A.O. Smith Cyclone BFC-28 Troubleshooting guide

0310 878
Innovation has a name.
Installation, User and Service
Manual
High Efficient Condensing
Water Heater
BFC - 28/30/50/60/80/100/120
BFC

A.O. Smith UK, Unit B8 Amstrong Mall,
Southwood Business Park, Farnborough, Hampshire GU14 0NR
www.aosmith.co.uk
“A.O. Smith Water Heaters” is a trading name of Advance Services (Sales) Ltd. Reg.
your installer

E1
Errata
The amendments below apply to finishing of maintenance (15.5 "Finalizing maintenance").These instructions supersede
the previous instructions of the solar heating control.
15.5 Finalizing
maintenance
To finalize the maintenance, carry out the following steps:
1. Fill the water heater (5 "Filling").
2. Start the water heater (9 "Starting the water heater").
3. Check the CO2value (3.12.3 "CO2adjustment").
4. Check the switching pressure of the pressure switch. (3.12.4 "Switching pressure
measurement")
5. Erase the message SERVICE REQUIRED. The displayed message can be reset in
either of two ways.
1. Temporary reset:
To postpone the message, press RESET once. The message will reappear on the
display 7 days later.
2.Full reset:
To fully reset the message, press and hold both RESET and ENTER at the same
time for 5 sec.
On completion of the full reset of the message, the message below will appear on the
display. This message will NOT be shown after a temporary rest of the message.

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Instruction manual BFC 3
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Read this manual carefully Warning
Read this manual carefully before starting the water heater. Failure to read
the manual and to follow the printed instructions may lead to personal injury and
damage to the water heater.
Copyright © 2013 A.O.Smith Water Products Company
All rights reserved.
Nothing from this publication may be copied, reproduced and/or published by
means of printing, photocopying or by whatsoever means, without the prior
written approval of A.O.Smith Water Products Company.
A.O.Smith Water Products Company reserves the right to modify specifications
stated in this manual.
Trademarks Any brand names mentioned in this manual are registered trademarks of their
respective owners.
Liability A.O.Smith Water Products Company accepts no liability for claims from third
parties arising from unauthorised use, use other than that stated in this manual,
and use other than in accordance with the General Conditions registered at the
Chamber of Commerce.
Refer further to the General Conditions. These are available on request, free of
charge.
Although considerable care has been taken to ensure a correct and suitably
comprehensive description of all relevant components, the manual may
nonetheless contain errors and inaccuracies.
Should you detect any errors or inaccuracies in the manual, we would be
grateful if you would inform us. This helps us to further improve our
documentation.
More information If you have any comments or queries concerning specific aspects related to the
water heater, then please do not hesitate to contact:
A.O.Smith Water Products Company
PO Box 70
5500 AB Veldhoven
The Netherlands
Telephone: (free) 0870-AOSMITH
0870-2676484
General: [phone]
Fax: [phone]
E-mail: [e-mail]
Website: aosmith.co.uk
In the event of problems with your gas, electricity or water supply connections,
please contact the supplier/installation engineer of your installation.

