wall mounted cast iron, gas fired boiler for central heating ... - Ferroli

SIGMA 

wall mounted cast iron, 

gas fi red boiler for central heating 

fan assisted, room sealed, 

electronic fl ame ig ni tion and control 

INSTALLATION AND SERVICING INSTRUCTIONS 

Sigma 20 - 40 GC N° 41-267-17 

Sigma 40 - 60 GC N° 41-267-18 

cod. 3543556/3 - 04/05 Appr. Nr. B 98.06 A - 0461 AT 0344

INDEX PAGE 

1. TECHNICAL CHARACTERISTICS ......................................................................................3 

2. INSTALLATION ..................................................................................................................6 

3. COMMISSIONING AND TESTING ..................................................................................22 

4. ADJUSTMENT..................................................................................................................23 

5. GAS CONVERSION .........................................................................................................24 

6. MAINTENANCE AND CLEANING .................................................................................25 

7. REPLACEMENT OF PARTS..............................................................................................27 

8. FAULT FINDING ..............................................................................................................30 

9. USER INSTRUCTIONS......................................................................................................33 

BENCHMARK...................................................................................................................34 

 

IMPORTANT 

Sigma 

Your "benchmark" Installation, Commissioning and Service Record Log Book is enclosed in the last pages 

of this manual. This record must be completed and left with the end user. 

Ferroli is a member of the Benchmark initiative and fully supports the aims of the programme. Benchmark 

has been introduced to improve the standards of installation and commissioning of central heating 

systems in the UK and to encourage the regular servicing of all central heating systems to ensure 

safety and efficiency. 

CE MARK 

CE mark documents that the Ferroli gas appliances comply with the requirement contained in European 

directives applicable to them. 

In particular, the appliances comply with the following CEE directives and the technical specifications 

provided from them: 

• Gas appliances directive 90/396 

• Efficiencies directive 92/42 

• Low tension directive 73/23 (modified from the 93/68) 

• Electromagnetic compatibility directive 89/396 (modified from the 93/68) 

C.O.S.H.H. 

Materials used in the manufacture of this appliance are non hazardous and no special precautions are 

required when servicing.

Sigma 

1. TECHNICAL CHARACTERISTICS 

1.01 Introduction 

The Sigma is defined as a “room sealed” boiler, all air required for combustion is taken from outside the room in which it 

is installed. It is a new high performance gas fired heat generator, which is designed to provide indirect hot water and/or 

central heating. The cast iron heat exchanger is suitable for use on fully pumped hot water/central heating systems, 

which may be sealed or open vented. A special feature of this boiler is its built-in electronic flame ignition and control 

unit making burner operation completely automatic and safe. 

The main components are as follows: 

Cast iron heat exchanger specifically shaped for high efficiency. 

Ceramic fibre insulated combustion chamber 

One stainless steel bladed burner specifically designed for this boiler. 

Fan for discharge of combustion products and intake of combustion air. 

Differential air pressure switch. For safety reasons, this ensures the burner ignites only when the fan is 

functioning correctly. 

Hermetically sealed compartment made from corrosion-resistant steel enclosing the above components. 

Combination gas safety valve, complete with pressure stabiliser. 

Central heating flow temperature adjustment thermostat. 

Overheat safety thermostat. 

Electronic control unit for automatic flame ignition and control. 

Front view 

Central heating flow temperature sensor. 

A 

1.02 Dimension 

Right side view 

B 85 132 

Key 

1 - Ø 22 mm flow outlet 

2 - Ø 22 mm return inlet 

3 - Ø 15 gas inlet 

4 - Rear air inlet/flue outlet 

5 - Top air inlet/Flue outlet 

Model 

Sigma 20-40 

Sigma 40-60 

A 

mm 

320 

400 

B 

mm 

53 

133 

C 

mm 

35 

30 

600 

D 

mm 

60 

55 

120 50 

1 

3 

50 

50 

2 

15 

Fig. 1 

620 

147 

78 

25 

5 

25 

Top view 

200 

200 

4 

D 

 

C 

220

1.03 Technical data 

 

Model 

Sigma 20/40 

Sigma 40/60 

Model 

Sigma 20/40 

Sigma 40/60 

Model 

Sigma 20/40 

Sigma 40/60 

Flow 

1 

Ø 

22 

22 

Heat 

output 

Max 

kW 

11,7 

17,6 

G20-NG 

mbar 

20 

20 

Min 

kW 

5,5 

11,4 

Gas supply pressures 

IP 40 

IP 40 

Sigma 

Connections Max. working 

Boiler 

Protection Weight water 

Gas valve 

pressure 

C.H.circuit level 

contents 

Ø 1/2” 

Honeywell 

Return 

2 

Ø 

22 

22 

Max 

kW 

13,0 

19,5 

Heat 

input 

(net) 

G31-LPG 

mbar 

37 

37 

Gas inlet 

3 

Ø 

15 

15 

Min 

kW 

6,1 

12,7 

Max 

kW 

14,4 

21,7 

Heat 

input 

(gross) 

bar 

3 

3 

Min 

kW 

6,8 

14,1 

Minimum 

mbar 

3,1 

6,4 

G20-NG 

Ø 

3,0 

3,60 

G20-NG 

Injectors 

(mm) 

Burner gas pressures 

Nominal 

mbar 

14,0 

15,3 

G31-LPG 

Ø 

1,8 

2,30 

N.B. • Maximum working temperature 82°C, adjustable between 60°C and 82°C. 

kg 

30 

35 

Max 

1,37 

2,06 

Minimum 

mbar 

9,0 

16,0 

Gas flow rates 

G20 m 3 /h-NG G31 kg/h-LPG 

litres 

1,3 

1,6 

Min 

0,64 

1,34 

G31-LPG 

Max 

1,02 

1,53 

Nominal 

mbar 

36 

36 

Min 

0,48 

0,99 

VK 4105 A 

VK 4105 A

Sigma 

1.04 General Layout and Main Components 

5 

90 

28 

132 

27 

19 

1 91 16 1 

1.05 Boiler water fl ow diagram 

Pressure drop mm wg 

1 = Sigma 20-40 

2 = Sigma 40-60 

300 

200 

100 

90 

80 

70 

60 

50 

40 

30 

20 

10 

22 21 7 

Pressure loss diagram 

.1 .2 

10 

43 

49 

34 

11 

86 

121 

68 

63 

24 

83 

44 

151 

Fig. 2 

Fig. 3 

Key 

.3 .4 .5 .6 .7 .8 .9 1 

2 3 

Water flow rate (m 3 /h) 

1 

2 

1 Fixing points 

5 Room sealed compartment 

7 Inlet gas-cock 

10 Central heating flow outlet 

11 Central heating return inlet 

16 Fan 

19 Combustion chamber 

21 Gas injector 

22 Burner 

24 Spark and sensor electrode 

27 Cast iron heat exchanger 

28 Flue collector from heat exchanger 

34 Central heating flow 

temperature sensor 

43 Air pressure switch 

44 Gas valve 

49 Safety overheat thermostat 

63 Central heating temperature setting 

68 Control box with P.C.B. 

83 Full sequence automatic control 

86 Automatic control reset switch 

90 Flue outlet pressure test point 

91 Air pressure test point 

121 Boiler shut-down warning 

132 Flue gas deflector 

151 Drain tap 

Air in 

Flue out 

C.H. 

out 

Gas in 

 

C.H. 

in

2. INSTALLATION 

2.01 Important notices 

 

Sigma 

Assembly, installation, first start up and maintenance must be carried out by competent persons only, in accordance 

with all current technical regulations and directives. 

