REMEHA P 420 Manual

P 420
Fuel oil/gas boilers
Remeha
Installation and
Service Manual
300016839-03
en

2P 420 16/03/2016 - 300016839-03
Declaration of conformity 1
The appliance complies with the standard model described in
declaration of compliance 1. It is manufactured and distributed
pursuant to the requirements of european directives. The original
declaration of conformity is available from the manufacturer.
C001880

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Contents
1 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.1 General safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
1.3 Liabilities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2 About this manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.1 Symbols used in the manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.2 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.3 Homologations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
3 Technical description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3.1 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3.2 Technical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
4.1 Regulations governing installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
4.2 Package list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
4.3 Choice of the location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
4.4 Example of an installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
4.5 Hydraulic connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
4.6 Chimney connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
4.7 Fuel-oil or gas connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.8 Electrical connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
4.9 Filling the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
5 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
6 Switching off the boiler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
6.1 Precautions required in the case of long boiler stops. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
6.2 Precautions required if the heating is stopped when there is a risk of freezing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
7 Checking and maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
7.1 System maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
7.2 Type plate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
7.3 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
7.4 Cleaning the casing material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
7.5 Maintenance of the burner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
8 Spare parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

4P 420 16/03/2016 - 300016839-03
1 Safety instructions
Danger
This appliance can be used by children aged
from 8 years and above and persons with
reduced physical, sensory or mental capabilities
or lack of experience and knowledge if they have
been given supervision or instruction
concerning use of the appliance in a safe way
and understand the hazards involved. Children
shall not play with the appliance. Cleaning and
user maintenance shall not be made by children
without supervision.
Any operation on the installation must be
performed by a qualified technician respecting
professional regulations and in accordance with
this document.
Before any work, switch off the mains supply to
the appliance. Protect the installation against
any unwanted restarts.
For a proper operating of the boiler, follow
carefully the instructions.
The manufacturer is not liable for any improper
use of the appliance or failure to maintain or
install the unit correctly (the user shall take care
to ensure that the system is installed by a
qualified engineer).
Work on electrical equipment must be carried out
by a qualified professional in compliance with
the prevailing regulations.
Check that the appliance is properly set for the
type of gas used.
Keep to the polarity shown on the terminals:
phase (L), neutral (N) and earth 4.
Check the seal on the gas and water pipe
connections.
We shall not accept any responsibility for any
damage and disturbance arising from not
following these instructions.
Incorrect use or unauthorised modifications to
the installation or the equipment itself invalidate
any right to claim.
1.1 General safety instructions
1.1.1 Fire hazard
Do not stock products of an inflammable nature
close to the appliance.
It is forbidden to store inflammable products and
materials in the boiler room or close to the boiler,
even temporarily.
If you smell gas, do not use a naked flame, do not
smoke, do not operate electrical contacts or
switches (doorbell, lights, motor, lift, etc.):
1. Shut off the gas supply .
2. Open the windows .
3. Extinguish all flames.
4. Evacuate the premises.
5. Contact a qualified professional.
6. Inform the gas supplier.
1.1.2 Risk of intoxication
Do not obstruct the air inlets in the room (even
partially).
If you smell flue gases
1. Switch the appliance off
2. Open the windows
3. Evacuate the premises
4. Contact a qualified professional
1.1.3 Risk of being burnt
Depending on the settings of the appliance:
- The temperature of the flue gas conduits may exceed
60°C
- The temperature of the radiators may reach 95°C
- The temperature of the domestic hot water may reach
65°C

