Installation Instructions

Type C Boilers
G.C.N: 41-116-01
47-116-08
47-116-09
47-116-13
LEAVE THESE INSTRUCTIONS
ADJACENT TO THE GAS METER

Country of destination: GB

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 TABLE OF CONTENTS 1. GENERAL INFORMATION
1.1 General Instructions
1.2 Technical Information
1.3 Overall View

2. INSTALLATION
2.1 Reference Standards
2.2 Siting the Appliance
2.3 Overall Dimensions
2.4 Clearances
2.5 Mounting the Appliance
2.6 Electrical Connection
2.7 Gas Connection
2.8 Water Connections
2.9 Flue Connection
2.10 Room Thermostat Connection
2.11 Electrical/System Diagrams
2.12 Water Circuit Diagrams

3. COMMISSIONING
3.1 Initial Preparation
3.2 Removing the Casing
3.3 Control Panel
3.4 Initial Start-up
3.5 Operational Adjustments
3.6 Combustion Analysis
3.7 Fume Discharge Monitoring
3.8 Boiler Safety Systems
3.9 Draining the System

4. GAS ADJUSTMENTS
- Gas Adjustment Table
4.1 Changing the Type of Gas

5. MAINTENANCE

6. MISCELLANEOUS
6.1 Wiring Diagram for Two Heating Zones
6.2 Wiring Diagram for Connection to Ariston Unvented Cylinder

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 1. GENERAL This manual is an integral and essential part of the product. It should be kept
with the appliance so that it can be consulted by the user and our authorised
INFORMATION personnel.

Please carefully read the instructions and notices about the unit contained in
this manual, as they provide impor tant information regarding the safe
installation, use and maintenance of the product.

For operating instructions please consult the separate User’s Manual.

User’s
Manual

1.1 General Information Read the instructions and recommendations in these Installation Instructions
carefully to ensure proper installation, use and maintenance of the appliance.
Keep this manual in a safe place. You may need it for your own reference while
our Servicing Centre technicians or your installer may need to consult it in the
future.
This is a combined appliance for the production of central heating (C.H.) and
domestic hot water (D.H.W.).
This appliance must be used only for the purpose for which it is designed.
The manufacturer declines all liability for damage caused by improper or
negligent use.

No asbestos or other hazardous materials have been used in the fabrication of

this product.

Before connecting the appliance, check that the information shown on the data
plate and the table on pages 4-5 comply with the electric, water and gas mains
of the property. You will find the data plate on the reverse of the control panel.
The gas with which this appliance operates is also shown on the label at the
bottom of the boiler.
Do not install this appliance in a damp environment or close to equipment
which spray water or other liquids.
Do not place objects on the appliance.
Do not allow children or inexperienced persons to use the appliance without
supervision.
If you smell gas in the room, do not turn on light switches, use the telephone or
any other object which might cause sparks.
Open doors and windows immediately to ventilate the room.
Shut the gas mains tap (on the gas meter) or the valve of the gas cylinder and call
your Gas Supplier immediately.
If you are going away for a long period of time, remember to shut the mains gas
tap or the gas cylinder valve.
Always disconnect the appliance either by unplugging it from the mains or
turning off the mains switch before cleaning the appliance or carriyng out
maintenance.
In the case of faults or failure, switch off the appliance and turn off the gas
tap. Do not tamper with the appliance.
For repairs, call your local Authorised Servicing Centre and request the use of
original spare parts. For in-guarantee repairs contact MTS (GB) Limited
Check the following at least once a year:
1 - Check the seal of water connections, replacing the gaskets if necessary.
2 - Check the seal of the gas connections, replacing the gaskets if necessary.
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 3 - Check the general condition of the appliance and of the combustion
chamber visually.
4 - Visual check of the combustion: clean burners if necessary.
5 - With reference to point 3, dismantle and clean the combustion chamber if
necessary.
6 - With reference to point 4, dismantle and clean the injectors if necessary.
7 - Visual check of the primary heat exchanger:
- check for overheating of the exchangers fins;
- clean the exhaust side of the exchanger and fan if necessary.
8 - Regulate the gas pressure, ignition pressure, partial flame, maximum flame.
9 - Check proper operation of the heating safety system:
- maximum safety temperature;
- maximum safety pressure.
10 - Check the proper operation of the gas safety system:
- gas or flame safety device;
- gas valve safety device.
11 - Check that the electrical connections have been made in compliance with
the instructions shown in the Installation Instructions.
12 - Check the efficiency of the hot water supply (flow and temperature).
13 - Check general operation of the appliance.
14 - Check the exhaust system for the combustion products.