Gas Safety (Installation & Use) Regulations: 1996 

In the interest of safety, it is the law that all gas appliances are installed by a competent person in accordance with the 

above Regulations, Building Regulations/Building Standards Scotland, Codes of Practice, current I.E.E. Regulations and 

the byelaws of the Local Water Undertaking. Failure to comply with the Regulations may lead to prosecution; it is your 

responsibility to ensure that the law is complied with. 

This appliance must be installed strictly in accordance with these instructions and regulations: 

The Gas Safety Regulations (Installations & Use) 1996. 

The Local Building Regulations. 

The Building Regulations. 

The Buildings Standards (Scotland - Consolidated) Regulations. 

British Standards Codes of Practice: 

B.S. 5440 Part 1 2000 Flues 

B.S. 5440 Part 2 1989 Air supply 

B.S. 5449 1990 FORCED CIRCULATION HOT WATER SYSTEMS 

B.S. 6798 1987 INSTALLATION OF GAS FIRED HOT WATER BOILERS 

B.S. 6891 1989 GAS INSTALLATIONS 

B.S. 7671 1992 IEE WIRING REGULATIONS 

B.S. 4814 1990 SPECIFICATION FOR EXPANSION VESSELS 

B.S. 5482 1994 INSTALLATION OF LPG 

B.S. 7593 1992 TREATMENT OF WATER IN DOMESTIC HOT WATER CENTRAL HEATING SYSTEMS 

Model Water Bye Laws 

For Northern Ireland the rules in force apply 

N.B. For Northern Ireland the rules in force apply. 

Important - If the boiler is to be fitted in a timber framed building it should be fitted in accordance with 

the institute of gas engineers publication IGE/UP/1. If in doubt advice should be sought from the Local Gas 

Region of British Gas Plc. 

2.01.01 Location of Boiler 

The installation of the Sigma must be on a suitable non-combustible load bearing wall which will provide an adequate fixing 

for the boiler mounting bracket assembly. The location should be in an area where the water pipes will not be subjected 

to frost conditions. In siting the boiler the following limitations must be observed: 

The boiler may be installed in any room or internal space, although particular attention is drawn to the requirements of the 

current I.E.E. wiring regulations and in Scotland the electrical provisions of the building regulations applicable in Scotland, 

with respect to the installation of the boiler in a room or internal space containing a bath or shower. 

Where a room sealed appliance is installed in a room containing a bath or shower any electrical switch or 

appliance control utilising mains electricity must be situated so that it cannot be touched by a person using 

the bath or shower. 

2.01.02 Air Supply 

The room or compartment in which the boiler is installed does not require a purpose provided vent when using 

the standard concentric flue. 

2.01.03 Flue System 

The boiler allows the flue outlet to be taken from the rear of the boiler, from either side or vertically. 

It is absolutely essential, to ensure that products of combustion discharging from the terminal cannot re-enter 

the building, or enter any adjacent building, through ventilations, windows, doors, natural air infiltration or 

forced ventilation/air conditioning.

Sigma 

2.01.04 Gas Supply 

If necessary the local Gas supplier should be consulted, at the installation planning stage, in order to establish 

the availability of an adequate supply of gas. 

An existing service pipe must not be used without prior consultation with the Local Gas supplier. 

A gas meter can only be connected by the Local Gas supplier, or by a Local Gas suppliers Contractor. 

Installation pipes should be fitted in accordance with BS6891-1988. 

Appliance inlet working pressure must be 20mbar MINIMUM (Natural gas - G20) or 37 mbar MINIMUM (LPG - G31). 

Pipework from the meter to the combination boiler must be of an adequate size. 

Do not use pipes of a smaller size than the combination boiler inlet gascock connection. 

The complete installation must be tested for gas soundness and purged as described in BS6981-1988. All pipework 

must be adequately supported. 

2.02 Water System (sealed systems) 

Central heating 

Detailed recommendations are given in BS6798, BS5449, BS6700 and CP342 Part 2. Pipework not forming part of the 

useful heating suface should be insulated to prevent any heat losses or possible freezing (i.e. in roof spaces or ventilated 

underfloor spaces). Drain taps should be positioned at the lowest point of the system in accessible locations to permit 

the whole system to be drained down. The drain taps should be in accordance with BS2879. Copper tubing to BS2871, 

Part 1 is recommended for water carrying pipework. Pipework in horizontal runs should have a gradient where possible 

to facilitate the removal of air. Ensure that the boiler heat exchanger is not a natural point for air collection. A 

typical sealed heating system illustrated in fig. 4. 

Typical sealed fully pumped heating system 

Gas 

Pump 

1 

2 

Expansion 

vessel 

Fig. 4a 

3 

Filling point 

Cold water 

Note: A bypass must be fitted as far 

as possible from the boiler if 

thermostatic radiator valves 

are fitted thoughout.

Schematic layout for gravity DHW and pumped CH for Sigma Boiler 

Static Head 

 

min. 1 m 

15 mm 

22 mm 

Flow 

Open 

Vent 

Motorised valve 

28 mm 

gravity DHW 

28 mm 

Return 

28 mm 

Open 

Vent 

max. 150 mm 

Isolating valve 

CH Pump 

Fig. 4b 

By-pass 

To DHW taps 

Isolating valve 

Drain 

Sigma 

Motorised valve 

22 mm CH Radiator Radiator

Sigma 

Important - If thermostatic radiator valves are fitted throughout a bypass must be fitted to ensure a minimum flow rate 

through the boiler of 6 l/min. The bypass should be fitted as far as possible from the boiler. 

2.02.01 Safety valve 

A safety valve complying with the requirements of BS 6750 Part 1 must be fitted close to the boiler on the flow pipe by 

means of a horizontal or vertically upward connection with no intervening valve or restrictions and should be positioned 

to facilitate testing. The valve should be pre-set and nonadjustable to operate at a pressure of 3 bar (45 Ibf/in2 ). It must be 

arranged to discharge any water or steam through a pipe to a safe outlet position. 

2.02.02 Pressure gauge 

A pressure gauge of minimum range 0-4 bar (0-60 Ibf/in2) with a fill pressure indicator must be fitted to the system, 

preferably at the same point as the expansion vessel in an easily visible position. 

2.02.03 Venting 

A method of venting the system during filling and commissioning must be provided by fitting automatic air 

vents or by venting manually. 

2.02.04 Expansion vessel 

In a sealed system an expansion vessel complying with the requirements of BS 4814 must be fitted to the system 

by means of a connection close to the inlet side of the circulating pump in accordance with the manufacturers 

instructions, the connecting pipe being unrestricted and not less than 15 mm (1/2 in) nominal size. The volume 

of the vessel should be suitable for the system water content and the nitrogen or air charge pressure should 

not be less than the system static head. 

Further details of sealed system design can be obtained from BS 5449: Part 1 and the British Gas publication entitled 

Specifications for Domestic Wet Central Heating Systems. 

2.02.05 Water treatment 

If water treatment is used ferroli limited recommend only the 

use of Fernox or Sentinel water treatment products, which must 

be used in accordance with the manufacturers instructions. For 

further information contact: 

Fernox Manufacturing Co. LTD. Sentinel Division 

Tandern house, Marlowe Way Betz Dearborn LTD 

Croydon, surrey, CRO 4YS Widnes, Cheshire WA8 8ND 

Tel: 0870 5601 5000 Tel: 0151 424 5351 

Note - If the boiler is installed in an existing system any 

unsuitable additives must be removed by thorough cleansing. 

All systems should be cleansed according to B.S. 7593. 

Note - In hard water areas treatment to prevent lime scale 

may be necessary. 

