Saunier Duval ISOFAST F 28 E User manual

1
Heating and hot water for the professionals
ISOFAST
THIS IS A CAT I2E+ APPLIANCE
01773 828100
IN WARRANTY
TECHNICAL HELPLINE
01773 828400

2
INSTALLATION AND OPERATING INSTRUCTIONS
ISOFAST F 28 E - ISOFAST F 35 E
Note!
The boiler serial number is marked on the label attached to the inside of the drop down door. Refer to the
'Introduction' section page 3 for a description of the basic functions of the boiler. The 'Users' section
describes how to safely operate the boiler.
INSTALLATION SECTION
Introduction.................................................... Page 3
Commissioning..........................................................3
Controls & lighting .................................................... 4
Clock-Instructions for use ........................................ 5
Draining ..................................................................... 5
Servicing/maintenance .......................................... 5
Introduction.................................................. Page 3
Technical data ...................................................... 6
Dimensions ............................................................. 7
Heating system design ......................................... 7
Domestic hot water system design..................... 8
Boiler schematic .................................................... 8
Fixing jig .................................................................. 9
Piping system installation...................................... 9
Boiler location ...................................................... 10
Boiler installation .................................................. 11
Flue installation ............................................. 11 - 12
Electrical installation ........................................... 13
Commissioning.............................................. 14 - 17
Safety devices .............................................. 17 - 18
Settings.................................................................. 19
USERS SECTION
Mandatory warning for CEE countries
Warning: This appliance is designed, approved and inspected to meet the requirements of the English
market. The identification plate located on the inside of the appliance certifies the origin where the
product was manufactured and the country for which it is intended.
If you see any exception to this rule, please contact your nearest Saunier Duval dealer.
Thank you in advance for your assistance.
Routine cleaning and inspection ........................... Page 20 - 21
Replacement of parts ......................................................... 21 - 25
Boiler schematic .......................................................................... 26
Technical data ............................................................................ 27
Schematic wiring diagram ........................................................ 28
Fault finding........................................................................... 29 - 31
Spare parts ................................................................................... 31
SERVICING SECTION

3
INTRODUCTION
The ISOFAST F boiler is a wall mounted modulating
combination boiler with electronic ignition provid-
ing central heating and instantaneous hot water.
The boiler is equipped with a 4 litre domestic hot
water storage vessel that ensures maximum hot
water temperature stability during domestic
demand.
The boiler is of the I2E+ category for use with Natu-
ral Gas (G20) as distributed in the United Kingdom,
or Butane (G30), Propane (G31) or Towns Gas
(G130) with the appropriate conversion kit.
The boiler has a fan assisted balanced flue which
both discharges the products of combustion to and
draws the combustion air from the outside of the
room.
The boiler is suitable for top outlet flue connection
only but, can be fitted with horizontal flue, vertical
flue or twin-pipe flue. Refer to flue catalogue for
further details.
Both the central heating and domestic hot water
temperature are user adjustable from the boiler
control panel.
Domestic hot water demand always has priority
over heating demand.
The boiler is designed for use as part of a sealed
water central heating system with fully pumped
circulation. The pump, expansion vessel and asso-
ciated safety devices are all fitted within the boiler.
The boiler can be installed against either an exter-
nal wall or on an adjacent inside wall, that is, the
flue system will pass directly to the rear or to either
side to the terminal fitted on the outside wall face.
The installation must be carried out by a compe-
tent person in accordance with the relevant re-
quirements of The Building Regulations, The Water
Byelaws, The Building Standards (Scotland) Regu-
lations and any applicable local regulations.
These instructions should be carefully followed for
the safe and economical use of your boiler.
Ancillary equipment
A range of flue accessories are available includ-
ing vertical flues, twin-pipe flues, bends etc.
For further information contact your supplier.
Substances Hazardous to Health
The adhesives and sealants used in this appliance
are cured and give no known hazard in this state.
INSULATION PADS/CERAMIC FIBRE, GLASSYARN,
MINERAL WOOL
These can cause irritation to skin, eyes and the
respiratory tract. If you have a history skin complaint
you may be susceptible to irritation. High dust levels
are usual only if the material is broken.
Normal handing should not cause discomfort, but
follow normal good hygiene and wash your hands
before eating, drinking or going to the toilet.
If you do suffer irritation to the eyes or severe irritation
to the skin, seek medical attention.
Hab 263
COMMISSIONING
Gas safety (Installation and use) Regulations
In your interests and that of gas safety, it is the law
that ALL gas appliances are installed and serviced
by a competent person in accordance with the
above regulations.
Gas leak or fault
If a gas leak or fault exists or is suspected, turn the
boiler off and consult the local gas supply com-
pany or your installation/service company.
Air in the heating system
Persistent air in the heating system may indicate
leaks in the system or corrosion taking place. Call
your Installation/Servicing company.
1-On/Off button
2-Summer/Winter mode selector
3-Hot water temperature adjuster
4-Hot water set point display
5-Graphic display
6-Heating temperature adjuster
7-Heating set point display
8-Display backlight
IO
1.5 bar
mode
0
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
158 7 26 34
Diagram 1
Overheating safety
In the event of a problem, the overheating safety
devices cause safety shutdown of the boiler. If this
happens, call your Installation/Servicing company.
Boiler controls
The control panel, located at the lower front of the
boiler casing, see diagram 1, allows the boiler to
be started, shut down, controlled and monitored
during use.
Flue
Do not obstruct the outside terminal of the boiler.

