Ariston MICROCOMBI 23 MFFI User guide

microCombi 23/27 MFFI
Installation and Servicing
Instructions
Type C Boilers
G.C.N: 47-116-16 (23kW)
G.C.N: 47-116-24 (27kW)
LEAVE THESE INSTRUCTIONS WITH
THE END-USER
Country of destination: GB, IE

2
TABLE OF CONTENTS
1. GENERAL INFORMATION PAGE.3
1.1 GENERAL INSTRUCTIONS PAGE.3
1.2 OVERALL VIEW PAGE.4
2. INSTALLATION PAGE.4
2.1 REFERENCE STANDARDS PAGE.4
2.2 SITING THE APPLIANCE PAGE.5
2.3 OVERALL DIMENSIONS PAGE.6
2.4 CLEARANCES PAGE.6
2.5 MOUNTING THE APPLIANCE PAGE.7
2.6 ELECTRICAL CONNECTION PAGE.7
2.7 GAS CONNECTION PAGE.8
2.8 WATER CONNECTION PAGE.8
2.9 FLUE CONNECTION PAGE.10
2.10 CONTROL PANEL PAGE.17
2,11 REMOVING THE FRONT PANEL PAGE.17
2.12 ROOM THERMOSTAT
CONNECTION PAGE.18
2.13 ELECTRICAL/SYSTEM DIAGRAMS PAGE.19
2.14 WATER CIRCUIT DIAGRAM PAGE.20
3. COMMISSIONING PAGE.21
3.1 INITIAL PREPARATION PAGE.21
3.2 INITIAL START-UP PAGE.22
3.3 OPERATIONAL ADJUSTMENTS PAGE.22
3.4 COMBUSTION ANALYSIS PAGE.23
3.5 PRODUCT OF COMBUSTION
DISCHARGE MONITORING PAGE.23
3.6 BOILER SAFETY SYSTEMS PAGE.23
3.7 DRAINING THE SYSTEM PAGE.24
3.8 COMPLETION PAGE.24
3.9 OPERATIONAL CHECKS PAGE.24
3.10 INSTRUCTING THE END USER PAGE.25
4. GAS ADJUSTMENTS
4.1 CHANGING THE TYPE OF GAS PAGE.26
4.2 ADJUSTING THE GAS PRESSURES
(SIT SIGMA)PAGE.26
ADJUSTING THE GAS PRESSURES
(HONEYWELL)PAGE.28
5. MAINTENANCE PAGE.30
6. SERVICING INSTRUCTIONS PAGE.31
6.1 REPLACEMENT OF PARTS PAGE.31
6.2 TOGAIN GENERAL ACCESS PAGE.31
6.2.1 REMOVING THE FRONT
PANEL PAGE.31
6.2.2 REMOVING THE SEALED
CHAMBER FRONT PANEL PAGE.32
6.2.3 REMOVING THE SIDE
PANELS PAGE.32
6.3 ACCESS TO THE COMBUSTION
CHAMBER PAGE.33
6.3.1 REMOVING THE
COMBUSTION CHAMBER PAGE.33
6.3.2 REMOVING THE BURNER
AND JETS PAGE.33
6.3.3 REMOVING THE
ELECTRODES PAGE.33
6.3.4 REMOVING THE MAIN HEAT
EXCHANGER PAGE.34
6.3.5 REMOVING THE AIR
PRESSURE SWITCH PAGE.35
6.3.6 REMOVING THE FAN PAGE.35
6.4 ACCESS TO THE GAS VALVE PAGE.36
6.4.1 REMOVING THE SPARK
GENERATOR (SIT SIGMA)PAGE.36
6.4.2 REMOVING THE SPARK
GENERATOR (HONEYWELL)PAGE.36
6.4.3 REMOVING THE GAS VALVE
(SIT SIGMA)PAGE.37
6.4.4 REMOVING THE GAS VALVE
(HONEYWELL)PAGE.37
6.5 ACCESS TO THE WATER CIRCUIT PAGE.38
6.5.1 REMOVING THE PUMP
PRESSURE SWITCH PAGE.38
6.5.2 REMOVING THE SAFETY
VALVE PAGE.38
6.5.3 REMOVING THE AUTOMATIC
AIR VENT PAGE.38
6.5.4 REMOVING THE PUMP PAGE.39
6.5.5 REMOVING THE PRESSURE
GAUGE PAGE.40
6.5.6 REMOVING THE EXPANSION
VESSEL PAGE.40
6.5.7 REMOVING THE OVERHEAT
THERMOSTAT PAGE.41
6.5.8 REMOVING THE CENTRAL
HEATING TEMPERATURE
SENSOR (N.T.C.) PAGE.41
6.5.9 REMOVING THE D.H.W.
TEMPERATURE SENSOR
(N.T.C.) PAGE.41
6.5.10 REMOVING THE D.H.W.
FLOW SWITCH PAGE.42
6.6 ACCESS TO THE CONTROL SYSTEM PAGE.42
6.6.1 CHECKING THE FUSES PAGE.42
6.6.2 REMOVING THE TIME CLOCK PAGE.43
6.6.3 REMOVING THE P.C.B. PAGE.43
7. FAULT FINDING PAGE.44
7.1 FAULT FINDING GUIDE
(FLOW-CHARTS)PAGE.44
8. SHORT SPARE PARTS LIST PAGE.49
9. TECHNICAL INFORMATION PAGE.52

