Buderus 800 User manual

Users manual Wall-mounted
condensing gas boiler
Buderus 800 - 24/29/43/60 and
Buderus 800 - 24T25/29T25 H/V
7212 3900 (03/2010) GB
For the user
Please read thoroughly
before operating the unit

Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
2
Subject to technical modifications !
Constant development efforts may result in minor deviations in
illustrations, functional steps and technical data.
Updating the documentation
If you have suggestions for improvement or have found
discrepancies, please do not hesitate to contact us.
Contents
1 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
1.1 Dimensions, connections and assembly . . . . . . . . .6
1.2 Boiler assembly - exploded view. . . . . . . . . . . . . . .8
1.3 Flue Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . .9
1.4 Items supplied with unit. . . . . . . . . . . . . . . . . . . . .11
1.5 Gas boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
1.6 Water circulation system. . . . . . . . . . . . . . . . . . . .12
1.7 Pipe connections. . . . . . . . . . . . . . . . . . . . . . . . . .12
1.8 Flue installation . . . . . . . . . . . . . . . . . . . . . . . . . . .15
1.9 Electrical connections . . . . . . . . . . . . . . . . . . . . . .18
2 Initial start-up . . . . . . . . . . . . . . . . . . . . . . . . . . .23
2.1 Preparing the boiler for operation . . . . . . . . . . . . .23
2.2 Start-up work. . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
3 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
3.1 Preparing the heating boiler for inspection . . . . . .34
3.2 Checking for internal leaks . . . . . . . . . . . . . . . . . .34
3.3 Visual inspection . . . . . . . . . . . . . . . . . . . . . . . . . .34
4 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
4.1 Cleaning the heat exchanger, burner and syphon 35
5 Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
5.1 Operating codes . . . . . . . . . . . . . . . . . . . . . . . . . .39
5.2 Fault codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
5.3 Checking and replacing parts . . . . . . . . . . . . . . . .48
6 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
6.1 Technical data. . . . . . . . . . . . . . . . . . . . . . . . . . . .63
6.2 Residual pump lift for wall-hung gas boilers . . . . .65
6.3 Short list of spare parts . . . . . . . . . . . . . . . . . . . . .66
7 Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
7.1 Start-up report. . . . . . . . . . . . . . . . . . . . . . . . . . . .67
7.2 Inspection and service reports . . . . . . . . . . . . . . .68
The boiler meets the basic requirements of the
appropriate standards and directives.
Conformity has been substantiated by the
proper documents which - together with the
declaration
of conformity - are filed with the manufacturer.