1.2 Technical Information

23 MFFI 27 MFFI 27 RFFI SYSTEM 30 MFFI

CE Certification
Heat Input max/min kW 25.6/11.0 29.8/12.0 29.8/12.0 33.0/12.0
Heat Output max/min kW 23.1/9.2 27.3/10.1 27.3/10.1 30.3/10.2
Efficiency of Nominal Heat Input % 90.2 91.6 91.6 92.0
Efficiency at 30% of Nominal Heat Input % 87.8 88.3 88.3 88.6
Heat Loss to the Casing (³T=50°C) % 1.2 1.3 1.3 1.4
Flue Heat Loss with Burner Operating % 8.6 7.1 7.1 6.6
Flue Heat Loss with Burner Off % 0.4 0.4 0.4 0.4
Maximum Discharge of Fumes (G20-G25) Kg/h 59 62 62 61
Residual Discharge Head mbar 1.15 1.4 1.4 1.4
Consumption at Nominal Capacity (G20-G25) m3/h 2.72/3.32 3.16/3.86 3.16/3.86 3.49/4.05
Gas Consumption after 10 Minutes* m3 0.32/0.39 0.37/0.45 0.37/0.45 0.41/0.47
(15°C, 1013 mbar) (G30-G31) Kg/h 2.02/2.00 2.35/2.32 2.35/2.32 2.60/2.57
Temp. of exhaust fumes at nominal
capacity (G20-G25) °C 137 128 128 135
CO2 Content % 5.8 6.6 6.6 7.5
O2 Content % 9.2 8.0 8.0 8.0
CO Content ppm 32 34 34 49
Minimum Ambient Temperature °C +5 +5 +5 +5
Head Loss on Water Side (max) (³T=20°C) mbar 200 200 200 200
Residual Head of System bar 0.25 0.25 0.25 0.25
Heating Temperature max/min °C 82/42 82/42 82/42 82/42
Domestic Hot Water Temperature max/min °C 56/36 56/36 --- 56/36
D.H.W. Flow Rate ³T=35°C l/min 9.5 11.2 --- 12.3
D.H.W. Flow Rate ³T=35°C gal/min 2.1 2.5 --- 2.7
D.H.W. Flow Minimum Rate l/min 2.6 2.6 --- 2.6
Pressure of Domestic Hot Water max/min bar 6/0.2 6/0.2 --- 6/.02
Expansion Vessel Capacity l 7 7 7 7
Expansion Vessel Pre-load Pressure bar 1 1 1 1
Maximum Water Content in System l 145 145 145 145
Maximum Heating Pressure bar 3 3 3 3
Nominal Pressure Natural Gas (G20-G25) mbar 20-25 20-25 20-25 20-25
Liquid Gas (G30-G31) mbar 30-37 30-37 30-37 30-37
Electrical Supply V/Hz 230 / 50 230 / 50 230 / 50 230 / 560
Power Consumption W 150 190 190 190
Protection Grade of Electrical System IP X4D X4D X4D X4D
Internal Fuse Rating FAST 2 AT FAST 2 AT FAST 2 AT FAST 2 AT
Weight Kg 47 47 46.5 47

G.C. Number 47-116-08 47-116-09 41-116-01 47-116-13

*Calculated at 70% maximum output

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 1.3 Overall View

GENUS 23/27/30 MFFI GENUS 27 RFFI SYSTEM

Fig. 1.1
Legend:

1. Flue Connector
2. Combustion Chamber Hood
3. Main Heat Exchanger
4. Combustion Chamber Insulation Panel
5. Burner
6. Expansion Vessel
7. Overheat Thermostat
8. Spark Generator
9. Diverter Valve (MFFI)
Motorised Valve (RFFI)
10. Main Circuit Temperature Probe
11. Main Circuit Flow Switch
12. Domestic Hot Water Temperature Probe
13. Diverter Valve Microswitch
14. Filter Seat
15. Drain Valve
16. Secondary Heat Exchanger
17. Safety Valve (3 bar)
18. Circulation Pump with Automatic Air Release Valve
19. Gas Valve
20. Detection Electrodes
21. Ignition Electrodes
22. Fan
23. Venturi
24. Air Pressure Switch

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 2. INSTALLATION The technical information and instructions provided herein below are intended
for the installer so that the unit may be installed correctly and safely.

The installation and initial startup of the boiler must be by a CORGI Approved
Installer in compliance with the installation standards currently in effect, as well
2.1 Reference Standards as with any and all local health and safety standards i.e. CORGI.

This appliance must be installed by a competent installer in

accordance with the current Gas Safety (installation & use)
Regulations

The installation of this appliance must be in accordance with the relevant

requirements of the current Gas Safety (installation & use) Regulations, the
Local Building Regulations, the current I.E.E. Wiring Regulations, the byelaws
of the local water authority, and in Scotland, in accordance with the Building
Standards (Scotland) Regulation and Health and Safety document No. 635
“Electricity at work regs. 1989”.
Installation should also comply with the following British Standard Codes of
Practice:

Low pressure
pipes BS 6891 1988
Boilers of rated input
not exceeding 60 kW BS 6798 1987
Forced circulation hot
water system BS 5449 1990
Installation of gas hot water
supplies for domestic purposes
( 2nd family gases) BS 5546 1990
Flues BS 5440-1 1990
Air supply BS 5440-2 1989

2.2 Siting the Appliance The appliance may be installed in any room or indoor area, 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 combined appliance in a room
containing a bath or shower.
Where a room-sealed appliance is installed in a room containing a bath or
shower the boiler and any electrical switch or appliance control, utilising
mains electricity should be situated so that it cannot be touched by a
person using the bath or shower.
The location must permit adequate space for servicing and air circulation
around the appliance as indicated in paragraph 2.4.
The location must permit the provision of an adequate flue and termination.
For unusual locations special procedures may be necessary.
BS 6798-1987 gives detailed guidance on this aspect.
A compartment used to enclose the appliance must be designed specifically for
this purpose. No specific ventilation requirements are needed for an installation
within a cupboard
This appliance is not suitable for outdoor installation.

The type C appliances (in which the combustion circuit, air vent intake
and combustion chamber are air-tight with respect to the room in which
the appliance is installed) can be installed in any type of room.
There are no limitations with respect to ventilation and the volume of the room
itself. The boiler must be installed on a solid, permanent wall to prevent access
to the electrical parts (when live) through the aperture on the back frame.

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 2.3 Overall Dimensions GENUS 23/27/30 MFFI

890
(A-B-D-E)

(C)

GENUS 27 RFFI SYSTEM

38
5

465

Legend:

A = Central Heating Flow (3/4”)

49
B = Domestic Hot Water Outlet (1/2”)

30
C = Gas Inlet (3/4”) 99 99
85 (F - G)
D = Domestic Cold Water Inlet (1/2”) 155 (A - D - E)
132 67 65
E = Central Heating Return (3/4”) 208 (C)
F = Cylinder Flow (3/4”)
G = Cylinder Return (3/4”) AF C DGE
Fig. 2.1

2.4 Clearances In order to allow for access to the interior of the boiler for maintenance purposes, the
boiler must be installed in compliance with the clearance requirements indicated in the
diagram below.

