Certikin MBD 200 User guide

NG: GC No. 47 555 18 Corgi Work Code 1014356
LPG: Corgi Work Code 1014373
0087
Note to the Installer: Please leave these Instructions adjacent to the meter.
Operating, Installation and
Servicing Instructions for
MBD200
Condensing
De-Humidifier Boiler
Serial No: NG LPG

User Instructions
You are the owner of a High Efficiency Condensing
Boiler and due to the way it works it will appear to
produce a lot of steam from the terminal; this is harm-
less, low temperaure water vapour and quite normal.
The boiler requires a drain to be permanantly con-
nected and this will have been done by your installer, it
must not be disconnected or removed. In freezing
conditions ensure this drain is kept free of ice.
The Gas Safety (Installations and Use) Regulations
makes it illegal for gas appliances to be installed or
serviced by persons not Corgi Registered Operatives.
All Corgi Registered Operatives carry a Corgi ID card
and have a registration number. This can checked by
calling Corgi on 01256 372300.
IMPORTANT:
DO NOT DISTURB THE APPLIANCE CASE
The appliance must be connected to a 230V AC 50 Hz
supply with a 5 Amp fuse rating and must be Earthed.
The Certikin MBD 200 appliance is made with two
independant condensing boilers that can work together
or separately. It is designed to work simply and auto-
matically with your de-humidifier and heating controls.
To operate it has to be connected to both gas and
electricity, the Front Panel switches in an On position,
and the De-Humidifier or Heating controls calling for
heat.
Quick Start
Set the De-Humidifier or Heating Controls to On. Turn
both Thermostat Knobs fully cockwise to Normal then
select the required service.
Pool and Heating (A only), for periods of light de-
mand, like during the Summer.
Pool Boost (A & B), for rapid pool only heating.
Pool and Heating (A & B), during periods of heavy
demand, like during the Winter.
The operation is now fully automatic.
Indicators (a set for each boiler)
Power:
Off - Mains not connected.
On - The boiler is connected to the Mains.
MBD200
1 14/02/04
Running:
Off - There is no demand from the external controls.
On - There is a call for a boiler to fire.
Flashing - The boiler thermostat is off.
Fan, Pilot and Burner:
These are diagnostic indicators for fault finding.
Lockout:
The boiler has shut itself off. Wait for the boiler to
cool and then reset by turning the boiler Thermostat
Knob Off then On.
Selector Switch:
Pool and Heating (A only) - Only boiler A will be
working, heating Pool water, Air, and secondary
Space Heating.
Pool Boost - Both boilers will be working for Pool
water and Air heating.
Pool and Heating (A & B) - Both boilers are avail-
able for heating the Pool water, Air, and secondary
Space Heating.
To Turn Off for a Short Period
Turn the Thermostat Knobs fully anti-clockwise and
set all external controls to Off. In this condition the
boilers will protect themselves from freezing by firing
if the temperature falls below about 4°C
To Turn Off for a Long Period
Turn the Thermostat Knobs fully anti-clockwise, set
all external controls to Off and the switch off the
Mains supply. Please note there is no boiler Frost
Protection once the Mains supply is Off. If the
appliance is going to be off during the Winter it is
recommended that a Frost Thermostat is fitted, the
system is drained or it is filled with a suitable anti-
freeze.
Maintenance
There are no user servicable parts. To clean the
case wipe with a damp cloth, do not use an abrasive
cleaner.
It is recommended that the appliance is serviced
twice a year by a CORGI Registered Engineer.