Preface
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 3
Preface
These installation and servicing instructions apply to:
Buderus wall-mounted condensing gas boilers
800 – 24/29/43/60 and 800 – 24T25/29T25 H/V.
Model B23, B33, C13, C33, C43, C53 and C73
800 – 24/29/43: Category GB II2H3P 20 mbar; 37 mbar
(natural gas Hand LPG)
In this document LPG = 3P-G31-37 mbar
800 – 60: Category GB I2H 20 mbar
(natural gas H)
Power rating: 230 VAC, 50 Hz, IP4X
Fuse rating: 1.25 slow blow
G. C. Aplliance No. :
Buderus 800 – 24 41-110-19
Buderus 800 – 29 41-110-20
Buderus 800 – 24 T25/V
Buderus 800 – 29 T25/V
Buderus 800 – 24 T25/H
Buderus 800 – 29 T25/H
Buderus 800 – 43 41-110-14
Buderus 800 – 60 41-110-15
Important general instructions for use
Only use the boiler in accordance with its designated
use and the installation and servicing instructions.
Servicing and repair must be carried out by Gas Safe
registered installer. Only use the boiler in combinations
and with the accessories and spare parts indicated in
the installation and servicing instructions. Other
combinations, accessories and consumables may only
be used if they are expressly provided for the designated
use and if system performance and safety are not
affected in any way.
The boiler is suitable for connection to fully pumped,
sealed water systems ONLY. Adequate arrangements
for completely draining the system by provision of
draining valves must be provided in the installation
pipework.
Pipework from the boiler is routed downwards as
standard, but may be routed upwards behind the boiler
using the distance frame (supplied in a seperate kit).
Subject to technical modifications.
As a result of our policy of constant development, there
may be small differences between illustrations,
functional steps and technical data.
BENCHMARK' Log Book
All Buderus gas fired boilers now include an installation,
commissioning and service record log book. The details
of the log book will be required in the event of any
warranty work being requested. Please complete the
appropriate sections on completion of the installation
and commissioning.
REMEMBER: Please hand the log book back to the
user.
Regulations and directives
It is law that all gas appliances are installed and serviced
by a Gas Safe registered installer in accordance with the
regulations. Failure to install appliances correctly could
lead to prosecution. It is in your own interest, and that of
safety, to ensure the law is complied with.
The installation of the boiler MUST be in accordance
with the latest I.E.E. (BS7671) Wiring Regulations, local
building
regulations, water regulations, the building regulations
and the Building Standard (Scotland) and any relevant
requirements of the local authority.
Detailed recommendations are contained in the
following British Standard Codes of Practice:
BS. 5440:1 Flues (for gas appliances of rated input
not exceeding 70 kW).
BS. 5440:2 Ventilation (for gas appliances of rated
input not exceeding 70 kW).
BS. 5449 Forced circulation hot water systems.
BS. 5546 Installation of gas hot water supplies for
domestic purposes (2nd. family Gases).
BS. 6798 Installation of gas fired hot water boilers
of rated input not exceeding 60 kW.
BS. 6891 Low pressure installation pipes.
IGE/UP/1b Tightness testing and purging domestic
sized gas installations.
Health and & Safety Document No. 635.
The Electricity at Work Regulations, 1989.
The manufacturer's notes must not be taken, in any way,
as overriding statutory obligations.
The design and construction of the Buderus wall-
mounted condensing gas boilers 800 – 24/29/43/60 and
800 – 24T25 /29T25 conforms to the basic
specifications listed in the European directive governing
gas-fired appliances 90/396/EEC, and with respect to
EN 625, EN 483 and EN 677.

Preface
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
4
Timber Framed Buildings
If the boiler is to be fitted in a timber framed building it
should be fitted in accordance with the Institute of Gas
Engineering document IGE/UP/7:1998.
Bathroom Installations
This appliance is rated IP4X.
The boiler may be installed in any room or internal
space, although particular attention is drawn to the
requirements of the current IEE (BS. 7671) Wiring
Regulations and, in Scotland, the electrical provisions of
the building regulations applicable in Scotland, with
respect to the installation of the boiler in a room or
internal space containing a bath or shower.
If the appliance is to be installed in a room containing a
bath or shower then, providing water jets are not going
to be used for cleaning purposes (as in communal
baths/showers), the appliance can be installed in Zone
3, as detailed in BS. 7671.
Compartment Installations
A compartment used to enclose the boiler should be
designed and constructed especially for this purpose.
An existing cupboard or compartment may be used,
provided that it is modified for the purpose.
In both cases, details of essential features of cupboard/
compartment design, including airing cupboard
installation, are to conform to the following:
BS 6798 (No cupboard ventilation is required - see 'Air
Supply' for details).
It is not necessary to have a porpose-provided air vent
in the room or internal space in which the boiler is
installed. Neither is it necessary to ventilate a cupboard
or compartment in which the boiler is installed, due to
the low surface temperatures of the boiler casing during
operation; therefore the requirements of BS 6798, Clause
12, and BS 5440:2 may be disregarded.
The position selected for installation MUST allow
adequate space for servicing in front of the boiler.
For the minimum clearances required for safety and
subsequent service, see the wall mounting template.
In addition, sufficient space may be required to allow
lifting access to the wall mounting plate.
Wall-mounted condensing gas boilers must only be
operated with the combustion air/flue gas systems
especially devised and authorised for this type of boiler.
Observe the relevant standards, regulations and
legislation of the country of final use.
NOTE
Observe the corresponding technical rules
and the building supervisory and statutory
regulations when installing and operating
the system.
WARNING!
Keep the burner-control unit housing
CLOSED when working on water-bearing
components.
NOTE
It is mandatory to clean and service the
system once a year. This includes an
inspection of the entire system to see if it is
in full working order. Defects and faults
must be eliminated immediately.
NOTE
When instructions aren’t followed, warranty
expires.
CAUTION
Use this device for its intended purpose
only.