GENUS 23/27/30 MFFI GENUS 27 RFFI SYSTEM

110

400
160
197

60 60

450
0 n x - 5 ai 3 m

300

Fig. 2.2

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 2.5 Mounting the Appliance Fasten the boiler in place using the template and anchors supplied with the
unit. It is highly recommended that a spirit level be used to position the boiler so
that it is perfectly level.
For additional information, please consult the instructions contained in the
connection kit and the flue kit.

2.6 Electrical Connection For safety purposes, have a competent person carefully check the electrical
system in the property, as the manufacturer will not be held liable for damage
caused by the failure to earth the appliance properly or by anomalies in the
supply of power. Make sure that the residential electrical system is adequate for
the maximum power absorbed by the unit, which is indicated on the rating plate.
In addition, check that the section of cabling is appropriate for the power
absorbed by the boiler.

The boiler operates with alternating current, as indicated in the technical data
table (1.2), where the maximum absorbed power is also indicated. Make sure
that the connections for the neutral and live wires correspond to the indications
in the diagram. The appliance electrical connections are situated on the reverse
of the control panel (see the servicing manual for further information)

Fig. 2.3

Important!
In the event that the power supply cord must be changed, replace it with one
with the same specifications. Make the connections to the terminal board
located within the control panel, as follows:
- The yellow-green wire should be connected to the terminal marked with the
earth symbol; make sure to re-use the ferrule mounted on the other supply
cord;
- The blue wire should be connected to the terminal marked “N”;
- The brown wire should be connected to the terminal marked “L”.
Note: The diagrams for the electrical system are indicated in section 2.11.

Warning, this appliance must be earthed.

External wiring to the appliance must be carried out by a qualified technician
and be in accordance with the current I.E.E. Regulations and applicable local
regulations. The Genus range of boilers are supplied for connection to a 230 V~
50 Hz supply.
The supply must be fused at 3 A.
The method of connection to the electricity supply must facilitate complete
electrical isolation of the appliance, by the use of a fused double pole isolator
having a contact separation of at least 3 mm in all poles or alternatively, by
means of a 3 A fused three pin plug and unswitched shuttered socket outlet
both complying with BS 1363.
The point of connection to the Electricity supply must be readily accessible and
adjacent to the appliance unless the appliance is installed in a bathroom when
this must be sited outside the bathroom.

2.7 Gas Connection The local gas supplier contractor connects the gas meter to the service pipe.
If the gas supply for the boiler serves other appliances ensure that an adequate
supply is available both to the boiler and the other appliances when they are in
use at the same time.
Pipe work must be of an adequate size. Pipes of a smaller size than the boiler
inlet connection should not be used.

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 2.8 Water Connections View of the Boiler Connections

GENUS 23/27/30 MFFI GENUS 27 RFFI SYSTEM

C C
A B D E A D E
I I
F G

Legend Fig. 2.4

A = Central Heating Flow
B = Domestic Hot Water Outlet
C = Gas Inlet
D = Domestic Cold Water Inlet
E = Central Heating Return
F = Cylinder Flow
G = Cylinder Return
I = Safety Valve

Central Heating
Detailed recommendations are given in BS 6798:1987 and BS 5449-1:1990,
the following notes are given for general guidance.
Pipe Work:
Copper tubing to BS EN 1057:1996 is recommended for water pipes. Jointing
Fig. 2.5 should be either with capillary soldered or compression fittings.
Where possible pipes should have a gradient to ensure air is carried naturally
Fitting the connection kit to the to air release points and water flows naturally to drain taps.
Genus 27 RFFI System only. The appliance has a built-in automatic air release valve, however it should be
ensured as far as possible that the appliance heat exchanger is not a natural
It will be noted that the kit has two
connections not required for this boiler collecting point for air.
i.e. the domestic cold inlet “E” and the Except where providing useful heat, pipes should be insulated to prevent heat
domestic hot water outlet “B” (see fig. loss and avoid freezing.
2.4). Particular attention should be paid to pipes passing through ventilated spaces
Although the cold water main supply in roofs and under floors.
must be connected to the isolation valve By-pass:
for the purpose of operating the filling- The appliance includes an automatic by-pass valve, which protects the main
loop, the isolation valve is NOT heat exchanger in case of reduced or interrupted water circulation through
connected to the boiler and should be left
the heating system, due to the closing of thermostatic valves or cock-type
in the OFF position.
The D.H.W. outlet is capped-off on the valves within the system.
boiler, therefore not requiring the System Design:
isolation valve to be used. This boiler is suitable only for sealed systems.
The Genus 27 RFFI System has 2 x 3/4" Drain Cocks:
B.S.P. male threads for the cylinder flow These must be located in accessible positions to permit the draining of the
and return. It is recommended that 2 x whole system. The taps must be at least 15mm nominal size and
22mm x 3/4" female iron fittings (not manufactured in accordance with BS 2870:1980.
supplied) be used on these connections Safety Valve Discharge:
(using P.T.F.E. tape), before the boiler is
The discharge should terminate facing downwards on the exterior of the
mounted on the wall.
building in a position where discharging (possibly boiling water & steam) will
not create danger or nuisance, but in an easily visible position, and not cause
damage to electrical components and wiring.
The discharge must not be over an entrance or a window or any other type of
public access.
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 Air Release Points:
These must be fitted at all high points where air naturally collects and must
be sited to facilitate complete filling of the system.
The appliance has an integral sealed expansion vessel to accommodate the
increase of water value when the system is heated.
It can accept up to 7 l (1.5 gal) of expansion water. If the heating circuit has
an unusually high water content, calculate the total expansion and add an
additional sealed expansion vessel with adequate capacity.
Mains Water Feed - Central Heating:
There must be no direct connection to the mains water supply even through a
non-return valve, without the approval of the Local Water Authority.
Filling:
A temporary method for initially filling the system and replacing lost water
during servicing and initial filling (in accordance with Water Supply Byelaw
14), is provided as an intergal part of the connection kit (see fig. 2.5). The
flexible hose must be removed once the system has been filled. The D.H.W.
inlet valve on the connection kit has two postions, one for winter and one for
the summer. This enables the flow-rate through the appliance to be adjusted
so that a sensible D.H.W. temperature may be achieved throughout the year.