Note - It is important that the correct concentration of the 

water treatment product is maintained in accordance with the manufacturers instructions. 

2.03 Gas connection 

VESSEL CHARGE 

PRESSURE (bar) 

INITIAL SYSTEM 

PRESSURE (bar) 

TOTAL WATER 

CONTENT of SYSTEM 

Litres 

25 

50 

75 

100 

125 

150 

175 

200 

For syst. volumes other than 

those given above, mult. the syst. 

volume by the factor across. 

Sizing of expansion vessels: 

Gas connection must be carried out using a rigid pipe. 

The flow at the gas meter should be sufficient for the simultaneous use of all appliances connected to it. Connect 

the gas supply to the boiler according to current regulations. The diameter of the gas cock leaving the boiler is not 

the determining factor in choosing the diameter of the pipe between the appliance and the meter. This must be 

selected in relation to length and pressure drop. 

The whole of the gas installation including the meter should be inspected and tested for soundness and purged 

in accordance with BS6891-1988. 

1.0 

3.5 

7.0 

10.5 

14.0 

17.5 

21.0 

24.5 

28.0 

0.140 

0.5 1.0 

1.5 

2.0 

1.5 

2.0 

EXPANSION VESSEL VOLUME (litres) 

6.5 

12.9 

19.4 

25.9 

32.4 

38.8 

45.3 

51.8 

0.259 

2.0 

13.7 

27.5 

41.3 

55.1 

68.9 

82.6 

96.4 

110.2 

0.551 

1.5 

4.7 

9.5 

14.2 

19.0 

23.7 

28.5 

33.2 

38.0 

0.190 

10.3 

20.6 

30.9 

41.2 

51.5 

61.8 

72.1 

82.4 

0.412 

8.3 

16.5 

24.8 

33.1 

41.3 

49.6 

57.9 

66.2 

0.33

2.04 Wall Mounting 

2.04.01 Drilling Template 

 

Model 

Sigma 20-40 

Sigma 40-60 

Ø118 

80 

B 

C 

200 min. 

111 

A 

320 

400 

135 

A 

B 

60 min. 

140 min. 

WARNING: 

C.H. connection 

on this side 

C 

120 

200 

Fig. 5 

Fig. 6a Fig. 6b 

230 min. 

620 

200 min 

810 min 

200 min 610 

Ø90 

Ø90 

147 

80 

100 

Boiler 

mounting 

plate 

B 

C 

200 min. 

165 min. 

91 

A 

100 

Ø* 

200 

205 min 

135 

A 

105 min 

254,5 

620 

5 min 

WARNING: 

C.H. connection 

on this side 

350 min. 

620 

Sigma 

Minimum clearances and drilling template for standard 

rear flue. 

Drilling template for orizontal concentric flue. Drilling template for two pipe system with orizontal 

air inlet.

Sigma 

2.04.02 Wall mounting instructions for Rear Flue Application 

1 

Fig. 7 

Select suitable mounting position for 

boiler. Refer to fig. 6 for dimensions and 

minimum clearance. Using the template 

or mounting plate mark flue outlet and 

boiler mounting points. 

2 

Fig. 8 

Drill four 10 mm holes 70 mm deep to 

accept the wall plug. Using a core drill 

cut hole for the flue. 

Drill cut a 118 mm diameter hole if it 

is possible insert the flue-pipe from 

outside of the room; drill cut a 127 mm 

diameter hole if to insert the flue-pipe 

from inside of the room. 

4a 4b 

5a 5b 

3 

Fig. 9 

Insert the plastic plugs. 

Ø 127 


Insert flue-pipe from inside of the room (core drill 127 mm hole)... 

Ø 118 


... or insert flue-pipe from outside of the room (core drill 118 mm hole).

6 7 

Fig. 12 Fig. 13 

Gently pull back until wall seal is flush with the wall. 

8 

Fig. 14 Fig. 15 

Through plate into air tube, drill two holes and fix in place 

using two self tapping screws n° 6 x 6mm long. 

10 

Fig. 16 Fig. 17 

Insert the aluminium flue pipe into white plastic outer flue, 

making sure the aluminium pipe sits fully and centrally 

into the flue terminal. 

 

9 

11 

15 mm 

Sigma 

Position the wall plate on the wall. Fix plate to wall with the 

square gasket between the wall and the plate use the large 

diameter washers for the bolts ad screws. 

Cut the outer flue flush with the flange on the hanging 

plate. 

Mark the aluminium flue pipe at the point it is flush with 

the mounting plate. Add 15 mm to this mark and cut the 

aluminium inner flue pipe at this point.

Sigma 

12 13 14 

Fig. 18 Fig. 19 Fig. 20 

Install the inner metal flue "a" into the 

adapter "b". 

2.05 Top outlet fl u e conversion 

1 

Fig. 21a 

Remove fan by pulling off electrical connections. Pull off air 

pressure switch tubes from the air pressure switch. Remove 

the two screws "b" and rotate the fan upward to disengage 

it from the securing pin "a". 

3 

Fig. 22a 

Take off the four screws which fix the top sealed chamber 

cover, remove the cover and gasket. 

Lift boiler with flue pipe in place, 

engage inner and outer flue, slide into 

position. 

2 

Fig. 21b 

4 

Fig. 22b 

Make sure the inner flue is fully engage 

in the flue terminal, secure boiler with 

two nuts and washers "a" and "b". 

Rotate the fan upward to disengage it from the securing 

pin "a". Remove the securing screw that locates the 

fan nozzle extension to the fan and remove the nozzle 

extension. 

Rotate the cover and gasket through 90° and fit it to 

the rear of the boiler to cover the original flue outlet. 

Secure them both in place with the four screws removed

5 

c 

6 

Fig. 23 

10 

Fig. 28 

Fix the restrictor with the two screws 

"a" inside the pipe connection "b". 

 

d 

c- 

d 

Common 

For top outlet 

For rear outlet 

Remove fan mounting plate by undoing 

the three fixing screws "c". 

11 

b 

b 

Fig. 29 

a 

9 

Fig. 27 

Insert the correct restrictor. 

(See section 2.07). 

Sigma 

Boiler is fitted as standard with Ø36 (Sigma 20-40) or Ø41 (Sigma 40-60) restrictor. Identify on 2.07 the correct restrictor for 

your flue system. If it is necessary to change it. follow instructions at step 7-10, if not, go to step 11. 

7 8 

Remove the two screws "a" from pipe 

connection "b". 

c 

d 

For rear 

outlet 

Fig. 24 

Fig. 25 Fig. 26 

Remove restrictor "c". 

For top 

outlet 

Rotate the fan through 90° so that the fan nozzle points upward. Secure the fan 

to the plate in the new position using screws in position "d". 

Refit wiring connections to fan and air 

pressure switch tubes ensuring correct 

orientation. I.E. red tube to air pressure 

switch connection with red dot (+) 

and clear tube to air pressure switch 

connection with no paint marking (-). 

Fit the fan into the boiler rotating 

the front upwards to engage with the 

pin "a". 

Secure with the screws "b".

Sigma 

2.06 Top outlet Flue Connection 

Three different connection are available from top of the boiler, using accessories as reported on fig. 30a, b e c and 

on examples a next page. 

1 Top outlet horizontal 2 Top outlet two 3 

2.06.01 Examples of top fl ue connection 

1 Example of concentric flue Ø 100 

with appliance bend use 

Fig. 31 

Note • Bear in mind that the two concentric 

pipes must slope downwards away from the 

boiler at a rate of about 3 mm/m to avoid 

rainwater entering the boiler. Outside, the 

pipes should protrude from the wall between 

10 and 60 mm. 