Preface
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 5
DANGER!
Notes relating to the heating system water.
Thoroughly flush the system before it is
filled with water. Use only untreated water
or water treatment product such as Sentinal
X100 to fill and top up the system.
When using water treatment, only products
suitable for use with Buderus heat
exchangers are permitted (eg Sentinel
X100). Your warranty is at risk if an
incorrect water treatment product is used in
conjunction with this appliance. For more
information, contact Buderus Product
Support Department.
It is most important that the correct
concentration of the watertreatment product
is maintained in accordance with the
manufacturer's instructions.
If the boiler is used in an existing system
any unsuitable additives MUST be removed
by thorough cleaning. BS.7593:1992 details
the steps necessary to clean a domestic
central heating system.
In hard water areas, treatment to prevent
lime scale may be necessary - however, the
use of artificially softened water is NOT
permitted.
Under no circumstances should the boiler
be fired before the system has been
thoroughly flushed.
Do not use water softened in a salt
bedding exchanger.
Do not use inhibitors, anti-freeze or
other additives.
The expansion vessel must be of
sufficient size.
When oxygen-permeable pipes are used
(e. g. for floor heating systems) the system
must be separated by means of heat
exchangers. Unsuitable heating water
promotes sludge formation and corrosion.
This may cause malfunctions and damage
in the heat exchanger.
NOTE:
Notes relating to domestic hot water.
The domestic hot water service must
be in accordance with BS 5546 and BS
6700.
The boilers are suitable for connection
to most types of washing machine and
dishwasher appliances.
When connecting to suitable showers,
ensure that:
a. The cold inlet to the boiler is fitted with
an approved anti-vacuum or syphon
non-return valve.
b. Hot and cold water supplies to the
shower are of equal pressure.
Where the water hardness exceeds
150 mg/litre, it is recommended that a
proprietary scale reducing device is
fitted into the boiler cold supply with
the requirements of the local water
company.
CAUTION
Provision must be made to accomodate
the expansion of DHW contained within
the appliance, if a non-return valve is fitted
to the DHW inlet, as detailed in
BS. 6798: 5.4.3.

Installation1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
6
1 Installation
1.1 Dimensions, connections and
assembly
800 - 24T25V / 800 - 29T25V 800 - 24 / 800 - 29
800 - 43 / 800 - 60
CH flow
CH return
CWDO
GAS
CH flow
CH return
CWDO
GAS
CH flow
CH return
CWDO
GAS
DHW warm
DHW cold
1250 mm (49 ")
15
55 mm (2 ")
17
152 mm
(6")
152 mm
(6")
560 mm (22")
335 mm (13 ")
17
55 mm (2 ")
17
46 (1 ")
45
46 (1 ")
45
30 (1 ")
15
30 (1 ")
15
431 mm (17")
431 mm (17")
55
17
(2 ")
75
(3")
75
(3")
150
(6")
150
(6")
55
17
(2 ")
75
(3")
4 x 75 (3")
150
(6")
152 mm
(6")
46 (1 ")
45
30 (1 ")
15
431 mm (17")
75
(3")
55
17
(2 ")
323 209
(8 ")
14
(12 ")
4
3
335 mm
(13 ")
17
115 mm
(4 ")
12
900 mm (35 ")
12
(7 ")
12
190
(7 ")
12
190
(26 ")
15
665 mm
685 mm (27")
685 mm (27")
(7 ")
12
190
420 mm
12
(16 ")
420 mm
12
(16 ")
420 mm
12
(16 ")
560 mm (22")
335 mm (13 ")
17
DHW warm out = hot water outlet 15 mm dia.
DHW cold in = cold water inlet 15 mm dia.
GAS = gas connection R½ (800 - 24/29/43)
and (800 - 24T25V/29T25V)
gas connection R¾ (800 - 60)
CH return = boiler return line 28 mm dia.
CH flow = boiler flow line 28 mm dia.
CWDO = condensate water drain 32 mm dia.