Domestic Water
The domestic water must be in accordance with the relevant recommendation
of BS 5546:1990. Copper tubing to BS EN 1057:1996 is recommended for
water carrying pipe work and must be used for pipe work carrying drinking
water.

Residual Head of the Boiler

27/30 kW

23 kW

2.9 Flue Connections Flue System

The provision for satisfactory flue termination must be made as described
in BS 5440-1.
The appliance must be installed so that the flue terminal is exposed to outdoor air.
The terminal must not discharge into another room or space such as an
outhouse or lean-to.
It is important that the position of the terminal allows a free passage of air
across it at all times.
The ter minal should be located with due regard for the damage or
discolouration that might occur on buildings in the vicinity.
In cold or humid weather water vapour may condense on leaving the flue
terminal.
The effect of such “steaming” must be considered.
If the terminal is less than 2 metres above a balcony, above ground or above a
flat roof to which people have access, then a suitable terminal guard must be
fitted. When ordering a terminal guard, quote the appliance model number.

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 A suitable terminal guard is available from:
TOWER FLUE COMPONENTS
Morley Road
Tonbridge
Kent TN9 1RA
The minimum acceptable spacing from the terminal to obstructions and
ventilation openings are specified in Fig. 2.6

BC
F
F D G
J
HI
A E

L K
TERMINAL POSITION mm
G

A - Directly below an open window or other opening 300

Fig. 2.6 B - Below gutters, solid pipes or drain pipes 75
C - Below eaves 200
D - Below balconies or car-port roof 200
E - From vertical drain pipes and soil pipes 75
F - From internal or external corners 300
G - Above ground or below balcony level 300
H - From a surface facing a terminal 600
I - From a terminal facing a terminal 1200
J - From an opening in the car port
(e.g. door, window) into dwelling 1200
K - Vertically from a terminal in the same wall 1500
L - Horizontally from a terminal in the same wall 300

The boiler is designed to be connected to a coaxial flue discharge system.

Ø 60/100 mm

Fig. 2.7

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 In addition, it is also possible to use a split system by fitting a special adapter to
the flue discharge collar and using one of the apertures for the air vent intake
located on the top part of the combustion chamber (A).

Ø 80 mm

A
Ø 80 mm

Fig. 2.8

This procedure must be done as follows:

1 - Remove the air vent intake you want to use, in the area indicated in
Fig. 2.9, by breaking the perforated ring.
2 - Use a tool to grasp the lid and remove it completely.
3 - Clean any burrs or sharp edges with a knife or an appropriate tool.

Fig. 2.9 Fig. 2.10

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 In Fig. 2.11 below, several different types of flue systems are shown.
For additional information regarding the flue accessories, please consult the
Flue Pipe Accessories manual.

Fig. 2.11

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 In calculating the lengths of the

Twin Pipe
Systems

Systems
Coaxial
pipes, the maximum length must also
take into consideration the values for
the exhaust/air intake end terminals,
as well as 90° elbows for coaxial

Exhaust Type
systems.

C52 (xy)

C42 (xy)

C32 (xy)

C12 (xy)

C42 (xx)

C32 (xx)

C12 (xx)
The C52 types must comply with the
following requirements:
1. The discharge/intake vent pipes
must have the same diameter of ø
80 mm.
2. The maximum combined flue

23 kW

23 kW - 27 kW
17 m

54 m

54 m

54 m

Maximum Extension
length is 17 m for Models Genus
23/27 MFFI/RFFI and 15 m for

4m

4m

4m

Exhaust/Air
Model Genus 30 MFFI. In this case

27 kW
the minimum length for the air

17 m

46 m

46 m

46 m
intake pipe is 1 meter ; the
maximum length of ver tical
exhaust pipe must be a maximum

30kW
30 kW
15 m

50 m

50 m

50 m
of 12 m.

3m

3m

3m
3. If an elbow is inserted into the
discharge/ventilation system, the
calculation of the overall extension

Diameter of
must take into consideration the

ø 60/100

ø 60/100

ø 60/100
values for each curve, as indicated

Pipes
(mm)
ø 80

ø 80

ø 80

ø 80
in the table.
4. The exhaust pipe must extend at
least 0.5 m above the ridge of the
roof if it is located on a side other
than that for the air intake (this is

L * < 0.5 m

L * < 0.5 m

L * < 0.5 m

Use of Restrictor on Discharge Side

L<7m

L<7m

L<7m

L<7m

not obligatory if the exhaust and air

23kW
intake pipes are located on the

42 mm
same side of the building).

L * < 0.5 m

L * < 0.5 m

L * < 0.5 m

27 kW
L<5m

L<5m

L<5m

L<5m

L * < 0.5 m

L * < 0.5 m

L * < 0.5 m
L < 7.5 m

L < 7.5 m

L < 7.5 m

L < 7.5 m

45 mm
30 kW
L > 4.9 m

L > 4.9 m

L > 4.9 m

L > 4.9 m

Risk of Condensation Forming

23kW
L < 5.3 m

L > 6.5 m

L > 6.5 m

L > 6.5 m

27 kW
(*) L = Length of Piping

L > 4.5 m

L > 4.5 m

L > 4.5 m

L > 4.5 m

30 kW

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 2.10 Room Thermostat In order to perform this procedure, remove the boiler casing as indicated in
Connection section 3.2. Then proceed as follows:
1 Remove the two screws “A” in order to remove the cover, release the two
clips “B” and lift and rotate down the control panel box.
2 Open the cover “C” on the left hand side of the compartment.
3 Insert the wire for the connection of the room thermostat into the cable
clamp “D”, as indicated in photo 3.