Warning • Back exit with coaxial bend is 

not possible 

concentric fl ue 

Vertical Connection, concentric bend 

and two pipe separator can be 

supplied on request. 

2 Example of direct roof flue outlet 

and wall air inlet with 2 pipe system 

Fig. 32 

pipe system 

Fig. 30a Fig. 30b Fig. 30c 

Warning • Back exit with Air/Flue T separator 

is not possible 

Top outlet vertical 

concentric fl ue 

3 Example of concentric flue Ø 100 

with vertical outlet flue use. 

Fig. 33 

Fig. 30

2.07 Restrictor and max fl ue length 

2.07.01 Concentric Flue System 

First table below shows the maximum flue lengths available for boilers with concentric systems. 

For correct calculation remember to include the reduction for bend and flue terminals listed on second table. 

Maximum flue 

length permissible 

Sigma 20/40 

Sigma 40/60 

 

100 mm concentric 

Vertical *Horizontal 

125 mm concentric 

Vertical *Horizontal 

100 mm 

concentric 

back exit 

4 m 3 m 5 m 5 m 1 m 

* For horizontal flueing the reduction for appliance bend are already included. 

A 

B 

C 

Sigma 

20-40 

Sigma 

40-60 

Reduction for bend 

100 mm concentric bend 90° 




A Horizontal concentric B Back concentric C Vertical concentric 

L (max. 3 m.) 

Fig. 34 Fig. 35 

Restrictor pipe 

configuration 

L 1m 

1m L 3m 

L 1m 

L 2m 

L 2m 

Ø36 

Ø39 

Ø36 

Ø36 

Ø39 

Ø41 

Ø46 

Ø46 

Ø41 

Ø46 

L (max. 1 m.) 

To calculate the restrictor, identify your flue pipe configuration (A, B or C) and 

choose the correct restrictor diameter from the restrictor table below. 

Boiler is fitted as standard with Ø36 and Ø46 restrictor. 

For instruction on changing restrictor refer to step 7-10 at pages 14. 

L (max. 4 m.) 

Fig. 36 

Sigma 

1 m 

0,5 m 

0,5 m 

0,25 m

Sigma 

2.07.02 Two pipe fl ue system 

1. Utilise the pipes and fittings flows resistance tables on the following pages and calculate the total flow resistance in 

metres-air, by adding the flow resistances of the components in the whole air-flue system, based on their position 

(vertical or horizontal, air inlet or flue outlet). 

Please note that the same fitting, identified by a one code (i.e. 1 pipe diameter 80, code KWMA83A), can offer 

different flow resistances if positioned as air inlet or flue outlet, if placed vertically or horizontally. 

The fl ow resistance of the special two pipe fl ue-air adapters do not have to be included in the calculation as 

they are already included in the maximum length calculation. 

IMPORTANT: the pipes and fittings flow resistance (reduction) have been summarised on the following page. The 

fl ow resistance values written refer only to Ferroli pipes and fi ttings. 

2. Verify that the total flow resistance calculated is less or equal to 40 metre. 

3. Choose the more suitable restrictor from table below. 

Tab. 5 

Ref. 

1 

2 

3 

4 

5 

6 

7 

Description 

Tab. 3 

Connection for concentric pipe cod. KWMR52A 

Air/Flue T separator cod. KWMA90U 

Male - Female flue Ø 80 mm 

Air 

Flue bend 80 mm 

Air wall terminal outlet flue Ø80 

Air wall terminal air Ø80 

Flue 

Total fl ow resistance 17,5 m: 

use restrictor Ø41 

Total flow resistance 

0 - 20 metres 

20 - 30 metres 

30 - 40 metres 

Horizontal 

Vertical 

Horizontal 

Vertical 

N° of 

pieces 

1 

1 

1 

/ 

1 

5 

1 

1 

1 

Total 

Length 

reduction 

/ 

already included 

1 

/ 

2 

5 

2,5 

5 

2 

17,5 

Sigma 20/40 

Example of calculation for wall inlet/outlet with 2 pipe system maximum total fl ue length: 40 metres 

Fig. 37 

Ø36 

Ø39 

Ø39 

Use restrictor: 

7 

6 

Sigma 40/60 

Ø41 

Ø46 

Ø46 

4 

1 m 

3 

Sigma 60 

4 

2 

5 m 

 

5 

1

Pipe and fi ttings reduction table (shown in Metres) 

 

Sigma

Sigma 

2.07.03 Terminal Position 

Dimensions Terminal position 

(kW input expressed in net) 

Aa Directly below an opening, air brick, (0-7 kW) 

300 mm 300 mm Not allowed 300 mm 

opening windows, etc. (>7-14 kW) 

600 mm 

(>14-32 kW) 

1500 mm 

(>32-70 kW) 

2000 mm 

Ba Above an opening, air brick, (0-7 kW) 



300 mm 

(>14-32 kW) 

300 mm 

(>32-70 kW) 

600 mm 

Ca Horizontally to an opening, air brick, (0-7 kW) 



400 mm 

(>14-32 kW) 

600 mm 

(>32-70 kW) 

600 mm 

D Below gutters, soil pipes or drain pipes 


E Below eaves 


F Below balconies or car port roof 


G From a vertical drain pipe or soil pipe 

300 mm 150 mmb Not allowed 150 mm 

H From an internal or external corner 


I Above ground roof or balcony level 


J From a surface facing the terminal 

(also see 6.1.2) 

600 mm 600 mm N/A 600 mm 

K From a terminal facing the terminal 

600 mm 1200 mm N/A 1200 mm 

L From an opening in the car port ( e.g. door, 

window) into the dwelling 

1200 mm 1200 mm N/A 1200 mm 

M Vertically from a terminal on the same wall 

1500 mm 1500 mm N/A 1500 mm 

N Horizontally from a terminal on the same wall 

300 mm 300 mm N/A 300 mm 

O From the wall on which the terminal is mounted 

N/A N/A N/A 50 mm 

P From a vertical structure on the roof 

N/A N/A See Table 2 

and Fig. 6b 

N/A 

Q Above intersection with roof 

N/A N/A See Table 2 

and Fig. 4 

150 mm 

NOTE N/A = Not applicable 

2.08 Electrical connection 

The boiler must be connected to a single phase 230V 50Hz electricity supply with a 3 A max. fuse and a bipolar switch 

with contact opening of at least 3 mm fitted between the boiler and the electricity supply. The boiler must always be 

connected to an efficient earth installation. In the electrical box, there is a 3 pole terminal block for connecting the 

boiler to the mains (230V 50Hz) and a 3 pole block for connecting a 

circulating pump (not supplied). See Wiring diagram (fig. 41a) for the 

connection of external control. 

Temp. kOhm 

When the boiler is connected to an electricity main, it is essential TO 

ENSURE CORRECT POLARITY (LIVE: brown cable, NEUTRAL: blue 

cable, EARTH: yellow-green cable). 

25°C 1000 kOhm 

All wiring must conform to current I.E.E. regulations. 

Note: If the power supply cable has to be replaced, use “0.75mm 

(24/0.20) cable only to BS6500 with a maximum external 

diameter of 8 mm. 

Key 

63. CH temperature setting 

86. Reset switch 

101. Main P.C.B. 

121. Boiler shut-down warning (Led) 

X3-X4-X5-X8. Connectors 

JP. Link 

J 

F 

l 

L 

Balanced flues room 

sealed 

Natural 

draught 

Fanned 

draught 

Natural 

draught 

Q 

G 

Open flues 

Fig. 39 

Q 

B C 

Fanned 

draught 

a In addition, the terminal should not be nearer than 150 mm (fanned draucht) or 300 mm (natural draught) to an opening in the building fabric formed for the purpose of accommodating 

a built-in element such as a window frame, (see Figure C2). Separation distances are linked to the rated heat inputs as shown. 

b This dimension may be reduced to 75 mm for appliances of up to 5 kW heat input. 