3
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
personnel.
Please carefully read the instructions and notices about the unit contained in
this manual, as they provide important information regarding the safe
installation, use and maintenance of the product.
For operating instructions please consult the separate Users Manual.
Read the instructions and recommendations in these Installation and Servicing
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
Servicing 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 in section 7 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 or off 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 (at or adjacent to 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 carrying 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 Agent and request the use of
original spare parts. For in-guarantee repairs contact MTS (GB) Limited.
1. GENERAL
INFORMATION
1.1 GENERAL INSTRUCTIONS

4
2.1 REFERENCE STANDARDS
2. INSTALLATION
LEGEND:
1. Flue connector
2. Air intake for twin pipe flue systems
3. Fan
4. Combustion chamber hood
5. “Twin-pass” heat exchanger
6. Domestic hot water temperature probe
7. Combustion chamber
8. Combustion chamber insulation panel
9. Burner
10. Detection electrode
11. Ignition electrodes
12. Gas valve
13. Spark generator
14. Pump pressure switch
15. Safety valve (3 bar)
16. Automatic By-pass
17. D.H.W. Flow switch
18. Domestic hot water inlet filter
19. Circulation pump with automatic air release valve
20. Safety thermostat
21. Main circuit temperature probe
22. Expansion vessel
23. Air pressure switch tube
24. Air pressure switch
25. Combustion analysis points
1.2 OVERALL VIEW
FIG. 1.0
IN028C
The technical information and instructions provided herein
below are intended for the installer / Servicing Technician
so that the unit may be installed and serviced correctly and
safely.
In the United Kingdom the installation and initial start up of
the boiler must be by a CORGI Registered Installer in
accordance with the installation standards currently in
effect, as well as with any and all local health and safety
standards i.e. CORGI.
In the Republic of Ireland the installation and initial start up
of the appliance must be carried out by a Competent
Person in accordance with the current edition of I.S.813
“Domestic Gas Installations”, the current Building
Regulations, reference should also be made to the current
ETCI rules for electrical installation.
This appliance must be installed by a competent
installer in accordance with current Gas Safety
(installation & use) Regulations.
The installation of this appliance must be in accordance
with the relevant requirements of the Local Building
Regulations, the current I.E.E. Wiring Regulations, the
bylaws of the local water authority, in Scotland, in
accordance with the Building Standards (Scotland)
Regulation and Health and Safety document No. 635

5
“Electricity at work regulations 1989” and in the Republic of
Ireland with the current edition of I.S. 813, the Local
Building Regulations (IE).
C.O.S.H.H.
Materials used in the manufacture of this appliance are
non-hazardous and no special precautions are required
when servicing.
Installation should also comply with the following British
Standard Codes of Practice
and in the Republic of Ireland in accordance with the
following Codes of Practice:
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, the location of the boiler in a room containing a
bath or shower should only be considered if there is no
alternative.
Where a room-sealed appliance is installed in a room
containing a bath or shower the appliance 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,
specifically in accordance with current IEE Wiring
Regulations.
The location must permit adequate space for servicing and
air circulation around the appliance as indicated in Section
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 the installation
BS 7593:1992 Treatment of water in domestic hot water
central heating systems
BS 5546:1990 Installation of hot water supplies for
domestic purposes
BS 5440-1:2000 Flues
BS 5440-2:2000 Air supply
BS 5449:1990 Forced circulation hot water systems
BS 6798:1987 Installation of gas fired hot water boilers of
rated input not exceeding 60kW
BS 6891:1989 Installation of low pressure gas pipe up to
28mm
BS 7671:2001 IEE wiring regulations
BS 4814:1990 Specification for expansion vessels
BS 5482:1994 Installation of L.P.G.
I.S. 813 Domestic Gas Installations
2.2 SITING THE APPLIANCE