4
Appuyer sur +ou -pour ajuster la température
maximale souhaitée du circuit chauffage
60
°C
Visualisation de la température demandé
e
Appuyer sur +ou -pour ajuster la température
maximale de l'eau chaude sanitaire (38
° C à 60 ° C)
Visualisation de la température demandée
50
°C
Appuyer sur mode pour sélectionner la position été
1.5 bar
Appuyer sur mode pour sélectionner la position hiver
Température actuelle
dans le circuit chauffage
1.5 bar
10
°C
Apparaît lorsque le brûleur
est en fonctionnement
Apparaît lorsque le
brûleur fonctionne
mode
mode mode
mode
CONTROLS AND LIGHTING
To stop the boiler : Press button (1)
Adjusting the hot water temperature Adjusting the heating temperature
Lighting the boiler :
Make sure that:
●The boiler is connected to the electrical supply.
●The gas service cock is open.
Then follow the instructions below :
Press the On/Off button (1)
Hab 264
1
IO
1.5 bar
mode
0
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1
The pressure must be between 1 and 2 bar. If not, the system must be filled by a competent person.
Setting to the SUMMER position
(Hot water only) Setting to the WINTER position (Heating + hot water)
2
Press the mode button to select the summer symbol Press the mode button to select the winter symbol
The flame symbol appears
when the boiler is running
The actual temperature
of the heating system Illuminates when
the boiler lights
Hab 261
Press + or - to adjust the maximum temperature
of the hot water (38 ° C to 60 ° C) Press + or - to adjust the maximum temperature
of the heating (38 ° C to 87 ° C)
3
To obtain domestic hot water, open a hot water tap. Hot water always has priority over central heating.
Visual indication of set temperature Visual indication of set temperature

5
CLOCK - INSTRUCTIONS FOR USE
The boiler must be conected to the electrical sup-
ply and switched on.
Setting the time
Rotate the clock actuater mechanism clockwise,
by hand, until the current time is indicated by the
arrow, see diagram 2.
Note: The time is set in 24 hour format, for example,
1300 for 1pm.
SERVICING/MAINTENANCE
To ensure the continued efficient and safe opera-
tion of the boiler, it is recommended that it is
checked and serviced at regular intervals.
The frequency of servicing will depend upon the
installation conditions and usage but, in general,
once a year should be enough.
Cleaning
The boiler casing can be cleaned with a damp
cloth followed by a dry cloth to polish.
Do not use abrasive or solvent cleaners.
Boiler casing
CAUTION. Do not remove or adjust the casing in
any way, as incorrect fitting may result in faulty
operation. If in doubt, consult your installation/serv-
ice company.
Setting the programme "On" and "Off" times
●Select the "On" times by pushing the white tap-
pets to the outside, see diagram 2.
●Select the 'Off' times by pushing the white tap-
pets to the inside, see diagram 2.
The clock shown in diagram 2 is set as follows:
ON ➜07.00am to 09.00am (7-9)
OFF ➜09.00am to 4.00pm (9-16)
ON ➜4.00pm to 10.00pm (16-22)
OFF ➜10.00pm to 07.00am (22-7)
Reg 049
Diagram 2 Diagram 3
To override or advance the
clock
The clock has a manual On/
Off switch, see diagram 3,
which operates as follows :
Upper position
Heating On/Off as set by the
tappets.
Middle position
Heating Off continuously
Lower position
Heating On continuously
Reg 050
DRAINING
Protection against freezing
If the boiler is to be out of use for any long periods
during severe weather conditions, it is recom-
mended that the whole system, including the boiler,
be drained to avoid the risk of freezing.
If in doubt, consult your servicing company.
The
ISOFAST has a built in frost protection device
that protects the boiler from freezing. If the boiler is
to be left and there is a risk of frost, ensure that the
gas and electrical supplies are left connected. The
frost protection device will light the boiler when the
temperature of the boiler water falls below 6°C.
When the temperature reaches 16°C, the boiler
stops.
Note: This device works irrespective of any room
thermostat setting and will protect the complete
heating system.
Draining and filling
Caution: The boiler is installed as part of a sealed
system which must only be drained and filled by a
competent person.
Heating safety valve
CAUTION: A heating safety valve with a discharge
pipe is fitted to this boiler.
The valve MUST NOT BE TOUCHED except by a com-
petent person. If the valve discharges at any time,
switch the boiler off and isolate it from the electri-
cal supply. Contact your installation/service com-
pany.
Pressure relief valve
CAUTION: A domestic hot water pressure relief
valve, with a discharge pipe is fitted to this boiler.
The valve MUST NOT BE TOUCHED except by a com-
petent person. If the valve discharges at any time,
switch the boiler off and isolate it from the electri-
cal supply. Contact your installation/service com-
pany.

