Chaffoteaux & Maury MINIMA MX2 24 FF NG Operating manual

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Fanned Flue Combination Boiler
Heating and Instantaneous Domestic HotWater
MAINTENANCE AND
SERVICE GUIDE
Dimensions
Technical data
Heat input C/H & DHW MX2 24 : 12 to 26,1 kW
Gross MX2 30 : 12 to 32,25 kW
Heat output C/H & DHW MX2 24 : 10 to 24 kW
Gross MX2 30 : 10 to 30kW
Max. operating pressure C/H circuit : 3 bar
Expansion vessel net capacity : 6 l (24kW) 8 l (30 kW)
Expansion vessel initial pressure : 0.7 bar(24kW) 1bar (30kW)
Electrical consumption : 150 w Max
Voltage : 230 v
Electrical protection index : IP44
Fuses : 2 A , 1.25 A and 0.315 A
DHW flow rate at 30°C MX2 24 : 11,4 l/min
MX2 30 : 14,3 l/min
DHW flow rate at 35°C MX2 24 : 9,85 l/min
MX2 30 : 12,25 l/min
Minimum DHW operating flow rate : 2 l/min
Minimum DHW working pressure : 0.1 bar
Maximum DHW working pressure : 10 bar
Gas category : II 2H 3+
Nominal gas flow rate at 15°C and 1013 mbar MX2 24 MX2 30
Maximum Minimum Maximum Minimum
power 24 kW power 10 kW power 30 kW power 10 kW
- Natural gas ( G 20) at 20 mbar 2.76 m3/h 1.27 m3/h 3.41 m3/h 1.27 m3/h
- Butane gas ( G 30) at 28 mbar 2.06 kg/h 0.94 kg/h 2.50 kg/h 0.94 kg/h
- Propane gas ( G 31) at 37 mbar 2.02 kg/h 0.93 kg/h 2.47 kg/h 0.93 kg/h
Injectors and gas valves seat diameter MX2 24 MX2 30
Natural gas Butane or Propane Natural gas Butane or Propane
- Manifold injectors (11 for 24 kW) 1.35 mm 0.80 mm 1,30 mm 0,80 mm
(14 for 30 kW)
ISafety valve outlet
JHeating flow
K D.H.W. flow
LGas supply
MCold water inlet
N Heating return
The boiler is suitable for the flue types:
• type C 12
• type C 32
• type C 52
Outer case dimensions :
- Height : 720
- Width : 390 (minimum space required 400)
- Depth : 296
c
All dimensions in mm
Fig. 1
These Instructions Must Be LeftWithThe Appliance.

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Pump and expanssion vessel characteristics
Components location
8. Steel chassis
9. Flow control thermistor
10. Return control thermistor
11. Over heat security
12. Expansion vessel (not visible)
13. Gas valve
14. Electrical box
15. ON/OFF push button and power on
indicator light
16. Domestic hot water temperature
adjustment
17. Heating flow temperature adjustment
18. CH pressure gauge
19. Heating temperature indicator
20. Reset button and Red indicator
- Lock out / flame failure
21. Orange indicator - Burner ON
22. Three way valve
23. 3 way valve motor
24. Multigas burner comprising:
-25. 11 or 14 burner heads
-26. Manifold
-27. Ionization electrode
-28. Ignition electrode
29. Main heat exchanger
30. Water/water heat exchanger
31. DHW flow sensor
32. Combustion chamber made of
aluminium coated steel with 4
ceramic fibre panels to insure
heat insulation
33. Right hydraulic assy
34. Left hydraulic assy
35. Single speed pump
36. Automatic air separator and
automatic vent
37 Automatic by-pass
38. Flue hood with fan
39. Air Pressure switch
40. Flue sampling point
1. Pressure relief valve
2. Heating Flow isolating valve
3. DHW outlet
4. Gas service tap
5.Water service tap
7. CH Return isolating valve
1 2 3 4 5 7
Note : The system initial pressure should be over the following value :
System static height (in metre) + 0.7 = Initial pressure (in bar)
10
Head available / flow
System capacity chart
Fig. 2
PUMP HEAD AVAILABLE
Minimum flow rate (with all heating thermostatic valves closed)
mCE Central heating initial pressure when cold (in bar)
C liters

