
49 Safety thermostat
Version - 09.2002
50 Heating thermostat
56 Expansion tank
74 Heating system cock
81 Ignition electrode
82 Detection electrode
84 1st gas valve operator
114 Water pressure switch
187 Fume diaphragm
A Boiler
B External boiler
C Boiler expansion tank
D Tap water inlet
E Tap water outlet
F Heating circuit
15
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DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
Electrical and plumbing connections
The terminal block for the electrical connections is designed for hooking up the diverter valve and the sensor.
It is necessary to take out the 1.8 KOhm resistor on the probe connection whose job was to simulate a virtual,
always-satisfied boiler.
Boiler connection kit assembly instructions
1KWMK18Y
1KWMK19Y
24 Kw
Fig. 1
30 Kw
Fig. 1
- Connect the pipes and 3-way valve as shown
in Fig. 1.
- Make the electrical connection to the terminal
block A (Fig. 2) as shown in the diagram
Fig. 3.
Connect the 3-way valve (Ref. 95).
Connect the boiler sensor (Ref. 155).
Take out the resistor between terminals 3
and 4.
- Open the instrument panel, take out the plug
C (Fig. 4) and insert the knob D (Fig. 5)
to adjust the tap water temperature.
155
95
72
16
87654321
A
5011434
X4
X9
12
3
12345678910111213
Fig. 3
Fig. 2
Fig. 4 Fig. 5
Version - 09.2002
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FERELLA GOLD HF 24 - 30 MEL
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2.3 Gas circuit
Gas circuit diagram
DOMITOP HF 24 - 30 E
29-187
16
49
222
82
20
34
114
14
74
-
+
5
10
7
11
43
50
56
81
44
32
Key
5 Airtight chamber
7 Inlet
10 System delivery
11 System return
14 Safety valve
16 Fan
20 Burner assembly
29 Fume outlet manifold
32 Heating circulator
34 Heating temp. 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
84 1st gas valve operator
114 Water pressure switch
187 Fume diaphragm
222 Copper exchanger
Version - 09.2002
17
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DOMITOP HF 24 - 30 E
C
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FERELLA GOLD HF 24 - 30 MEL
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 systems 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 doesnt 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).
B
25+/-50V DC
COMMON
80+/-110V D
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
Page 19
DOMITOP HF 24 - 30 E
24 kW version
30 kW version
kW
mbar
18
19 20 21 22 23
5
10
15
20
25
30
35
9 10 11 12 13 14 15 16 17
8
24 25 26 27 28 29 30 31 32 33 34
G31
LPG
G20
Nat. gas
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FERELLA GOLD HF 24 - 30 MEL
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
F
E
B
A
D
C
25+/-50V DC
COMMON
80+/-110V DC
Key
After checking or
adjusting the
pressure, it is mandatory to
seal the adjustment screw
with paint or a specific seal.
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
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DOMITOP HF 24 - 30 E
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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 units 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
pressures, 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
Page 21
DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
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.
±0.5
3.5
Version - 09.2002
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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
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DOMITOP HF 24 - 30 E
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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
Page 24
DOMITOP HF 24 - 30 E
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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.
C
NC
NO
Key
NO = Normally open
NC = Closed
C=Common
Pressure gauge
pa
24
Version - 09.2002
Page 25
DOMITOP HF 24 - 30 E
Pipe length
calculated in
linear metres
Diaphragm
to use
45 mm
47 mm
50 mm
No diaph.
Min
0 m
10 m
20 m
35 m
Max
10 m
20 m
35 m
45 m
HF 24
HF 30
47 mm
50 mm
52 mm
No diaph.
Diaphragm
to use
Min
0 m
15 m
30 m
40 m
Max
10 m
30 m
40 m
45 m
Pipe length
calculated in
linear metres
Ø
N.B. The
diameter of
the hole Ø is
stamped on the
diaphragm
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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 highresistance diaphragm (small hole diameter) is used and vice versa.
Choosing the diaphragm using
coaxial pipes
Diaphragm
Type
Coaxial
60/100
Coaxial
80/125
Length up to:
1 bend + 1 metre
1 bend + 3 metres
1 bend + 3 metres
1 bend + 4 metres
1 bend + 5 metres
to use
HF 24
50 mm
No diaph.
45 mm
50 mm
No diaph.
HF 30
52 mm
No diaph.
50 mm
No diaph.
No diaph.
Choosing the diaphragm using
separate 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.
.
1
Boilers are
fitted as standard
with the smallest
diaphragm in the series.
Before inserting the fume outlet pipe, it is
Version - 09.2002
therefore necessary to check there is the right
diaphragm (when it is to be used) and that it is
correctly positioned.
.
2
25
Page 26
DOMITOP HF 24 - 30 E
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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.
6
Ref.