6
TECHNICAL DATA
Heating output ajustable from ... (kW) 10,4 11,7
to ... (kW) 27,6 34,6
from ... (BTU/H) 35,485 39,920
to ... (BTU/H) 94,170 118,053
Efficiency (%) 82 83
Maximum heating temperature (°C) 87 87
Expansion vessel effective capacity (l) 7 12
Expansion vessel charge pressure (bar) 0,5 0,5
Maximum system capacity at 75°C (l) 160 275
Safety valve,
maximum service pressure (bar) 3 3
Products outlet diameter (mm) 60 60
Fresh air inlet diameter (mm) 100 100
ISOFAST F 28 E
ISOFAST F 35 E
0
10
20
30
40
50
60
120010008006004002000
1
23
45
Pom 010 a
Flow rate through heating system (I/h)
(10 kPa = 1 m WG)
123 4 5
Bypass fully shut
Pump 28 kW
0
10
20
30
40
50
60
70
80
120010008006004002000
1
2
3
4
5
Pom 058
Open 1/4 turn Open 1/2 turn Open 1 turn Open 2 turns
Available pressure (kPa) between
heating supply and return lines
Pump 35 kW
Ø Burner injector (mm) 1,20 1,20
Inlet pressure (mbar) 20 20
Burner pressure (mbar) 13,8 14,1
Gas rate maximum (m3/h) 3,20 3,98
Gas rate minimum (m3/h) 1,32 1,48
Heating
ISOFAST F 28 E
ISOFAST F 35 E
Hot water output
automatically variable from ... (kW) 10,4 11,7
to ... (kW) 27,6 34,6
from ... (BTU/H) 35,485 39,920
to ... (BTU/H) 94,170 118,053
Maximum hot water temperature (°C) 60 60
Specific flow rate (for 30°C temp rise)
(l/min.) 13,2 16,5
Threshold flow rate (l/min.) 1 1
Nominal water flow rate (l/min.) 11,3 16,5
Maximum supply pressure (bar) 8 8
Minimum operating pressure (bar) 0,7 0,7
Hot water
Electrical supply (V) 230 230
Maximum absorbed power (W) 220 220
Level of protection IP44 IP44
Natural Gas (G20)
Flow rate through heating system (I/h)
Available pressure (kPa) between
heating supply and return lines
(10 kPa = 1 m WG)

7
DIMENSIONS
The ISOFAST is delivered in three separate packages:
- the boiler itself
- the fixing jig
- the flue system
7422
Diagram 5
380
X
890
65
234
Weight: 51,2 kg
HEATING SYSTEM DESIGN
●The ISOFAST is compatible with any type of ins-
tallation.
●Heating surfaces may consist of radiators, con-
vectors or fan assisted convectors.
●The ISOFAST can be piped directly to an under-
floor heating system without the need for a mixing
bottle. The maximum central heating flow tem-
perature can be set to 53°C.on the boiler printed
circuit board during commissioning.
●Pipe sectional areas shall be determined in ac-
cordance with normal practices, using the output/
pressure curve (diagram 4). The distribution system
shall be calculated in accordance with the output
requirements of the actual system, not the
maximum output of the boiler. However, provision
shall be made to ensure sufficient flow so that the
temperature difference between the flow and re-
turn pipes be less than or equal to 20°C. The mini-
mum flow is 400 l/h.
●The piping system shall be routed so as to avoid
any air pockets and facilitate permanent venting
of the installation. Bleed fittings must be provided
at every high point of the system and on all radia-
tors.
●The total volume of water permitted for the heat-
ing system depends, amongst other things, on the
static head in the cold condition. The expansion
vessel on the boiler is pressurised at 0,5 bar (corre-
sponding to a static head of 5 m w.g.) and allows
a maximum system volume of 160 litres for an aver-
age temperature of 75°C and a maximum service
pressure of 3 bar. This pressure setting can be modi-
fied at commissioning stage if the static head dif-
fers. An additional expansion vessel can be fitted
to the system if required, see diagram 8.
●Provision shall be made for a drain valve at the
lowest point of the system.
●Where thermostatic radiator valves are fitted, not
all radiators must be fitted with this type of valve,
and in particular, where the room thermostat is in-
stalled.
●In the case of an existing installation, it is ESSEN-
TIAL that the system is thoroughly flushed prior to
installing the new boiler.
Filling the system
The
ISOFAST is supplied with a built-in filliing de-
vice, see diagram 7.
X= 470 ( Isofast F 28 E )
552 (
Isofast F 35 E )

8
●Copper tubing or plastic Hep 20 may be used for
the domestic hot water system. Unnecessary
pressure losses should be avoided.
●A flow restrictor limiting the flow through the boiler
to a maximum of 16 l/min is fitted to the boiler.
●The boiler will operate with a minimum supply
pressure of 0,7 bar, but under reduced flow rate.
Best operating comfort will be obtained from a sup-
ply pressure of 1 bar.
DOMESTIC HOT WATER SYSTEM DESIGN
'Hard Water Areas'
In areas where the water is 'hard', more than
200mg/litre, it is recommended that a proprietary
scale reducer is fitted in the cold water supply to
the boiler.
Shy 120
Diagram 6
BOILER SCHEMATIC
1-Domestic thermistor
2-Three way valve
3-Gas valve
4-Gas valve ignition module
5-Heating element
6-Micro accumulation vessel
7-Burner
8-Ignition electrode
9-Combustion chamber
10 - Micro accumulation vessel thermistor
11 - Main heat exchanger
12 - Air pressure switch
13 - Heating safety valve (3 bar)
14 - Electronic control (PCB)
15 - Domestic water flow sensor
16 - Bypass
17 - Domestic heat exchanger
18 - Pump
19 - Expansion vessel
20 - Heating thermistor
21 - Overheat safety thermostat
22 - Flame sense electrode
23 - Fan
24 - Domestic safety valve
25 - Loss of water sensor
A-Heating return
B-Cold water inlet
C-Heating flow
D-Domestic hot water outlet
E-Gas
AB C DF
23
2
3
4
7
8
9
1
13
14
18
17
15
16
19
20
22
24
11
12
25
21

