Saunier Duval ISOTWIN CONDENS F 35 E User guide

Instructions for use
Installation and servicing
ISOTWIN CONDENS F 35 E
HIGH EFFICIENCY CONDENSING COMBINATION BOILER

GUARANTEE REGISTRATION
Thank you for installing a new Saunier Duval appliance in your home.
Saunier Duval appliances are manufactured to the very highest standard so we are
pleased to offer our customers a Comprehensive Guarantee.
This product is guaranteed for 24 months from the date of installation or 30 months from
the date of manufacture, whichever is the shorter, for parts. In addition, this product is
guaranteed for 12 months from the date of installation or 18 months from the date of
manufacture, whichever is the shorter, for the labour.
The second year of the parts guarantee, from the beginning of the 13th month onwards
after installation or manufacture, is conditional upon the boiler having been serviced by a
CORGI registered gas installer,
in accordance with the manufacturer’s recommendations. We strongly recommend
regular servicing of your gas appliance, but where the condition is not met, any
chargeable spare parts or components issued within the applicable guarantee period still
benefit from a 12 month warranty from the date of issue by the manufacturer.
We recommend you complete and return as soon as possible your guarantee registration
card.
If your guarantee registration card is missing, you can obtain a copy or record your
registration by telephoning the Saunier Duval Customer Service number below.
For customer service call:
01773 525 914
Technical helpline: 01773 828400
For General and Sales enquiries:
Tel. [phone]
To register your Saunier Duval appliance call:
0800 073 2144
Please complete the Benchmark Log Book at the end of this manual, if the appliance fails
to operate then the condition should be reported immediately to our service organisation
Saunier Duval Service 01773 525 914.
DO NOT REMOVE the appliance from the system until the engineer has confirmed and
signed the report allowing the return of the appliance to the merchant.
The merchant will NOT accept any returns unless supported by Saunier Duval Service
the engineer’s signed report.

1
Instructions for Use
Instructions for use
Index
1 General points
.........................................................................2
2 Documents .............................................................................2
3 Safety ......................................................................................2
3.1 Gas Leak or Fault ..............................................................................2
3.2 Safety regulations and recommendations
..........................................2
4 Guarantee / Responsibility
......................................................3
5 Appliance use
..........................................................................4
6 Servicing .................................................................................4
7 Recycling
.................................................................................4
8 Appliance use
..........................................................................6
8.1 Control panel
......................................................................................6
8.2 Commissioning and lighting ...............................................................6
8.3 Temperature adjustment ....................................................................7
9 Turn the boiler off ....................................................................7
10 Fault finding
.............................................................................7
11 Frost protection .......................................................................8
11.1 Boiler frost protection .........................................................................8
11.2 Installation frost protection .................................................................8
12 Maintenance/After Sales Service
............................................8

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1 General points
ISOTWIN CONDENS F 35 E boiler
is an appliance that uses condensing
technology, which recovers heat present
in waste gas.
Thanks to this operating principle,
the boiler consumes less energy and
decreases NOx and CO2 emissions.
ISOTWIN CONDENS F 35 E boiler has a
double use (heating + instantaneous hot
water).
This appliance of the room-sealed type
is equipped with a flue exhaust and air
intake for combustion products called the
flue system. This flue system connection
principle offers the possibility to install the
appliance in any room and with no specific
ventilation requirements.
The installation and the commissioning
of the appliance has to be carried out by
a skilled professional who is responsible
for the compliance of the installation and
the commissioning according to current
regulations.
You also have to call on a skilled
professional for the maintenance and the
repairing of the appliance as well as for
any gas adjustment.
Saunier Duval has specially designed
different accessories for your appliance
depending on your installation.
If you want to have a detailed list, please
contact your supplier or visit our website
www.saunier-duval.co.uk.
2 Documents
Please keep this manual as well as any
documents enclosed with it safe for
future reference.
We accept no liability in case of damage
due to the non-compliance of the
instructions of the present manual.