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FUNCTIONING
Switching on
1) Check that the gas service tap is opened at the gasmeter and
main power is on.
2) Check that pressure in central heating system is above 0.8
bar and below 1.5 bar with the pressure gauge 18.
3) Open the gas tap 3.
4) The boiler is now ready to use.
5) Push on the knob 15 . The knob 15 "power on" will light.
Hot Water
1) Turn the DHW thermostat clockwise 16.
2) Turn on a hot water tap, the orange "burner on" indicator
will light 21 and the water will become hot.
Control panel
MX2 FUNCTIONAL DIAGRAM
39
8
29
32
24
36
35
14
11
38
34
12
22
33
10
25
28
26
30
15 20171618
19
21
Fig. 3 Fig. 4
Fig. 5
Fig. 6 Heating mode Hot water mode
13
40
9
27

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Heating
1)Turn the CH thermostat clockwise 17.
2) If the room thermostat (if fitted), the
boiler temperature control and the
clock (if fitted) are all calling for heat, the
orange "burner on" indicator 21 will
light and the heating will be on.
When there is a need for hot water while
the heating is on, it is only necessary to
turn on a hot tap. The heating will be
interrupted momentarily while the hot
water is being delivered. The boiler will
switch back automatically to heating when
the tap is turned off.
Note: if the boiler has been push off for
some time the first attempt to light it may
result in a lockout . If this happens
press the reset button 20 and the boiler
will light.
To put Boiler Off Completely
1) Push the on/off button 15 and the light
is off.
2) Turn the gas tap 4 Fig. 2 OFF.
Domestic Hot Water Mode
In order to supply hot water, the main
switch 15 Fig. 4 must be in ON position I
This will be confirmed by the green light
15 Fig. 4. Turn the selector switch 16
clock .
When a tap or shower is turned on, the
flow of mains water, above 2 litres per
min., will activate the 3 way valve 22 Fig. 5
to move to the DHW position.
The pump will now circulate primary water
heated by the main heat exchanger
through the secondary heat exchanger.
The gas valve 13 Fig. 5 open to allow gas
to the burner. The ignition sequence
begins and a continuous high speed spark
ignites the gas. As soon as a flame is
detected the orange indicator bulb 21
Fig. 4 will light and the modulating
solenoid opens to allow the full gas rate. If
a flame is not detected, after 8 seconds,
the security solenoids close and shut off
the gas. The red lockout indicator bulb
20 Fig. 4 will show. The domestic hot
water temperature is controlled by the
flow and return control thermistor 9- 10
Fig.5. This system anticipates the
changes of temperature in the secondary
heat exchanger and ensures accurate
temperature regulation.
When the tap is closed the burner is
extinguished and the pump stops.
Priority will be given to a demand for hot
water. This will interrupt the central
heating for the duration of hot water
delivery.
Central Heating Mode
To be able to supply heating, the main
button 15 Fig. 4 must be in Iposition. This
will be confirmed by the green light.
Turn the selector switch 17 clock.
When there is a demand for heating
(either from the room thermostat or the
clock) and the boiler temperature control
is calling for heat. The pump starts
allowing the ignition sequence to begin.
The gas valve 13 Fig. 5 open to allow
gas to the burner. The ignition sequence
begins and a continuous high speed
spark ignites the gas. As soon as a
flame is detected the orange indicator
bulb 21 Fig. 4 will light. After 45
seconds the modulating solenoid opens
to allow the full gas rate. If a flame is not
detected, after 8 seconds, the security
solenoids close and shut off the gas. The
red lockout indicator bulb 20 Fig. 4
will show.
The central heating flow temperature is
controlled by the central heating control
thermistor 9Fig. 5. The boiler has been
designed to minimise cycling and will not
attempt to relight for 3 minutes after the
boiler thermostat has been satisfied (it is
possible to reduce the time to 30 s if
necessary). When the room thermostat
is satisfied the burner will switch off and
the pump will remain running for a
further 3 minutes before it stops.
NB : it is possible to override the 3 minute
delay by putting off and on the central
heating selector switch 17.
WIRING DIAGRAM