6
FIG. 2.2 DM001B
In order to allow access to the interior of the boiler for
maintenance purposes, the boiler must be installed in
compliance with the minimum clearances indicated in FIG.
2.2
2.4 CLEARANCES
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.
Secondary ventilation is not required with this boiler. The
boiler must be installed on a solid, non-combustible,
permanent wall to prevent access from the rear.
LEGEND:
A = Central Heating Flow (3/4”)
B = Domestic Hot Water Outlet (1/2”)
C = Gas Inlet (3/4”)
D = Domestic Cold Water Inlet (1/2”)
E = Central Heating Return (3/4”)
2.3 OVERALL DIMENSIONS
FIG. 2.1 QT002A

7
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 Information table in Section 10, 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.
IMPORTANT!
In the event that the power supply cord must be changed,
replace it with one with the same specifications.
Note: The diagrams for the electrical system are indicated
in section 2.13.
Warning, this appliance must be earthed.
External wiring to the appliance must be carried out by a
competent person and be in accordance with the current
I.E.E. Regulations and applicable local regulations.
The appliance is supplied with a fly-lead already
connected, this must be connected to a 240v supply fused
2.6 ELECTRICAL CONNECTION
FIG. 2.3
After removing the boiler from its packaging, remove the
template from the separate box containing the connection
kit. NOTE: Pay particular attention to any test water that
may spill from the appliance.
Place the template in the position the appliance is to be
mounted and after ensuring it is hanging squarely, use it to
drill the holes for the hanging bracket and flue pipe(s) NB:
For further information relating to the flue installation
please refer to Section 2.9 FLUE CONNECTION. (If the
appliance is to be fitted on a wall of combustible material,
the wall must be protected by a sheet of fireproof
material).
If the appliance is to be fitted into a timber framed building,
guidance should be sought from the Institute of Gas
Engineers document REF: IGE/UP/7.
2.5.1. Drill the wall and plug using those supplied with
the connections kit, position the bracket and secure with
the wall bolts supplied. NOTE:It is highly recommended
that a spirit level be used to position the appliance to
ensure that it is perfectly level.
2.5.2. Position the appliance on the hanging bracket and
connect the isolating valves supplied in the connection kit
as shown on the wall template (see also Sections 2.7 Gas
Connections, 2.8 Water Connections & FIG. 2.3).
2.5 MOUNTING THE APPLIANCE

8
VIEW OF THE BOILER CONNECTIONS
LEGEND:
A = Central Heating Flow
B = Domestic Hot Water Outlet
C = Gas Inlet
D = Domestic Cold Water Inlet
E = Central Heating Return
F = Safety Valve Outlet
2.8 WATER CONNECTIONS
2.7 GAS CONNECTION The local gas region 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.
at 3A and 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 (see section 2.2).
Should external controls be required, the design of the external electrical
circuits should be undertaken by a competent person, see section 2.12 for
further information.
FIG. 2.4
FIG. 2.5 KT007A
SC005A
FF
PIPE WORK:
Copper tubing to BS EN 1057:1996 is recommended for water pipes.
Jointing should be either with capillary soldered or compression fittings.
Where possible pipes should have a gradient to ensure air is carried
naturally to air release points and water flows naturally to drain taps.
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 collecting point for air.
Except where providing useful heat, pipes should be insulated to prevent
heat loss and avoid freezing.