Installation 1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 7
800 - 24T25H / 800 - 29T25H
(7 ")
12
190
685 mm (27")
420 mm
12
(16 ")
75
(3")
40 (1 ")
12
30 (1 ")
15
431 mm (17")
75
(3")
55
17
(2 ")
335 mm
(13 ")
17
115 mm
(4 ")
12
900 mm (35 ")
12
75
(3")
300
(11 ")
5
4
152 mm
(6")
CH flow
CH return
CWDO
GAS
DHW warm
DHW cold
DHW warm
out
= hot water outlet 15 mm dia.
DHW cold in = cold water inlet 15 mm dia.
GAS = gas connection R½ (800 - 24T25H/29T25H)
CH return = boiler return line 28 mm dia.
CH flow = boiler flow line 28 mm dia.
CWDO = condensate water drain 32 mm dia.
Minimum side clearance required for all boilers is 100 mm (4")

Installation1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
8
1.2 Boiler assembly - exploded view
Single unit (type 800 – 24 / 800 – 29)
Legend
10 Casing complete
20 Door
30 Casing clamp
40 Casing seal
50 Back panel
60 Mounting bracket
70 Seal lid for air vent
80 Heat exchanger
90 Revision set for air vent
100 Seal
110 Sight glas complete with
sealing rings
120 Restriction plate
130 Seal for condensate collector
140 Condensate collector incl. seal
150 Sensor complete with O-ring
160 Mounting clip
170 Seal for hot surface ignitor/
ionisation electrode
180 Hot surface ignitor
190 Ionisation electrode with cable and
connector
200 Safety sensor-ntc complete
210 Flue gas collector
220 Lip ring seal DN 80mm
230 Condensate by-pass
240 Syphon complete
260 Safety valve pipe
270 Seal set for syphon
280 Burner housing
290 Burner thermostat 107 °C
300 Burner seal
310 Gas/air distribution plate
320 Secondary gas/air distribution plate
330 Burner plaque assembly
340 Gas/air manifold
350 O-ring gas/air manifold to burner
360 Gas injector, natural gas (G20)
incl. O-ring
370 Air restrictor natural gas (G20)
375 Connection tube, fan/burner
380 Connection tube, fan/burner
430
420
360
340
350
290
280
370
230
220
330
320
310
300
210
70
100
110
90
80
120
260
270
240
60
530
550
560 565
540
545
570
520
510
470
500
480
490
40
30
630
540
640
590
620
610
650
580
600
375 380
410
390 400
460
430
440 170 180
190
200
160
130
140
20
10
150
150
50
660
390 Air inlet pipe incl. gasket
400 Support mounting bracket fan anti
vibration
410 Fan
420 Connection pipe gas valve/burner
430 Connection nipple 3/4"x1/2" with O-ring
440 Gas unit
460 Gas inlet pipe 1/2"
470 Control uba
480 Temperature / pressure gauge
490 Bracket for uba
500 Power switch
510 230V cable
520 Cable harness complete
530 Supply pipe heat exchanger
540 O-ring
550 Spring clip heat exchanger/supply
560 Pressure relief valve
570 Non return valve R 1/4''
580 Pump
590 Gasket for pump DN 44 x 2.5
600 Pump power cable complete with
connector
610 Ring
620 Nut for heat exchanger 1 1/2''
630 Nut for heat exchanger 1 1/2''
640 Return pipe
650 Filling-, draining valve
660 RTH converter