1 B 2 3

4 Remove the grommet “E” shown in the photo 4, make a hole in it and pass
the room thermostat wire through.
5 Remove the link located in the terminal block and connect the wire.
6 Replace the grommet and the terminal block to their original positions, close
the cover on the grommet compartment and fasten the wire-clamp “D” in
place.
7 If a remote time clock is to be fitted, disconnect the integral time clock plug
from the P.C.B.
8 Using a volt-free switching time clock, connect the switching wires from the
time clock following points 1-6 above.
9 If using a time clock and room thermostat, these must be connected in
series as per points 1-8 above.
Note: Only a two-wire type room thermostat can be used.

For details on fitting the D.H.W. probe (Genus 27 RFFI only),

please consult the separate instruction sheet supplied with the
probe.

An anti-frost device is built-in to the appliance’s electronic

regulation system.

4 5 6

E D

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 2.11 Electrical Diagram Legend:

AT = High Voltage P.C.B.

BT = Low Voltage P.C.B.
A = Remote Connector Kit
B = Flame Failure L.E.D.
C = Insufficient Water Pressure L.E.D.
D = Water Temperature Indicator L.E.D.s
E = Overheat Thermostat Warning L.E.D.
F = System Reset Button
G = Selector Knob for Operating Mode
H = Domestic Hot Water Temp. Adjustment
I = Central Heating Temp. Adjustment
J = Wire Connector for Room Thermostat
K = Connector for Total Check System
L = Selector for Local/Remote Control
M = Anti-cycling Device Adjustment for Heating
N = Soft-light Adjustment
O = Max Heating Temperature Adjustment
P = Time Clock Connection
Q = On/Off L.E.D.
R = On/Off Switch
S = Interface Wire for P.C.B.s
T = Relay Motorised Valve
U = Ignitor Relay
V = Gas Valve Relay
W = Fan Relay
X = Circulation Pump Relay
Y = Selector TCS2
Z = Link for Continuous Pump Run
Aa = Adaptor (British Gas use only)

A01 = Air Pressure Switch

A02 = Fan
A03 = Gas Valve
A04 = Ignitor
A05 = Motorised Valve
A06 = Circulation Pump
A07 = Flame Detector
A08 = Earth Terminal
A09 = Flame Detection Circuit
A10 = Flame Indicator L.E.D.
A11 = Transformer
A12 = Filter

B01 = Over Heat Thermostat

B02 = External Thermostat
B03 = Gas Valve Modulator
B04 = D.H.W. Probe Sensor Cylinder (RFFI SYSTEM models only)

B05 = Heating Sensor

B06 = Pressure Switch for Heating Circuit
B07 = Microswitch for Diverter Valve (MFFI models only)

Colours

Gry = Grey
Rd = Red
Bl = Blue
Grn/Yll = Yellow/Green
Wh = White
Brn = Brown
Blk = Black
Wh/Rd = White/Red
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 GENUS 23/27/30 MFFI

Aa

GENUS 27 RFFI SYSTEM

Aa

B004 17

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 GENUS 23/27/30 MFFI

CN202
P

GENUS 27 RFFI SYSTEM

P

18 B004

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 2.12 Water Circuit Diagram

Legend
GENUS 23/27/30 MFFI
1. Air Pressure Switch
2. Fan
3. Main Heat Exchanger
4. Burner
5. Electronic Ignitor and
Electronic Flame Detector
6. Gas Valve
7. Overheat Thermostat
8. Heating Sensor
9. Diverter Valve (MFFI)
Motorised Valve (RFFI)
10. Main Flow Switch Including
Safety Pressure Switch for
Primary Circuit
11. Automatic By-pass
12. Microswitch for Diverter Valve
13. Sensor for Domestic Hot Water
14. Secondary Heat Exchanger
15. Domestic Water Inlet Filter
16. Drain Valve
17. Safety Valve
18. Water Pressure Gauge
GENUS 27 RFFI SYSTEM
19. Circulation Pump with Automatic
Air Valve
20. Expansion Vessel

A. Central Heating Flow

B. Domestic Hot Water Outlet
C. Gas Inlet
D. Domestic Cold Water Inlet
E. Central Heating Return
F. Cylinder Flow
G. Cylinder Return

B004 19

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 3. COMMISSIONING

3.1 Initial Preparation Preliminary electrical system checks to ensure electrical safety must be carried
out by a competent person i.e. polarity, earth continuity, resistance to earth and
short circuit.

Filling the Heating System:

Remove the panels of the case and lower the control panel (see point 3.2. for
further information).
Open the central heating flow and return cocks supplied with the connection
kit.
Unscrew the cap on the automatic air release valve one full turn and leave
open permanently.
Close all air release valves on the central heating system.
Gradually open valve(s) at the filling point (filling-loop) connection to the
central heating system until water is heard to flow, do not open fully.
Open each air release tap starting with the lower point and close it only when
clear water, free of air, is visible.
Purge the air from the pump by unscrewing anticlockwise the pump plug and
also manually rotate the pump shaft in the direction indicated by the pump
label to ensure the pump is free.
Close the pump plug.
Continue filling the system until at least 1 bar registers on the pressure
gauge.
Inspect the system for water soundness and remedy any leaks discovered.

Filling of the D.H.W. System:

Close all hot water draw-off taps.
Open the cold water inlet cock supplied with the connection kit.
Open slowly each draw-off tap and close it only when clear water, free of
bubbles, is visible

Gas Supply:
Inspect the entire installation including the gas meter, test for soundness and
purge, all as described in BS 6891:1988.
Open the gas cock (supplied with the connection kit) to the appliance and
check the gas connector on the appliance for leaks.
When the installation and filling are completed turn on the central heating
system (sect. 3.4) and run it until the temperature has reached the boiler
operating temperature. The system must then be immediately flushed through.
The flushing procedure must be in line with BS 7593:1992 Code of practice for
treatment of water in domestic hot water central heating systems.
During this operation, we highly recommend the use of a central heating
flushing detergent (Fernox Superfloc or equivalent), whose function is to
dissolve any foreign matter that may be in the system.
Substances different from these could create serious problems to the
pump or other components.
The use of an inhibitor in system such as Fernox MB-1 or equivalent is strongly
recommended to prevent corrosion (sludge) damaging the boiler and system.
Failure to carry out this procedure may invalidate the appliance warranty.