3 Safety
3.1 Gas Leak or Fault
Do not switch on nor switch off the light.
Do not activate the electrical switch.
Do not use the phone in this risky area.
Do not light up a flame (for example, a
lighter or a match).
Do not smoke.
Turn off the gas emergency control
valve immediatly.
Open all windows and doors to
ventilate the area.
Warn any person in the house.
Inform the Gas Utility company or a
skilled professional.
3.2 Safety regulations and
recommendations
Please observe the following safety
regulations and recommendations:
Do not use any aerosols, solvents,
abrasive cleaner, detergents with
chlorine, paint, glue, etc. near the
appliance. Under unfavourable
conditions, these substances can be
very corrosive even for the flue.
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3
Instructions for Use
Do not use or store any explosive
material or easily flammable (for
example, petrol, paint, etc.) in the room
where the appliance is situated.
Never switch off the safety devices and
do not try to handle these devices as
this could lead to a malfunction.
Do not change:
- The appliance,
- The appliance environment,
- Water, air, gas and electric supply,
- Flue system.
Never carry out by yourself
maintenance or repairing operations on
the appliance.
In case of a water leakage, immediately
close the cold water inlet of the
appliance and call a skilled professional
to repair the leakage.
Do not break sealed mechanisms.
Do not modify the technical conditions
close to the appliance, as these are
very important as far as the appliance
safety is concerned.
For example: the minimum clearances
of the external sides.
Warning!
A heating safety valve with a discharge
pipe and a domestic hot water pressure
relief valve with a discharge pipe are fitted
to this appliance. The valves must not be
touched except by a skilled professional.
If the valves discharges at any time, switch
the appliance off and isolate it from the
electrical supply.
Warning!
We advise you to be very careful when
adjusting hot water temperature: water
can be very hot when releasing from the
draw off tap.
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4 Guarantee / Responsibility
Your appliance is guaranteed for a
period of 24 months from the date of
installation or 30 months from the date of
manufacture whichever is the shorter and
covers manufacturing defects only.
We, Saunier Duval, undertake to repair or
replace parts free of charge which
are recognised by us to be of faulty
manufacture - if necessary after return to
our factory for examination - on condition
that:
The appliance was installed by a
qualifled gas installer in accordance
with installation instructions, and all the
relevant codes of practice, standards
and legislation in force.
The appliance has been used for
normal domestic purposes and in
accordance with the manufacturer’s
operating and maintenance
instructions.
The appliance has not been serviced,
maintained, repaired dismantled or
tampered with during the guarantee
period, by anyone other than a
competent person.
The repair or replacement of parts
during the guarantee period does not
have the effect of extending the period.
This guarantee does not cover:
Any defects or damage resulting
from incorrect or poor installation,
inadequate servicing, or maladjustment
of the gas or water used.
Any defects in the system to which the
appliance is connected.
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Any deterioration or maladjustment
following changes in the nature or
pressure of the gas or the water used,
or a change in the characteristics of the
electrical supply voltage.
Notification of any fault should be made
to the appliance installer. No repairs
should be undertaken upon the appliance,
intending it to be covered by the product
guarantee without prior authorisation from
Saunier Duval.
IMPORTANT: The appliance serial number
must be quoted on all correspondence/
contact made with Saunier Duval.
This guarantee is in addition to your
statutory and other legal rights, which
will not be excluded or diminished by the
return of the guarantee registration card.
5 Appliance use
Saunier Duval’s appliances are
manufactured according to the latest
technical evolutions and current safety
regulations.
This appliance is used to produce
hot water using gas. Any other use
is considered as inappropriate and is
forbidden.
The manufacturer shall not be responsible
for any damage caused by another
use. In that case the user shall be the
responsible.
•6 Servicing
Clean the case of the appliance with
wet soapy cloth.
Do not use any abrasive cleaning
product as they could damage the
housing or plastic parts.
7 Recycling
The appliance comprises many recyclable
parts. The packaging, the appliance and
the content of the package shall not be
thrown together with domestic waste
but eliminated according to the current
regulations.