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Adjustment on the PCB :
- P1 : Potentiometer to adjust the CH power
- P2 : Potentiometer to adjust the lighting power
- P3 : Not use
After completling adjustments replace rubber cover and
refit outer casing
ADJUSTMENTS ON CONTROL PCB
ROUTINE SERVICING
To ensure continued efficient operation of
the appliance, it is recommended that it is
checked and serviced as necessary at
regular intervals. The frequency of
servicing will depend upon the particular
installation condition and usage, but in
general, once a year should be adequate.
It is the law that any service work must be
carried out by a competent person such
as your local Chaffoteaux Service Centre,
British Gas or other CORGI registered
personnel in accordance with the current
Gas Safety (Installation and Use)
Regulations.
The service schedule should include
the following operations:
- Check the pressure in the system.
- Check the correct operation of the
appliance.
- Check the correct operation of the gas
controls.
- Check the functions of the safety
controls.
- Check combustion chamber insulation
panels for damage.
- Clean the burner.
- Clean the heat exchanger.
- Check the burner manifold injectors.
- Clean gas and water filters.
- Check expansion vessel charge
pressure.
- Clean and check operation of safety
valve.
Additional Procedures that may be
necessary:
- Check burner pressure and gas flow
rates.
- Check that the fan blades are clean.
- Check, clean and replace components
as necessary.
- Carry out combustion test utilising the
test points in the flue turret.
SUGGESTED SEQUENCE for
SERVICING
Before disconnecting or removing any
parts, isolate the gas and electricity
supplies. Ensure that the appliance is
cool.
(for detail please see section on Parts
Removal and Replacement)
Preliminary Checks
- Remove outer case
- Check the system pressure is at least
0.8 bar cold
- Check operation of solenoids.
- Check that the burner is extinguished
fully when solenoids are closed in both
DHW and C/H modes.
- Test ionisation functions and check that
lockout occurs by turning off gas tap.
CLEANING THE BOILER
Any cleaning work must only be done
when the boiler is switched off.
Under normal circumstances dusting
should be enough. An occasional wipe
over with a damp cloth will remove any
marks from the casing. On no account
use an abrasive cleaning powder or
liquid.
Temperature regulation for C/H and DHW
circuits are controlled by 2 thermistors.
The C/H knob allows the adjustment of
temperature between 35 and 85°C.
The DHW knob allows the adjustement of
the DHW temperature between 40 and
60°C. The 2 thermistors are identical and
interchangeable.
Resistance value are
- 10000 Ωat 25 °C
- 5828 Ωat 40 °C
- 1669 Ωat 80 °C
- 973 Ωat 100 °C
REGULATION
The air flow rate is detected by a pressure
differential created by a venturi located in
the flue duct.
ON threshold ∆P > 137 Pa
OFF threshold ∆P < 117 Pa
AIR PRESSURE SWITCH
COMBUSTION TESTING
Nox Values
MX2 Natural Gas G20
MX2 24
MX2 30
CO Values ( mg/kWh )
Natural Gas G20 max power
MX2 24 44
MX2 30 58
Célectic
Domestic flowmeter time 1.5 sec Domestic flowmeter time 0 sec.
AON operation Modulating operation
Maximum heating setting 40 °C Maximum heating setting 85 °C
Low-speed pump High-speed pump
Anti-cycle 30 secs Anti-cycle 3 min
Detail
P1