Contents
Section Page
User Instructions 1
Introduction 2
Boiler Location 3
Gas Supply 3
Flueing 3
Air Supply 4
Water Supply 4
Condensate Drain 4
Sealed Systems 4
Electricity Supply 5
Installation 5
Removing Case 5
Boiler Location 6
Flue and Air Duct 6
Terminals 6
Plumbing 6
Gas Connection 6
Condensate 6
Heating Design 7
Electrical Connections 7
Commissioning 7
Fault Finding 18
Servicing 20
Technical Data 21
List of Figures Page
Fig 1. Gas Valve 10
Fig 2. Installation Dimensions 11
Fig 3. Schematic Wiring 13
Fig 4. Physical Wiring 14
Fig 5. Low Voltage Connections 15
Fig 6. Boiler Panel Assembly 16
Fig 7. Concentric Flue & Air duct 19
Positions
Fig 9. Electrical Components 23
Fig 10. Major Components 24
Fig 11. Example Condensate Disposal 25
Fig 12. Condensate Drain Trap 25
Introduction
These Instructions cover the MBD200, a frame
mounted, gas fired, condensing boiler which is room
sealed and fan assisted on the flue side. The flue
systems are Concentric, left, right, or rear, up to 2
metres.
The appliance is two boilers mounted on the frame,
which are plumbed to common pipework so that they
can work together or independantly.
It is designed to work with a De-humidiifer and an
optional sealed heating system. These systems must
be pumped and use the pumps integral to the appli-
ance.
The boiler casing is powder coated mild steel.
The boilers include pump overrun devices so it is
essential that there is an open circuit for water to
flow between the flow and return. An automatic
bypass is provided on the Heating circuit.
The boilers also contain integral frost protection, a
boiler will fire if the temperature within it approaches
4 to 5 degrees Centigrade. It will do this even when
turned to Off, and can only be inhibited by removing
the Permanent Live supply to the boiler.
Adequate arrangements for completely draining the
system, by provision of drain cocks MUST be pro-
vided.
Gas Safety (Installation and Use)
Regulations, (as amended).
It is the law that all gas appliances are installed by a
competent person (e.g. a CORGI registered opera-
tive) in accordance with the above Regulations.
Failure to install appliances correctly could lead to
prosecution.
It is in your own interest, and that of safety, to ensure
that the law is complied with. The installation of the
boiler MUST also be in accordance with the current
I.E.E.. Wiring Regulations, the Local Building Regu-
lations, Building Standards (Scotland), the Bye Laws
of the Local Water Undertaking, any relevant re-
quirements of the Local Authority, and Health and
Safety document No 635, “Electricity at Work Regu-
lations”.
Detailed recommendations are contained in the
following British Standard Codes of Practice.
Codes of Practice.
BS.6798 Installation of gas fired hot water boilers of
rated input not exceeding 70kW.
BS.5449:1 Forced circulation hot water systems
(small bore and microbore domestic central heating
systems).
BS.5546 Installation of gas hot water supplies for
domestic purpose (2nd Family Gases).
BS.5440: Part1. Flues (for gas appliances of rated
input not exceeding 60kW).
BS 6891 Specification for installation of low pressure
gas pipework.
BS 7074:1 Application, selection and installation of
expansion vessels and ancillary equipment for
sealed water systems.
BS5482:1 Code of practice for domestic butane &
propane gas burning installations.
Building Regulations Part L1.
MBD200
2 14/02/04

IMPORTANT. It is important that no external
control devices are directly connected to this
appliance - unless covered by these ‘Installation
and Servicing Instructions’ or otherwise recom-
mended by the manufacturer. If in doubt, please
enquire.
A 12V DC circuit is provided for system control
devices located in wet areas.
Any direct connection of a control device not
recommended by the manufacturer could infringe
the Gas Safety (Installation & Use) Regulations, the
above regulations and the normal appliance war-
ranty.
Manufacturer’s notes must NOT be taken, in any
way, as overriding statutory obligations.
Location of Boiler
The boiler MUST be fixed to a floor or vertical non-
combustible wall, capable of adequately supporting
the weight of the boiler and any ancillary equip-
ment.
THE BOILER IS NOT SUITABLE FOR
EXTERNAL INSTALLATION.
IMPORTANT NOTICE.
If the boiler is to be fitted in a timber framed building
it should be fitted in accordance with the British Gas
publication ‘Guide for Gas Installations in Timber
Frame Housing’, reference DM2. If in doubt, advice
must be sought from the Local Gas Region of
British Gas.
The boiler may be installed in any room or internal
space. Particular attention is drawn to the require-
ments of the current I.E.E Wiring regulations and, in
Scotland, the electrical provisions of the Building
Regulations applicable to 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 then the appli-
ance and any electrical switch or appliance control,
utilising mains electricity should be so situated that
it cannot be touched by a person using the bath or
shower.
Where installation will be in an unusual location
then special procedures may be necessary and
BS.6798 gives detailed guidance on this aspect.
A compartment used to enclose the boiler MUST be
designed and constructed specially for this purpose.
An existing cupboard, or compartment, may be
used provided it is modified for the purpose. Details
of essential features of cupboard compartment
design, including airing cupboard installations are
given in BS.6798.
In siting the boiler, the following limitations MUST be
observed:
1. The position selected for installation MUST allow
adequate space for servicing in front of the boiler
and for air circulation around the boiler.
2. This position MUST also permit the provision of a
satisfactory balanced flue termination.
3. This position MUST also permit the provision of a
satisfactory connection to the condensate drain.
Gas Supply
An existing meter (NG) and pipework should be
checked, preferably by the Gas region, to ensure that
they are adequate to deal with the rate of gas supply
required.
Supply pipes should be sized to suit installation and
obtain a working pressure of 20 mbar (NG) or 37
mbar (Propane). Installation pipes should be fitted in
accordance with BS.6891.
A Natural Gas appliance must be connected to a
governed meter.
Conversion
The appliance can be converted from NG to LPG or
vice versa by change of the Burner, Main and Pilot
Injectors and re-setting the Gas Valve. Contact your
supplier for the necessary parts.
Flueing
Only flue components provided by the Manufacturer
should be used with these appliances. Detailed
recommendations for flueing are given in BS.5440: 1.
The following notes are intended for general guid-
ance.
1. Be aware of the plume from the flue and the
wetting effect it has to adjacent property.
2. The flues can be taken left, right or to the rear of
the appliance.
3. The appliance is supplied with two standard flue
sets. There are two lengths of Concentric Flue.
Standard, that will reach 500mm, and Extended
that will reach up to 2000mm. (Part No. M3838).
4. The boiler MUST be installed so that the termi
nals are exposed to external air.
5. It is important that the terminals allow the free
passage of air across them at all times.
6. The acceptable spacing from the terminal to
obstructions and ventilation openings are
specified in Table 1.
7. Because the flue gases and terminal are at very
low temperature it is not necessary to fit a
Terminal guard to protect against burns. If a
guard is required for any other reason the
following is recommended.
MBD200
3 14/02/04