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5
Instructions for Use

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8 Appliance use
8.1 Control panel
1
2
4
3
7
6
5
Legend
1 Operating indicator
2 Display of the available pressure in the
heating circuit
3 Operating mode selection
4 DHW temperature adjustment
5 Display of the measured temperature in
the heating circuit
6 On/off switch
7 Heating temperature adjustment
8.2 Commissioning and lighting
Make sure that:
the boiler is connected to the electrical
supply.
the gas service cock is open.
Push the switch (6) until the “I” symbol
appears.
The operating indicator on the control
panel turns on: the boiler is ready to
run.
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Push “MODE” to modify the operating
mode of the boiler. The ◄ symbol is
then situated in front of the selected
mode:
Central heating and
domestic hot water
Central heating only
Domestic hot water only
Appliance frost protection
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Instructions for Use
8.3 Temperature adjustment
8.3.1 Domestic hot water temperature
adjustment
The domestic hot water must be set at
max 63°C.
Push + or – on the side to adjust the
max temperature.
The ECO symbol remains until 49°C.
8.3.2 Heating temperature adjustment
Push + or – on the side to change
water temperature between 22°C and
the maximum value allowed by your
installer.
Observation:
A quick push on +/- or / side
displays the temperature value previously
selected
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9 Turn the boiler off
Push the switch (6) until the “O” symbol
appears.
The appliance is no longer supplied
with electric power.
We advise you to turn off the appliance
gas supply if you leave home for a long
period.
10 Fault finding
If there is a fault, then a fault symbol
displays and the operating indicator on the
control panel flashes red.
Warning !
Never try to service or repair the appliance
by yourself and only start the appliance
once a skilled professional repaired the
fault.
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Symbol and
fault code
Cause Corrective action
The operating
indicator is OFF.
Power failure Check the mains power supply is on and that
the appliance is switched on at the spur or
socket. The appliance starts automatically
once the power supply is on. If the fault
persists, please contact a skilled professional.
code F1, F4
Ignition fault Deactivate the boiler
Wait 5 seconds and then start the boiler again.
If the fault continues, please contact a skilled
professional.
code F2, F3
Air flow failure
code F5 Overheating fault Please contact a skilled professionnal
Insufficient water
pressure in the system
Open the blue tap situated under the boiler
until you obtain a pressure between 1 and
2 bars on the indicator. If you have to fill it
this might be caused by a leakage in your
appliance. In this case, contact a skilled
professional to check the boiler and system.
Other defects Please contact a skilled professionnal

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11 Frost protection
11.1 Boiler frost protection
In case of frost risk, do as follows:
Make sure the boiler is supplied with
electrical power and gas.
Select the operating mode on the
control panel.
The frost protection system operates the
boiler as soon as the temperature in the
heating circuit is under 4°C. The boiler
stops as soon as the water temperature in
the heating circuit reaches 16°C.
11.2 Installation frost protection
If you leave home for a few days, select
the minimum heating temperature on
the control panel of the boiler and just
decrease the setpoint temperature on
your room thermostat.
If you leave home for a long period, see
chapter “Draining of the appliance” in
the installation manual.
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12 Maintenance/After Sales Service
Please note that an incorrect servicing can
affect the safety of the appliance and can
lead to injury.
To ensure the continued efficient and
safe 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 conditions
and usage, refer to guarantee registration.
If this appliance is installed in a rented
property there is a duty of care imposed
on the owner of the property by the current
issue of the Gas Safety (Installation and
Use) Regulations, Section 35. Servicing/
maintenance should be carried out by
a competent person in accordance with
the rules in force in the countries of
destination. To obtain service, please call
your installer or Saunier Duval service.