9
FIXING JIG
C- Heating flow fitting with isolating valve (q),
drain knob (r) and safety valve (s1).
D- Domestic hot water outlet fitting with safety
valve (s2).
F- Gas fitting.
G- Filling device.
Sch 173a
The fixing jig is made up, from left to right, as fol-
lows:
A- Heating return fitting with isolating valve(v) and
drain knob (u).
B- Cold water inlet fitting with isolating valve
(m)and factory fitted flow regulator and filter (not
shown).
Diagram 8
Pla 213
v
AB
m
C
q
D
r
t
GF
u
Diagram 7
PIPING SYSTEM INSTALLATION
●Heating system connections - Pipe diam. 22mm
●Hot water system connections - Pipe diam. 15mm
●Gas connection - Pipe diam. 22mm
●Domestic safety valve connection - Pipe
diam.15mm
●Heating safety valve connection - Pipe diam.
15mm
Water connection
Connect the copper connections supplied, to the
fixing jig fittings, see diagram 7. Connect the sys-
tem pipework to the boiler observing the correct
flow and return format as shown in diagram 8.
Safety valve discharge
Tee the domestic safety valve outlet pipe to the
heating safety valve outlet pipe and extend hori-
zontally to the outside wall.
WARNING. It must not discharge above an en-
trance or window or any type of public access
area.
Connect the safety valve discharge pipe to the
outlets of both the heating safety valve and the
hot water safety valve, the discharge must be ex-
tended using not less than 15 m o.d. pipe, to dis-
charge in a visible position outside the building, fac-
ing downward preferably over a drain.
The pipe must have a continuous fall and be routed
to a position so that any discharge of water, possi-
bly boiling or steam, cannot create any danger to
persons, damage to property or external electri-
cal components and wiring. Tighten all pipe con-
nection joints.
Gas connection
●The supply from the governed gas meter must be
of adequate size to provide a constant inlet work-
ing pressure of 20 mbar (8 in w.g.).
To avoid low gas pressure problems, it is recom-
mended that the gas supply is connected using 22
mm pipe.
●On completion, the gas installation must be
tested using the pressure drop method and purged
in accordance with the current issue of BS6891.
Gas Safety (Installation and use) Regulations
In your interests and that of gas safety, it is the law
that ALL gas appliances are installed and serviced
by a competent person in accordance with the
above regulations.
Flow
control valve Drain point
Filling device
Bypass
valve
Domestic
water
Heating
circuit
Return
Additional
expansion
vessel
(if required)
Boiler
Hot
Cold supply

10
Ins 050b
Clearances
The position of the boiler must be such that there is
adequate space for servicing.
The recommended clearances are:
20 mm either side of the boiler.
600 mm at the front of the boiler.
300 mm below the boiler.
●Place template on wall in required position, mak-
ing allowances for the necessary clearances etc.
Note: It is permissible to install the boiler with smaller
clearances than those quoted above PROVIDING
that adequate consideration is given for Servicing/
Repairs at a later date. If any doubt exists, contact
the Saunier Duval Technical Helpline 01773 828400.
●Mark the position of the holes for the hanging
bracket.
●Drill, plug and fix the hanging bracket to the wall
using suitable screws.
●Check that the hanging bracket is level.
●For horizontal flue system, mark the position for
the flue hole as follows:
Flue to rear of boiler
●Mark correct position of hole from template.
Flue to side of boiler
●Mark the horizontal centre line for the hole on the
rear wall. Extend the horizontal centre line to the
side wall and mark the vertical centre line of flue
hole as shown in diagram 9.
Cutting the flue hole
●Making allowance for the slope of the flue, cut
hole in external wall, preferably using a core drill.
For installations with internal and external access
use a 10 5 mm diameter core drill.
For installations with internal access only use a 125
mm diameter core drill.
Important
When cutting the flue hole and when extending
the flue centre line to a side wall, remember that
the flue system must have a fall of about 35 mm
per metre of flue DOWNWARD towards the termi-
BOILER LOCATION
Diagram 9
nal. There must NEVER be a downward incline to-
wards the boiler.
Terminal position
The minimum acceptable spacings from the ter-
minal to obstructions and ventilation openings are
shown in diagram 10.
The boiler must be installed so that the terminal is
exposed to the external air.
Should any doubt exist as to the permissible posi-
tion of the terminal, contact the Saunier Duval
Technical Helpline 01773 828400.
Terminal guard
If a terminal guard is required, a suitable guard can
be obtained from your supplier, Saunier Duval part
number 85373.
Cupboard or compartment ventilation
The boiler can be fitted in a cupboard or compart-
ment without the need for permanent ventilation.
Minimum dimensions (in mm) for the positioning of flue terminals
A-Under a window .................................................... 300
B-Under an air vent .................................................. 300
C-Under a gutter ......................................................... 75
D-Under a balcony ................................................... 300
E-From an adjacent window .................................. 300
F-From an adjacent air vent ................................... 300
G-From vertical or horizontal air pipes.................... 300
H-From an external corner of the building ............ 300
I-From an internal corner of the building ............. 300
L-From the ground or from another floor .............. 300
M- Between two terminals vertically ...................... 1500
N-Between two terminals horizontally .................... 600
Ven 060b
NC
D
M
AB
EF
G
IHL
Diagram 10