4Instruction manual BFC
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Instruction manual BFC 5
Contents
1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - 9
1.1 About the water heater - - - - - - - - - - - - - - - - - - - - - - - - - - - 9
1.2 What to do if you smell gas- - - - - - - - - - - - - - - - - - - - - - - - - 9
1.3 Regulations - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 9
1.4 Target groups - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 10
1.5 Maintenance - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 11
1.6 Notation conventions- - - - - - - - - - - - - - - - - - - - - - - - - - - 11
1.7 Overview of this document - - - - - - - - - - - - - - - - - - - - - - - - 12
2 Working principle of the water heater - - - - - - - - - - - - - 13
2.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 13
2.2 General working principle of the water heater - - - - - - - - - - - - - - - 13
2.3 Water heater operating cycle - - - - - - - - - - - - - - - - - - - - - - - 15
2.4 Protection for the water heater - - - - - - - - - - - - - - - - - - - - - - 15
2.5 Safety of the installation - - - - - - - - - - - - - - - - - - - - - - - - - 16
3 Installation - - - - - - - - - - - - - - - - - - - - - - - - - - - 17
3.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 17
3.2 Packaging - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 17
3.3 Ambient conditions- - - - - - - - - - - - - - - - - - - - - - - - - - - - 17
3.4 Technical specifications - - - - - - - - - - - - - - - - - - - - - - - - - 19
3.5 Installation diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - 25
3.6 Unvented water connections - - - - - - - - - - - - - - - - - - - - - - - 26
3.7 Vented water connections - - - - - - - - - - - - - - - - - - - - - - - - 27
3.8 Gas connection - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 27
3.9 Air supply and chimney flue discharge - - - - - - - - - - - - - - - - - - 28
3.10 Electrical connection - - - - - - - - - - - - - - - - - - - - - - - - - - - 33
3.11 Check the supply pressure, gas controller pressure, CO2value and
switching pressure - - - - - - - - - - - - - - - - - - - - - - - - - - - - 36
4 Conversion to a different gas category - - - - - - - - - - - - 45
4.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 45
5 Filling - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 47
5.1 Filling unvented installations - - - - - - - - - - - - - - - - - - - - - - - 48
5.2 Filling vented installations - - - - - - - - - - - - - - - - - - - - - - - - 48
6 Draining - - - - - - - - - - - - - - - - - - - - - - - - - - - - 49
6.1 Draining unvented installations - - - - - - - - - - - - - - - - - - - - - - 50
6.2 Draining vented installations - - - - - - - - - - - - - - - - - - - - - - - 50
7 The control panel- - - - - - - - - - - - - - - - - - - - - - - - 51
7.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 51
7.2 Control - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 51
7.3 Explanation of icons - - - - - - - - - - - - - - - - - - - - - - - - - - - 51
7.4 ON/OFF switch on controller - - - - - - - - - - - - - - - - - - - - - - - 51
7.5 Navigation buttons - - - - - - - - - - - - - - - - - - - - - - - - - - - - 51
7.6 PC connection - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 52
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Contents
6Instruction manual BFC
8 Status of the water heater - - - - - - - - - - - - - - - - - - - 53
8.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 53
8.2 Operating modes - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 53
8.3 Error conditions - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 54
8.4 Service condition - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 54
8.5 Anode warning - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 55
9 Starting the water heater - - - - - - - - - - - - - - - - - - - - 57
9.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 57
9.2 Starting the appliance - - - - - - - - - - - - - - - - - - - - - - - - - - - 57
9.3 The appliance's heating cycle - - - - - - - - - - - - - - - - - - - - - - - 57
10 Shutting down - - - - - - - - - - - - - - - - - - - - - - - - - 59
10.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 59
10.2 Decommissioning the water heater for a short period- - - - - - - - - - - - 59
10.3 Isolating the water heater from the mains - - - - - - - - - - - - - - - - - 59
10.4 Decommissioning the water heater for a long period - - - - - - - - - - - - 59
11 Main menu - - - - - - - - - - - - - - - - - - - - - - - - - - - 61
11.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 61
11.2 Notation convention for menu-related instructions - - - - - - - - - - - - - 61
11.3 Switching to "ON mode" - - - - - - - - - - - - - - - - - - - - - - - - - - 61
11.4 Setting the water temperature - - - - - - - - - - - - - - - - - - - - - - - 61
11.5 Week program - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 62
11.6 Starting and stopping the week program - - - - - - - - - - - - - - - - - - 62
11.7 Changing the appliance's standard week program - - - - - - - - - - - - - 62
11.8 Adding times to a week program- - - - - - - - - - - - - - - - - - - - - - 64
11.9 Deleting times from a week program- - - - - - - - - - - - - - - - - - - - 65
11.10 Extra period - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 66
11.11 Settings- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 67
12 Service program - - - - - - - - - - - - - - - - - - - - - - - - 69
12.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 69
12.2 Setting the hysteresis - - - - - - - - - - - - - - - - - - - - - - - - - - - 69
12.3 Displaying the error history - - - - - - - - - - - - - - - - - - - - - - - - 69
12.4 Displaying the water heater history - - - - - - - - - - - - - - - - - - - - 69
12.5 Display the selected water heater - - - - - - - - - - - - - - - - - - - - - 70
12.6 Switching the pump on or off - - - - - - - - - - - - - - - - - - - - - - - 70
12.7 Setting the service interval - - - - - - - - - - - - - - - - - - - - - - - - 70
12.8 Service mode - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 70
12.9 Setting legionella prevention- - - - - - - - - - - - - - - - - - - - - - - - 71
13 Errors - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 73
13.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 73
13.2 Troubleshooting table for general errors - - - - - - - - - - - - - - - - - - 74
13.3 Troubleshooting table for displayed errors - - - - - - - - - - - - - - - - - 76
13.4 Warnings on the display - - - - - - - - - - - - - - - - - - - - - - - - - - 84
14 Service interval - - - - - - - - - - - - - - - - - - - - - - - - - 85
14.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 85
14.2 Determining service interval - - - - - - - - - - - - - - - - - - - - - - - - 85