1
2
3
4
5
6
No.Pieces
1
1
1
1
36
1
Description
Air bend Ø80
Horizontal air pipe Ø80
Windproof end piece
Condensate collection cup coupling
Vertical fume pipe Ø80
Outlet flue + coupling
Tot al
5
4
1 2 3
Equivalent
loss
1.5 m
1.0 m
2.0 m
3.0 m
36.0 m
4.0 m
47.5 m
26
Version - 09.2002
Page 27
DOMITOP HF 24 - 30 E
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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
81 82
BL
BL
Y/G
Y/G
155
95
87654321
LN
44491643
MV1
MV2
MV3
MV4
WOV
BR
BlueBRBlueBRBlue
X6
X8
R
Blue
X1
PMF03F
101
X7
32
Blue
BR
Blue
X2 X3
12121312345678910 12345678910111213
230V
98
BR
BlueBRBR
X9
X4
123
24V
X12
12
X10
123456789
175
R
W
W
ROO
X11
Nat/LPG
JP01
5011434
Blue
JP02
BR
BL
BL
JP03
21
X5
72
R
TEST
Key
16 Fan
32 Heating circulator
34 Heating temperature sensor
43 Air pressure switch
44 Gas valve
50 Limit thermostat
72 Room thermostat (not supplied)
81 Ignition electrode
82 Detection electrode
95 Diverter valve
49 Safety thermostat
N.B. Respect the phase and neutral connections
Version - 09.2002
230V 24V
98 Switch
101 Electronic card
114 Water pressure switch
155 Boiler sensor
175 Transformer
R Resistance 1.8 Ohm
27
Page 28
DOMITOP HF 24 - 30 E
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Main electronic card
The electronic card is a Honeywell PMF03: 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 located on the left-hand side of the exchanger in an appropriate
flat seat.
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 located on
the right-hand side of the exchanger in an appropriate flat seat.
28
Version - 09.2002
Page 29
DOMITOP HF 24 - 30 E
NTC sensor
0
3
6
9
12
15
18
21
24
27
30
33
0 20 40 60 80 100 120
Temperature (°C)
Resistance (K Ohm)
15
50
70
30
90
5
25
40
60
80
100
Temperature (°C)
Resistance (K Ohm)
3,6
1,7
8
0,92
10
5,3
2,5
1,25
0,68
15,6
25,3
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FERELLA GOLD HF 24 - 30 MEL
Heating temperature probe
These are NTC sensors that increase their resistance as the temperature
decreases and are connected directly to the main card X4-24V(12-13). The
sensor performs the antifreeze function too.
Version - 09.2002
29
Page 30
3. OPERATION
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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.
Test function
Bridging the terminals of connector X5 turns on Test operation. In this mode the boiler works as in heating
mode, but idle time and modulation are turned off. The test lasts 5 minutes.
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.
DOMITOP HF 24 - 30 E
FERELLA GOLD HF 24 - 30 MEL
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.
30
Version - 09.2002
Page 31
DOMITOP HF 24 - 30 E
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3.2 Operating diagram
Winter
System pressure > 0.8 bar:
LED 5 not blinking
Room thermostat, heating potentiometer on call:
LED 4 on
Heating circulator comes on
Heating and boiler sensor enabling signal
88°C limit thermostat enabling signal.
Air thermostat "NO" contact open, fan starts.
Intake and outlet ducts open, resistance under table limit.
Pressure difference at air pressure switch >180 Pascal (18.00 mm approx.)
Air pressure switch "NO" contact closed.
100°C safety thermostat enabling signal
Electric discharge to ignition electrode (81).
Continuous voltage of 230 V to the gas valve operators.
Main burner ignition
Flame detection at ionization electrode within 10 sec. (safety time)
End of electric discharge:
Ionization working range
- 1 micro Ampere minimum for safety
- 2/3 micro Ampere minimum for working
Ignition gas adjustment (natural gas or LPG) with potentiometer P4
Version - 09.2002
Heating temperature adjustment trips;
burner and fan switch off
LED 4 off
LED 1 off
The circulator is working
At the end of the 2 min delay, the burner re-ignites
when required
LED 4 on
LED 1 on
Room thermostat trips on reaching the set
temperature:
LED 4 off
LED 1 off
Heating circulator operates for 6 min.
(post-circulation)
31
Page 32
3.3 Control panel
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OFF
ON RESET
DOMITOP HF 24 - 30 E
FERELLA GOLD HF 24 - 30 MEL
4
3
12
60
50
40
°C
bar
70
80
3
4
2
1
5
0
6
AB C E
D
Table 1
LED
ab d e
ITEM DESCRIPTION
A OFF/ON/RESET switch
a
Burner on
b
Shutdown
Standby for heating (blinking light)
d
Heating required (steady light)
Low system pressure (blinking light)
e
bar
Electrical power supply (steady light)
B Heating temperature
setting
C Water gauge
D Boiler temp. adjustment
(with optional kit)
E Arrangement for clock
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 D on the control panel we can set the tap water temperature from 40°C to 55°C (with optional
kit).