For the Concentric Terminal:
Model K3 6.5 x 11 (plastic coated) (GC No 393554)
All are available from:
Tower Flue Components Ltd.
Tower House.
Vale Rise.
Tonbridge
KENT
TN9 1TB
01732 351555
Table 1 .
IMPORTANT.
It is absolutely ESSENTIAL to ensure, in practice,
that products of combustion discharging from the
terminal cannot re-enter the building, or any other
adjacent building, through ventilators, windows,
doors, other sources of natural air infiltration or
forced ventilation/air conditioning.
If this should occur, the appliance MUST be turned
OFF IMMEDIATELY and the Local Gas Region
consulted.
Air Supply
It is NOT necessary to have a purpose provided air
vent in the room or internal space in which the
boiler is installed.
Where the boiler is installed in a cupboard or
compartment no air vents are required. However
the User may wish to ensure that is ventilated to
provide air circulation.
Water Supply
Aheating system should be in accordance with the
relevant recommendations given in BS.6798, BS
7593:1992 and, in addition, for smallbore and
microbore systems - BS.5449:1.
The domestic hot water system, if applicable, should
be in accordance with the relevant recommenda-
tions of BS.5546.
Copper tubing to BS 2871:1 is recommended for
water carrying pipework.
The hot water storage cylinder MUST be of the
indirect type and should preferably be manufactured
of copper.
The hot water cylinder, & ancillary pipework, not
forming part of the useful heating surface should be
lagged, to prevent heat loss and any possible
freezing, particularly where pipes run through roof
spaces and ventilated underfloor spaces.
A Drain Tap is provided and should be installed in
an accessible position on an unused end of the
Heating manifold. Any other installed Draining taps
should be at least ½” nominal size and be in accord-
ance with BS.2879 .
Condensate Drain
Refer to Fig. 2, and 12.
A condensate drain is provided on the boiler, this
drain must be connected to the household drainage
point, or soakaway on site. All pipework and fittings
in the condensate drainage system MUST be made
of plastic. Refer to British Gas publication “Guidance
notes for installation of domestic condensing boil-
ers”
No other materials may be used.
The drain outlet on the boiler is :
Polypipe, 21.5mm pushfit overflow pipe.
Sealed Systems
The sealed system should follow the guidelines
given in the Code of Practice BS 7074 :1. The
appliance includes a 3 bar (45 lb/in²) safety valve to
BS 6750
Pt 1. It should be installed on an unused end of the
Return manifold and discharge through a pipe to a
safe outlet.
A 10l expansion vessel, complying with BS 4814 is
also fitted on the return side of the pumps. If addi-
tional system pipework is added the size of the
vessel should be checked using the table below. If
the fitted unit is not large enough the following steps
should be taken to determine the required size.
MBD200
4 14/02/04
Terminal Position Minimum
Below window or vent 300 mm
Below gutter or pipes 75 mm
Below eaves 200 mm
Below balcony or roof 200 mm
From a window 200 mm
From vertical pipe 75 mm
From corners 300 mm
Above ground, roof or balcony 300 mm
From facing surface 600 mm
From facing terminal 1200 mm
From opening under a car port 1200 mm
Vertically from a terminal 850mm
Horizontally from a terminal 300 mm