A 

P 

D, E 

H H 

Fig. 38 

Temp. 

sensor 

NTC 34 

101 

X3 

G C P 

X8 

JP 

M 

N 

M 

A approved terminal guard (part. No. C2) should be screwed 

to the wall centrally over the terminal, when the distance 

is less than 2 m from the outside floor. 

N 

60°C 

82°C 

Q 

X4 X5 

1 4 1 5 

63 

K 

185 kOhm 

80 kOhm 

121 

86

2.08.01 Schematic wiring diagram for fully pumped system 

 

72 

24 

230V ~ 

50 Hz 

32 

SwL L N PL PN 

YG 

Blue 

YG 

Blue 

12 11 10 

BR 

V 

G 

W 

Blue 

BR 

BL 

Key 

16 Fan 


32 Central heating pump (not fitted) 

34 Central heating flow temperature sensor 


49 Safety thermostat 

63 C.H. temperature adjustment 

72 External controls 

83 Full sequence automatic control on gas valve 

86 Reset switch 

101 Main P.C.B. 

121 Boiler shut-down warning (Led) 

9 

83 

8 

7 

6 

5 

4 

Blue 

Fig. 40a 

3 

34 

2 

1 

101 

X3 

43 

NO NC 

BL 

BL 

C 

G C P 

X8 

JP 

Fully 

pumped 

W 

R W 

Sigma 

X4 X5 

1 4 1 5 

Colors key 

BR Brown 

Blue Blue 

BL Black 

W White 

O Orange 

63 

49 

BR 

16 

O 

P 

121 

G Grey 

R Red 

V Violet 

P Pink 

YG Yellow-Green 

If there are no external 

controls fi tted, connect the 

SWL terminal to permanent 

live in the junction box 

Blue 

86

Sigma 

2.08.02 Schematic wiring diagram for fully pumped CH and gravity DHW 

24 

230V ~ 

50 Hz 

SwL L N PL 

YG 

Blue 

from pump 

YG 

Blue 

12 11 10 

BR 

V 

G 

W 

Blue 

BR 

BL 

Key 

16 Fan 


34 Central heating flow temperature sensor 


49 Safety thermostat 

63 C.H. temperature adjustment 

83 Full sequence automatic control on gas valve 

86 Reset switch 

101 Main P.C.B. 

121 Boiler shut-down warning (Led) 

9 

83 

If there are no external controls fi tted, connect 

the SWL terminal to permanent live in the 

junction box 

ATTENTION: In gravity system is necessary to 

move the jumper JP From CP to GC contact 

in 8X. 

8 

7 

6 

5 

4 

Blue 

3 

34 

Fig. 40b 

2 

1 

101 

X3 

43 

NO NC 

BL 

BL 

G C P 

C 

W 

R W 

X4 X5 

X8 

JP 

Gravity domestic 

hot water 

Colors key 

BR Brown 

Blue Blue 

BL Black 

W White 

O Orange 

1 4 1 5 

63 

49 

BR 

16 

O 

P 

121 

G Grey 

R Red 

V Violet 

P Pink 

YG Yellow-Green 

Blue 

86

3. COMMISSIONING AND TESTING 

3.01 Checks to be carried out before starting up for the fi rst time 

 

Sigma 

When firing the boiler up for the first time, it is good practice to check: 

that the isolation valves between the boiler and central heating systems are open; 

that the central heating system is well filled and vented; 

that there are no gas or water leaks from the central heating system or boiler; 

that the electric connections are correct and the earth wire of the boiler is connected to an efficient earthing 

installation; 

that there are no inflammable liquids or materials near the boiler; 

that the central heating gas pressure and flow rate are as required. 

3.02 Starting up the boiler 

• Open the gas cock of the boiler. 

• Vent air present in the pipe upstream of the gas valve. 

• Turn on the switch (if present) or plug upstream of the boiler. 

• Rotate the C.H. temperature adjustment knob above Min position. 

• Set the room thermostat (if fitted) to maximum. 

• At this point, the burner ignites and the boiler starts to function automatically, controlled by its control 

and safety devices. 

Note - If after completing the start-up procedure correctly, the burner fails to ignite and the boiler shut down warning 

lights up, wait about 15 seconds then press the reset switch. The reset electronic control unit will repeat the start-up cycle. 

If after a second attempt the burners still fail to ignite, consult the paragraph “Troubleshooting”. 

Note - If there is a power failure while the boiler is in operation, the burners automatically go out and re-ignite 

when the power returns. 

WARNING 

If the system is filled with very cold water, the boiler will automatically light due to the frost thermostat sensing the low 

temperature. The boiler will not shut down, until the water temperature reaches 10°C. 

3.03 Shutting down 

To shut down the boiler for short periods 

• Set the temperature adjustment knob to "Off" position. 

To shut down the boiler for long periods 

• Turn off gas supply. 

• Turn off the electricity supply. 

IMPORTANT 

The boiler is protected by integral frost protection, but if the boiler is not to be used for a long period of 

time, the system should be drained. 

Note: The frost thermostat operates even if the temperature adjustment knob is in the OFF position and it is necessary 

therefore, if the system is drained, for the external electrical and gas supplies to be isolated. 

It is recommended that a label be affixed to the appliance to draw attention to the fact that the system 

has been drained. 

3.04 Checks and tests after fi rst start-up 

Check there are no leaks in the gas and water circuits. 

Check correct boiler start up by carrying out start up and shut down tests using the boiler stat. 

Check the integrity of the air-flue pipes during boiler operation. 

Check that the gas consumption indicated on the meter corresponds to that given in Technical Data (paragraph 

1.03). 

Check that water is circulating correct. Balance the radiators to ensure that the flow and return differential 

does not exceed 20°C.

Sigma 

4. ADJUSTMENT 

4.01 Adjusting the gas pressure and heat output 

The following adjustments must be carried out by qualified 

personnel only. 

To adjust boiler heat input simply adjust the burner 

pressure gas via the pressure regulator on the gas valve 

(fig. 41). 

Adjust the gas pressure at the burner by turning the pressure 

regulating screw: turn it clockwise to increase the burner 

pressure and anticlockwise to decrease it. 

The diagrams indicate the variation in heat output to 

the water as burner working pressure is varied (fig. 42a 

and 42b). 

Adjusting boiler output to the actual requirements of 

the central heating system will minimise boiler cycling 

thus saving fuel, varying the output has virtually no 

effect on the efficiency and combustion characteristics 

of the boiler. 

Note: with LPG (G31) the pressure regulating screw must be all the way in. Fig. 41 

mbar 

17 

16 

15 

14 

13 

12 

11 

10 

9 

8 

7 

6 

5 

4 

3 

4 

5 

Diagram of pressures and outputs 

with Natural gas (G20) 

6 

1 

7 8 9 10 11 12 

kW 

13 14 15 16 17 18 19 20 

Fig. 42a 

2 

mbar 

35 

30 

25 

20 

15 

10 

1 = Sigma 20-40 

2 = Sigma 40-60 

4 

5 

6 

Outlet 

pressure 

Test Point 

Inlet 

pressure 

Test Point 

Pressure regulator 

protection plug 

Diagram of pressures and outputs 

with LPG (G31) 

7 

8 

OUT 

I 

Inlet 

gascock 

1 

9 10 11 12 13 14 15 16 17 

kW 

Fig. 42b 

2 

18 19 20

4.02 Adjusting central heating fl ow temperature 

 

Fig. 43 

Sigma 

Central heating water temperature is adjusted by rotating the control knob (fig. 52). Rotate the knob clockwise 

to increase water temperature, anticlockwise to reduce water temperature. Temperature can be varied from a 

minimum of 60°C to a maximum of 82°C. 