Installation 1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 9
1.3 Flue Installation
1.3.1 Siting the flue terminal
The flue must be installed in accordance with the
recommendations of BS. 5440-1:2000.
Pluming will occur at the terminal so terminal positions
where this could cause a nuisance should be avoided.
The air supply and the flue gas exhaust must meet the
applicable general regulations. Please consult the
instructions provided with the flue terminal kits prior to
installation.
The boiler MUST be installed so that the terminal is
exposed to external air.
It is important that the position of the terminal allows the
free passage of air at all times.
Minimum acceptable spacing from the terminal to
obstructions and ventilation openings are specified in
table 1.
If the terminal is fitted within 1000 mm of a plastic or
painted gutter or within 500 mm of painted eaves, an
aluminium shield of at least 1000 mm long should be
fitted to the underside of the gutter or painted surface.
If the lowest part of the terminal is less than 2 metres
above the level of the ground, balcony, flat roof or place
to which any person has access, the terminal must be
protected by a guard. Protective guards are available
from Quinnell Barrett and Quinnell, Old Kent Road,
London.
Ensure that the guard is fitted centrally.
The flue assembly shall be so placed or shielded as to
prevent ignition or damage to any part of the building.
The air inlet/products outlet duct and the terminal of the
boiler MUST NOT be closer than 25 mm (1'') to
combustible material. Detailed recommendations on the
protection of combustible material are given in BS.
5440- 1:2000.
If this could occur the appliance MUST be turned off
(with the owners permission), and labelled as unsafe
until corrective action can be taken.
fig. 1 Flue terminal position
A
A
FM
G
M
B,C
FF
B,C
K
G
K
K
G
C
LL
FJ
K
G
D
H, I
under carport
Terminal Position Minimum
Spacing
A. Directly below or alongside an opening
window, air vent or other ventilation opening 300 mm (12")
B. Below guttering, drain pipes or soil pipes 75 mm (3")
C. Below eaves 200 mm (8")
D. Below balconies or a car port roof 200 mm (8")
E. From vertical drain pipes or soil pipes 150 mm (6")
F. From internal or external corners 300 mm (12")
G. Above adjacent ground, roof or balcony level 300 mm (12")
H. From a surface facing the terminal 600 mm (24")
I. From a terminal facing a terminal 1200 mm (48")
J. From an opening in a car port (e.g. door or
window) into dwelling 1200 mm (48")
K. Vertically from a terminal on the same wall 1500 mm (60")
L. Horizontally from a terminal on the wall 300 mm (12")
M. Adjacent to opening 300 mm (12")
table 1 Balanced flue terminal position
NOTE
It is absolutely essential to ensure, in
practice, that products of combustion
discharging from the terminal cannot re-
enter the building or any other adjacent
building through ventilators, windows,
doors, other sources of natural air
infiltration, or forced
ventilation/airconditioning.

Installation1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
10
1.3.2 Air supply and flue gas exhaust in a closed
installation
To ensure optimal operation, the 800 Series appliances
must be connected to a Buderus wall-mounted or roof-
mounted flue terminal. These terminals have been
developed specifically for the 800 Series condensing
gas boilers and have been comprehensively tested. The
Buderus wall and roof-mounted flue terminal kits ensure
trouble-free operation.
The following items for the flue (see fig. 2) are included
in the delivery of the boiler:
– pos. 1: 1 Concentric bend 80/125;
– pos. 2: 1 Horizontal flue terminal 80/125;
– pos. 3: 1 Flue finishing kit.
1.3.3 Maximum Flue length
The maximum pipe length of the air supply and flue gas
exhaust pipes for the 800 Series condensing gas boilers
(see table 2) is determined by the total pressure loss of
all components in the flue gas exhaust / air supply
system.
Maximum wall thickness without extensions is 550 mm.
Maintain a minimum side wall clearance of 50 mm (see
fig. 3).
1.3.4 Additional flue parts
Additional flue parts (see table 3) can be ordered from
your supplier.
fig. 2 Horizontal flue pack
1
2
3
fig. 3 Side flue and rear flue installation
550 mm
50 mm
L
Boiler Maximum
pipe length
For every 90° bend the
maximum pipe length has
to be reduced by
800 – 24 / 24T25 H/V L = 14 m 0 m
800 – 29 / 29T25 H/V L = 14 m 0 m
800 – 43 L = 14 m 1.5 m
800 – 60 L = 9 m 1.5 m
table 2 Pipe length
Flue parts Order No.
Concentric pipe, 500 mm long, adjustable NE 83713
Concentric pipe, 1000 mm long, adjustable NE 83714
Concentric bend 90° NE 83715
Concentric bend 45° NE 83716
24-43 kW adaptor plate NE 79061
60 kW adaptor plate NE 79064
table 3 Additional flue parts

Installation 1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 11
1.4 Items supplied with unit
Check the contents against the packing list to ensure
that nothing is missing.
Requirements to be met by the place of installation
1.5 Gas boiler
Remove the packing and discard to ensure proper
recycling.
Do not remove the polystyrene foam bottom slab
protecting the connection nozzles. During installation
the gas boiler and the flue gas adapter must be
protected to prevent site dirt from entering, e.g. using
aluminum foil.
Fit the wall bracket.
Removing the casing:
Open the cover of the control panel (fig. 5, item 1).
fig. 4 Items supplied with unit
Key to fig. 4:
1: wall-mounted condensing gas boiler
2: wall bracket
3: technical documents
4: wall-mounting template
5: screw fittings for connecting the boiler (heating system)
gas service valve ½" (800-24/29/43)
gas service valve ¾" (800-60)
2
3
5
1
4
6
NOTE
Observe all statutory building regulations
applying to the place of installation.
DANGER!
Inflammable materials or liquids must not be
stored or used near wall-mounted
condensing gas boilers. The site of
installation must be frost-protected.
fig. 5 Removing the casing
6
1
2
5
5
5
4
3
NOTE!
Note the clearance required to install the
flue system (see chapter 1.8 "Flue
installation").
Note the side wall minimum clearance of
100 mm. If a storage-type water heater is
installed underneath, take care that the
minimum clearances according to the
installation instructions are adhered to.