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
Page 33
DOMITOP HF 24 - 30 E
JP01
Inserted
Not inserted
3-way valve system
Not contemplated
Jumper JP01: If using an external boiler for the tap water
The boilers are made with JP01 not inserted
JP02
Inserted
Not inserted
Natural gas operation
LPG operation
Jumper JP02: Boiler operation with natural gas or LPG
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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.
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
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DOMITOP HF 24 - 30 E
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FERELLA GOLD HF 24 - 30 MEL
4. Troubleshooting
Flow Diagram 1
Checking Electric Power Supply - System Pressure and Antifreeze Protection
First of all, check the following points
The gas cock is open
The electricity is on
The polarity is correct
The system pressure is between 1 and 1.5 bar
The pump turns correctly
Selector on
summer position " "
Turn the selector onto ON
Is the pressure
of the water not
between
1 and 1.5 bar?
NO
Check the
electrical connection
of the water
pressure switch
Check and if
necessary change
the water
pressure switch
YES
Proceed with
diagram 2
YES
YES
Take the pressure
to 1 - 1.5 bar
Is LED5 blinking?
circulator turn?
If the boiler temperature is
under 5°C the antifreeze
protection is active
Disconnect the heating
temperature sensor
Is the burner out?
Check and if necessary
change the main card
Is LED5 on?
YES
NO
Does the
burner ignite?
YES
Does the
YES
NO
NO NO
NO
NO
Are there 230V between
the terminals X1-1 X1-2?
YES
Check and if necessary
change the 2A fuse
Is LED5 on?
YES
Proceed with
diagram 2
The relay RY 1
is closed
NO
YES
Check the
electrical connection
of the circulator
Check and if
necessary change
the circulator
Repair the fault with
the external line
NO
Change the
main card
34
Version - 09.2002
Page 35
DOMITOP HF 24 - 30 E
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Flow Diagram 2
Checking Heating Operation
Set the temperature for
heating to maximum
Make sure the room
thermostat is activated
Is LED4 blinking?
YES
Wait for 2 minutes
Is LED4 blinking?
NO
Check and if necessary
change the heating sensor
NO
NO
Flow Diagram 3
Controllo Ventilatore/Circuito Fumi
Does the circulator turn?
YES
Proceed with
diagram 3
Is the relay
RY100 closed?
YES
Proceed with
diagram 4
NO
NO
Is the relay
RY 101 closed?
Check and if
necessary change
the main card
Check the limit
thermostat
YES
NO
Check the electrical
connections of
the pump
Check and if
necessary change
the pump
NO
YES
Check the electrical connection
of the air pressure switch
change the air pressure switch
Is the relay RY3 closed?
NO
Proceed with diagrams 2-3
Are there 230V at the
fan terminals?
NO
NO
Check and if necessary
Does the fan turn?
YES
Check and if necessary
change the fan
YES
Is the air pressure
switch activated?
NO
Is the pressure
difference in the air
pressure switch
180 Pascal?
NO
Check and
clean the fan
Check that the air inlet
and fume outlet are
correct and clean
Check that the Venturi tube
and the air pressure switch
tubes are clean
Check that
the diaphragm is correct
YES
Proceed with
diagram 5
YES
Check and if
necessary change
the air pressure
switch
Version - 09.2002
35
Page 36
Flow Diagram 4
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Checking ignition
DOMITOP HF 24 - 30 E
FERELLA GOLD HF 24 - 30 MEL
NO
Check and if necessary
change the ignition card
Is LED1 on?
Is there an ignition spark?
YES
Does the burner ignite?
NO
Is LED2 come on
after 10 seconds?
YES
Reset lockout
Does the burner ignite now?
NO
Is there the flame before
the shutdown?
YES
Using P4, adjust the
burner ignition pressure
NO
YES
YES
NO
Proceed with
diagram 4
Check and if necessary change
Check and if necessary change
Check and vent the
gas supply
LED2 (shutdown) comes
on without the
boiler lighting
NO
the safety thermostat
Check electrodes
and leads for damage
and correct connection
the ignition card
YES
Check and if necessary
clean the burner
Check and if necessary
clean the nozzles
Check and if necessary
clean the detection electrode
Check that the ignition electrode
is in the right position
Check the connections
Flow Diagram 5
Check the Modulation of the Hot Water and Heating
The boiler works in
heating mode
YES
Is there flame modulation
at the burner?
Check and if necessary
change the gas valve
NO
The boiler
works normally
change the heating sensor
36
Check and if necessary
Versione - 09.2002
Page 37
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Page 38
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Page 39
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Page 40
37047 SAN BONIFACIO - VR - ITALY
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tel. 045/6139411 - tlx 480172
fax 045/6100233-6100933
cod. 354M007/0
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