9
VR003A
RESIDUAL HEAD OF THE BOILER
Particular attention should be paid to pipes passing through ventilated
spaces in roofs and under floors.
BY-PASS:
The appliance includes an automatic by-pass valve, which protects the main
heat exchanger in case of reduced or interrupted water circulation through
the heating system, due to the closing of thermostatic valves or radiators.
SYSTEM DESIGN:
This boiler is suitable only for sealed systems.
DRAIN COCKS:
These must be located in accessible positions to permit the draining of the
whole system and should be fitted at all low points. The taps must be at least
15mm nominal size and manufactured in accordance with BS 2870:1980.
SAFETY VALVE DISCHARGE:
The discharge should terminate facing downward on the exterior of the
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.
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 volume when the system is heated.
It can accept up to 6 litres (1.3 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. This should
be located on the return pipe work as close as possible to the pump inlet.
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,
therefore a temporary method for initially filling the system and replacing lost
water during servicing in accordance with current Water Regulations and
bylaws must be provided (FIG. 2.6). NOTE: The installer should ensure that
there are no leaks as frequent filling of the heating system can lead to
premature scaling of the main exchanger and failure of hydraulic
components.
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, a scale reducer should also be used to reduce the
risk of scale forming in the domestic side of the heat exchanger.
CENTRAL HEATING
Detailed recommendations are given in BS 6798:1987 and BS 5449-1:1990,
the following notes are given for general guidance.
FIG. 2.6 Fill01

10
Ø 60/100 mm
FIG. 2.8
2.9 FLUE CONNECTIONS FLUE SYSTEM
The provision for satisfactory flue termination must be made in accordance
with BS 5440-1.
The appliance must be installed so that the flue terminal is exposed to outside 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 terminal should be located with due regard for the damage or
discolouration that might occur on buildings in the vicinity and consideration
must be given to adjacent boundaries.
In cold or humid weather water vapour may condense on leaving the flue
terminal. The effect of such “pluming” 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.
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. 2.7.
T ERMINAL P OSITION mm
A - Directly below an openable window or other opening 300
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 150
F - From internal or external corners 300
G - Above ground or 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
M - Horizontally from an opening window 300
N - Fixed by vertical flue terminal
FIG. 2.7 FU010ARev1
FU003A
FU002A/Rev.1
IMPORTANT!
FOR ALL FLUE SYSTEMS,A
RESTRICTOR MAY NEED TO BE
INSERTED INTO THE EXHAUST
MANIFOLD,THE SIZE OF THE
RESTRICTOR AND DETAILS OF FITTING
REQUIREMENTS ARE SHOWN IN TABLE
2.1 (PAGE 16).
NOTE:THE FLUE MUST NOT TERMINATE IN A PLACE LIKELY TO CAUSE NUISANCE

11
FITTING THE COAXIAL FLUE (HORIZONTAL)
(For Telscopic Instructions see below and
for Vertical Flue and Twin Pipe Instructions
see page 12)
CONTENTS:
1XSILICONE O-RING (60mm)
1XELBOW (90O)
2XWALL SEALS (INTERNAL &EXTERNAL)
1XALUMINIUM FLUE PIPE INCLUDING TERMINAL
(1 METRE - 60/100)
2XFLUE CLAMPS
8XSCREWS
2XSEALS
Once the boiler has been positioned on the
wall, insert the elbow into the socket (FIG
2.8) and rotate to the required position.
NOTE: It is possible to rotate the elbow 360o
on its vertical axis.
Using the flue clamps, seals and screws
supplied (FIG 2.8) secure the elbow to the
boiler.
The 1 metre horizontal flue kit (705958)
supplied is suitable for an exact X
dimension of 823mm, and the 750mm
horizontal flue kit (705785) is suitable for an
exact X dimension of 573mm.
Measure the distance from the face of the
external wall to the face of the flue elbow (X
-F
IG 2.8), add 22 mm to this measurement,
you now have the total length of flue
required (including the terminal), this figure
must now be subtracted from 860mm, you
now have the total amount to be cut from
the plain end of the flue.
FIG 2.9
FIG 2.10
Cut the flue to the required length ensuring that the distance
between the inner and the outer flue is maintained (FIG 2.10).
e.g. X = 508mm + 22mm = 530mm
860 - 530 = 330mm (Length to be cut from the plain end
of the flue).
Once cut to the required length, ensure that the flue is free
from burrs and reassemble the flue. If fitting the flue from
inside of the building attach the grey outer wall seal to the flue
terminal and push through the flue through the hole, once the
wall seal has passed through the hole, pull the flue back until
the seal is flush with the wall. Alternatively, the flue can be
installed from outside of the building, the grey outer seal
being fitted last.
FITTING THE TELESCOPIC FLUE KIT (HORIZONTAL)
CONTENTS:
1XSILICONE O-RING (60mm)
1XELBOW (90O)
2XWALL SEALS (INTERNAL &EXTERNAL)
FIG 2.11
IMPORTANT!
FOR ALL FLUE SYSTEMS,A RESTRICTOR MAY
NEED TO BE INSERTED INTO THE EXHAUST
MANIFOLD,THE SIZE OF THE RESTRICTOR AND
DETAILS OF FITTING REQUIREMENTS ARE
SHOWN IN TABLE 2.1 (PAGE 16).