1. Choose a vessel pressure by taking the static
head of the system, adding 0.3 bar, and taking
the nearest larger size.
2. Select the Vessel Volume from the table below
by finding the system volume and vessel pres-
sure.
3. Subtract 10 for the vessel in the appliance then,
choose that size or larger from the
manufacturers’ range.
Vessel System Volume Litres
Pressure 50 60 70 100 150
Bar Vessel Volume
0.5 4 4 8 8 12
1.0 8 8 8 12 18
1.5 8 12 12 18 24
A pressure gauge with a fill pressure indicator and a
range of 0-4 bar is fitted on the appliance front
panel.
A Filling Loop incorporating a BS 1010 stop valve, a
double non-return valve is provided with the appli-
ance. It should be installed on the unused end of the
LPHW Flow manifold with the approval of the local
Water Undertaking.
Electricity Supply
Refer to Figs. 3, 3a and 4.
Wiring external to the appliance MUST be in accord-
ance with the current I.E.E. Wiring Regulations and
any Local Regulations that apply.
The boiler is supplied for 230V ~ 50Hz. Single
phase. Fuse rating is 5A.
The method of connection to the mains electricity
supply MUST facilitate complete electrical isolation
of the boiler, preferably by the use of a fused double
pole switch having a 3mm (1/8in.) contact separation
in both poles and servicing only the boiler and
system controls.
The point of connection to the mains should be
readily accessible and adjacent to the boiler, except
that, for bathroom installations, the point of connec-
tion to the mains MUST be situated outside the
bathroom.
Note. Where a room sealed appliance is installed in
a room containing a Pool, Bath or Shower, the
appliance, any electrical switch or appliance control
utilising mains electricity should be so situated that it
cannot be touched by a person using the bath or
shower.
The appliance incorporates a 12V DC switching
circuit for connection to system controls in wet areas.
All such system controls MUST be voltage free.
Installation Of Boiler
Suggested procedure:
1. Site to suit system and terminal limitations.
2. Mark & Drill Flue holes. See Fig. 2
3. Fix Boiler Frame to the wall and/or floor.
4. Remove the Electrical tray and the Cases from
boiler module.
5. Fit the flues.
6. Plumb to the system and gas.
7. Fit the Filling Loop provided to an unused end of
the LPHW manifold.
8. Fit the Drain Tap provided and unused end of the
Heating manifold.
9. Fit the Safety Valve provided to an unused end of
the Return manifold.
10.Test for leaks.
11.Wire Mains supply and System Controls.
12.Replace the Cases and Electrical tray.
Space Required for Installation and
Service.
Right or Left 30 mm 1¼ in.
Above 30mm 1¼ in.
Below 25mm 1 in.
In Front 450mm 18 in.
Removal of the Case
Refer to Fig. 6
1. Remove the Lower Cover by pulling forward.
2. Remove the Electrical Cover. This is detached by
pulling the cover towards you and carefully
lowering. Care should be taken to prevent strain
on the cables and connections.
MBD200 5 14/02/04
ALTERNATIVE METHODS OF FILLING A SEALED
SYSTEM
Method A
Method B
Hose Unions
Air Inlet
Valve
Temporary Hose
Mains
Water
Supply
Mains
Water
Supply
Test Cock
Stop Valve
Drain &
Fill
Double
Check
Valve
Assembly
Drain &
Fill
Cistern &
Overflow Pressure
Pump &
Reducing
Valve If
Required
Stop Valve