Installation and servicing instructions strictly reserved for qualified gas installers
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Installation and servicing
Index
1 Comments on the instructions ............................................... 11
2 Appliance description
............................................................ 11
2.1 Data label ......................................................................................... 11
2.2 Mandatory WARNING for EEC countries ......................................... 11
2.3 Block diagram ..................................................................................12
3 Appliance location .................................................................13
4 Safety instructions and regulations .......................................14
4.1 Safety instructions ............................................................................14
4.2 Regulations ......................................................................................15
5 Appliance installation ............................................................16
5.1 Recommendations before mounting ................................................16
5.2 Dimensions ......................................................................................18
5.3 List of delivered equipment ..............................................................18
5.4 Fixing to the wall ..............................................................................18
5.5 Gas and water connection ...............................................................20
5.6 Connection to the condensate trap ..................................................24
5.7 Flue connection ................................................................................24
5.8 Electrical connection ........................................................................27
5.9 Wiring diagram .................................................................................28
6 Commissioning ......................................................................30
7 Specific adjustments .............................................................30
7.1 Heating circuit adjustment ................................................................30
7.2 Access to the boilers technical data
(for professional and After Sales Service use only) .........................32
8 Draining of the appliance ......................................................34
8.1 Heating circuit ..................................................................................34
8.2 Domestic Hot Water circuit ...............................................................34

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9 Gas conversion .....................................................................34
9.1 Maximum rate ..................................................................................34
9.2 Minimum rate ...................................................................................35
9.3 Reactivation .....................................................................................35
10 Fault finding ...........................................................................36
11 Control / Commissioning
.......................................................38
12 User information
....................................................................38
13 Spare parts ............................................................................38
14 Maintenance
..........................................................................39
14.1 Casing ..............................................................................................39
14.2 Hydraulic block .................................................................................40
14.3 Heating Return Filter ........................................................................41
14.4 Condensate trap ..............................................................................41
14.5 Combustion block ............................................................................42
15 Remplacement of parts .........................................................44
15.1 Hydraulic block .................................................................................46
15.2 Combustion block ............................................................................48
15.3 DHW storage vessel / Expansion vessel .........................................50
15.4 Condensate trap ..............................................................................52
15.5 Control panel ....................................................................................52
16 Technical data .......................................................................54

Installation and servicing instructions strictly reserved for qualified gas installers
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1 Comments on the instructions
Please give all of the instructions to
the user. The user shall keep them for
future reference.
We accept no liability in case of damage
due to the non-compliance of the
instruction manual.
2 Appliance description
2.1 Data label
The data label certifies the origin where
the product was manufactured and the
country for which it is intended.
Warning! The appliance shall only be used
with the gas types indicated on the data
label.
2.2 Mandatory WARNING for EEC
countries
This appliance is designed, approved and
inspected to meet the requirements of the
intended market. The data label indicates
where the product was manufactured and
the country for which it is intended.
This appliance meets the requirements
of Statutory Instrument, No. 3083 The
Appliance (Efficiency) Regulations,
and therefore is deemed to meet the
requirements of Directive 92/42/EEC
on the efficiency requirements for new
hot water appliances fired with liquid or
gaseous fuels.
Type test for purposes of Regulation 5
certified by: Notified body 0063. Product/
production certified by: Notified body
0086.
The CE mark on this appliance shows
compliance with:
Directive 90/396/EEC on the
approximation of the laws of the
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Member States relating to appliances
burning gaseous fuels.
Directive 73/23/EEC on the
harmonisation of the Laws of the
Member States relating to electrical
equipment designed for use within
certain voltage limits.
Directive 89/336/EEC on the
approximation of the Laws of
the Member States relating to
electromagnetic compatibility.
IMPORTANT. With regards to the
Manual Handling Operations, 1992
Regulations, the following lift operations
are recommended as the appliance weight
exceeds a one-man lift.
Clear the route before attempting the
lift.
Ensure safe lifting techniques are used
- keep back straight - bend using legs.
Keep load as close to body as possible.
Do not twist - reposition feet instead.
If two persons performing lift, ensure
co-ordinated movements during lift.
Always use assistance if required.