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1.1.4 Risk of damage
Do not stock chloride or fluoride compounds
close to the appliance.
Install the appliance in frost-free premises.
Do not neglect to service the appliance: Contact a
qualified professional or take out a maintenance contract
for the annual servicing of the appliance.
1.2 Recommendations
For a proper operating of the boiler, follow
carefully the instructions.
Any intervention on the appliance and heating
equipment must be carried out by a qualified
engineer.
The manufacturer is not liable for any improper
use of the appliance or failure to maintain or
install the unit correctly (the user shall take care
to ensure that the system is installed by a
qualified engineer).
Work on electrical equipment must be carried out
by a qualified professional in compliance with
the prevailing regulations.
Check that the appliance is properly set for the
type of gas used.
Keep to the polarity shown on the terminals:
phase (L), neutral (N) and earth 4.
Check the seal on the gas and water pipe
connections.
We shall not accept any responsibility for any
damage and disturbance arising from not
following these instructions.
1.3 Liabilities
1.3.1 Manufacturer's liability
Our products are manufactured in compliance with the
requirements of the various applicable European
Directives. They are therefore delivered with CE marking
and all relevant documentation. In the interest of
customers, we are continuously endeavouring to make
improvements in product quality. All the specifications
stated in this document are therefore subject to change
without notice.
Our liability as the manufacturer may not be invoked in
the following cases:
- Failure to abide by the instructions on installing the
appliance
- Failure to abide by the instructions on using the
appliance
- Faulty or insufficient maintenance of the appliance
1.3.2 Installer's liability
The installer is responsible for the installation and
commissioning of the appliance. The installer is required
to observe the following instructions:
- Read and follow the instructions given in the manuals
provided with the appliance
- Install the appliance in acordance with the legislation
and standards currently in force
- Perform the initial start up and carry out any checks
necessary
- Explain the installation to the user
- If a maintenance is necessary, warn the user of the
obligation to check the appliance and maintain it in
good working order
- Give all the instruction manuals to the user

6P 420 16/03/2016 - 300016839-03
2 About this manual
2.1 Symbols used in the manual
Caution danger
Risk of injury and damage to equipment. Attention must be
paid to the warnings on safety of persons and equipment.
Specific information
Information must be kept in mind to maintain comfort.
ZReference
Refer to another manual or other pages in this instruction
manual.
2.2 Abbreviations
`DHW: Domestic hot water.
`PPS: Polypropylene hardly inflammable.
`3CE: Collective conduit for sealed boiler
Hi: Lower heating value LHV (Nett)
Hs: Higher heating value HHV (Gross)
2.3 Homologations
This product will be marketed in the following European Union
member states:
NL - BE - ES - GB - HU - SE
with a gas or oil-burner of the associated category.
2.3.1 Directive 97/23/EC
Gas and oil boilers with a maximum operating temperature of 110°C
and hot water tanks with a maximum operating pressure of 10 bar
pertain to article 3.3 of the directive, and therefore, cannot be CE-
marked to certify compliance with the directive 97/23 EC.
The boilers and hot water tanks are designed and manufactured in
accordance with the sound engineering practice, as requested in
article 3.3 of the directive 97/23/EC, it is certified by compliance with
the directives 90/396/EC, 92/42/EC, 2006/95/EC and 2004/108/EC.