Installation1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
12
Remove the screw (fig. 5, item 2).
Open the locks (fig. 5, item 3) with the radiator key
(fig. 5, item 4).
Release the clasps (fig. 5, item 5).
Remove the boiler casing forwards (fig. 5, item 6).
Do not carry the casing by the clasps !
Combination unit type 800 - 24T25V / 29T25V:
Vertical boilers:
Pull forward the casing of the hot water reservoir and
lift it clear from the top holders. This is only possible
with the upper casing removed.
Attach the gas boiler to the wall bracket (fig. 6).
1.6 Water circulation system
The central heating system should be in accordance
with BS.6798 and, in addition, for smallbore and
microbore systems, BS.5449.
1.7 Pipe connections
1.7.1 Heating circuit connection
On type 800 – 60 an automatic air-release valve must
be fitted in the return line.
A servicing valve has to be installed in the flow and
return lines to allow the gas boiler to be serviced and
repaired.
Make sure that the expansion vessel, pressure relief
valve and draining valve are installed between the
service valve and the boiler.
In order to ensure an optimum and efficient operation of
the heating system, care must be taken that the heating
boiler always has the required minimum amount of
circulation water.
In single-circuit systems the required minimum amount
of circulation water can be provided e.g. by means of an
bypass valve.
A bypass valve is not needed when a hydraulic shunt is
installed.
fig. 6 Installation

Installation 1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 13
Thoroughly flush pipes and radiators !
For sizes of pipe connections please refer to the wall
mounting template.
Fit expansion vessel in compliance with the separate
installation instructions
or
install the expansion vessel in the boiler return line.
Fit the service valve in the flow and return lines (see
subsection 1.1 on pages 6 and 7).
Connect pipes free of tension.
1.7.2 Gas Supply
The gas installation must be installed in accordance with
BS6891.
The complete installation MUST be tested for gas
tightness and purged as described in IGE/UP/1b.
1.7.3 Gas connection
For the size of the pipe connection please refer to the
wall mounting template.
Connect the boiler to the gas supply in accordance
with the relevant standards. Fit the supplied service
valve in the gas feed line. Connect the pipe free of
tension (fig. 7).
Fit a gas service valve with a size of R¾ on type 800 –
60.
1.7.4 Hot water connection
On type 800 – 24/29/43/60:
Connect the external storage-type water heater in
accordance with the appropriate installation instructions
using the connection kit.
fig. 7 Gas connection
CAUTION!
Pipework from the meter to the boiler MUST
be of adequate size.
CAUTION!
Work on gas-bearing components may only
be carried out by a Gas Safe registered
installer.

Installation1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
14
On type 800 – 24T25 H/V and 800 – 29T25 H/V:
When using plastic pipes, note the information provided
by the pipe manufacturer. This particularly applies to the
mode of connection recommended by manufacturer.
In certain situations to prevent hammering within the
system when closing taps, controls can be installed
to counter act this action. For further information
please contact Buderus.
For the size of pipe connections please refer to the
wall mounting template.
1.7.5 Condensate water drain
When shorter aluminium flue-gas systems are used
There is no integrated condensate water outlet in the
flue gas adapter of the aluminium exhaust flue.
The condensate water from the exhaust flue flows via
the gas boiler and into the boiler's odour trap (syphon,
see fig. 10).
fig. 8 Hot water connection vertical boilers
(type 800 – 24T25V / 800 – 29T25V)
CAUTION!
Do not use galvanised pipes or fittings. The
hot water heat exchanger is made of copper
and risks electrolytic corrosion.
fig. 9 Hot water connection horizontal boilers
(type 800 – 24T25H / 800 – 29T25H)
fig. 10 Condensate water outlet for exhaust flue systems
made of aluminium
NOTE!
The condensate water collecting in the gas
boiler and possibly in the flue gas line must
be drained. Local regulations must also be
noted.
CAUTION!
If the flue gas adapter is made of aluminium,
the sealing cap (fig. 12, item 1) MUST NOT
be removed.