Manufacturer’s instructions must not be
taken as overriding statutory requirements.
Reference in these instructions to British
standards and statutory regulations/
requirements apply only to the United
Kingdom. For Ireland the current edition of
I.S.813 «Domestic Gas Installations» must
be used.
This appliance certificated to the
current issue of EN 483: 2000 for
performance and safety. It is important
that no alteration is made to the appliance,
without permission, in writing, from
Saunier Duval. Any alteration that is
not approved by Saunier Duval could
invalidate the warranty and could also
infringe the current issue of the Statutory
Requirements.
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2.3 Block diagram
D2
D1

Installation and servicing instructions strictly reserved for qualified gas installers
13
Legend
1 Flue outlet
2 Main heat exchanger
3 Burner
4 Ignition and control electrode
5 Fan
6 Gas control valve
7 DHW storage vessel
8 Condensate drain
9 Overheat safety thermostat
10 Temperature sensor for DHW storage
vessel
11 Expansion vessel
12 Heating return thermistor
13 Heating flow thermistor
14 Ignition module
15 Heating Pump
16 Water pressure sensor
17 Domestic plate to plate heat exchanger
18 Three way valve
19 Domestic expansion vessel
20 Drain cock
21 Flow switch
22 Heating discharge safety valve
23 DHW temperature sensor
24 DHW discharge safety valve
25 Heating isolating valve
26 Filter on cold water inlet
27 Filling system
28 Filter on heating circuit
29 Heating isolating valve
30 Domestic cold water isolating valve
31 Heating isolating valve
32 Gas isolating valve
33 DHW pump
34 Storage anode protection
35 Non return valve
36 Temperature / pressure relief valve
37 Tapping (plug connection) for the
recirculation loop
38 Pressure reducing valve and check
valve
A Heating return
B Cold water inlet
C Heating flow
D Domestic hot water outlet
D1 Discharge from HTG safety valves
D2 Discharge from temp / press and
expansion valve (to tundish)
E Gas
F Cold water supply
3 Appliance location
This appliance is not suitable for
outdoor installation.
This appliance may be installed in any
room, although particular attention is
drawn to the installation of an appliance
in a room containing a bath or shower
where reference must be made to the
relevant requirements. In GB this is the
current I.E.E. WIRING REGULATIONS
and BUILDING REGULATIONS.
In IE reference should be made to the
current edition of I.S.813 «Domestic
Gas Installations» and the current ETCI
rules.
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Make sure you keep an appropriate
distance between the sides of the
appliance to ensure total accessibility
for servicing.
The appliance must be mounted on a
flat wall, which is sufficiently robust to
take its weight.
The appliance is room sealed, so when
it is installed in a room or space, a
permanent air vent is not required.
Do not install the appliance above
another appliance that could damage
it (for example, above a cooker that
might emit steam or grease) or in a
room, which has a lot of dust in the
atmosphere which is corrosive.
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4 Safety instructions and
regulations
This appliance is tested and certificated
for safety and performance. It is, therefore,
important that no alteration is made to the
appliance, without permission, in writing,
from Saunier Duval.
Any alteration not approved by Saunier
Duval, could invalidate the certification,
appliance warranty and may also
infringe the current issue of the statutory
requirements.
4.1 Safety instructions
If the gas pressure at the inlet of the
appliance is outside the range specified,
you shall not start the appliance. If the
cause of the problem cannot be found
nor solved, please contact the Gas Utility
company.
Warning! Incorrect installation can cause
electric shock or appliance damage.
When making the connections, locate
the sealing washers properly so as to
avoid any gas or water leakage.
Never use a wire brush or stiff-bristle
scrubbing brush to clean the heat
exchanger as this could damage the
appliance.
Under no circumstances must the User
interfere with or adjust sealed parts.
Under Section 6 of The Health and
Safety at Work Act 1974, we are required
to provide information on substances
hazardous to health.
The adhesives and sealants used in this
appliance are cured and give no known
hazard in this state.