11
ee a
a
X
X
∆L1
∆L2
∆L1
∆L2
BOILER INSTALLATION
Statutory requirements
The installation of this boiler must be carried out by
a competent person in accordance with the rel-
evant requirements of the current issue of:
The Gas Safety (Installation and Use) Regulations
The Building Regulations
The local water company Byelaws
The Building Standards Regulations (Scotland)
The Health and Safety at Work Act
Sheet metal parts
WARNING. When installing or servicing this boiler,
care should be taken when handling the edges of
sheet metal parts to avoid the possibility of personal
injury.
Installing the boiler
Prior to starting work, the system must be thoroughly
flushed using a propriety cleanser such as Sentinel
X300 to eliminate any foreign matter and contami-
nation e.g. metal filings, solder particles, oil, grease
etc.
Note. Solvent products could cause damage to the
system.
●Engage boiler upper part onto the hanging
bracket.
●Fit the washers between the boiler pipes and the
inlet and outlet fittings on the fixing jig and con-
nect the various couplings between the boiler and
jig.
FLUE INSTALLATION
Top outlet flue - kit 85090
The boiler is only suitable for top outlet flue con-
nection.
Calculation of flue cutting lengths
●Measure wall thickness e (mm), see diagram 11.
●For side flues, measure distance from inside face
of side wall to centre line of boiler and subtract 235
to get dimension a (mm).
●Refer to table 2 for cutting lengths of both inner
and outer flue pipes for each of the various flue
options available.
Important: All flue cutting lengths must be meas-
ured from the terminal end of the flue pipes, see
diagram 12.
When the dimension X measured on site is greater
than that given in table 2, a flue extension kit will
be required, refer to table 3 for details.
Extended flue
The horizontal flue is extended by using one or more
of the 1000 mm extension pipes, Saunier Duval part
number 85091. These are connected together by
push fit type joints, clamps and seals.
Calculation of flue cutting lengths for extended flue
●Using the correct number of extension kits as ta-
ble 3, measure dimensions a and e, see diagram
12. Cut both the inner and outer pipes to the di-
mensions given in table 4
Important: All cutting lengths should be measured
from the push fit joint end of the extension pipe.
Do not leave any burrs or sharp edges on the cut
ends of the pipes.
Table 2
Flue cutting lengths
Cutting length (mm)
Flue option outer pipe inner pipe Comments
Rear flue e + 160 e + 244 maximum
wall thickness 'e'
without
extension 756 mm
side flue e + a + 145 e + a + 229 maximum
(left or right) distance 'x'
without
extension 990 mm
Table 3
Number of extension kits required
Flue option Dimension 'X' No. of
extension kits
Side flue 991 to 1991 mm 1
(left or right) 1991 to 2991 mm 2
Hab 210/30a
Diagram 11
Ven 089
Diagram 12
Cutting length
Outer pipe
Inner pipe
Cutting length
Note: Maximum flue length for 35kW model is 2 metres

12
FLUE INSTALLATION
Installation of flue assembly
●Fit rubber sealing collar (A), see diagram 13, into
groove at the outer end of pipe (B).
●Fit outer pipe (B) into wall with groove to the out-
side.
●Pull pipe inwards to bring rubber sealing collar
hard up against external wall, see diagram 14.
●Fit internal plastic flange (C) onto outer pipe. Push
along the pipe until engaged against internal wall.
●From inside, insert inner pipe (D) into outer pipe.
●Fit both ‘O’ rings (E) into the flue elbow (F), one
at the inlet, one at the outlet. By necessity, they
are a loose fit, apply a small amount of silicone
grease to each ‘O’ ring when fitting.
●Slacken the two screws and fit the clamp and
seal (G) onto the elbow.
●Take hold of the inner flue and push gently onto
the elbow outlet taking care not to tear the ‘O’
ring.
Important: If the flue has been cut, ensure that there
are no burrs that could damage the ‘O’ ring.
●Push the elbow clamp and seal over the outer
flue.
●For flue systems less than 1,5 m long, leave the
restrictor (a) fitted in the fan outlet, see diagram
15.
The standard flue kit 85090, see diag. 13, comprises :
- External rubber sealing collar ............................... A
- Outer pipe ................................................................ B
- Plastic flange ........................................................... C
- Inner pipe ................................................................. D
- 2 ‘O’ rings ................................................................. E
- Elbow ........................................................................ F
- Clamp and seal ...................................................... G
- Gasket ......................................................................H
- Four screws ............................................................... I
●Remove the backing from the self adhesive gas-
ket (H) and carefully fit gasket to base of flue el-
bow.
●Fit elbow onto boiler and secure with the four
screws (I).
Concentric flue system
The maximum permissible length (L) for the concentric flue system is 3,5 m (F 28 E) or 2 m (F 35 E). For flue
systems up to 1,5 m length, the restrictor (a) supplied fitted to the boiler, inside the fan outlet, must be left
in place. For longer flue systems, the restrictor must be removed.
For each 90°flue elbow used, (or two 45°elbows) the maximum permissible length (L) must be reduced
by 1 metre.
Table 4
Flue extension cutting lengths
Cutting length
Flue option outer pipe inner pipe Comments
Side flue e + a -755 e + a - 755 maximum
(left or right) dimension 'X'
without
extension 990 mm
Pho 088
A C G
I
E
H
D
B
F
Pho 087
Diagram 14
Diagram 13
Hab 249a
Diagram 15
L
a
Gasket