12
1XALUMINIUM FLUE PIPE INCLUDING TERMINAL (TELESCOPIC -
60/100)
2XFLUE CLAMPS
8XSCREWS
2XSEALS
The telscopic flue is suitable for use with an exact
minimum X dimension of 270mm and an exact maximum
X dimension 470mm.
IMPORTANT!!
Do not extend the telescopic flue to an X dimension of
more than 470mm. If longer lengths are required use
extension pieces as necessary. Under no
circumstances must the flue be cut.
The wall must then be made good around the flue
(ensuring a fall of 1ois maintained away from the boiler to
the flue terminal).
Once made good, place the inner (white) wall seal over the
flue and push up to the wall, secure the flue to the elbow
by using the clamp supplied.
For each additional 90oelbow 1 metre must be removed
from the total flue length (maximum 4 metres including the
1st elbow). For each additional 45oelbow 0.5 metre must
be subtracted from the total flue length (FIG 2.13).
FITTING THE COAXIAL FLUE (VERTICAL)
(For Twin Pipe Instructions see page 13)
CONTENTS:
1XSILICONE O-RING (60mm)
1XCONICAL ADAPTOR (60/100mm)
1XVERTICAL FLUE KIT (80/125mm)
3XSCREWS
The vertical flue kit is supplied with a specially designed
weather proof terminal fitted, it can be used either with a
flat roof or a pitched roof. (see FIGS 2.12, 2.13).
The Vertical flue kits maximum and minimum useable
lengths with both flat and pitched roof flashings are
indicated in (Figs. 2.14 & 2.15).
Before proceeding to fit the flue, ensure that the maximum
flue length has not been exceeded and that all elbows and
bends have been taken into consideration, the maximum
flue length is 4 metres, for each additional 90oelbow 1
metre must be subtracted from the total flue length, and for
each 45o0.5 metres must be subtracted from the total flue
length (the offset and height of 2 x 45ocan be seen in
Fig. 2.16).
Mark the position of the flue hole in the ceiling and/or roof
(see FIG. 2.14 for distance from wall to the centre of the
flue).
Cut a 110mm diameter hole through the ceiling and/or roof
and fit the flashing plate to the roof.
Should it be necessary to cut the flue DO NOTcut the
outer white ar inlet tube, cut the aluminium exhaust flue
6mm longer than the outer white air tube when used at
minimum length. DO NOTcut more that 250mm from the
NOTE:MAX LENGTH = a+a+a +
b+b = a+a+a+0.5+0.5
COMBINED LENGTH NOT
TO EXCEED 3m
FIG 2.12
FIG 2.13
FIG 2.14