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3 Technical description
3.1 General description
The boilers of the P 420 range are pressurised hot water boilers
designed for connecting to a flue pipe which require a separate
automatic fuel-oil or gas burner.
The useful power of P 420 boilers is between 250 and 700 kW.
Boiler with control panel, which may be fitted with an optional
Rematic 2945 C3 control unit for heating only or heating and
domestic hot water production.
3.2 Technical specifications
Maximum operating pressure: 6 bar
Boiler thermostat setting: 30 to 90°C
Maximum operating temperature: 100°C
*Maintenance consumption: total heat emission when the burner is
off as a percentage of the nominal input power when the difference
between the mean boiler temperature and the room temperature is
30 K.
(1) Nominal operation (top boiler power)
(2)CO2= 13.1 to 13.5% with fuel oil and 9.5% with natural gas.
(3) Boiler temperature: 80 °C - Ambient temperature: 20 °C
Boiler P 420-8 P 420-9 P 420-10 P 420-11 P 420-12 P 420-13 P 420-14
Useful output kW 300-390 390-450 450-540 540-600 600-670 670-720 720-780
Power input kW 329-434 429-502 495-599 594-670 661-751 737-804 789-871
Number of sections 8 9 10 11 12 13 14
Water content l 366 409 452 495 538 581 624
Water resistance
∆T = 10K
mbar
31 48 80 101 130 158 194
∆T=15K 14213645587087
∆T = 20K 8 12 20 25 33 40 49
Pressure in the furnace for nozzle pressure =
0 (1) (3) (2)) mbar 1.1 1.5 2.0 2.5 2.5 2.5 3.5
Smoke temperature (1) (3) (2)* °C < 220 < 220 < 220 < 220 < 220 < 220 < 220
Mass flue gas flow
rate (1) (2)
Fuel oil Kg/h 650 750 900 1000 1116 1200 1450
Gas 700 810 972 1080 1207 1297 1405
Combustion chamber
Diameter, combus-
tion chamber mm 530 530 530 530 530 530 530
Width, combustion
chamber mm 638 638 638 638 638 638 638
Depth, combustion
chamber mm 1183 1343 1503 1663 1823 1983 2143
Volume m30.310 0.354 0.396 0.439 0.481 0.523 0.565
Maintenance con-
sumption* à 50°C W 315 358 413 451 494 505 555
Shipping weight kg 1470 1650 1830 2010 2190 2370 2550

8P 420 16/03/2016 - 300016839-03
4 Installation
4.1 Regulations governing installation
Installation must be carried out in accordance with the
prevailing regulations, the codes of practice and the
recommendations in these instructions.
4.2 Package list
ZSee assembly instructions.
4.3 Choice of the location
4.3.1 Main dimensions
(a) Boiler flow - weld
(b) Sludge removal hole Ø Rp 2 1/2 - plugged
(c) Boiler return - weld
(d) Rp 2 draining outlet - plugged
Boiler type P 420-8 P 420-9 P 420-10 P 420-11 P 420-12 P 420-13 P 420-14
ø A 250 250 250 300 300 300 300
ø B 2" 1/2 2" 1/2 2" 1/2 3" 3" 3" 3"
ø C plate intact or pre-drilled to the diameter specified on order
D 235 235 235 254 254 254 254
E 1427142714271447144714471447
J 1800195021202305246526252785
L 1505166518251985214523052465
S 1183134315031663182319832143

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4.3.2 Position of the boiler
For the assembly and because of their design, P 420 boilers require
no special base. Their closed furnace system means that the floor
need not have refractory properties. All you have to ensure is that the
floor can support the weight of the boiler when it is fitted for operation.
If the boiler location is not determined precisely, leave enough space
around the boiler to facilitate monitoring and maintenance
operations.
(1) Top view
(2) Burner door
Caution: adapt the dimensions on the basis of the
dimensions of the burner when the door is open.
P 420-8 P 420-9 P 420-10 P 420-11 P 420-12 P 420-13 P 420-14
A 1505 1665 1825 1985 2145 2305 2465
B 130 -40 120 -40 120 -40 120
C 1.5 2 2 2 2.5 2.5 2.5

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4.3.3 Ventilation
The location of air inlets in relation to the high ventilation openings
shall ensure that the air is renewed in the entire volume of the boiler
room.
It is in any case imperative to conform to the local regulations in force.
Caution:
In order to avoid damage to the boiler, it is necessary to prevent the
contamination of combustion air by chlorine and/or fluoride
compounds, which are particularly corrosive.
These compounds are present, for example, in aerosol sprays,
paints, solvents, cleaning products, washing products, detergents,
glues, snow clearing salts, etc.
Therefore:
• Do not pull in air evacuated from premises using such products:
hairdressing salons, dry cleaners, industrial premises (solvents),
premises containing refrigeration systems (risk of refrigerant
leakage), etc.
• Do not stock such products close to the boilers.
If the boiler and/or peripheral equipment are corroded by such
chloride or fluoride compounds, the contractual guarantee
cannot be applied.