Instruction manual BFC 7
15 Performing maintenance - - - - - - - - - - - - - - - - - - - - 87
15.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 87
15.2 Preparation for maintenance - - - - - - - - - - - - - - - - - - - - - - - 87
15.3 Water-side maintenance - - - - - - - - - - - - - - - - - - - - - - - - - 88
15.4 Gas-side maintenance - - - - - - - - - - - - - - - - - - - - - - - - - - 89
15.5 Finalizing maintenance- - - - - - - - - - - - - - - - - - - - - - - - - - 90
16 Warranty (certificate) - - - - - - - - - - - - - - - - - - - - - - 91
16.1 General warranty - - - - - - - - - - - - - - - - - - - - - - - - - - - - 91
16.2 Tank warranty - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 91
16.3 Conditions for Installation and use - - - - - - - - - - - - - - - - - - - - 91
16.4 Exclusions - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 92
16.5 Scope of the warranty - - - - - - - - - - - - - - - - - - - - - - - - - - 92
16.6 Claims - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 92
16.7 Obligations of A.O.Smith - - - - - - - - - - - - - - - - - - - - - - - - - 92
17 Appendices- - - - - - - - - - - - - - - - - - - - - - - - - - - 93
17.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 93
17.2 Menu structure- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 94
17.3 Electrical diagram - - - - - - - - - - - - - - - - - - - - - - - - - - - - 96
17.4 Declaration of conformity - - - - - - - - - - - - - - - - - - - - - - - - - 98
17.5 Week program card - - - - - - - - - - - - - - - - - - - - - - - - - - - 99

Contents
8Instruction manual BFC

Instruction manual BFC 9
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1 Introduction
1.1 About the water
heater
This manual describes how to install, service and use the BFC water heater.
The BFC water heater is a condensing water heater with a fan in the air intake.
The BFC can be installed as either an open or room-sealed water heater. A
concentric chimney connector is fitted standard to the water heater.
Alternatively, the water heater can be connected using a parallel system.
The possible installation types are B23, C13, C33, C43, C53 and C63.
The information in this manual applies to types: BFC 28, BFC 30, BFC 50,
BFC 60, BFC 80, BFC 100 and BFC 120.
The water heater has been manufactured and equipped in accordance with the
European standard for gas-fired storage water heaters for the production of
domestic hot water (EN 89). The water heaters are therefore compliant with the
European Directive for Gas water heaters, and and are entitled to bear the CE
mark.
Warning
Read this manual carefully before starting the water heater. Failure to read
the manual and to follow the printed instructions may lead to personal injury and
damage to the water heater.
1.2 What to do if you
smell gas
Warning
If you smell gas:
No naked flames! No smoking!
Avoid causing sparks! Do not use any electrical equipment or switch, i.e. no
telephones, plugs or bells!
Open windows and doors!
Shut off the mains gas supply valve!
Warn occupants and leave the building!
After leaving the building, alert the gas distribution company or your installation
engineer.
1.3 Regulations Gas Safety (installations and Use) Regulations 1998 (as amended). It is law
that all gas appliances are installed by competent persons, in accordance with
the above regulations. Failure to install appliances correctly could lead to
prosecution. It is in your own interest and that of safety, to ensure that this law
is complied with.
The installation of the water heater MUST be in accordance with the relevant
requirements of the Gas Safety Regulations, Building Regulations, IEE
Regulations and the Water Supply (water fittings) Regulations.
The installation should also be in accordance with any relevant requirements of
the HSE, local gas region and local authority and the relevant recommendations
of the following documents:
0063