13
inner aluminium exhaust flue.
To connect the vertical flue kit directly to the boiler, place
the adaptor (see FIG 2.12) (supplied with vertical flue kit)
onto the exhaust manifold and secure with the clamp, the
vertical flue kit must then be inserted through the roof
flashing, this will ensure that the correct clearance above
the roof is provided as the terminal is a fixed height.
Should extensions be required, they are available in 1
metre (Part No. 705786), 500mm (Part No. 705790) and
160mm lengths (Part No. 705812), they must be
connected directly to the boiler and secured with the clamp
supplied before connecting the adaptor to allow the
vertical flue kit to be fitted. In the event that extension
pieces need to be shortened, they must only be cut at the
male end and it must be ensured that the distance
between the inner and outer flue are kept (Fig. 2.10).
When utilising the vertical flue system, action must be
taken to ensure that the flue is supported adequately to
prevent the weight being transferred to the appliance flue
connection.
When the flue passes through a ceiling or wooden floor,
there must be an air gap of 25mm between any part of the
flue system and any combustible material. The use of a
ceiling plate will facilitate this. Also when the flue passes
from one room to another a fire stop must be fitted to
prevent the passage of smoke or fire, irrespective of the
structural material through which the flue passes.
FITTING THE FLUE (TWIN PIPE)
Where it is not possible to terminate the flue within the
distance permitted for coaxial flues, the twin flue pipe can
be used by fitting a special adaptor to the flue connector
and using the aperture for the air intake located on top of
the combustion chamber.
Considerations necessary for twin flue installation;
It is most important to avoid any possible condense
formation entering the appliance.
According to Table 2.1 (Page 16) decide if condensation
will form within the flue. If yes, there are two options;
1) Where condense will form but can be negated with
insulated flue, install insulated the flue with a fall of 5mm in
every metre away from the boiler.
2) The exhaust flue will have a fall of 3oback to the boiler
and a suitable trap will be fitted on the exhaust as close
to the boiler as possible, condense will then be suitably
disposed of.
Where the flue runs through cold spots, i.e. loft areas,
condense is likely to be formed, therefore a fall back to the
boiler and a trap is required.
Always ensure that the flue is adequately supported,
avoiding low points. (MTS supply suitable clamps as Part
No. 705778).
IMPORTANT!
FOR ALL FLUE SYSTEMS,A
RESTRICTOR MAY NEED TO BE
INSERTED INTO THE EXHAUST
MANIFOLD,THE SIZE OF THE
RESTRICTOR AND DETAILS OF FITTING
REQUIREMENTS ARE SHOWN IN TABLE
2.1 (PAGE 16).
FIG 2.15
FIG 2.16
Minimum offset distance when using 2x 45obends

FIG 2.17
IMPORTANT!!!
WHERE CONDENSE WILL FORM WITHIN
THE FLUE SYSTEM,ENSURE THERE IS A
FALL BACK TO THE BOILER OF 3OAND A
SUITABLE TRAP IS FITTED AS CLOSE TO
THE BOILER AS POSSIBLE. MTS SUPPLY
A SUITABLE COLLECTOR PART NO.
705798 OR A CONDENSATE DISCHARGE
T WITH BUILT IN TRAP PART NO.
705774.
14
FIG 2.16
FIG 2.18
To utilise the air intake it is necessary to:
Remove the ‘knockout’ of the air intake by cutting it with a
suitable knife (FIG. 2.16).
Insert the elbow/flue pipe into the air intake until it stops.
The twin flue pipes can be fitted with or without additional
elbows and need no clamps, simply ensure that the red o-
ring is inserted in the female end of the flue pipe and push
the extension piece fully into the previous section of flue
pipe or elbow, check that the o-ring is not dislodged when
assembling the flue.
Twin pipe can also be converted back to Coaxial flue to
enable vertical termination with a coaxial kit by using the
pipe bridge (Twin - Coaxial Adaptor - Part No. 705767).
When running the twin flue pipe vertically, a condense trap
must always be used on the exhaust pipe.
It is not recommended that the pipe bridge for horizontal
termination, however in the unlikely event that this proves
to be a necessity it is extremely important that the entire
flue has a fall of 3oback to the boiler, is suitably trapped
and where the 60mm inner flue of the concentric terminal
connects to the pipe bridge, this point must be adequately
sealed with silicone sealant to avoid condense leakage at
this point.
NOTE:Vertical twin flue installations must have a trap on
the exhaust. MTS supply a suitable condense
trap Part No. 705774 and recommend that this be
used in the event that the flue may not form
condense.
When siting the twin flue pipe, the air intake and exhaust
terminals must terminate on the same wall, the centres of
the terminals must be a minimum of 280 mm apart and
the air intake must not be sited above the exhaust
terminal (refer to FIG. 2.20). The air intake pipe can be
run horizontally, however, the terminal and the final 1
metre of flue must be installed with a fall away from the
boiler to avoid rain ingress.
It is also strongly recommended that the air intake pipe run
be constructed of insulated pipe to prevent condense
forming on the outside of the tube.
The maximum permissible flue length for twin flue is
dependent on the type of run used.
For flue runs with the intake and exhaust pipes under the
same atmospheric conditions (TYPE 4) the maximum
length is 43 metres (23kW) and 28 metres (27kW), for
runs with the terminals under different atmospheric
conditions (TYPE 5) the exhaust terminal must extend 0.5
metres above the ridge of the roof (this is not obligatory if
the exhaust and air intake pipes are located on the sa,e
side of the building). For TYPE 5 also, the maximum
permissible combined length is 40 metres.
The maximum length is reached by combining the total
lengths of both the air intake and exhaust pipes. Therefore
a maximum length of 40 metres for example, will allow a
flue run of 20 metres for the air intake and 20 metres for
the exhaust pipes, also for each 90oelbow 1.3 metres must
be subtracted from the total length and for each 45oelbow
1 metre must be subtracted from the total flue length.
Some of the acceptable flue configurations are detailed on
below (FIG. 2.19).
For further information relating to flue runs not illustrated,
please contact the Technical Department on 01494
539579.