3.2 Removing the Casing 1

To dismantle the front part of
the casing, proceed as follows:
1. Loosen the two screws “F”
located on the bottom part
of the boiler until the
first thread on the screws
appears;

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 2 3 4

2. Lift the front panel up until it stops after the click;

3. Remove the front panel from the rest of boiler casing;
4. Unhook the two cords from the location slots.
3.3 Control Panel

A - Ignition Lockout Reset

GENUS 23/27/30 MFFI
Button/Safety
(Overheat)Thermostat Reset
B - Ignition Lockout L.E.D.
C - Selector Knob for
Summer/Winter/Flue Analysis
Modes*
D - Low System Water Level L.E.D.
E - Temperature Adjustment Knob
for Domestic Hot Water
F - Heating System Thermometer
G - Safety (Overheat)Thermostat
Intervention L.E.D.
GENUS 27 RFFI SYSTEM H - Adjustment Knob for Heating
Temperature
I - On/Off L.E.D.
L - On/Off Switch
O - System Pressure Gauge

* Warning the flue analysis mode must only be selected by a qualified service engineer.

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 3.4 Initial Start-up The checks to be run before initial start-up are as follows:
1. Make sure that:
- the screw on the automatic air valve has been loosened when the
system is full;
- If the water pressure in the system is below 1 bar, bring it up to the appro-
priate level;
- Check to see whether the gas cock is closed;
- Make sure that the electrical connection has been made properly and that
the earth wire is connected to an efficient earthing system;
- Supply power to the boiler by pressing the On/Off switch <L> - the L.E.D. “I”
will turn on - turn the selector knob “C” to the <winter> setting. This will
start the circulation pump. After 7 seconds, the boiler will signal a shut-
down due to failure ignition. Leave the boiler as it is until all of the air has
been bled from the lines.
- Loosen the cap on the head of the pump to eliminate any air pockets;
- Repeat the procedure for bleeding the radiators of air;
- Open the taps for a brief period;
- Check the system pressure and, if it has dropped, open the filling loop
again to bring the pressure back up to 1 bar.
2. Check the exhaust flue for the fumes produced by combustion.
3. Make sure that all gate valves are open;
4. Turn on the gas cock and check the seals on the connections, including the
one for the burner, making sure that the meter does not signal the passage
of gas. Check the connections with a soap solution and eliminate any leaks.
5. Press the reset button “A” for the lighting system; the spark will light the
main burner. If the burner does not light the first time, repeat the procedure.
6. Check the minimum and maximum pressure values for the gas going to the
burner; adjust it if needed using the values indicated in the table in
section 4.
(See sect of the servicing manual).

3.5 Operational The boiler was designed to make regulation easy. To access the adjustment
Adjustments and control area, simply remove the cover by unscrewing the screws “A” and
“C” and lift up the small service panels “B1” and “B2” respectively. The first
provides access to the control (low voltage) P.C.B., while the second makes it
possible to work on the power supply P.C.B.

B1 B2
A C

The service panel “B2” also provides access to:

- the power supply cord connector;
- the fuses;
- the selector knob for continuous
operation of the circulation pump.
The service panel “B1” also provides access to:
- the potentiometer for regulating the ignition delay (anti-cycling) feature, which
can be set from 0 to 2 minutes (factory set at 1 minute);
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 - the potentiometer for regulating the soft-light feature, the setting for which
can range from the minimum thermal power to the maximum:
G20 5 mbar
G25 18 mbar
G30-31 19 mbar

- the potentiometer for the maximum thermal power for the heating system,
maximum thermal power setting (factory set at the maximum value, unless
indicated otherwise on the adhesive sticker located in proximity to the
potentiometer);
- The connection to the diagnosis device (TCS-TCS2).

3.6 Combustion Analysis The boiler is designed to make it easy to analyse the combustion by-products.

Using the especially designed apertures, readings can be taken on the

temperature of the combustion by-products and of the combustion air, as well
as of the concentrations of O2 and CO2, etc.
The best maximum-power test conditions for the heating system are when the
selector “C” is turned to the flue analysis setting.

3.7 Fume Discharge The discharge/ventilation of the exhaust fumes can be monitored to check for
Monitoring losses in general pressure in the system. This is done to eliminate the cause of
lighting failure with the main burner not indicated by a shutdown status.
With a differential manometer connected to the test socket on the combustion
chamber, the DP value for the air pressure switch can be taken. The measured
value should not be less than 10 mbar under maximum thermal power
conditions (with the knob “C” on the flue test setting) in order for the unit to
function properly and without interruption.

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 3.8 Boiler Safety The boiler is equipped with the following safety systems (see section 3.3 for
Systems references):
1. - Ignition Failure
This control signals an ignition failure on the burner 7 seconds after a lighting
failure. The L.E.D. “B” will turn on to signal the shutdown status.
The system can be reset by pressing and releasing the button “A” after
checking to make sure that the gas valve is open. Repeat this process until the
burner lights.
2. - Circulation Failure
This control signals that the safety pressure switch on the primary circuit has
not sensed a pressure of at least 1 bar within 40 seconds of the activation of
the circulation pump, it shuts off the boiler and lights the L.E.D. “D” The system
can be reset (after the pressure has been brought up to the proper level) by
using the On/Off switch “L”.
3. - Overheating
This control shuts off the boiler in the case where the primary circuit reaches a
temperature in excess of 110°C. The L.E.D. “G” will come on to signal this shut-
off status. After the system has been allowed to cool, the system can be reset
by pressing the button “A”.
4. - Limescale Build-up
This is an indirect control (actuated through the regulation of the temperature in
the primary heat exchanger) on the formation of limescale in the secondary
heat exchanger. Regardless of the flow rate and the temperature in the circuit
for the domestic hot water, the temperature is limited to 62°C.
5. - Anti-frost Device
The boiler is equipped with a device that automatically lights the main burner
when the temperature in the delivery line to the system drops below 5°C. The
boiler will continue to operate until the temperature in question reaches about
58°C.
This device is activated on a properly operating boiler if:
- the system pressure is between the acceptable values;
- the power supply to the unit is on;
- the unit is supplied with gas.
This feature is enabled also when the boiler is in summer operating mode.
6. - Safety Shut-off
At the start of every lighting phase, the P.C.B. performs a series of internal
controls. If a malfunction occurs, the boiler will shutdown until the problem has
been resolved.