Introduction
10 Instruction manual BFC
1gis
British and European Standards
•BS 6891:
Installation of low pressure gas pipework of up to 35 mm (R1¼) in domestic
premises (2nd family gas) - Specification. Note: for lager installations see
IGE/UP/2 below.
•BS 6798:
Specification for installation and maintenance of gas-fired boilers of rated
input not exceeding 70 kW net.
•BS 6644:
Specification for installation of gas-fired hot water boilers of rated inputs
between 70 kW (net) and 1.8 MW (net) (2nd and 3rd family gases).
•BS 6700:
Design, installation, testing and maintenance of services supplying water for
domestic use within buildings and their cartilages - Specifications
•BS EN 806-2:
Specification for installations inside buildings conveying water for human
consumption. Part 2: Design.
•BS 5546:
Specification for installation of hot water supplies for domestic purposes,
using gas-fired appliances of rated input not exceeding 70 kW.
•BS 5440:
Flueing and ventilation for gas appliances of rated input not exceeding 70
kW net (1st, 2nd and 3rd family gases).
Part 1: Specification for installation of gas appliances to chimneys and for
maintenance of chimneys.
Part 2: Specification for installation and maintenance of ventilation for gas
appliances.
Institute of Gas Engineers and Managers (IGEM) Publications
•IGE/UP/1:
Soundness testing and purging of industrial and commercial gas
installations.
•IGE/UP/1A:
Soundness testing and direct purging of small low pressure industrial and
commercial natural gas installations.
•IGE/UP/2:
Gas installation pipework, boosters and compressors on industrial and
commercial premises.
•IGE/UP/10:
Installation of flued gas appliances in industrial and commercial premises.
CIBSE Publications
•Guide G: Public Health Engineering.
1.4 Target groups The three target groups for this manual are:
• (end) users;
• installation engineers;
• service and maintenance engineers.
Symbols on each page indicate the target groups for whom the information is
intended. See the table.

Instruction manual BFC 11
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Target group symbols
Caution
This water heater is not intended for use by persons with reduced physical,
sensory or mental capacities, or who lack the necessary experience or
knowledge, unless the person responsible for their safety is supervising them or
has explained to them how the water heater should be used.
Caution
This water heater is not intended to be used by children. Always supervise
children, and ensure that they do not play with the water heater.
1.5 Maintenance A service should be carried out at least once a year, both on the water side and
on the gas side. Among other things, the service interval depends on the water
quality, the average burning time per day and the set water temperature.
Note
To determine the correct service interval, it is recommended to arrange for
the service and maintenance engineer to check the water heater on both the
water and gas side within three months following installation. Based on this
check, the best service interval can be determined.
Note
Regular maintenance extends the service life of the water heater.
Both the end user and the service and maintenance engineer are responsible
for regular maintenance. They will need to establish clear agreements on this.
Note
If the water heater is not regularly serviced, the warranty will become void.
1.6 Notation
conventions
The following notation is used in this manual:
Note
Important information.
Caution
Ignoring this information can lead to the water heater being damaged.
Warning
Failure to carefully read this information may lead to danger of personal
injury, and serious damage to the water heater.
Symbol Target Group
(End) user
Installation engineer
Service and maintenance engineer