MBD200 6 14/02/04
3. Remove the case by unscrewing the two
pozidrive screws located at the bottom and rear of
the case, and lifting and pulling forward off the two
pegs which are located at the top. The case
should be kept vertical as it is removed. Examine
the sealing strip for damage and replace if neces-
sary.
IMPORTANT: FAILURE TO CORRECTLY
LOCATE THE APPLIANCE CASE COULD
RESULT IN LEAKAGE OF COMBUSTION
PRODUCTS INTO THE ROOM.
Boiler Location
1. Site to suit system and terminal limitations.
2. Secure the frame to the wall and/or floor with the
brackets supplied.
Assembly Of Flue Pipe &
Air Duct Pipe to the Boiler
The following is based on the flue tube being sup-
plied with the straight and elbow connectors being
pre-assembled, the one NOT required to be cut off
during installation.
Right or Left Outlet
1. Secure the 50mm flue tube with ELBOW connec-
tor on the saddle using the Velcro strap.
See Fig. 7
2. Measure carefully and saw off the 50mm tube to
give required projection from wall. See Fig. 7
3. Measure carefully and saw off the 110mm Air
duct tube to give required projection from wall.
The flue pipe must project more than the outer air
duct when assembled. See Fig. 7
Note:
It is acceptable to obtain this dimension by pulling
the air duct away from the air duct stop, provided
there is a minimum of 10mm (1/2 in.) insertion
into the Boiler Mounting Box and that a satisfac-
tory seal is achieved.
4. For extended flues, position the air duct support
clips provided every 700mm.
Rear Outlet
Install as above but using the STRAIGHT connector
in the Boiler Mounting Box. Follow the instructions
under Right or Left Outlet, points 1,2,3 and 4.
Terminals
Fix to the outside wall with the ‘T’ cutout, towards the
top face which contains no holes. If a guard is fitted,
the terminal should be at its centre.
Plumbing
If the requirement for Heating exceeds 50,000 Btu/h
(15kW), the Flow and Return pipework from the
appliance must be 28mm until the heat load allows
smaller bore pipework.
The appliance includes a pump overun devices and
there must be a flow path in the system at all times.
An automatic bypass has been provided in the
Heating circuit for this reason.
New pipework must be flushed through before
connecting.
Gas Connection
The 28m Copper gas connection is shown in Fig.2 .
A minimum of 20mb. (NG), 37mb (LPG) must be
available at the boiler inlet, with the boiler and other
connected appliances firing. Check for gas sound-
ness (B.S. 6891) in pipework to boiler using a
manometer. Open the gas cock. Gas soundness
within the boilers should be checked using sense of
smell and/or leak detection fluid. Check the burner
bar pressures with a manometer connected to the
control and adjust if required, with the pressure
regulator on the Gas Valve.
Condensate Connection
The position of the plastic condensate drain pipe is
shown in Fig 2 .
Where possible an internal termination of the Con-
densate discharge pipework should be used.
Installation pipework must be in plastic to a suitable
drain location with a gradient of 2.5° (45mm/ metre
run) minimum. If connected to another drainage trap,
an air break is required between the boiler drain and
that trap. ( see Fig.11 ). Internal runs must be in a
minimum of 19mm pipe. External runs MUST be
made in a minimum of 32mm pipe, starting inside
the building, and if possible insulated to defer prob-
lems from freezing.
Whichever method is used it should be checked
during commissioning to prove there is a leakfree
working connection from the boiler to the drain. The
simplest way to do this is to carefully pour some
water into the boiler flue and check it emerges at the
drain.
The British Gas booklet “Guidance for the installation
of Domestic Condensing Boilers” should also be
referred to.

MBD200 7 14/02/04
Heating Design
General principals
The system should be designed to conform with
the latest requirements of the Building Regula-
tions.
Condensing Boilers give their best performance
when the system water temperature is as low as
possible and still achieve the desired room tempera-
tures. Oversized radiators make this easier to
achieve but are not essential as, even in a standard
designed installation, most of the boilers’ working
hours are spent with the system producing much
less than the designed output. This is because the
outside temperature is often higher than the figure
used for the design, typically -1 to -2º C.
The Manufacturer recommends the use of a voltage
free, programable room thermostat, alternatively a
separate timeswitch and room thermostat can be
used.
The boilers include pump overrun devices so it is
essential that there is an open circuit for water to
flow between the LPHW flow and return. In some
system designs this may require the addition of a
bypass, an automatic bypass is reccommended.
They also contain integral frost protection, a boiler
will fire if the temperature within it approaches
freezing. It will do this even when turned to Off, and
can only be inhibited by removing the Permanent
Live supply to the boiler.
Thermostatic radiator valves can be used. An
automatic bypass is incorcporated in the appliance
for the heating circuit.
The boiler waterside is completely copper so all
good corrosion inhibitors are suitable.
Designs
The following designs are all acceptable:
1. Sealed system to BS.6798 and BS.5449:1
2. Combined Feed and Vent systems.
3. Separate Cold Feed and Vent systems.
The pump is on the return, careful note of its posi-
tion relative to the feed and vent MUST be made to
avoid pumping over, or sucking in air. The design
temperature difference across the boiler for opti-
mum operating efficiency is 20ºC. If thermostatic
valves or zone valves are used ensure the minimum
flow shown in the Technical Data on page 21 is
possible.
Electrical Connections
WARNING: The appliance MUST be earthed.
All wiring for the boiler and system controls MUST
conform to I.E.E. Wiring Regulations, and work
should be tested using a suitable meter, for Earth
Continuity, Polarity, Short Circuit and Resistance to
Earth.
The supply must be through a common isolator, a
double pole 3A fused isolating switch with a contact
separation of 3mm minimum on both poles. The
cable used should be no less than 0.75mm2to
BS.6500 PVC, 3 core, and fixed ensuring the earth
connection is longer than the Live and Neutral.
Access to the boiler connections is made by with-
drawing the Electrical Tray then releasing the screw
retaining the cover over the push fit screw terminals.
The boiler internal wiring is shown in Fig.3, Fig.4
and Fig.5.
Connections are as follows :-
Supply Connection
Earth
N Mains Neutral
L Permanent Live
Pump Connections
Earth
N Pump Neutral
Lp1 Pump No1 Live
Lp2 Pump No2 Live
Controls
1 +12 V DC to External controls.
2 +12V DC from Dehumidifier
3 +12V DC from Heating control
E Earth, 2 Port Valve
N Neutral, 2 Port Valve
4 2 Port Valve, Br
5 2 Port Valve, Or
6 2 Port Valve, Gy
The appliances includes pump overrun and the
Pumps have been factory connected to their respec-
tive push-fit connectors.
External controls MUST BE voltage free and con-
nected to terminals 1, 2 and 3.
Commissioning
General
The elimination of air from systems is essential to
minimise the occurrence of heat exchanger and
general system noise. It is particularly important for
lightweight boilers.
Metal swarf and flux chemicals make a very aggres-
sive mixture, the destructive nature of which can be
drastically reduced by flushing. Consequently this is
a mandatory step in the commissioning procedure.