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4.4 Example of an installation
Installation must be carried out in accordance with the prevailing
regulations, the codes of practice and the recommendations in these
instructions.
The expansion vessel must be connected directly to the boiler
without valves or stop valves.
Likewise, the safety valve must be connected directly to the boiler
without valves or stop valves.
Example of an installation:
The example of an installation shown below does not cover every
possible configuration.
8219N008C
92
14
12
17
11
27
9
56
32
9
10
1
9
57
9
27
26
15
9
17
18
919 20 9
17
16
13
3
79
7
30
28
9
29
27
9
31
56
9
9
9
1Heating flow
2Heating return
33-bar safety valve + Pressure gauge
5Flow switch
6Air separator
7Automatic air vent
9Isolating valve
10 3-way mixing valve
11 Boiler pump
12 Sludge decanting pot (particularly recommended on older
installations)
13 Flush valve
14 Water low safety pressure-sensitive switch
15 Shunt pump
16 Expansion vessel
17 Drain cock
18 Heating circuit filling (with disconnector depending on prevailing
regulations)
19 Water treatment
20 Water meter
26 DHW load pump
27 Non-return valve
28 Domestic cold water inlet
29 Pressure reducer (if mains pressure > 5.5 bar)
30 Safety unit calibrated to 7 bar with indicator type discharge
31 Independent domestic hot water tanks
32 Domestic hot water loop pump (optional)
56 Domestic hot water circulation loop return
57 Domestic hot water outlet

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4.5 Hydraulic connections
4.5.1 Flushing the system
Installing the boiler in new installations
(installations less than 6 months old)
`Clean the installation with a universal cleaner to eliminate
debris from the system (copper, hemp, flux).
`Thoroughly flush the installation until the water runs clear and
shows no impurities.
Installing the boiler in existing installations
`Remove sludge from the installation.
ZSee: Sludge removal.
`Flush the installation.
`Clean the installation with a universal cleaner to eliminate
debris from the system (copper, hemp, flux).
`Thoroughly flush the installation until the water runs clear and
shows no impurities.
4.5.2 Sludge removal
A tapped Rp 2’’ 1/2 hole with a plug has been provided on the bottom
of the front of the boiler.. Fit a 1/4 turn valve (not supplied) on the
opening to remove the sludge.
Sludge removal leads to the draining of large quantities of water, so
remember to refill the system after the operation.
After this operation, go ahead and fill the installation.
ZSee: Filling the system.
never replace a boiler in an existing system without carefully
rinsing the system first. Install a sludge decanting pot on the
return pipe, very close to the boiler.
4.5.3 Hydraulic connection of the heating circuit
Water flow in the boiler
The water flow in the boiler when the burner is operating must
correspond with the following formulae:
- Nominal water flow Qn = 0.86 Pn/20.
- Minimum flow Qmin = 0.86 Pn/45 (this flow also corresponds with
the minimum recycle flow in the boiler).
- Maximum water flow Qmax = 0.86 Pn/5.
Qn = flow in m3/h.
Pn = Nominal output (full boiler output) in kW.
Operation in cascade
After stopping the burner:
- Timeout required before the order to close a 2 way valve: 3 min.
- Switch a possible shunt pump (located between the boiler and a
butterfly valve) off via the end of run contact of the butterfly valve.
Operation with 2-stage burner
- The water temperature in the boiler is maintained at 50°C or more;
The first stage must be set to a minimum of 30% of the nominal
stage.
- Operation at modulated low temperature (minimum outlet
temperature: 40°C); The first stage must be set to a minimum of
50% of the nominal stage.
Operation with modulating burner
- The water temperature in the boiler is maintained at 50°C or more:
The burner can modulate down to 30% of the nominal stage.
- Operation at modulated low temperature (minimum outlet
temperature: 40°C); The burner can modulate down to 50% of the
nominal stage.