13
Ins 060
Diagram 16
The boiler is supplied with a mains lead at-
tached. Connect this to the electrical supply.
Sch 171
E
Sch 172
°C
E E
Without room
thermostat
With voltage free room
thermostat
Diagram 17
ELECTRICAL CONNECTION
Warning. This boiler must be earthed
All system components must be of an approved
type.
Connection of the whole electrical system and any
heating system controls to the electrical supply must
be through a common isolator.
Isolation should preferably be by a double pole
switched fused spur box having a minimum con-
tact separation of 3 mm on each pole. The fused
spur box should be readily accessible and prefer-
ably adjacent to the boiler. It should be identified
as to its use.
A fused three pin plug and shuttered socket outlet
may be used instead of a fused spur box provided
that:
a) They are not used in a room containing a fixed
bath or shower.
b) Both the plug and socket comply with the cur-
rent issue of BS1363.
The mains electrical supply must be maintained at
all times in order to provide domestic hot water.
Do not interrupt the mains supply with a time switch
or programmer.
WARNING: ON NO ACCOUNT MUST ANY EXTERNAL
VOLTAGE BE APPLIED TO ANY OF THE TERMINALS ON
THE HEATING CONTROLS CONNECTION PLUG.
Warning: This appliance must be wired in accord-
ance with these instructions. Any fault arising from
incorrect wiring cannot be put right under the terms
of the Saunier Duval guarantee.
External controls
The ISOFAST boiler is designed to operate at maxi-
mum efficiency at all times, but will be most effi-
cient and economical when connected to a room
thermostat.
A suitable room thermostat is available as an ac-
cessory, Saunier Duval part number 40011. Please
contact your supplier.
The boiler will work for heating without a room ther-
mostat being connected provided that the wire
link fitted between the two terminals of the con-
nector (E) is left in place, see diagram 17.
Alternatively, a 230V room thermostat can be used
but do not make any connection to the compen-
sating resistor, see diagram 17.
ON NO ACCOUNT must any electrical voltage be
applied to any of the terminals of the external con-
trols plug.
Note: For further information, see the building
regulations 1991 - Conservation of Fuel and Power
- 1995 edition - appendix G, Table 4b.
Do not use
Leave link in place for no external controls.

14
2
3
Undo cap
on auto-
matic air
vent on
top of
pump and
leave un-
done.
Open the boiler isolating valves (vand q), the slot of the screw
corresponds to flow direction.
Fully open valve mby unscrewing anti-clockwise.
➜
➜
v m q
COMMISSIONING
Reg 018
Diagram 18
The commissioning and first firing of the boiler must
only be done by a competent person.
Gas installation
It is recommended that any air is purged from the
supply at the gas inlet test point on the gas valve,
see diagram 18.
Filling the system
4
➜
t
IO
mode
0
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
0.0 bar
The display will indicate 0 bar pressure in the system
The warning light will illuminate
Hab 265
1Press the mains 'On/Off' button
1
1.5 bar
mo
d
The pressure must be between 1 and 2 bar
Hab 265
Open the tap (t) on the filling device and fill the system until the pressure indicated on the display
is between 1 and 2 bar.
Pla 213
Pla 213
Reg 008

15
COMMISSIONING
Make sure the display indicates a system pressure of between 1 and 2 bar. Re-fill system as
necessary.
IO
1.5 bar
mode
0
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
The pressure must be between 1 and 2 bar
Hab 265
8
5 76
➜
➜
Bleed each radiator to re-
move the air, re-tighten
bleed screws.
Open various hot
water taps to bleed
system.
Leave the cap on the
pump auto air vent open.
Reg 008
Ins 061
Ins 062