MBD200 8 14/02/04
Carry out electrical tests as stated in Electrical
Connections if not already done so.
With all valves fully open, and the filling loop con-
nected, fill from the mains supply, then follow the
procedure below.
Check for water soundness and rectify where neces-
sary.
Check that there is a leakfree working connection from
the boiler to the drain. The simplest way to do this is to
carefully pour some water into the boiler flue and
check it emerges at the drain.
DO NOT TURN ON GAS
Drain the system by opening all draincocks. This
will flush the system of flux and swarf.
Pour in all the inhibitor, and fill to required pressure
plus 0.3 bar to allow for venting.
Switch on the electrical supply to the boiler and
switch the Thermostat/Timeswitch ON.
Switch off after about five seconds and vent all
points again.
Repeat this for 5 minutes.
Re-pressurise if required.
Turn on pump (do not turn on gas) and run for at
least 30 minutes with all valves open.
Stop pump at five minute intervals and vent until no
more air can be removed and air noises are no
longer produced at the boiler. While the system is
venting check again for water soundness.
TURN ON THE GAS
Check for gas soundness (BS 6891) in pipework to
boiler using a manometer.
Select each boiler in turn, open the gas cock and
after purging the system, the boiler will light auto-
matically.
Run system at maximum thermostat setting.
Gas soundness within the boiler should be checked
using sense of smell and/or leak detection fluid.
Continue running for 15 minutes, venting every 5
minutes.
The Pilot is factory set.
The Main Gas Valve, GV2, gradually raises the
pressure to the set point. Allow at least 60 seconds
for the final pressure to stabilise.
IMPORTANT. It is essential when setting the
burner pressure that the inlet pressure is at
least 20 mbar (NG), 37 mbar (LPG) with the
boiler and any other connected appliances
running.
Set the burner pressures to the correct pressure by
using a manometer connected to the control and
adjusting the regulator to the desired input. (see the
charts below and Fig.1)
Low water content, fabricated boilers are vulnerable
to damage by air, particularly when the system water
is ‘hard’. (Contains a lot of dissolved calcium salts).
The result of this damage is evident in noisy boilers
and reduced service life.
Removal of air from a system mainly takes place
when the water is stopping, starting or not moving at
all. It is removed most easily when it is in large
bubbles, but the action of the pump is to chop it up so
that it becomes a foam, which is extremely difficult to
remove.
Two or three second bursts on the pump at the initial
stage will reduce the risk of foam formation.
Sloping the pipe runs towards the vent points will
greatly aid air removal. Sloping pipes are not just a
feature of gravity systems but can greatly aid the
pumped system because air can move towards a
vent when the pump stops.
Air is dissolved in water but is released when heated.
Always run a system at maximum temperature for at
least 15 minutes to enable this potential problem to be
removed during commissioning.
Commissioning Procedure
The boiler is fitted with automatic ignition and will start
when the gas cock is open, mains is connected to the
boiler and the controls calling for heat.
NOTE: If the boiler has just been filled with very cold
water, the built in Frost Thermostat will attempt to fire
it if it has a permanent live and no switched live, this
is completely normal. It is recommended that the gas
cock is turned off during this early stage. Because of
a built in delay, the boiler is always held off for a
minimum of 120 seconds. However, for commission-
ing purposes, switch off using the System Isolating
Switch will avoid the delay.
It is strongly suggested that the following stages of
commissioning are followed, and not an immediate
connection of all services. This procedure prevents
substantial amounts of air being dispersed through
the system as small bubbles.