Introduction
12 Instruction manual BFC
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1.7 Overview of this
document
The table provides an overview of the contents of this document.
Contents of this document
Chapter Target groups Description
Working principle of the water
heater
This chapter describes the working principle of the
appliance.
Installation This chapter describes the installation activity to be
completed before you start the appliance for the first time.
Conversion to a different gas
category
This chapter describes how to convert the appliance to a
different gas category and/or family of gases.
Filling This chapter describes how to fill the appliance.
Draining This chapter describes how to drain the appliance.
The control panel This chapter describes the general control of the water
heater using the display.
Status of the water heater This chapter describes the status (mode or condition) that
the water heater may have, and possible actions to take.
Starting the water heater This chapter describes how to start the water heater. The
general operating cycle of the water heater is also
described.
Shutting down This chapter describes how to decommission the water
heater for a brief or long period of time.
Main menu This chapter describes the main menu of the display. This
is the actual menu for the user. However, the installation
engineer and service and maintenance engineers will also
need to use this menu.
Service program This chapter describes the service menu. It is mainly
intended for the installation engineer and service and
maintenance engineers. End users may also refer to this
chapter for additional information about the water heater.
Errors This chapter is mainly intended for the installation
engineer and the service and maintenance engineer. It
describes water heater errors. These errors are reported
on the display. A troubleshooting table of possible causes
and solutions is provided. End users may also refer to this
chapter for additional information about the water heater.
Service interval This chapter describes how to determine the optimum
service interval (frequency of regular maintenance). Both
the end user and the service and maintenance engineer
are responsible for regular maintenance. They need to
reach clear agreement on this.
Note
If the water heater is not regularly serviced, the
warranty will become void.
Performing maintenance This chapter sets out the maintenance tasks to be carried
out.
Warranty (certificate) This chapter states the warranty terms and conditions.

Instruction manual BFC 13
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2 Working principle of
the water heater
2.1 Introduction This chapter covers the following topics:
• General working principle of the water heater;
• Water heater operating cycle;
• Protection for the water heater;
• Safety of the installation.
2.2 General working
principle of the water
heater
The water heater is fitted with a modulating premix burner system with 1:1 gas-
to-air ratio regulation. The air required for combustion is delivered by the fan
(18). The gas is supplied via the gas control valve (16) and the venturi (30) on
the intake side of the fan. The 1:1 gas-to-air ratio always guarantees the most
efficient gas/air mixture.
In this water heater, the cold water enters the bottom of the tank through the cold
water inlet (14). The tap water, heated by the combustion chamber (8) and heat
exchanger (11), leaves the tank through the hot water outlet (2). Once the water
heater is completely filled with water, it will constantly be under mains water
pressure. As hot water is drawn from the water heater, cold water is immediately
added.
The special design of the heat exchanger (11) ensures that the flue gases are
first led downwards via the combustion chamber, then upwards via the heat
exchanger, and downwards again alongside the water in the tank. The flue
gases gradually become cooler in the process. Because the cooled flue gases
flow alongside the cold water lower down in the tank, they start to condense.
This condensation causes latent heat energy to be transferred to the cooler
water, thereby increasing the performance of the unit. The condensate yielded
by this process is discharged via the condens trap (23).
The insulation layer (24) prevents heat loss. The inside of the tank is enamelled
to protect against corrosion. The anodes (9) provide extra protection against
corrosion.
The water heater has an inspection and cleaning opening (12) for maintenance.

14 Instruction manual BFC
Cut-away view of the water heater
Legend BFC 28, 30, 50, 60 BFC 80, 100, 120
Unused numbers are not applicable
1. cover
2. hot water outlet
3. electrical connector block
4. controller
5. pressure switch
6. control panel
7. temperature sensor T1
8. combustion chamber
9. anode
10. tank
11. heat exchanger
12. inspection and cleaning
opening
13. temperature sensor T2
14. cold water inlet
15. drain valve
16. gas control valve
17. burner
18. fan
19. air supply hose
20. hot surface igniter
21. flame probe
22. chimney pipe
23. condens trap
24. insulation layer
28. potentiostat
29. base
30. venturi
58. flue gas test point
59. pressure-reducing valve