However, we recommend not operating the boiler below 50°C. 

4.03 Adjusting room temperature (when a room thermostat is fitted) 

Room temperature is controlled by positioning the room thermostat knob to the required value. The thermostat 

automatically controls the boiler, temporarily interrupting the electrical supply subject to the room heat 

requirements. 

4.04 Adjusting central heating system pressure 

The pressure of water in the central heating system is adjusted as described in the paragraph 2.02.07. 

N.B. - To avoid incurring unnecessary expense, in the event of boiler shut down, check that this is not caused by a lack of 

electricity or gas, or low water pressure before calling the Customer Technical Service Helpline. 

4.05 Determining combustion effi ciency and the composition of the fl ue gases 

On the boiler there are two test points, one for flue gas and the other for air. 

To carry out the tests, proceed as follows: 

1) Open the air and flue gas test points; 

2) Introduce the probes; 

3) Switch ON the boiler; 

N.B. To ensure correct readings the boiler must have reached normal operating temperature. Testing the boiler 

before thermal equilibrium has been attained will give incorrect readings. 

5. GAS CONVERSION 

The following adjustment and conversion operations must be carried out by qualified personnel. FERROLI Limited 

accepts no liability for damage to property or personal injury resulting from tampering with the boiler by 

unauthorised persons. 

To convert the boiler from Natural gas to LPG and vice 

versa, the burner injector must be replaced (see fig. 43). 

Gas valve 

Gas pressures must then be adjusted on the gas valve as 

described in the paragraph 4.01. 

Note: After converting the boiler from natural gas to 

liquid gas, fi t the orange plate in the conversion kit 

near the data plate. 

Note: injector diameters and pressures at the main 

burner are given in Technical Data (1.03). 

Injector 

Full sequence 

automatic control 

Gas cock

Sigma 

6. MAINTENANCE AND CLEANING 

The following operations must be carried out by Corgi registered engineers only. 

6.01 Annual Servicing 

The following should be checked at least once a year: 

Water pressure in the central heating system when cold should be 

about 1 bar. If this is not the case, bring it back to this value. 

Check control and safety devices (gas valve, thermostats, etc) 

are functioning correctly. 

The burner and heat exchanger must be clean. To avoid damage, 

always clean them with a soft brush or compressed air. Never 

use chemical products. 

The expansion vessel (if fitted) must be checked. 

Check there are no leaks in the gas and water circuits. 

Check the air-flue gas duct terminal is free from obstructions 

and sound. 

The electrode must be free from corrosion build up and correctly 

positioned (see fig. 44). 

Gas flow and pressure must correspond to the values given in the 

Technical Data (paragraph 1.03). 

The pump must be free to rotate. 

6.02 Cleaning the boiler and burner 

The boiler should be serviced annually. Before starting check the boiler is operating correctly then isolate the electrical and 

gas supply to the boiler. The heat exchanger may be cleaned by insertion of a thin metal strip e.g. steel rule, from above 

or below. Clean the front and rear fin sections and ensure that any blockages are cleared. 

The burner must never be cleaned with chemical products or steel brushes. Particular attention must be paid to all 

seals and fixings associated with the room-sealed compartment (gaskets, grommets, etc). Air leakage would cause 

pressure inside the compartment to drop, possibly tripping the differential pressure switch and thus shutting down 

the boiler. After cleaning particular attention should also be paid to checking stages of start-up and operation of 

the thermostats, gas valve and pump. 

If performing combustion analysis prior to servicing, the CO/CO 2 ratio must not exceed 0.0004. If it does, a full service is 

required. After a full service the CO/CO 2 ratio must not exceed 0.0008. 

6.03 Sigma Servicing Procedure (only to carried out by a competent person) 

1) Visually check the boiler for correct installation and flueing. 

2) Isolate electricity supply. 

3) Remove cover (2 screws at bottom light and pull forward). 

Electrode 

Sectioned 

burner 

4) Carry out preliminary electrical checks at the boiler junction box. This is situated to the right of the sealed 

compartment and is accessed by lowering the control PCB compartment (1 screw). 

Note: The boiler electrical supply will need to be isolated, whilst carrying out polarity checks. Any faults must 

be rectified before proceeding. 

5) If electrical checks prove o/k replace control panel and secure with fixing screw. 

Fig. 44 

6) Using the inlet pressure test point on the gas valve check the inlet WORKING gas pressure, this should be 20 

millibar MINIMUM for N.G. and 37 millibar MINIMUM for LPG. 

This should be available at all times i.e. when all other gas appliances from the same supply are working 

fully. If this is not the case, installation may be deemed AT RISK and the gas supply pipework throughout 

the system may have to be increased in size. 

3.5 ±1

Sigma 

7) If inlet working pressure is ok using the test point on the gas valve marked OUT check the burner 

pressure. Burner pressures for the required heat output can be obtained from fig. 42a for natural gas 

and fig. 42b for LPG. 

The burner pressure is adjusted by the pressure regulating screw on the gas valve see section 4.01 for detail. 

8) Turn off the boiler and isolate the gas and electricity supplies. 

9) Remove the sealed compartment cover (4 screw). 

10) Remove the fan assembly and clean with a soft brush. 

11) Remove combustion chamber front panel (4 screws) lift out flue hood and baffle plate. 

12) Slide the burner forward, disconnect the lead from the spark electrode, remove the burner and clean. 

13) Clean injector. 

14) Clean the heat exchanger with a suitable soft brush. DO NOT DAMAGE THE REAR INSULATION and clean 

out the combustion chamber. 

15) EXAMING seals on the room sealed compartment from panel and if necessary replace. 

16) Re-assemble in reverse order. 

17) Re instate gas and electric supply. 

18) Fire the boiler and check all gas joint for soundness. 

19) Re check burner pressure. 

20) Check flame picture and all controls for correct operation. 

21) Check room sealed cover for leakage. 

22) Check all safety devices for correct operating. 

23) Check the gas rate to the boiler is correct. 

24) If a combustion analyzer is to be used, there are 2 test point on the front of the room sealed cover at the 

top, the lower one is for the flue gases the upper one for incoming air. The boiler should be operated for at 

least 10 minutes before carrying out this test. 

CO/CO 2 ratio should not exceed 0.004 prior to servicing and 0.008 immediately after servicing. 

25) Refit cover and leave boiler set to customer requirements.

Sigma 

7. REPLACEMENT OF PARTS 

Before commencing with the replacement of any parts, ensure the gas and electricity are isolated. 

7.01 Boiler exploded view 

Short Spares List 

16 43 34 

Fig. 45 

Key N° Description PART N° 

16 Fan assembly (Sigma 20-40, 40-60) 800480 

21 Injector Plate 3.00 (NG) Sigma 20-40 806296 

" Injector Plate 1.80 (LPG) Sigma 20-40 806298 

" Injector Plate 3.60 (NG) Sigma 40-60 806278 

" Injector Plate 2.30 (LPG) Sigma 40-60 806282 

34 Flow Temperature Sensor NTC. (all models) 806051 

43 Air Pressure Switch (all models) 800150 

44 Gas Valve Honeywell VK 4105 A 1092 1/2" (all models) 806267 

49 Overheat Thermostat (all models) 801240 

83 Full Sequence Control PLB (all models) 806659 

21 

83 

44 

 

49

7.03 To remove Outer Cover 

a. Remove 3 fixing screws from the bottom of the cover. 

b. Gently pull out the sides of the cover at the bottom 

and lift off the top fixing lugs. 