In the event of the appliance overheating
the safety devices will cause a safety
shutdown. If this happens, call your
installation/servicing company.
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Warning! This appliance must be
earthed. This appliance must be wired in
accordance with these instructions. Any
fault arising from incorrect wiring cannot
be put right under the terms of the Saunier
Duval guarantee.
The following safety instructions must
be imperatively followed during the
maintenance and the replacement of
spare parts.
Stop the appliance (see chapter “Turn
the boiler off” of the Instructions for
use).
Disconnect the appliance from the
mains power supply with the socket or
the double-pole switch (with a minimum
gap of 3mm for both poles).
Turn off the gas control valve.
Close the shut off valves located on the
connection sockets.
Drain the appliance if you want to
change hydraulic parts of the appliance.
Let the appliance cool down before
undertaking any maintenance work.
Protect all the electrical components
from water when you carry out any
work.
Use only new O-rings and gaskets.
After having completed work on gas
components, check their tightness.
When the replacement work is
completed, perform an operation test of
the replaced parts and the appliance.
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Installation and servicing instructions strictly reserved for qualified gas installers
15
4.2 Regulations
When installing and commissioning the
appliance, the regulations below shall be
observed in their current version:
In your own interests and that of safety, it
is the Law that ALL gas appliances must
be installed by a competent person only,
in accordance with the current issue of the
above regulations.
In GB the installation of the appliance
must be carried out by a competent
person as described in the following
regulations:
The manufacturer’s instructions
supplied.
The Gas Safety (Installation and Use)
Regulations.
The appropriate Buildings Regulations
either The Building Regulations, The
Building Regulations (Scotland), The
Building Regulations (Northern Ireland).
The Water Fittings Regulations or
Water byelaws in Scotland.
The Health and Safety at Work Act,
Control of Substances Hazardous to
Health (COSHH).
The Current I.E.E. Wiring Regulations.
Where no specific instructions are given,
reference should be made to the relevant
British Standard Code of Practice.
In IE, the installation must be carried out
by a competent person and installed in
accordance with the current edition of
I.S.813 «Domestic Gas Installations»,
the current Building Regulations and
reference should be made to the current
ETCI rules for Electrical Installation.
In GB the following Codes of Practice
apply: BS4814, BS6798, BS5440 Part 1
and 2, BS5546 Part 1, BS5449, BS6891,
BS6700, BS7074 Part 1 and 2, BS7593,
BS7671.
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In IE: I.S.813, BS5546, BS 5449, BS
7074, BS 7593.
Where no British Standard exists,
materials and equipment should be fit
for their purpose and of suitable quality
and workmanship. The installation of
this appliance must be carried out by
a competent person in accordance
the rules in force in the countries of
destination. Manufacturer’s instructions
must not be taken as overriding statutory
requirements.
If the appliance is to be installed in a
timber frame building it should be fitted
in accordance with the Institute of Gas
Engineers document IGE/UP/7/1998. If
in doubt seek advice from the local gas
undertaking or Saunier Duval.
The installation is subject to building
regulation approval, notify the Local
Authority of intention to install.

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5 Appliance installation
All the dimensions in this chapter are
expressed in mm.
5.1 Recommendations before
mounting
5.1.1 Domestic hot water circuit design
The circuit should be designed to avoid
any unnecessary flow losses (decrease
the number of elbows).
The boiler will operate with a minimum
supply pressure but with a low flow.
Optimum performance will be achieved
with a pressure of 1 bar.
5.1.2 Heating circuit design
ISOTWIN CONDENS boilers can be used
for any kind of installation: serial or
derivated double tube, single tube, hot
floor, etc...
Heating surfaces can be made up with
heaters, convectors or unit heaters.
Warning: If the materials used are of
a different type, some corrosion can
occur. In that case, we advise you to
add an inhibitor to the heating circuit
water (according to the manufacturer’s
recommendations) that could avoid gas
production and oxide formation.