15
EXHAUST
AIR INTAKE
AIR INTAKE
AIR INTAKE MUST NOT BE
FITTED ABOVE THE EXHAUST
FIG 2.20
FIG. 2.19
NOTE:DRAWINGS ARE INDICATIVE OF FLUEING OPTIONS ONLY.
TYPE 1
TYPE 5
TYPE 4
TYPE 3
TYPE 2

16
27 MFFI
Exhaust
Type
TYPE 4
TYPE 5
Use the
ø 45 mm
Restrictor
Up to 14 m
Up to 21 m
Maximum
Flue
Length
28 m
51 m
Do not use the
Restrictor
Between
14 m - 28 m
Between
21 m - 51 m
Risk of Condensation Forming With:
Twin Pipe
Systems
ø 80/80
7 m
with a
ø 45 mm
restrictor
10 m*
with a
ø 45 mm
restrictor
24 m*
with a
ø 45 mm
restrictor
Exhaust
Type
TYPE 1
TYPE 2
TYPE 3
Use the
ø 45 mm
Restrictor
Between
345 mm - 1 m
Maximum
Flue
Length
4 m
Do not use the
Restrictor
Between
1 m - 4 m
Risk of Condensation Forming
Coaxial
Systems
ø 60/100 NOT APPLICABLE NOT APPLICABLE
Standard Twin Pipe
After:
7 m
without a
ø 45 mm
restrictor
24 m*
without a
ø 45 mm
restrictor
28 m*
without a
ø 45 mm
restrictor
Insulated Twin Pipe
After:
*Where there is no risk of condense forming (and, therefore no requirement for a condense collector), ensure a minimum
fall of 5mm per metre away from the appliance.
NOTE:UNDER SOME CIRCUMSTANCES,CONDENSE MAY FORM AT THE EXHAUST TERMINAL,SPECIAL ATTENTION MUST BE PAID WITH
REGARD TO POSSIBLE CONDENSE DRIPPING FROM THE TERMINAL.
Exhaust
Type
TYPE 4
TYPE 5
Use the
ø 43 mm
Restrictor
Up to 11.5 m
Up to 11.4 m
Maximum
Flue
Length
43 m
40 m
Do not use the
Restrictor
Between
11.5 m - 43 m
Between
11.4 m - 40 m
Risk of Condensation Forming With:
Twin Pipe
Systems
ø 80/80
4.3 m
with a
ø 43 mm
restrictor
N/A*
5.7 m*
with a
ø 43 mm
restrictor
Exhaust
Type
TYPE 1
TYPE 2
TYPE 3
Use the
ø 43 mm
Restrictor
Between
0.5 m - 2 m
Maximum
Flue
Length
4 m
Do not use the
Restrictor
Between
2 m - 4 m
Risk of Condensation Forming
Coaxial
Systems
ø 60/100 NOT APPLICABLE NOT APPLICABLE
TABLE 2.1
23 MFFI
Standard Twin Pipe
After:
6.9 m
without a
ø 43 mm
restrictor
N/A*
21.7 m*
without a
ø 43 mm
restrictor
Insulated Twin Pipe
After:

17
In order to access the inside of the boiler, it is necessary to unscrew
the fastening screws “A” of the control panel located on the lower part
of the panel itself.
The control panel moves downward and when pulled forward rotates
on two lateral hinges.
The panel stays in a semi-horizontal position, which allows access to
the inner parts of the boiler.
In order to increase the manouvering space, it is possible to raise the
control panel and rotate it to a fully horizontal position.
2.11 REMOVING THE
FRONT PANEL
B
1
2
3
4
5
A
LEGEND:
A- On/Off button
B- Central heating temperature adjustment
C- Domestic hot water temperature adjustment
D- Heating system pressure gauge
E- Time clock
F- Central heating selector
G- Central heating L.E.D. (green)
H- Flue sensor L.E.D. (yellow)
I- Overheat and/or ignition failure (lockout) L.E.D. (red)
J- Ignition failure (lockout) and/or overheat reset
button/Flue Test analysis mode*
K- ON/OFF L.E.D. (green)
2.10 CONTROL PANEL
FIG. 2.20
To dismantle the front
casing panel it is necessary
to:
1 - Remove the two screws
“B”;
2 - Move the front casing
panel up and lift forward.
FR019A
* Warning the flue analysis mode must only be selected by a
qualified service engineer.

