Buderus 800-24 User guide

7212 3900 - 02/2006 GB(EN) For trade use
Please read thoroughly before installation and servicing
Installation and servicing
instructions
Gas wall hung Boiler condensing
Buderus 800 - 24/29/43/60 and
Buderus 800 - 24T25/29T25 H/V

2 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
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.
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.

Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 3
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
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. . . . . . . . . . . . . . . . . . . . . . 17
2 Initial start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.1 Preparing the boiler for operation . . . . . . . . . . . . . 22
2.2 Start-up work . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.1 Preparing the heating boiler for inspection . . . . . . 32
3.2 Checking for internal leaks . . . . . . . . . . . . . . . . . . 32
3.3 Visual inspection. . . . . . . . . . . . . . . . . . . . . . . . . . 32
4 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.1 Cleaning the heat exchanger, burner and syphon 33
5 Servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.1 Operating codes . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.2 Fault codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.3 Checking and replacing parts . . . . . . . . . . . . . . . . 46
6 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.1 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.2 Residual pump lift for wall-hung gas boilers . . . . . 61
6.3 Short list of spare parts. . . . . . . . . . . . . . . . . . . . . 62
7 Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
7.1 Start-up report . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
7.2 Inspection and service reports . . . . . . . . . . . . . . . 64
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 CORGI 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.

4 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
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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 CORGI registered installer in accordance with the regula-
tions. Failure to install appliances correctly could lead to pros-
ecution. 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.
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.
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.

Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 5
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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.
CAUTION
Use this device for its intended purpose only.
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.
zDo not use water softened in a salt bedding
exchanger.
zDo not use inhibitors, anti-freeze or other
additives.
zThe 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.
zThe domestic hot water service must be in
accordance with BS 5546 and BS 6700.
zThe boilers are suitable for connection to
most types of washing machine and
dishwasher appliances.
zWhen 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.
zWhere 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
6 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
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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
Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 7
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
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
8 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
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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 180190
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
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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
10 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
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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
Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 11
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1.4 Items supplied with unit
zCheck 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.
zFit the wall bracket.
Removing the casing:
zOpen the cover of the control panel (fig. 5, item 1).
zRemove the screw (fig. 5, item 2).
zOpen the locks (fig. 5, item 3) with the radiator key
(fig. 5, item 4).
zRelease the clasps (fig. 5, item 5).
zRemove the boiler casing forwards (fig. 5, item 6).
Do not carry the casing by the clasps !
Combination unit type 800 - 24T25V / 29T25V:
Vertical boilers:
zPull 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.
zAttach the gas boiler to the wall bracket (fig. 6).
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 installa-
tion instructions are adhered to.
fig. 6 Installation

Installation1
12 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
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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 gas 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.
Thoroughly flush pipes and radiators !
zFor sizes of pipe connections please refer to the wall
mounting template.
zFit expansion vessel in compliance with the separate
installation instructions
or
install the expansion vessel in the boiler return line.
zFit the service valve in the flow and return lines (see
subsection 1.1 on pages 6 and 7).
zConnect 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.
fig. 7 Gas connection
CAUTION!
Pipework from the meter to the boiler MUST be
of adequate size.

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Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 13
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
1.7.3 Gas connection
zFor the size of the pipe connection please refer to the wall
mounting template.
zConnect 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 connec-
tion kit.
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.
zIn 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.
zFor the size of pipe connections please refer to the wall
mounting template.
CAUTION!
Work on gas-bearing components may only be
carried out by a CORGI registered installer.
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)

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14 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
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).
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.
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.
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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Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 15
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
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 15.
1.8.1 Fitting the boiler's adaptor plate
zPlace the boiler's adaptor plate onto the boiler (fig. 13).
zSecure 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

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16 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
1.8.3 Flue duct preparation and assembly
zMeasure the flue length L. Refer to figure 16.
zMark 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.
zAssemble 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.
zPush the assembly through the wall and slide the turret
onto the flue connector. Refer to figure 14.
zEnsure 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 resistant 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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Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 17
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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 isola-
tion 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 regis-
tered Corgi 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.

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18 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
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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Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006 19
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
1.9.3 Connecting a three-way valve of an external
storage-type water heater
zThree-way valve with plug:
Connect the plug-and-socket connector to the plug of the
external storage-type water heater (fig. 21).
zThree-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);
If the boiler has to be temporarily put into operation without
control unit, place a conducting bridge in terminal 12 and set
the feed temperature and the required heating capacity on the
UBA.
1.9.5 Buderus room temperature control device
connection
zRemove the bridge in terminal 34 (fig. 22, item 2) and
connect the control unit to the terminal strap.
zRemove the wire in terminal 12 (fig. 22, item 1).
1.9.6 230V room-temperature control device connection
zRemove the cover of the RTH converter (fig. 22, item 6).
zLead the control device wire through the cable lead (fig. 22,
item 8).
zFix the wire to terminal 1 and 2 of the 230 Volt connection
(fig. 22, item 9).
zSecure the wire with the bracket and the two screws onto
the RTH converter.
1.9.7 Volt free external control device connection
zRemove the cover of the RTH converter (fig. 22, item 6).
zLead the control device wire through the cable lead.
zFix the wire to terminal 1 and 2 of the volt free connection
(fig. 22, item 10).
fig. 21 Connecting a three-way valve of an external storage-type
water heater
fig. 22 Connecting the control unit
Key to fig. 22:
Item 1: ON/OFF temperature controller (non-conducting bridge)
Item 2: Room temperature controller iRT (digital)
Item 3: I/O port/communication port
Item 4: Outdoor temperature sensor
Item 5: Power supply 24 VAC/max: 6 VA switching voltage
three-way valve (9+11)
Item 6: RTH converter
Item 7: 24 VAC connection
Item 8: 230 VAC connection
Item 9: Volt free connection
2
4
5
6
7
8
10
11
12
1
3
1
2
3
4
9
5
6
0 VAC
0 V
24 VAC
- max. 6VA
1
2
3
4
5
6
10
9
7
8
NOTE
RTH converter is no longer in use.

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20 Installation and servicing instructions condensing gas boiler 800 - 24/29/43/60 and 800 - 24T25/29T25 H/V • edition 02/2006
Subject to modifications resulting from technical improvements ! Buderus • http://buderus-domestic.co.uk
1.9.8 Service tool
The service tool allows you to determine the operating status
of the boiler, check components and carry out fast fault
diagnosis.
zOpen the flap at the front of the boiler unit and insert the
twin plug connector of the service tool into the sockets
provided (fig. 23, item 1).
fig. 23 Service-tool connection
1