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4.5.4 Safety valve
The safety valve must be connected to the boiler outlet and no other
valve or flap must be interposed between it and the boiler.
`Minimum safety valve flowrate as a function of maximum boiler nominal output:
Minimum relieving capacity
Maximum gross boiler output
Example
Maximum boiler nominal output is 500 kW.
Minimum safety valve flowrate must be 4000 Kg/h
4.5.5 Connection of the water circuit for domestic use
ZSee: Domestic hot water calorifier instructions.

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4.6 Chimney connection
The high-performance features of modern boilers and their use in
specific conditions as a result of the advance in burner technology
(e.g. first-stage or low modulation range operation) lead to very low
flue gas temperatures (<160°C).
For this reason:
- Use flue gas pipes designed to enable the flow of condensates
which may result from such operating modes in order to prevent
damage to the chimney.
- Install a draining tee at the bottom of the chimney.
The use of a draught moderator is recommended as well.
4.6.1 Flue size
Refer to applicable regulations while determining the size of the flue.
Please note that P 420 boilers have pressurised and tight furnaces
and that the pressure at the connection to the chimney must not
exceed 0 mbar, unless special sealing precautions have been taken,
for instance in order to connect a static condenser/regenerator.
4.6.2 Connection to the flue gas pipe
The connection shall be removable, and offer minimum load losses,
i.e. it must be as short as possible with no sudden change in section.
Its diameter shall always be at least equal to that of the boiler outlet,
i.e.:
ø 250 mm: for 7 to 10 sections
ø 300 mm: for 11 to 14 sections.

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4.7 Fuel-oil or gas connections
ZRefer to the instructions supplied with the burner. The burner head deflector must be flush with the insulation
of the burner door.
C: Furnace door insulation
D, E: Pressure gauge measurement socket
(1) Max attachment diameter:
- Max øB = 290 mm
- Max øB = 330 mm with 4 fastenings at 15° or 45°
4.8 Electrical connections
ZRefer to the connection instructions supplied with the control
panel..
4.9 Filling the system
Filling shall be performed with a low flow rate from a low point in the
boiler room in order to ensure that all the air in the boiler is bled from
the high point of the system.
All the pumps must be stopped before filling (included shunt
pump(s)).
Do not add cold water suddenly into the boiler when it is
hot.
VERY IMPORTANT: Instructions for starting up the boiler
for the first time after the system is fully or partly drained:
If all the air is not bled naturally to an expansion vessel
which opens out onto the air, the system must include
manual bleeder valves, in addition to automatic bleeder
valves with the capability to bleed the system by
themselves when it is operating, the manual bleeder valves
are used to bleed all the high points of the system and to
make sure that the filled system is free of air before the
burner is turned on.
D
E
8229N007-B
ØA 135 175 190 240 250 290
ØB 170 200 220 270 325 330
ØD 10 10 10 10 10 10
ØE 10 10 10 10 10 10
ØM 8 8 10 10 14 12

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5 Commissioning
ZSee:
- Control panel instructions .
- Burner instructions .
- Domestic hot water calorifier instructions .
6 Switching off the boiler
`Set the On/Off switch to O.
ZSee: Control panel instructions.
`Cut the gas supply to the boiler (if present).
6.1 Precautions required in the case of long boiler stops
- The boiler and the chimney must be swept carefully.
- Close all the doors of the boiler to prevent air from circulating inside
the boiler.
- We advise removing the pipe which connects the boiler to the
chimney and to close off the nozzle with a cover.
6.2 Precautions required if the heating is stopped when there is a risk of freezing
We recommend the use of a correctly dosed antifreeze agent to
prevent to the heating circuit from freezing.
If this cannot be done, drain the system completely.