3.9 Draining the System Draining the heating system.

The heating system must be emptied as follows:
- Turn off the boiler;
-Open the drain valve for the system and place a container below to catch
the water that comes out;
- Empty the system at the lowest points (where present). If you plan on not
using the heating system for an extended period of time, it is recommended
that you add antifreeze with an ethylene glycol base to the water in the
heating lines and radiators if the ambient temperature drops below 0°C during
the winter.
This makes repeated draining of the entire system unnecessary.

Draining the domestic hot water system.

Whenever there is the danger of the temperature dropping below the freezing
point, the domestic hot water system must be drained as follows:
- Turn off the general water valve for the household plumbing system;
- Turn on all the hot and cold water taps;
- Empty the remaining water from the lowest points in the system (where
present).

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 4. GAS ADJUSTMENTS

CATEGORY II2H3+ Methane Gas Liquid Butane Gas Liquid Propane Gas
G20 G30 G31

Lower Wobbe Index (15°C;1013mbar) MJ/m3h 45.67 80.58 70.69

Nominal Delivery Pressure mbar 20 30 37
Minimum Delivery Pressure mbar 17 20 25

23 MFFI

Main Burner: n. 13 jets (ø) mm 1.25 0.72 0.72

Consumption (15°C; 1013mbar) mc/h 2.72 ---- ----
Consumption (15°C; 1013mbar) Kg/h ---- 2.02 2.02
Gas Cock Outlet Pressure
max - min mbar 11.4- 2.0 27.5 (*) - 5.0 35.0 (*) - 7.0

27 MFFI - 27 RFFI System

Main Burner: n. 15 jets (ø) 1.25 0.72 0.72

Consumption (15°C; 1013mbar) mc/h 3.16 ---- ----
Consumption (15°C; 1013mbar) Kg/h ---- 2.35 2.32
Gas Cock Outlet Pressure:
max - min mbar 11.4-2.0 (*) - 5.0 (*) - 7.0

30 MFFI

Main Burner: n. 15 jets (ø) 1.30 0.77 0.77

Consumption (15°C; 1013mbar) mc/h 3.49 ---- ----
Consumption (15°C; 1013mbar) Kg/h ---- 2.60 2.57
Gas Cock Outlet Pressure:
max - min mbar 11.4-1.4 (*) - 4.1 (*) - 5.6

(1mbar = 10,197column of water)

The outlet pressure of the gas cock is obtained by completely loosening the
screw on the solenoid. The maximum pressure of the gas to the burner will be
equal to the nominal delivery pressure minus the head loss within the gas
valve.

4.1 Changing the Type of The boiler can be converted to use either methane (natural) gas (G20) or
Gas LPG (G30 - G31) by an Authorised Service Centre.
The operations that must be performed are the following:
1. Replace the jets on the main burner (see table in section 4);
2. Adjust the maximum and minimum thermal capacity values for the boiler
(see table in section 4);
3. Replace the gas rating plate;
4. Adjust the maximum thermal power setting;

CATEGORY II2H3+ Methane Gas Liquid Butane Gas Liquid Propane Gas

G20 G30 G31

Recommended Soft-light Pressure

(mbar) 5-5.5 17 - 18 18 - 19

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 5. Adjust the soft-light feature;
6. Adjust the delayed lighting feature for the heating system (can be set from
0 to 2 mins.).

5. MAINTENANCE It is recommended that the following checks be made on the boiler at

least once a year:
1 - Check the seals for the water connections; replacement of any faulty seals.
2 - Check the gas seals; replacement of any faulty gas seals.
3 - Visual check of the entire unit.
4 - Visual check of the combustion process or analysis of flue gas (see ref 3.6)
and cleaning of the burners if needed.
5 - If called for by check no. 3, dismantling and cleaning of the combustion
chamber.
6 - If called for by check no. 4, dismantling and cleaning of the injectors.
7 - Visual check of the primary heat exchanger:
- check for overheating in the blade assembly;
- clean the exhaust fan if needed.
8 - Adjustment of the flow rate of the gas: flow rate for lighting, partial load and
full load.
9 - Check of the heating safety systems:
- safety device for maximum temperature;
- safety device for maximum pressure.
10 - Check of the gas safety systems:
- safety device for lack of gas or flame ionisation (detection electrode);
- safety device for gas cock.
11 - Check of the electrical connection (make sure it complies with the
instructions in the manual).
12 - Check of domestic hot water production efficiency (delivery rate and tem-
perature)
13 - Check of the general performance of the unit.
14 - General check of the discharge/ventilation of the combustion by-
products.