Installation 1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 15
When longer aluminium flue-gas systems are used
There is no integrated condensate water outlet in the
flue gas adapter of the aluminium exhaust flue.
The condensate water from the exhaust flue flows via
the external condensate water outlet with odour trap
(syphon, see fig. 11).
This additional component is required:
– from 10 m expanded overall length of exhaust flue
with 800 Series to boiler size of 24 kW or
– from 5 m expanded overall length of exhaust flue with
type
800 – 29, 800 – 43 and 800 – 60.
1.8 Flue installation
The only flue systems that may be used are those
supplied by Buderus. The flue system must be installed
in accordance with the requirements of BS5440:1. 2000.
Standard 125 mm flue systems
See subsection 1.3.3 for the maximum horizontal
straight length of each type boiler. Full instructions for
fitting this flue are in Section 1.8.2: "Installation of the
horizontal flue“ on page 16.
fig. 11 Condensate water outlet for longer exhaust flue
systems made of aluminium
CAUTION!
If the flue gas adapter is made of aluminium,
the sealing cap (fig. 12, item 1) MUST NOT
be removed.
fig. 12 Remove sealing cap on condensate water bypass
(applies only to boiler connection pieces made of
plastic)
1
2

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Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
16
1.8.1 Fitting the boiler's adaptor plate
Place the boiler's adaptor plate onto the boiler
(fig. 13).
Secure with 6 screws.
1.8.2 Installation of the horizontal flue
The standard 125 mm diameter horizontal flue system is
suitable for length upto 595 mm. Flue length above this
will require extension duct assemblies.
See table 2 on page 10 for the maximum pipe length for
each type boiler.
fig. 13 Adaptor plate
IMPORTANT
Any horizontal flue system fitted to a
condensing boiler must be incline towards
the appliance at an angle of 3% (30 mm per
metre length) to prevent condensate
dripping from the flue terminal.
This means that the clearance above the
appliance must be increased to match the
duct length. See figure on page 6.
fig. 14 Elbow with flue gas testing point
fig. 15 Standard flue
Flue
Turret Maximum 595 mm
Terminal
assembly
Outer
Wall
NOTE
Use the wall-mounting template to help you
mark the position of the side flue opening

Installation 1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 17
1.8.3 Flue duct preparation and assembly
Measure the flue length L. Refer to figure 16.
Mark of the lengths shown onto the ducts and cut the
length. The cuts must be square and free from burrs.
Terminal assembly outer (air) duct - L-70 mm, inner (flue)
duct - L-50 mm. The measurement is made from the ridge
at the terminal indicating the outer face of the wall.
Refer to figure 18.
Extension air duct - L-70 mm, flue duct - L-50 mm.
The measurement is from the formed end.
Assemble flue system completely. Push the ducts
fully together. The slope of the terminal outlet must
be face downwards.
The assembly will be made easier if a solvent free
grease is lightly applied to the male end of the ducts.
Push the assembly through the wall and slide the tur-
ret onto the flue connector. Refer to figure 14.
Ensure that the turret is fully entered into the socket
on the boiler. From the outside fix the flue finishing kit
to the terminal and, after ensuring the duct is properly
inclined towards the boiler, fix the finishing kit to the
wall.
If the terminal is within 2 m of the ground where there
is access then an approved terminal guard must be
fitted.
The guard must give a clearance of at least 50 mm
around the terminal and be fixed with corrosion re-
sistant screws.
fig. 16 Flue length - rear
152
L
NOTE
The flue must be inclined to the boiler.
fig. 17 Flue length - side
L
NOTE
An inner wall sealing plate is provided which
should be fitted to the ducts before
assembly.
fig. 18 Flue terminal position
Outer
Wall
Face
Flue Terminal
Raised Ring
locating the
terminal relative
to the outside
wall face