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7 Checking and maintenance
7.1 System maintenance
7.1.1 Water level
Regularly check the level of water in the system and top up if
required, taking care that cold water is not added suddenly into the
boiler when it is hot.
The use of an automatic filling is strongly discouraged.
This operation should be required only a few times in each heating
season, with very low quantities of water; otherwise, look for the leak
and repair it.
7.1.2 Draining
We advise you against draining the system unless it is
absolutely necessary.
For example: Several months' absence with the risk of ice in the
building.
7.2 Type plate
The rating plate fixed on the side of the boiler during installation is
used to identify the boiler correctly and also provides the main
specifications of the boiler.
Boiler type
Nominal output
Nominal input
M000048-B

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7.3 Maintenance
The boiler will only operate efficiently if the exchange
surfaces are kept clean.
The boiler should be cleaned as soon as required and as the
chimney, at least once a year or more, depending upon applicable
regulations and specific needs.
The operations described below shall only be performed
with the boiler and power supply off.
7.3.1 Cleaning the flue gas circuit
- Remove the upper front panel.
- Take off the lower panels.
- Open the sweeping doors (upper doors) by unscrewing the 3 nuts
using a 19 mm spanner.
- Remove the baffle plates from the upper flue ways.
- Carefully sweep the flue ways with the brush supplied for that
purpose.
- Brush the baffle plates.
- If possible, use a vacuum cleaner.
- Replace the baffle plates.
- Close the doors.
7.3.2 Cleaning the combustion chamber
- Unscrew the 4 closing nuts and open the furnace door.
- Brush out the inside of the furnace.
- Use a vacuum cleaner to remove any soot which has accumulated
in the combustion chamber.
- Close the door and replace the front panel.
C003591-A
C003592-A
C003593-A

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7.3.3 Positioning of the baffle plates
- Put the baffle plates back in place and hook them into each other
before engaging them fully in the flue way.
- Close the sweeping doors.
Follow the order of assembly shown in the diagram.
The 8-figure part number of the baffle plate is cast in the metal.
Boiler P 420-8 P 420-9 - P 420-10 P 420-11 P 420-12 P 420-13 - P 420-14
Upper flue ways First 8229-0010 then
8229-0022 2 x 8229-0010 First 2 x 8229-0010 then
1 x 8229-0022
First 2 x 8229-0010 then
1 x 8229-0022 3 x 8229-0010
Central flue ways First 8229-0011 then
8229-0023 2 x 8229-0011 First 2 x 8229-0011 then 1 x 8229-0023
First 2 x 8229-0011 then
1 x 8229-0023 3 x 8229-0011
Lower flue ways First 8229-0012 then
8229-0024 2 x 8229-0012 First 2 x 8229-0012 then 1 x 8229-0024 2 x 8229-0012 2 x 8229-0012
C003370-B
8229-0022
8229-0010

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7.3.4 Cleaning the flue gas box
To do so:
- Open the left and right cleaning hatches on the flue gas box (2 nuts
H 12 + flat washers with a 19 mm spanner) and remove any soot
which has accumulated using a vacuum cleaner.
- Replace the cleaning hatches.
7.3.5 Chemical sweeping
General principle
Boilers are traidtionally swept mechanically. There are now chemical
sweeping methods which facilitate this maintenance work.
A chemical reagent is applied to the boiler's heating surfaces.
After application, the reaction is completed by igniting the burner. The
initial deposits are neutralised and pyrolised. The remaining
pulverent residues are easy to remove by sweeping or vacuum
cleaning.
The products
The product must be suitable for boilers with a cast iron body. Various
manufacturers offer products in the form of a concentrated liquid or
aerosol.
The aerosols are packaged in 0.5 to 1 l spray cans for treating
domestic boilers. Refer to the instructions supplied with the product.
The liquid products are available in 1 to 50 l containers. These
concentrated liquids are diluted before application with a spray.
Sprays exist in various forms suitable for their intended use:
- Low capacity (2 or 3 l) spray with built-in reservoir for small boilers
and moderate frequency. Manual pressurisation of the reservoir.
- 5 l spray with separate reservoir, nozzle and connecting tube. The
nozzles enable easy application at the back of the combustion
chamber. Manual pressurisation of the reservoir.
- Motor-assisted pressurisation spray with reservoir, nozzle and
connecting tube. These sprays are intended for intensive use.
8800N065
8800N063