MBD200 9 14/02/04
Rating Table (1040 Btu/ft³) (38.8 MJ/m³)
kW Btu/h sec/ft³m³/2 mins
20 68240 54.9 0.0619
22 75064 49.9 0.0680
24 81888 45.7 0.0742
26 88712 42.2 0.0804
Note: The boiler is fitted with a syphon trap
that includes a blocked drain device. This is
to safeguard the boiler and help defer the ef-
fects from the possible freezing of the con-
densate pipework in extreme weather.
The user should be made aware of this fea-
ture and, that in the event of blocked con-
densate pipework, for example frozen con-
densate pipework, the boiler will automati-
cally stop functioning. It will start again as
soon as the blockage has cleared.
For designs with a heating system check the
operation of the bypass with the system hot. The
minimum flow rate through the boiler should be as
shown in the Technical Data on Page 21.
Set the pump speed to the highest setting that
does not provoke unreasonable operational noise
within the system.
Re-pressurise to required pressure and set the
gauge indicator
With the system hot, check again for water sound-
ness.
Refit the case to the boiler.
For designs with heating circuits, balance the
system in the normal way to obtain even heating
of all radiators.
If fitted set the cylinder thermostat to 60oC, or
lower if preferred.
Commission Check List (hydraulic)
The key points which must be observed closely, are
shown below.
•With valves and vents open fill the system.
•Do not use pump. Do not light gas
•Check for and rectify leaks.
•Drain to flush system.
•Refill system, adding the inhibitor.
•Do not light boiler.
•Vent all radiator and air release points.
•Run pump for 5-10 second bursts and revent.
•Do not light boiler.
•Run pump for at least 30 minutes.
•Stop at 5 minute intervals to vent.
•Continue venting until no more air noise can be
heard.
•Light boiler and run at max thermostat setting.
Continue for 15 minutes, venting every 5
minutes.
Rating and Setting Pressures for each boiler
Input v Burner Pressure
18
20
22
24
26
9 10 11 12 13 14 15 16
mBar
Input (gross) kW

MBD200 10 14/02/04
Fig.1

Front View
C
L
Rear Flue
Side View
Left, Right or Rear
128 mm
Suggested core drill
Boiler service access
Front 450mm Above 30mm
Sides 30mm
Flue100to2000mm
SideFlue
495 515
1760
Flue Pipes
Degrees
0 to +3
195
55 mm
1650
Degrees
0 to +3
C
L
788
85
165
375
475
LPHWFlow
Return
CH Flow
Gas
MBD200 11 13/01/05
Installation Dimensions
and Service Access
Fig.2

MBD200 12 14/02/04
35mm
28mm
Gas Manifold
Heating Flow Manifold
LPHW Flow Manifold
Return Manifold
Safety
Valve
Valve
Bypass
Filling
Loop
Drain
Tap
35mm
28mm
2 Port
Valve
Condensate
Trap
Condensate
Connection
Fig.2a
Pipe Connections & Locations

SUPPLY PUMPS
EE
NN
Ls A
L
LpA
HT
N
Ls
L
Lp
COM
AIR
NOAIR
O/H O/H
SENSOR
SENSOR
12 Way connector
GV1
GV2
N
4 Core to Gas Valve
NC
Flue Stat
O/H Stat
Air presssure switch
Fan
4 way Molex
10 way Molex
Sensor
GV1
GV2
1 Amp 20mm
CONTROL BOARD
Or Or
Br Br
R
W
Bk Gy Br R
Bk
Br
Gy
G/Y
G/Y
G/Y
B
G/Y
V
Gy
Br
R
Or
W
Bk
Gy
V
G/Y
B
Brown
Red
Orange
White
Black
Blue Grey Violet Green & Yellow
B
NO
10/07/06
LpB
Control Board 'B'
CONTROLS
2 PORT
+12v DC
DEHUM
HEATING
Br
Or
Gy
VALVE
E
N
12
3
45 6
MBD200 13 14/2/04
Schematic Wiring (one boiler only)
Fig.3