7.04 Removal of Fan Assembly (rear fl ueing) fi g. 46 

a. Remove sealed compartment front panel (4 screws 

"a"). 

b. Remove 2 "b" screws that secure fan assembly to 

flue hood. 

c. Lift flue of locating pin at rear. 

d. Pull fan clear of the boiler and remove electrical 

connection and air pressure switch tubes, noting their 

relevant position "c". 

e. Remove fan unit from mounting bracket (3 screws). 

f. Replace in reverse order. 

7.05 Overheat Thermostat (fi g. 47) 

a. Pull overheat thermostat and securing clip "c" off 

the flow pipe. 

b. Remove securing clip and electrical leads from the 

overheat thermostat. 

c. Replace in reverse order adding more heat sink 

compound if necessary. 

7.06 Air Pressure Switch Removal (fi g. 47) 

a. Remove electrical connection and tubes from the air 

pressure switch, noting their position. 

b. Remove the 2 screws "a" that secure the air pressure 

switch to the electrical contacts cover. 

c. Replace in reverse order. 

7.07 Temperature Sensor (fi g.47) 

a. Remove electrical connection from sensor. 

b. Drain off the water from the boiler using the drain tap. 

c. Unscrew sensor from flow pipe. 

d. Replace in reverse order, ensuring both pins "b" are 

engaged on the sensor. 

7.08 Burner Removal (fi g. 48) 

a. Remove combustion chamber front panel (4 screws). 

b. Gently pull burner "a" forward or far as the ignition 

lead "b" will allow. 

c. Remove ignition lead "b" from electrode. 

d. Replace in reverse order. 

 

B 

Fig. 46 

Air 

pressure 

switch 

Fig. 47 

A 

A 

B 

C 

A 

C 

Overheat 

thermostat 

Temperature 

sensor 

Sigma

Sigma 

7.09 Gas Valve (fi g. 49) 

a. Remove 4 screws "a" that secure the gas inlet isolation 

cock to the bottom of the gas valve. 

b. Remove the full sequence PCB "b" and housing from 

the gas valve (1 screw) and place to one side. 

c. Remove balance tube and earth lead from the gas 

valve. 

d. From inside the combustion chamber remove the 3 

screws "c" which hold the gas valve in place. 

e. Remove gas valve and replace in reverse order. 

7.10 Control PCB (fi g. 50) 

a. Turn boiler thermostat down to the off position and 

pull the thermostat knob off "a". 

b. Remove fixing screw securing the control PCB "b" 

housing in place and hinge down the housing. 

c. Remove the electrical connections from the PCB, 

noting their position. 

d. Remove the 2 plastic nuts from outside the housing 

that hold the fixing pins in place and gently push the 

pin inside the housing. 

e. Very carefully, push the reset button "c" inside the 

housing and remove the PCB. 

f. Remove the fixing pins from the PCB and swap over 

to the replacement. 

g. Replace in reverse order. 

7.11 Heat Exchanger (fi g. 51) 

a. Lift fan and flue hood assembly "a" out of boiler, remove 

all connection from the fan, noting positions. 

b. Remove air pressure switch "b". 

c. Drop control PCB compartment out of the way "c". 

d. Disconnect flow and return unions "d" from heat 

exchanger. 

e. Remove heat exchanger connection nipples and lift 

out heat exchanger. 

f. Replace in reverse order. 

Fig. 48 

Fig. 49 

Fig. 50 

Fig. 51 

A 

C 

B 

A 

B 

A 

B 

A 

C 

B 

C 

D

8. FAULT FINDING 

 

Sigma 

Before commencing any fault finding procedure on the boiler, ensure electricity is on to the appliance, the gas supply is 

turned on, purged and is sound, and the system is full of water. 

Note: in certain condition the fan and overheat thermostat may have 230 v at their terminals, but the fan 

will not run. 

Intermittent problem may be due to the temperature sensor breaking down when under load although the resistance 

value may be within the stated range. 

Sticking gas valves may lead to boiler lock out problems. It is not possible to test for power to the gas valve due 

to the nature of the plug on sequence board. 

8.01 Boiler Operating Sequence 

Permanent live to boiler 

Switched live from controls read 

Boiler thermostat calling 

Temperature sensor calling 

When all the above is present, the pump connection becomes live and the pump runs. 

The grey wire of the control board on X5 becomes live, 230 v. 

Air pressure switch has 230 v to the normally open (N.O.) contact. 

Fan motor and overheat thermostat have 230 v al both terminals to earth. 

If the air pressure switch is open circuit between its N.O. and common contact, the voltage at the overheat thermostat to 

earth drops to almost zero. The white wire of the fan becomes a neutral and the fan runs. 

The air pressure switch operates to make a circuit between its N.O. and common contacts. 

If the overheat thermostat is closed circuit the ignition electrode will spark the gas, valve opens and the 

burner lights. 

8.02 Troubleshooting - Quick reference guide 

N.B.: To avoid incurring unnecessary expense, in the event of boiler shut down, check that this is not caused by a lack of 

electricity, gas or low water pressure before calling the Customer Technical Service. 

PROBLEM CAUSE and REMEDY 

Boiler lockout After a number of attempts at ignition, the electronic unit always shuts down 

the boiler 

 

Burner fails to ignite No electricity 

 

 

 

Blocked injector 

 

Faulty flow temperature sensor 

 

Faulty gas valve 

 

Fan not running 

 

Faulty pressure switch or obstructed pipes

Sigma 

No spark to the electrode During the ignition phase, there is no spark to the electrode 

 

 

 

 

 

 

 

 

Burner goes out Insufficient gas supply 

Boiler dirty 

 

Burner or injector dirty 

 

Faulty flow temperature sensor 

 

 

Boiler operates but Incorrect gas pressure 

temperature fails to 

rise 

Boiler dirty 

Boiler inadequate 

 

 

Condensate in boiler Thermostat set too low 

 

Incorrect gas rate 

 

 

Boiler sooting Faulty flame adjustment 

 

 

Burner air ports blocked 

 

Radiators cold in winter Faulty flow temperature sensor 

Room thermostat set too low or faulty 

 

Pump is stuck and fails to rotate 

 

 

 

The pump does not rotate

8.03 General test and fault fi nding chart 

 

yes 

yes 

check for 

continuity 

through 

overheat 

thermostat 

yes 

no 

change 

overheat 

thermostat 

fan runs 

yes no 

check resistance through coils of 

gas valve 

1320 ohms between top two pins 

2800 ohms between bottom two pins 

no 

yes 

burner lights but 

boiler continues to 

spark and locks out 

no 

eletrode 

sparks 

no 

boiler 

locks out 

no 

with fan running 

electrical 

connections to air 

pressure switch 

removed. check for 

continuity between 

common and 

normally open 

contacts of the air 

pressure switch 

change gas 

valve assembly 

no 

yes 

yes 

boiler does not work 

230V at live connection 

of terminal block 

yes 

230V at switched 

live connection of 

terminal block 

yes 

230 v on grey wire of 

block x5 on main pcb 

yes 

fan runs 

no 

230 v at both fan 

terminals to earth 

yes 

reverse 

polarity 

yes 

no 

check air 

pressure 

switch and 

change if 

necessary 

no 

yes 

retify 

no 

no 

no 

change sequence pcb 

on gas valve 

Sigma 

check mains supply 

and fuse 

check external 

controls 

resistance of the temp 

sensor between 80 

kohm at 80°c and 

1mohm at 25°c 

yes no 

change 

main pcb 

change 

temperature 

sensore 

no 

has the 

problem been 

intermittent 

at all 

yes

Sigma 

9. USER INSTRUCTIONS 

The boiler is designed for use with two types of gas: natural gas NG or propane (LPG). The type of gas can be selected 

when purchasing the boiler or the appliance can be converted later on site by a competent person. It operates with 

technologically advanced systems such as electronic adjustment, safety and control devices. 