18
To connect a room thermostat, it is necessary to:
1. - Open the control panel as indicated in SECTION 2.11.
2.- Remove the link “A” from the terminal block on the reverse of the control panel.
3. - Insert the thermostat cable through the cable grommet and fasten it by means of the
cable-clamp provided.
4. - Connect the thermostat wires to the terminal block (Diagram A).
5.- If a remote time clock is to be fitted, disconnect the integral time clock from the P.C.B.
6. - Using a volt-free switching time clock, connect the switching wires from the time clock
following points 1-4 above (Diagram B).
7. - If using an external time clock and room thermostat, these must be connected in
series as points 1-7 above (Diagram C).
Note: Only a low voltage room thermostat capable of volt free switching must
be used. Factory fitted integral wiring must not be disturbed when wiring
external controls.
2.12 ROOM THERMOSTAT
CONNECTION
A
FO016A FO017A
FIG. 2.21

19
2.13 ELECTRICAL/SYSTEM DIAGRAMS
B - Central Heating Temperature Adjustment
C - Connector for Remote Control (Climate Manager)
D - Domestic Hot Water Temperature Adjustment
E - Soft-light Adjustment
F - Maximum Heating Adjustment
G - Time Clock Connector
H - On/Off Switch
I - Fume Sensor L.E.D.
J - Central Heating Selector
K - Ignition Failure (Lockout) L.E.D.
L - On/Off L.E.D.
M - Reset Button
N - Central Heating L.E.D.
O - Transformer
P - Spark Generator I.C.
Q- Gas Valve Relay
R - Circulation Pump Relay
S - Fan Relay
A01 - Circulation Pump
A02 - Fan
A03 - Spark Generator/Gas Valve Supply
A04 - Detection Electrode
A05 - Main Circuit Temperature Probe
A06 - Domestic Hot Water Temperature Probe
A07 - D.H.W. Flow switch
A08 - Pump Pressure Switch
A09 - Modulator
A10 - Air Pressure Switch
A11 - Safety Thermostat
A12 - External (Room) Thermostat
COLOURS:
Gr - Grey
Bi - White
Rs - Red
Mr - Brown
Bl - Blue
Nr - Black
Ro - Pink
AB
CN103
CN104
CN201
CN300
CN204
CN202
CN200
CN102
CN100
CN101
5
4
3
2
1
BAC
DEF
G
H
IJ
L
K
MN
O
Q
R
P
AB
CN103
CN104
CN102
CN100
CN101
5
4
3
2
1
A
S
A - Jumper:
1 - Don’t move (jumper is factory set in position B)
2 - Anti-cycling Device Adjustment for Heating
Position A = 0 mins Position B = 2 mins
3 - Don’t move (jumper is factory set in position B)
4 - Don’t move (jumper is factory set in position B)
5 - Fan/Pump over-run selector
Position A = OFF Position B = ON
FIG. 2.22

20
10
16
LEGEND:
1. Fan
2. “Twin-pass” Heat Exchanger
3. Domestic Hot Water Temperature Probe
4. Burner
5. Detection Electrode
6. Ignition Electrodes
7. Gas Valve
8. Pump pressure switch
9. Safety Valve
10. D.H.W. inlet filter
11. D.H.W. Flow Switch
12. Automatic By-pass
13. Pressure Gauge
14. Circulation Pump with Automatic Air Release Valve
15. Overheat Thermostat
16. Main Circuit Temperature Probe
17. Expansion Vessel
18. Air Pressure Switch
A. Central Heating Flow
B. Domestic Hot Water Outlet
C. Gas Inlet
D. Domestic Cold Water Inlet
E. Central Heating Return
2.14 WATER CIRCUIT DIAGRAM
FIG. 2.23
SI016C