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 B004

6.1

6.
Two Heating Zones
Wiring Diagram for

MISCELLANEOUS
MAINS INPUT (3 AMP)

GREEN/YELLOW

GREEN/YELLOW
THERMOSTAT

THERMOSTAT
ORANGE

ORANGE
BROWN

BROWN
GREY

GREY
BLUE

BLUE
V4043H

V4043H
T6360B

T6360B
ROOM

ROOM
VALVE

VALVE
2
3
1

2
3
1
N
240V

ZONE 2

ZONE1
2
8
6

2
5
4
10

10
3

9
2
8

9
2
5
3
2
1

JUNCTION BOX
TYPICAL
• 10

• 9

• 8

• 7

• 6

• 5

• 4

• 3

• 2

• 1
If a room thermostat is not required on Zone 1, insert a link
If a room thermostat is not requied on Zone 2, insert a link

6 4 3 2 1 6 4 3 2 1 9 10 3 2 1

Honeywell ST 699B 1002 6 3 N L Pegler Sunvic 2 5 E N L A/27 MFFI - A/27 MFFI E N L

Link L-5-8 SP 50/100 (Link L-3) Genus 23-27-30 MFFI E N L
ST 6400/ST 6300 ST 6200 3 4 N L Switchmaster Genus 27 RFFI System E N L
1 4 N L
Symphony, Sonata
Drayton Tempus 7 3 4 N L
Switchmaster 400, 600 3 1 N L

BOILER ELECTRICAL SUPPLY CABLE

Horstmann 425, 525, 527 1 4 E N L
the junction box.
(see section 2.10) to 9 + 10 on
reverse of the boiler control panel
room stat terminal block on the
from the the P.C.B. then connect
Remove internal time clock plug
Link L-2-5 SWITCHMASTER 805, 900 3 1 N L
Landis & Gyr RWB2 Sunvic ET 1451
between 6 + 8 on the junction box.

between 4 + 5 on the junction box.

3 4 N L 7 4 E 1 2
Glowworm Mastermind Link 2-3-6
Landis & Gyr RWB20 3 4 N L Sunvic DHP 2201 6 3 E 1 2
Microgyr
Towerchron FP 6 1 0 2 1
Potterton Miniminder 3 4 N L Link 1-5/4-7-9
Potterton EP2000/3000 - 3 4 N L Towerchron MP 6 1 0 2 1
Link L-5 EP2001/3001 Link 1-4/6-11
Randall 102/102 E 1 2 E 5 6 Towerchron 2000 HW HTG N L
Link 3-6 ON ON
Randall 4033 4 2 E 7 6 ACL LS522, LS722 3 4 N L
Link 1-6
Randall 922, 972 3 6 E N L
Randall 701, 702 3 1 E N L Link L-2-5
Link L-6-5
Randall 3020 P 4 2 E N L
Sangamo M5 1 8 E 4 3 and 3060
Link 1-6
Sangamo 410 Form 1 1 8 E 4 3
Link 3-6

PROGRAMMER PROGRAMMER BOILER

ZONE 2 ZONE 1 ZONE 2 ZONE 1

27

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 6.2
28

MAINS INPUT (3 AMP)

HOT WATER VALVE

HEATING VALVE

Unvented Cylinder
Connection to Ariston
Wiring Diagram for
thermostat

GREEN/YELLOW

GREEN/YELLOW
2

THERMOSTAT
ORANGE

ORANGE
Cylinder

BROWN

BROWN
GREY

GREY
BLUE

BLUE
V4043H

V4043H

T6360B
ROOM
N
240V

2
3
1
C/P
1 C/P

Thermal
cut-out

2
5
4
10

10
3
2
1

9
2
8

9
2
5
2

1
used
Not

JUNCTION BOX
TYPICAL
• 10

• 9

• 8

• 7

• 6

• 5

• 4

• 3

• 2

• 1
6 4 3 2 1 6 4 3 2 1 9 10 3 2 1

Honeywell ST 699B 1002 6 3 N L Pegler Sunvic 2 5 E N L A/27 MFFI - A/27 MFFI E N L

Link L-5-8 SP 50/100 (Link L-3) Genus 23-27-30 MFFI E N L
ST 6400/ST 6300 ST 6200 3 4 N L Switchmaster Genus 27 RFFI System E N L
1 4 N L
Symphony, Sonata
Drayton Tempus 7 3 4 N L
Switchmaster 400, 600 3 1 N L

BOILER ELECTRICAL SUPPLY CABLE

Horstmann 425, 525, 527 1 4 E N L
the junction box.
(see section 2.10) to 9 + 10 on
reverse of the boiler control panel
room stat terminal block on the
from the the P.C.B. then connect
Remove internal time clock plug
Link L-2-5 SWITCHMASTER 805, 900 3 1 N L
Landis & Gyr RWB2 3 4 N L Sunvic ET 1451 7 4 E 1 2
Glowworm Mastermind Link 2-3-6
Landis & Gyr RWB20 3 4 N L Sunvic DHP 2201 6 3 E 1 2
Microgyr
Towerchron FP 6 10 2 1
Potterton Miniminder 3 4 N L Link 1-5/4-7-9
Potterton EP2000/3000 - 3 4 N L Towerchron MP 6 10 2 1
Link L-5 EP2001/3001 Link 1-4/6-11
Randall 102/102 E 1 2 E 5 6 Towerchron 2000 HW HTG N L
Link 3-6 ON ON
Randall 4033 4 2 E 7 6 ACL LS522, LS722 3 4 N L
Link 1-6
Randall 922, 972 3 6 E N L
Randall 701, 702 3 1 E N L Link L-2-5
Link L-6-5
Randall 3020 P 4 2 E N L
Sangamo M5 1 8 E 4 3 and 3060
Link 1-6
Sangamo 410 Form 1 1 8 E 4 3
Link 3-6

PROGRAMMER PROGRAMMER BOILER

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 NOTES

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 NOTES

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 31 B004

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 B004 - Cod. 23 99 84 1259 111 - Stampa: bieffe RECANATI

Manufacturer: Merloni TermoSanitari SpA - Italy

Commercial subsidiary: MTS (GB) LIMITED

MTS Building
Hughenden Avenue,
High Wycombe
Bucks HP13 5FT
Telephone: (01494) 755600 -
Fax: (01494) 459775
Technical Service Hotline: (01494) 539579

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