The pipework sections should be fixed by
using the following flow/pressure curve
(see chapter “Heating circuit adjustment”).
The system will be calculated according
to the flow corresponding to the power
that is really required without taking into
account the maximum power that the
boiler can supply. Nevertheless, we advise
you to have a flow big enough so that the
temperature difference between outgoing
and return is under or equal to 20°C. The
minimum flow rate is indicated in the
chapter “Technical Data” at the end of this
instruction manual.
The piping route should be designed in
such a way that it avoids any air locks
and make purging of gas from the system
easier. Bleeders should be placed at each
high point of the system as well as on any
radiators.
Total water volume accepted by the
heating circuit depends, amongst
other things, on the cold static load.
The expansion tank fitted in the boiler
is delivered factory set (see chapter
“Technical Data” at the end of this
instruction manual). At commissioning, it
is possible to change this pressure in case
of a larger static load. We advise you to
provide a drain valve at the lowest point of
the system.
If thermostatic radiator valves are used,
we advised you not to fit in a room where
a room thermostat is fitted.
In case of an old installation, flush the
heating system before installing the
new boiler.
If the boiler is not immediately installed,
protect all the pipe fittings so as to
avoid that any plaster or paint that
could impede the connection.
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Installation and servicing instructions strictly reserved for qualified gas installers
17
5.1.3 Tundish discharge
The internal safety valves, 24 and 36 have
been tee’d together and the discharge
pipe run so that it exits at the right hand
bottom of the boiler (see chapter «Block
diagram»). The tundish (supplied) must
be used with this outlet within the normal
guidelines and code of practice and must
be installed so that it is visible to the
occupants and positioned away from any
electrical devices.
It is necessary, during installation,
to connect a 22 mm diameter metal
discharge pipe to a suitable position
outside the building. It is permissible to
use copper pipe.
Warning! The discharge pipe from the
tundish should terminate in a safe place
where there is no risk to persons in the
vicinity of the discharge, be of metal and:
Be at least one pipe size larger than
the nominal outlet size of the safety
device unless its total equivalent
hydraulic resistance exceeds that of
a straight pipe 9m long i.e. discharge
pipes between 9m and 18m equivalent
resistance length should be at least
larger than the nominal outlet size of
the safety device, between 18m and
27m at least 3 sizes larger, and so on.
Bends must be taken in to account in
calculating the flow resistance.
Have a vertical section of pipe at least
300mm long, below the tundish before
any elbows or bends in the pipework.
Be installed with a continuous fall.
Be positioned away from any electrical
appliances.
Have discharges visible at both the
tundish and the final point of discharge
but where this is not possible or
practically difficult there should be
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clear visibility at one or these of these
locations. Examples of acceptance
discharge arrangements are:
Ideally below a fixed grating and above
the waterseal in a trapped gully.
Downward discharges at a low level;
i.e. up to 100mm above external
surfaces such as car parks, hard
standing, grassed areas etc. are
acceptable providing that where
children may play or otherwise come in
to contact with discharges, a wire cage
or similar guard is positioned to prevent
contact, whilst maintaining visibility.
Discharges at high level; e.g into metal
hopper and metal down pipe with
the end of the discharge pipe clearly
visible (tundish visible or not) or into
a roof capable of withstanding high
temperature discharges of water and
3m from any plastics guttering systems
that would collect such discharges
(tundish visible).
Where a single pipe serves a number
of discharges, such as in blocks of
flats, the number served should be
limited to not more than 6 systems
so that any installation can be
traced reasonably easily. The single
common discharge pipe should be
least one pipe size larger then the
largest individual discharge pipe to
be connected. If unvented hot water
storage systems are installed where
discharges from safety devices may not
be apparent i.e. in dwellings occupied
by blind, infirm or disabled people,
consideration should be given to the
installation of an electronically operated
device to warn when discharge takes
place.
Note: the discharge will consist of scalding
water and steam. Asphalt, roofing felt
and non-metallic rainwater goods may be
damaged by such discharges.
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