16
COMMISSIONING
To stop the boiler : Press button (1)
Make sure that:
●The boiler is connected to the electrical supply.
●The gas service cock is open.
Then follow the instructions below :
Press the On/Off button (1)
Hab 264
1
IO
1.5 bar
mode
0
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
The pressure must be between 1 and 2 bar. If not, the system must be filled by a competent person.
Appuyer sur +ou -pour ajuster la température
maximale souhaitée du circuit chauffage
60
°C
Visualisation de la température demandé
e
Appuyer sur mode pour sélectionner la position hiver
Température actuelle
dans le circuit chauffage
1.5 bar
10
°C
Apparaît lorsque le
brûleur fonctionne
mode
mode
Adjusting the heating temperature
Setting to the WINTER position
(Heating + hot water)
The actual temperature
of the heating system Illuminates when
the boiler lights
Hab 261
Press + or - to adjust the maximum temperature
of the heating (38 ° C to 87 ° C)
Visual indication of set temperature
Lighting the boiler :
Press the mode button to select the winter symbol
1
3
2
●Adjust heating temperature to maximum .
●Check that any external controls, if fitted, are
calling for heat (set room thermostat to maximum).
●Allow the temperature to rise to the maximum
value, with all radiator valves open. The tempera-
ture rise will cause release of the gases contained
in the water of the central heating system.
●Gases driven towards the boiler will be automati-
cally released through the automatic air vent.
●The gases trapped at the highest point of the sys-
tem must be released by bleeding the radiators.
On reaching maximum temperature, the boiler
should be turned off and the system drained as
rapidly as possible whilst still hot.
●Refill system to a pressure of between 1 and 2
bar and vent as before.
●Restart boiler and operate until a maximum tem-
perature is reached. Shut down boiler and vent
heating system. If necessary, top up heating sys-
tem and make sure that a pressure of 1 bar is indi-
cated when system is COLD.

17
COMMISSIONING
Setting the heating output
The heating output can be set without the use of a
pressure gauge; proceed as follows:
●Press the display light button
and keep pressed for 5 seconds, see diagram 20.
Note:The boiler has now been put into 'Service
Mode', allowing certain adjustments to be made
and diagnostic fault codes to be displayed. Refer
to the 'Servicing Instructions' for further details.
The heating output, in kW, is shown on the left hand
side of the display, see diagram 21.
●Remove the blanking plug from the front of the
control panel to gain access to the heating ad-
justing screw.
●Adjust the heating output by turning the screw
clockwise to increase, anti-clockwise to decrease.
●Refit blanking plug.
Note: Adjustment of the heating output does not
affect the domestic hot water output.
For kW to Btu/hr conversion refer to table 5.
Setting the heating output
20 01
5 s
1
2
mode
Reg 051/UK
Setting the heating output
Reg 052
Adjustment screw
The heating output, in kW,
is shown on the display.
Diagram 21
Diagram 22
Diagram 20
Table 5
kW to Btu/hr conversion
kW Btu/hr
10 34,120
12 40,940
14 47,770
16 54,590
18 61,420
kW Btu/hr
20 68,240
22 75,060
24 81,890
26 88,710
28 95,540
Setting the maximum heating temperature
The maximum heating temperature can be preset
at commissioning stage to suit the type of heating
system.
For example, for use with underfloor heating, the
maximum heating temperature can be set to 53°C.
To adjust the maximum temperature, proceed as
follows:
●Remove the blanking plug (b) from the rear of
the control panel to gain acess to selector switch
SW1 (see diagram 22).
Adjust toggles 1and 2 to give the desired maxi-
mum heating temperature, see diagram
Note: To adjust the maximum heating temperature
it is only necessary to change toggles 1 and 2. Do
NOT touch any other toggles.
●Refit blanking plug.
b
➦
Reg 053
SAFETYDEVICES
The ISOFAST incorporates a visual display that indi-
cates fault conditions, should they occur.
In the event of a fault, the diplay will indicate, by
means of pictograms and/or letters and numbers,
exactly in which area the fault lies.
Should the boiler fail to operate during Commis-
sioning, the most likely fault is that the gas supply
to the boiler has not been turned on or purged suf-
ficiently or that there is no pressure in the heating
system. These are indicated as follows :
1234567
O
N
SW1
1=ON, 2=ON ➜53°C. Maximum.
1=OFF, 2=OFF ➜73°C. Maximum.
1=OFF, 2=ON ➜87°C. Maximum.
Factory setting ➜ 73°C.
kW Btu/hr
30 102,360
32 109,180
34 116,000
35 119,420

18
SAFETYDEVICES
No gas supply This will be indicated
on the display as a
pictogram of a spark.
To rectify this, pro-
ceed as follows:
●Switch off the boiler at the On/
Off push button.
●Rectify the gas supply problem.
●Restart the boiler by pressing the
On/Off button.
--------------------------
Insufficient system pressure This will be indicated
on the display as a
flashing warning indi-
cating the system
pressure is low.
To rectify this the system must be re-filled, refer to
'Commissioning'.
--------------------------
Other faults
These are indicated on the display by a fault code
and a telephone symbol. Further information on the
fault codes can be found in the 'Servicing Instruc-
tions'.
General safety devices
Air flow rate safety device
If an obstruction, even partial, of the flue occurs,
for any reason whatsoever, the built in safety sys-
tem of the boiler will turn the boiler OFF and the
fan will continue to run.
The boiler will be ready to operate when the fault
has been cleared.
Overheat safety
In case of boiler overheating, the overheat ther-
mostat will turn the boiler off. The thermostat, lo-
cated on the heat exchanger flow pipe, will need
to be manually reset.
In case of power supply failure
The boiler no longer operates.
As soon as power supply is restored, the boiler will
be automatically restarted.
Frost protection
The ISOFAST has a built in frost protection device
that protects the boiler from freezing. If the boiler is
to be left and there is a risk of frost, ensure that the
gas and electrical supplies are left connected. The
frost protection device will light the boiler when the
temperature of the boiler water falls below 6°C.
When the temperature reaches 16°C, the boiler
stops.
Note : This device works irrespective of any room
thermostat setting and will protect the complete
heating system.
➜
IO
1
0.3 bar