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D
45
6
REMOVAL AND REPLACEMENT OF PARTS
Before removing appliance case, isolate
the gas and electrical supplies. Isolate
boiler from the system and drain before
removing any component in the
waterways. Ensure that the appliance is
1. Outer Case
Unlock the two clamps locking A,
which secure the front casing .
Remove the front panel
5. Ignition Electrode (rignt side)
Carry out steps 1and 2as above.
Unscrew the self taping screws (T20).
Disconnect the lead from the wiring loom.
Reassemble in reverse order.
6. Burner Assembly
Carry out steps 1,2,3disconnect
electrodes as mentionned in section 4
and 5. Remove two self taping screws
securing burner.
Reassemble in reverse order.
Carry out combustion tests using the test
points on the turret
7. Gas valve
Carry out step 1. Disconnect the gas
valve wire from the main wiring loom.
Disconnect the electrode wire.
Remove gas pipe nut (spanner 30).
Remove the two screws securing the gas
valve from the botton plate.
Reassemble in reverse order replacing
the gasket.
8. Fan Assembly
Carry out step 1. Disconnect the wire
connectors and the pressure pipes noting
positions. Remove the screws T25 fixing
the fan on the flue outlet, clean the
pressure points. Turn the fan
anticlockwise to disengage from flue
outlet and lift clear.
Reassemble in the reverse order
ensuring that the wiring is reconnected
correctly and the screw tightened.
9. DHW flow switch plunger
Carry out step 1.Close the water inlet
tap.Remove the clip securing the water
brass inlet connection.
Remove the brass connection and the
DHW flow switch plunger.
Reassemble in the reverse order take
care to the wise.
10. Pressure Switch
Carry out step 1. Disconnect the wire
from the pressure switch. Disconnect the
two pressure pipes.
Remove the T20 upper screws securing
the pressure switch from the chassis.
11. DHW Reed Relay
Carry out step 1. Disconnect the DHW
flow switch cable (orange) and remove
the clip to change the REED Relay .
Reassemble in reverse order.
2. Combustion Chamber
Carry out step 1. Unscrew five self
tapping screws to release the combustion
chamber front panel and lift clear.
Reassemble in reverse order.
Screw driver T20
3. Burner Manifold
Carry out steps 1as above. Remove the
nut between manifold and gas pipe.
Unscrew the 4 screws securing the
burner and lift clear.
Reassemble in reverse order.
4. Ionisation Electrode (left side)
Carry out steps 1and 2as above.
Unscrew the self taping screws (T20).
Disconnect the lead from the wiring loom.
Reassemble in reverse order.
12. Drain down
DWH : close the DWH inlet tap and open
a tap on the installation.
CH : Open the pressure relief value.
13. 3-Way valve
Carry out step 1. Drain boiler as in step 12.
Disconnect the wire from the 3 way valve.
Remove the clip and the 3 way valve
motor. Unscrew the two T20 screws using
a small screwdriver. Remove the 3 way
valve body using a pliers.Reassemble in
reverse order.
14. Secondary heat exchanger 45
Drain both circuits of the boiler as in step
12. Remove the 3 way valve motor as in
step 13. Unscrew the two T20 fixing
screws D. Reassemble in reverse order.
The heat exchanger is so designed that it
cannot be remounted incorrectly.
AA

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F
G
11
H
15. Main heat exchanger
and insulation pads
Carry out steps 1and 2as above. Drain
the boiler (only heating circuit). Remove
the 2 front clips Esecuring the heat
exchanger. Remove the NTC clips and
overheat clip. Unscrew the nut Ffrom the
pump. Remove the clip Cfrom the left
side hydraulic bloc, pull the 2 pipes
downward.
Pull the heat exchanger toward you to
remove . Reassemble in reverse order,
do not forget to grease o rings before
reassembly.
To replace insulation pads, carry out the
above procedure.
To remove the pads bend down the
retaining clip and retract the pads .
Reassemble in reverse order.
16 Pump
Drain the boiler. Open the electrical box
cover (two T20 screws G). Remove the
pump plug from the control board and
earth plug from earth socket.
Unscrew the pump nut Fof the flow pipe
from the volute. Remove the clip Hon the
pump volute and pull the pump toward
you. Reassemble in reverse order.
17. Pressure relief valve
Drain the boiler first, remove the clip
securing the valve and pull it toward you .
Remove in reverse order take care to the
valve positionning.
18. NTC and Overheat thermostat
Remove the casing as step 1. Remove
the clips securing NTC and thermostat .
19. Safety thermostat
Remove the casing as step 1unscrew
four self tapping screws securing the
sealed chamber front panel. Disconnect
the 2 cables, pull out the sensor with the
clip 11. Reassemble in reverse order.
20 Control board
Carry out step 1, Pivot the electrical box
downward. Unscrew the two T20 screws.
Replace the electrical box in the original
position. Unscrew the two T20 screws
and pull toward you.
Reassemble in reverse order.
21. Expansion vessel
Remove the boiler from the wall to
change it.
EF
C