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Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
18
1.9 Electrical connections
1.9.1 Mains connection
A mains supply of 230 V - 50Hz is required.
External controls are suitable for volt free or 230 V
installation.
Wiring to the boiler MUST be in accordance with the
current I.E.E. (BS.7671) Wiring Regulations and any
local regulations.
Wiring should be a 3 core PVC insulated cable, not less
than 0.75 mm2(24 x 0.2 mm), and to table 16 of
BS.6500.
Connection must be made in a way that allows complete
isolation of the electrical supply such as a double pole
switch having 3 mm (1/8'') contact separation in both
poles, or by a three pin connector, serving only the boiler
and system controls. This boiler is equipped with a
double pole switch see fig. 19, item 1. The means of
isolation must be accessible to the user after installation.
The electrical connection to the mains supply should be
readily accessible and adjacent to the boiler.
If the supply cord is damaged, it must be replaced by a
registered Gas Safe installer to avoid a hazard and must
be an original spare part.
The electrical supply for both the boiler and the system
must be taken from the same fused spur outlet.
fig. 19 UBA
1
NOTE
All Buderus boilers require a permanent
live.
WARNING!
Do not connect 230V to the connection
block on the UBA.

Installation 1
Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements! 19
1.9.2 Wiring Diagram
fig. 20 Wiring diagram
24 VAC
0 VAC
0
max 6 VA
12
RC
1)
12
Incandescent
firing electrode
Remove bridge when
carrying out connection
12 1234
MN
L
12
M
2311 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
20 pin connection strip 18 pin connection strip
12 34 56 78 9 1110
24V output (AC)
External sensor
Fuse, main switch, emergency OFF switches and safety measures to comply with local regulations and standards
STB
MV2 MV1 HT1
HT2
24Vdc
ATB
PA
FR FS
FB FK
Flame-monitoring electrode
Note:
Circulation pump (PH)
(max. 2A)
KIM
Ventilator
230V 50Hz
Mains power source
~
1) Only one room-temperature regulating
device may be connected.
ATB Flue-gas temperature-limiting device FB Mains-water temperature sensor FK Boiler water-temperature sensor (supply) FR Return-temperature sensor (return) FS Safety-temperature sensor (safety) HT Hand-held terminal KIM Boiler identification module MV1 1. Solenoid valve MV2 2. Solenoid valve PA Potential-free connection (bridge connector) STB Burner thermostat
Internal three-way
reversing valve
for mains water
(AC operation)
Digital Room
Controller
I/O
communication port
Turn-on voltage for
external, customer-supplied
three-way reversing valve
(AC operation)
Bridge is conductive (remove when connecting) Loop is non-conducting (remove when connecting)
UBA connection block
Burner-control unit (UBA)
Fuse 1.25 slow blow
21
2 1 1 2
12
external
230V controls
Volt free external control device
*) remove wirebridge when used
Volt free room thermostat when used with 230V timer *)
IMPORTANT The wires in this mains lead are coloured in accordance with the following code: GREEN AND YELLOW - EARTH ; BLUE - NEUTRAL ; BROWN - LIVE As the colours of the wires in the mains lead of of the appliance may not correspond with the coloured markings identifying the terminals in your plug proceed as follows: The wire coloured green and yellow must be connected to the terminal on the plug marked with the letter E or by the earth symbol or coloured green or green-and-yellow. The wire coloured brown must be connected to the terminal marked with the letter L or coloured red. The wire coloured blue must be connected to the terminal marked with the letter N or coloured black. WARNING THIS APPLIANCE MUST BE EARTHED Ensure that your appliance is connected correctly - if you are in any doubt consult a qualified electrician.
WARNING!
Do not connect 230V to the connection block on the UBA.

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Wall-mounted condensing gas boiler Buderus 800 - Subject to modifications resulting from technical improvements!
20
1.9.3 Connecting a three-way valve of an external
storage-type water heater
Three-way valve with plug:
Connect the plug-and-socket connector to the plug of
the external storage-type water heater (fig. 21).
Three-way valve without plug:
Connect the three-way valve to terminals 9 and 11 of
the terminal strap (fig. 22, item 5).
1.9.4 External controls
The wall-mounted condensing gas boiler can be fitted
with the following control devices:
– Buderus programmable room thermostat
(see subsection 1.9.5).
– A room-temperature control device at 230V
connected to the RTH converter (see subsection
1.9.6);
– ON/OFF temperature controller, volt free
(see subsection 1.9.7);
fig. 21 Connecting a three-way valve of an external storage-
type water heater