Instruction manual BFC 15
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2.3 Water heater
operating cycle
The temperature sensor T1(7) measures the water temperature at the top of the
water heater Ttop). This temperature is sent to the controller. As soon as T1is
lower than the set water temperature (Tset), the controller registers a "heat
demand". The fan (18) starts running and the gas control valve (16) is opened.
The fan runs at full speed and the gas is mixed with the air in the venturi (30).
This mixture is ignited by the hot surface igniter (20) and the water becomes
heated. As soon as the water temperature approaches Tset the fan rpm drops
to the partial load speed (this is also referred to as modulating). Once T1rises
above Tset, the heat demand ends and the controller stops the operating cycle.
When responding to both the start and end of the heat demand, the controller
assumes a certain margin. We refer to this margin as the
hysteresis (12.2 "Setting the hysteresis").
2.4 Protection for the
water heater
2.4.1 Introduction
The controller monitors the water temperature and ensures safe combustion.
This takes place using:
• the Protection for the water heater;
• the Gas control valve;
•theFan
• the Pressure switch;
• the Flame probe.
2.4.2 Water temperature protection
Using temperature sensors T1(7) and T2(13), the controller monitors three
temperatures that are important for safety. The table explains the functioning of
the temperature sensors.
Temperature protection
2.4.3 Gas control valve
The controller opens the gas control valve so that gas can be supplied to the
burner. As a safety measure, the gas control valve has two valves. Both valves
shut off the gas supply.
2.4.4 Fan
The fan (18) provides an optimum air supply when there is a heat demand. As
a safety feature, the fan ensures that any gases present in the combustion
chamber are removed, both before and after combustion. We refer to this as
pre- and post-purge.
The fan speed is continuously monitored by the controller (4). The controller
takes control if the fan rpm varies too much from the value set.
Safety Description
Anti-frost
(T1< 5°C or T2< 5°C)
The frost protection cuts in. The water is heated to 20°C.
Maximum water temperature:
(T1> 88°C or T2> 88°C)
The high-limit safeguard serves to prevent overheating and/or excessive
formation of scale in the appliance. If the high-limit safeguard is activated,
heating is stopped. This causes the water in the tank to cool down. Once the
water has cooled sufficiently (T1< 81°C), the controller resets the appliance.
For extra safety
(T1> 93°C or T2> 93°C)
A lockout error of the water heater controller takes place. The controller must
be manually reset before the appliance can resume operation (8.3 "Error
conditions"). The reset may only be performed if T1< 81°C.

Working principle of the water heater
16 Instruction manual BFC
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2.4.5 Pressure switch
The pressure switch only guarantees the supply of air during pre-purging of the
water heater. If the pressure difference during pre-purging is sufficient, the
pressure switch closes. The table (3.4.2 "General and electrical specifications")
shows the trip point for each water heater.
Note
The trip point of the pressure switch is not adjustable.
2.4.6 Flame probe
To ensure that no gas can flow when there is no combustion, the water heater
is fitted with a flame probe (21). The controller uses this probe to detect the
presence of a flame, by means of ionisation detection. The controller closes the
gas control valve the instant it detects that there is a gas flow but no flame.
2.5 Safety of the
installation
Excessive pressure in the tank can damage the enamelled layer (in the water
heater) or the tank itself. An inlet combination and pressure-reducing valve
prevents this. The inlet combination acts as a stop valve, non-return valve and
overflow valve. If the water mains pressure is too high (3.4.2 "General and
electrical specifications"), a pressure-reducing valve must be used. Both
components must be fitted in the cold water inlet (3.7 "Vented water
connections").
The use of an expansion vessel, expansion valve and/or pressure reducing
valve depends on the type of installation: unvented or vented.
2.5.1 Unvented installation
With an unvented installation, an expansion valve and expansion vessel prevent
the buildup of excessive pressure in the tank. This prevents damage being
caused to the enamel coating (in the water heater) or to the tank. A non-return
valve prevents excessive pressure build-up in the water supply system. This
valve also prevents water from flowing backwards from the tank into the cold
water supply system. The pressure-reducing valve protects the water heater
against excess mains water pressure (3.4.2 "General and electrical
specifications"). These components are installed in the cold water
inlet (3.7 "Vented water connections").
2.5.2 Vented installation
With a vented installation, excess pressure is taken up by the open cold water
head tank. The level of the cold water head tank determines the maximum
working pressure (3.4.2 "General and electrical specifications") in the tank. The
water heater must also be fitted with a vent pipe from the hot water pipe, which
opens into the cold water head tank.
Ideally, the vent pipe should discharge into a separate discharge channel/drain
or otherwise to the open cold water head tank. The water heater should also be
fitted with a stop valve (3.6.2 "Hot water side") on the hot water side.
2.5.3 T&P valve
A T&P valve is only mandatory in unvented installations. However, A.O.Smith
also recommends the use of a T&P valve in vented installations.
A T&P (Temperature and Pressure Relief) valve monitors the pressure in the
tank and the water temperature at the top of the tank. If the pressure in the tank
becomes too high (3.4.2 "General and electrical specifications"), the valve will
open. The hot water can now flow out of the tank. Because the water heater is
under water supply pressure, cold water will automatically flow into the tank.
The valve remains open until the unsafe situation has been rectified. The water
heater is fitted standard with a connection for a T&P valve (3.6.2 "Hot water
side").