19
SETTINGS
Gas valve setting
All boilers are tested and factory set during manu-
facture. Should it be necessary to reset a gas valve,
for example, after replacement, proceed as fol-
lows:
●Shut down boiler.
Minimum setting
●Remove one electrical connector from the
modulating gas valve coil, see diagram 23.
●Connect a suitable pressure gauge.
●Turn the OFF/Summer/Winter switch to the ‘Sum-
mer’ position.
●Turn the domestic hot water temperature adjuster
to maximum setting.
●Remove the protective cover from the gas valve
adjuster.
●Turn nut ‘A’, see diagram 23:
CLOCKWISE: To increase the pressure.
ANTICLOCKWISE: To decrease the pressure.
Maximum setting
●Reconnect the electrical connector removed
from the modulating gas valve coil.
●Remove the protective cover from the gas valve
adjuster.
●Turn nut ‘B’, see diagram 23:
CLOCKWISE: To increase the pressure.
ANTICLOCKWISE: To decrease the pressure.
After adjustment, refit the cover to the gas valve
adjuster.
Bypass
The ISOFAST has a built-in bypass. This must be ad-
justed according to the requirements of the system,
refer to the flow rate pressure curve (diagram 4).
The boiler is supplied with the built-in bypass open
a half a turn. It is adjusted by turning the bypass
screw (a), see diagram 24. Turn the screw clock-
wise to close the bypass.When using thermostatic
radiator valves (TRV’s) on all of the radiators, it is
essential that a separate, adjustable bypass of 15
mm minimum diameter is fitted between the flow
and return of the heating circuit, see diagram 8.
Any bypass must be fitted before system controls.
MODULATING COIL
Diagram 23
Reg 020
a
Diagram 24
Reg 054

20
ROUTINE CLEANING AND INSPECTION
To ensure the continued efficient and safe opera-
tion of the boiler it is recommended that it is
checked and serviced at regular intervals. The fre-
quency of servicing will depend upon the particu-
lar installation conditions and usage, but in gen-
eral once a year should be enough.
It is the law that any servicing is carried out by a
competent person.
Service Check and Preparation.
• Operate boiler and check for any faults that need
to be put right.
• Isolate boiler from the gas and electrical supplies.
• On completion check all gas carrying parts for
soundness with leak detection fluid.
• Remove boiler casing as follows:
Upper front panel
• Remove the two front panel retaining brackets
from the top of the boiler.
• Remove panel by lifting up and forward.
Sealed chamber cover
• Unclip two toggle clips holding the sealed cham-
ber cover, see diagram. 1.
• Lift cover up and off boiler.
Front control panel
• Lift control panel up and lower forwards to gain
access to lower part of boiler.
Side panels
• Unscrew and remove the four screws securing
lower grille onto boiler. Unhook grille from rear of
boiler and remove.
• Remove three screws from front of each side panel.
• Unclip the toggle clips securing top of each panel.
Lift each panel up and then forward to remove.
Combustion chamber cover
• Unclip two toggle clips and unscrew two screws
securing combustion chamber cover to combus-
tion chamber, see diagram 2.
• Remove combustion chamber cover from boiler.
• Undo, but do not remove, two burner support screws
at rear of burner chamber.
Burner
• Undo main gas supply nut from burner.
• Pull off the ignition and flame sense leads from the
gas valve remove burner from boiler by lifting up and
pulling forwards from keyhole slots.
Note: The washer between main burner and main
burner gas supply must be kept for use on
reassembly.
• Remove ignition and flame sense electrodes from
burner.
• Unscrew and remove injector bar retaining
screws and separate injector bar from burner.
• Examine and clean injectors as necessary.
Note: DO NOT use a wire or sharp instrument on
the holes.
Clean burner by washing in soapy water. Dry thor-
oughly before re-fitting.
Diagram 1
Car 025
Diagram 2
Ech 041
Heat exchanger
• Disconnect power supply leads and earth lead
from fan.
• Unscrew and remove, two fan retaining screws
at front edge of fan mounting plate.
• Remove fan with mounting plate attached by
pulling forwards out of boiler.
• Remove air pressure switch sensing tube from
sensing probe on flue hood.
• Unscrew and remove screws securing flue hood
to rear panel.
• Withdraw flue hood from boiler.
• Examine heat exchanger for any blockages or
build up of deposits.
• Clean heat exchanger with soft brush or vacuum
cleaner. Do not use any tool likely to damage
painted finish of heat exchanger.
Reassembly of parts removed for servicing
All parts are replaced in reverse order to removal.
➜
➜