The boiler is fitted with automatic electronic ignition so there is no pilot to worry about. 

Operating: 

Turn up the cover to reveal the control panel. 

Make sure that the gas, water and electricity supplies to 

the boiler are turned on. 

To obtain heating from the boiler, turn the temperature 

regulator (2) clockwise to the desired position, ensure that 

any other heating controls e.g. room thermostats, clock 

etc. are in the on position. 

The boiler flow temperature is adjusted by from panel knob 

(see fig. 42) from 60°C to 82°C. 

Once the flow temperature reached set value, the burner 

goes out and the electronic system imposes a delay of 3 

minutes before allowing re-ignition. Once heat demand is 

finished, pump and burner go out. 

In "gravity circulation system" (see paragraph 3.07) the 

pump signal is an input for electronic device. If the pump 

is not running and there is heat demand the temperature 

control is set on 50°C and after 3 minutes slow start 

time, this level switches to a fixed value of 70°C. With the knob in "OFF" position the call for heat is disabled; 

but if the temperature in the ambient comes below 5°C, a frost protection overrules the off-state and a heat 

demand is generated. 

IMPORTANT 

Front panel 

Your "benchmark" Installation, Commissioning and Service Record Log Book is enclosed in the last pages 

of this manual. "This record must be completed and left with the end user" 

Ferroli is a member of the Benchmark initiative and fully supports the aims of the programme. Benchmark 

has been introduced to improve the standards of installation and commissioning of central heating 

systems in the UK and to encourage the regular servicing of all central heating systems to ensure 

safety and efficiency. 

"All CORGI Registered Installers carry a CORGI ID card and have a registration number. Both should 

be recorded in your central heating log book. You can check the installer's CORGI registration by 

calling CORGI on 01256 372300". 

Fig. 52 

°C 

RESET 

MIN 

OFF 

MAX 

Reset 

switch 

Boiler 

shut-down 

warning 

C.H. temperature 

setting 

knob 

(Min = 60°C) 

(Max = 82°C)

CONTROLS To comply with the Building Regulations, each section must have a tick in one or other of the boxes 

TIME & TEMPERATURE CONTROL TO HEATING ROOM T/STAT & PROGRAMMER/TIMER PROGRAMMABLE ROOMSTAT 

TIME & TEMPERATURE CONTROL TO HOT WATER CYLINDER T/STAT & PROGRAMMER/TIMER COMBI BOILER 

HEATING ZONE VALVES FITTED NOT REQUIRED 

HOT WATER ZONE VALVES FITTED NOT REQUIRED 

THERMOSTATIC RADIATOR VALVES FITTED 

AUTOMATIC BYPASS TO SYSTEM FITTED NOT REQUIRED 

FOR ALL BOILERS CONFIRM THE FOLLOWING 

THE SYSTEM HAS BEEN FLUSHED IN ACCORDANCE WITH THE BOILER MANUFACTURER’S INSTRUCTIONS? 

THE SYSTEM CLEANER USED 

THE INHIBITOR USED 

COLLECTIVE MARK 

BOILER SERIAL No. NOTIFICATION No. 

FOR THE CENTRAL HEATING MODE, MEASURE & RECORD 

GAS RATE ft3 m /hr 

3 /hr 

BURNER OPERATING PRESSURE (IF APPLICABLE) N/A 

mbar 

CENTRAL HEATING FLOW TEMPERATURE °C 

CENTRAL HEATING RETURN TEMPERATURE °C 

FOR COMBINATION BOILERS ONLY 

HAS A WATER SCALE REDUCER BEEN FITTED? YES NO 

WHAT TYPE OF SCALE REDUCER HAS BEEN FITTED? 

FOR THE DOMESTIC HOT WATER MODE, MEASURE & RECORD 

GAS RATE ft3 m /hr 

MAXIMUM BURNER OPERATING PRESSURE (IF APPLICABLE) mbar 

3 /hr 

N/A 

COLD WATER INLET TEMPERATURE °C 

HOT WATER OUTLET TEMPERATURE °C 

WATER FLOW RATE lts/min 

FOR CONDENSING BOILERS ONLY CONFIRM THE FOLLOWING 

THE CONDENSATE DRAIN HAS BEEN INSTALLED IN ACCORDANCE WITH 

THE MANUFACTURER’S INSTRUCTIONS? YES 

FOR ALL INSTALLATIONS CONFIRM THE FOLLOWING 

BENCHMARK No. 

GAS BOILER COMMISSIONING CHECKLIST 

THE HEATING AND HOT WATER SYSTEM COMPLIES 

WITH CURRENT BUILDING REGULATIONS 

THE APPLIANCE AND ASSOCIATED EQUIPMENT HAS BEEN INSTALLED AND COMMISSIONED 

IN ACCORDANCE WITH THE MANUFACTURER’S INSTRUCTIONS 

IF REQUIRED BY THE MANUFACTURER, HAVE YOU RECORDED A CO/CO2 RATIO READING? 

THE OPERATION OF THE APPLIANCE AND SYSTEM 

CONTROLS HAVE BEEN DEMONSTRATED TO THE CUSTOMER 

THE MANUFACTURER’S LITERATURE HAS BEEN LEFT WITH THE CUSTOMER 

N/A YES CO/CO2 RATIO 

COMMISSIONING ENG’S NAME PRINT CORGI ID No. 

SIGN DATE 

2 6 7 

Please add the first 4 digits of the Boiler serial No to complete the BENCHMARK No.

SERVICE INTERVAL RECORD 

It is recommended that your heating system is serviced regularly 

and that you complete the appropriate Service Interval Record Below. 

Service Provider. Before completing the appropriate Service Interval Record below, please ensure you have carried out the service 

as described in the boiler manufacturer’s instructions. Always use the manufacturer’s specified spare part when replacing all controls 

SERVICE 1 DATE 

ENGINEER NAME 

COMPANY NAME 

TEL No. 

CORGI ID CARD SERIAL No. 

COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 


ENGINEER NAME 

COMPANY NAME 

TEL No. 


COMMENTS 

SIGNATURE 

FERROLI TECHNICAL HELPLINE - 08707 282 885

Phone numbers: 

Installer 

Service Engineer 

Should you require help with any difficulties 

call our Technical Service Helpline on 

08707 282 885 

BECAUSE OF OUR CONSTANT ENDEAVOUR FOR IMPROVEMENT DETAILS 

MAY VARY SLIGHTLY FROM THOSE QUOTED IN THESE INSTRUCTIONS. 

ALL SPECIFICATIONS SUBJECT TO CHANGE 

Please note - to avoid incurring unnecessary expense, in the event of a boiler shut down, check this in not 

caused by lack of electricity supply, gas supply or low water pressure before calling our 

Customer Service Helpline. 

Lichfi eld Road, Branston Industrial Estate, Burton Upon Trent, Staffordshire DE14 3HD 

Tel. 08707 282 885 - Fax 08707 282 886

wall mounted cast iron, gas fired boiler for central heating ... - Ferroli

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