Instruction manual BFC 17
is
3 Installation
Warning
The installation must be carried out by an approved installation engineer in
compliance with the general and local regulations imposed by the gas, water
and power supply companies and the fire brigade.
The appliance may only be installed in a room that complies with the
requirements stated in national and local ventilation
regulations (1.3 "Regulations").
3.1 Introduction This chapter describes the installation activities to be carried out before final
commissioning (9 "Starting the water heater"), namely:
• Packaging;
• Ambient conditions;
• Technical specifications;
• Unvented water connections;
• Vented water connections;
• Gas connection;
• Air supply and chimney flue discharge;
• Electrical connection;
• Check the supply pressure, gas control valve pressure, CO2value and
switching pressure;
For possible conversion to a different gas category, see
conversion (4 "Conversion to a different gas category").
3.2 Packaging To avoid damaging the water heater, remove the packaging carefully.
We recommend unpacking the water heater at or near its intended location.
Caution
The water heater may only be manoeuvred in an upright position. Take care
that the water heater is not damaged after unpacking.
3.3 Ambient conditions The water heater is suitable for either open or room-sealed combustion. If
installed as a room-sealed water heater, it is independent of the installation
site for the necessary external air supply. In this event, there are no additional
ventilation requirements.
If the water heater is to be installed as an open system, it must meet the
locally-applicable directives and ventilation regulations for open water
heaters.
The possible installation types are B23, C13, C33, C43, C53 and C63.
Caution
The water heater may not be used in rooms where chemical substances are
stored or used due to the risk of explosion, and corrosion of the water heater.
Some propellants, bleaching agents and degreasing agents etc. disperse
vapours that are explosive and/or cause accelerated corrosion. If the water
heater is used in a room in which such substances are present, the warranty will
be void.

Installation
18 Instruction manual BFC
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3.3.1 Air humidity and ambient temperature
The boiler room must be frost-free, or be protected against frost. The table
shows the ambient conditions that must be adhered to for correct functioning of
the electronics present in the appliance to be guaranteed.
Air humidity and ambient temperature specifications
3.3.2 Water heater maximum floor load
Allow for the water heater's weight and the maximum floor load; refer to the
table (3.4.2 "General and electrical specifications").
3.3.3 Water composition
The appliance is intended for heating drinking water. The drinking water must
comply with the regulations governing drinking water for human consumption.
The table gives an overview of the specifications.
Water specifications
Note
If the water specifications deviate from those stated in the table, then the
tank protection cannot be guaranteed (16 "Warranty (certificate)").
3.3.4 Working clearances
For access to the water heater, it is recommended that the following
clearances are observed (see figure):
• AA: around the water heater's control column and cleaning openings:
100 cm.
• BB: all sides of the water heater: 50 cm.
• Top of the water heater: 100 cm
Air humidity and ambient temperature
Air humidity max. 93% RH at +25°C
Ambient temperature functionality: 0 < T < 60°C
Water composition
Hardness
(alkaline earth ions)
> 1.00 mmol/l:
• German hardness> 5.6° dH
• French hardness > 10.0° fH
• English hardness > 7.0° eH
•CaCO
3> 100 mg/l
Conductivity > 125 µS/cm
Acidity (pH value) 7.0 < pH value < 9.5