MBD200 14 14/02/04
Physical Wiring Diagram (one boiler only)
Fig.4

MBD200 15 3/05/05
4
Fig.5
Low Voltage System Connections
3/05/05
MBD200
Selector Switch
Selector Switch
500 mA
a b
c
a b
c
a b
c
230 V AC
12 V DC
12V AC
+
-
6
2Port Valve
Or
Gy
Br B
N
E
G/Y
L
Clock
De-Humidifier
HTG
Thermostat
5
4
3
2 1
R
Bk
Or
Or
Y
Br
Br
V
R
Ls A Ls B
(Direct to Molex)
b: Pool Boost (A & B) a: Pool & Heating (A only) c: Pool & Heating (A & B)
Br
Gy
Br
Br
Y
N
7
(Delta/Variheat
terminals shown)
6
Models before Serial No 05017481

10/07/06
MBD200
Selector Switch
Selector Switch
500 mA
a b
c
a b
c
a b
c
230 V AC
12 V DC
12V AC
+
-
2Port Valve
E
L
Clock
De-Humidifier
HTG
Thermostat
Bk
Or
Br
V
R
Ls A Ls B
(Direct to Molex)
b: Pool Boost (A & B) a: Pool & Heating (A only) c: Pool & Heating (A & B)
Br
Br
Br
Y
N
7
(Delta/Variheat
terminals shown)
6
N
Y Or
R
Or
Gy
Br
B
G/Y
R
Br
R
Gy
6
5 4
3 2
1
MBD200 15 10/07/06
Low Voltage System Connections
Fig.5
Models after Serial No 05017481

MBD200 16 14/02/04
Boiler Panel Assembly
Fig.6
Concentric Flue
Boiler Mounting Box
Side Trim
Pressure
Cover
Front Burner Baffle
Lower Burner Baffle
Electrical Cover
Lower Trim
Controls Chassis

MDB200 17 14/02/04
Fault Diagnosis
(one boiler shown)

MBD200 18 14/02/04
Fault Finding (for boiler only)
The electrical sequence in the boiler is very straightforward and faults can easily be tracked down if this simple
sequence is followed.
System Controls - - - - Flue Stat - - - - Overheat Stat - - - - Pressure Switch - - - - Control Board - - - - Ignition
The lamps on the front panel indicate several of the stages in the ignition sequence.
Firstly a Permanent live has to be connected to the L terminal then the power lamp lights.
When the system controls and the programmer are calling for heat, power is fed to the boiler initiating the
following sequence.
A call for heat powers the Ls terminal and the running and pump lamps light.
Provided the Flue Stat, Overheat Stat and boiler are cold, the fan starts up. The pressure switch detects the
correct airflow and that the condensate drain is not blocked then, switches over. This is indicated by the
fan lamp illuminating.
The pilot lamp illuminates, the pilot gas valve opens and the Control Board provides a spark at the pilot elec-
trode. (If the L and N supply are reversed the boiler will not progress beyond pilot ignition. This is indicated by
the phase reversed neon behind the knob lighting.) The pilot flame is detected and the control board stops
sparking and then energises the main gas valve and the burner lamp is illuminated.
The pilot flame lights the burner, and it stays alight until turned off by the control thermostat, system controls, or
in the case of a fault condition a safety thermostat.
The flue thermostat will trip if the flue exceeds a pre-set temperature. The overheat thermostat will trip if the
water flow rate is insufficient, both are indicated by the lockout lamp illuminating.
NOTE :The boiler has a built-in delay timer. It is indicated by the running lamp flashing.
For testing, switching the Mains Supply off for a few seconds, then back on again will reset the delay.
WARNING : BEFORE COMMENCING OR COMPLETING ANY ELECTRICAL WORK ON
THE APPLIANCE, IT IS RECOMMENDED THAT THE BASIC SAFETY CHECKS FOR
EARTH CONTINUITY, SHORT CIRCUIT, POLARITY AND RESISTANCE TO EARTH ARE
MADE. ALL WORK CARRIED OUT SHOULD FOLLOW GUIDELINES LAID DOWN BY
THE I.E.E.
Fault Diagnosis
The Fault Diagnosis chart shows the normal and fault sequences for the boiler indicator lamps.
To diagnose a fault, use the following procedure.
· Turn off the system Mains supply.
· Set all thermostats and timers to a call for heat position.
· Turn on the system Mains supply and watch the boiler indicator lamps.
Compare the lamps with the diagnosis chart opposite to determine the fault and cause.