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FAULT FINDING CHART

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Incorrects functions is signalled by leds (rep 19) display flashing correspond with chart below.
INCORRECT FUNCTION
CODE FAULT INFORMATION
30 40 50 60 70 80
mmmmm lOverheating safety feature.
mmmm llNo flame detection.
mmm lm l Antifrost mode on (pump in operation).
mmm llm Antifrost mode on (burner and pump in operation).
mmm llllack of water circulation.
mm lmmm Primary water circulation defect
mm lm llCentral heating inlet thermistor faulty (open circuit).
mm llmm Central heating inlet thermistor faulty (short circuit).
mm llm lCentral heating oulet thermistor faulty (open circuit).
mm lllm Central heating oulet thermistor faulty (short circuit).
mlmmlm Firing problem
mlmlmmWiring problem (or fuse 1,25 A)
mlmlmlFan on but does not activate air pressure switch.
mlmllmFan off but air pressure switch fails to return to off position.
m lllllCommunication defect with the display PCB.
lmmmmm Communication defect with the main PCB.
m = LED off
l = LED blinking

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SHORT LIST
104 OVERHEAT THERMOSTAT 105°C 61010191 ..
108 THERMISTOR TEMP. SENSOR 990686 ..
110 IGNITION ELECTRODE 990436 ..
206 FAN ASSY 28KW 61304721 .
FAN ASSY 24KW 61310933 .
216 AIR PRESSURE SWITCH 61303146 .
AIR PRESSURE SWITCH 61313340 .
401 GAS VALVE NAT 61312123 ..
444 IGNITER 61312612 ..
502 MOTOR - 3 WAY VALVE 61302483 ..
506 VALVE KIT 61311597 ..
537 PRESSURE RELIEF VALVE 61312668 ..
538 PUMP + AIR SEPARATOR 15/50 61312183 .
PUMP + AIR SEPARATOR 15/60 61313464 .
541 THERMISTOR TEMP. SENSOR 61000733 ..
543 STOPPED WATER THROTTLE 61311745 ..
589 WATER / WATER HEAT EXCHANGER 61302409 ..
615 PRINTED CIRCUIT BOARD PRINC. 65100774 ..
616 PRINTED CIRCUIT BOARD AFF. 65100773 ..
622 IGNITION PUSH ROD 61312414 ..
649 PRESSURE GAUGE 61313561 ..
650 WHITE KNOB 61312413 ..
DescriptionKey N°
Manf. Pt. N°
Type G.C N°
FF FF
Manf. date
MX2 24
MX2 30
from to
206
216
108
104
589
541
537
401
444 506
502
538
110
543
650
615
616
622
649

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Ref. : 1313608 - 08/2003
Chaffoteaux & Maury are continuously improving their products and therefore reserve the right to change specifications
without prior notice and accepts no liability for any errors or omission in the information contained in this document.
Manufacturer: Chaffoteaux & Maury - France
Commercial subsidiary: M T S (GB) Limited
M T S Building
Hughenden Avenue
High Wycombe
Bucks HP13 5FT
Telephone: [phone]
Fax: [phone]
internet: www.chaffoteaux.co.uk
E-mail: [email protected]
Technical Support Help Line: [phone]