Keston Qudos 28s Manual

Qudos 28s
Fan Powered High Efficiency
Modulating Domestic Condensing
Gas System Boiler
User, Installation And Servicing
Instructions
CE/PI No : 87BR36
Qudos 28s - GC No : 41-930-17
Qudos 28sP - GC No : 41-930-18
These instructions must be left either with
the user or next to the site gas meter.
34 West Common Road
Hayes, Bromley, Kent BR2 7BX
Tel. [phone] Fax. [phone]
email : [email protected] web : www.keston.co.uk
COMPLIANT WITH BUILDING REGULATION PART L1 & L2
SEDBUK A RATED
WD420/3/2007 The Keston Qudos 28s & Qudos 28sP Boilers

CONTENTS
NB : These instructions are an integral part of the appliance. This document must be handed over to
the user on completion of the installation to ensure compliance with the Gas Safety (Installation
& Use) Regulations.
Section Description
0 HANDLING INSTRUCTIONS
0.1 List of contents
0.2 Recommended handling procedure
1 USER INSTRUCTIONS
1.1 Introduction
1.2 Maintenance
1.3 Boiler Setup and Operation
1.4 Safety Information
2 GENERAL INSTRUCTION
2.1 Description
2.2 Boiler Schematic
2.3 Related Documents
2.4 Physical Data
2.5 Optional Accessories
2.6 Performance Data
3 BOILER LOCATION
3.1 Dimensions & Minimum Clearances
3.2 Service Connections
3.3 Position
3.4 Electrical
3.5 Boiler Size Selection
3.6 Gas Supply
3.7 Water Systems
3.8 Flue System
3.9 Air Supply
3.10 Compartment Installation
3.11 Condensate Drainage
4 INSTALLATION OF THE BOILER
4.1 Wall Mounting Bracket
4.2 Mounting The Boiler
4.3 Assembly Practice
4.4 Installing Flue And Air Pipes
4.5 Condensate Drainage
4.6 Water System
4.7 Gas Supply
4.8 Electrical Supply
4.9 Exchanging A Boiler
5 COMMISSIONING OF THE BOILER
5.1 Initial Flushing
5.2 Gas Supply
5.3 Electrical Installation
5.4 LP Gas
5.5 Initial Firing
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5.6 Hot Flushing
5.7 Combustion Testing
5.8 Checking The Gas Pressure
5.9 Timing The Gas Meter
5.10 Handing Over To The User
6 FAULT FINDING
6.1 Electrical Control Sequence
6.2 Normal Operation
6.3 Fault Modes
6.4 Functional Flow Wiring Diagram
6.5 Electrical Wiring Diagram
6.6 Illustrated Wiring Diagram
6.7 Exploded Assembly Diagrams
7 SERVICING
7.1 Pre Service Checks
7.2 Recommended Routine Service
8 REPLACEMENT OF PARTS
8.0 General
8.1 Precautions
8.2 Access
8.3 Replacement Procedure
8.4 Electrical Components
8.5 Spark Ignition/Flame Detection Electrode
8.6 Burner
8.7 Heat Exchanger
8.8 Condensate Trap
8.9 Pump
8.10 Expansion Vessel
9 SPARE PARTS LISTINGS
10 GAS BOILER COMMISSIONING CHECKLIST
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0. HANDLING INSTRUCTIONS
0.1 LIST OF CONTENTS
The Keston Qudos 28s and Qudos 28sP are supplied almost totally pre-assembled. The units
use standard 50 mm muPVC (BS5255 and/or BSEN1566-1 and BSEN1329) pipe for the flue
and air intake systems. The boiler is packed in a single box without additional flue kit. All
additional components are packed inside the boiler cabinet itself. The following is a list of
components and their location in the boiler cabinet
Equipment List
Item Quantity Location
Wall Bracket Rawl Plugs 6 Inside accessories bag
Wall Bracket Wall Fixing Screws 6 Inside accessories bag
Wall Mounting Bracket 1 Secured to inside right
hand side of boiler case
Wall Mounting Bracket Nuts 1 Inside accessories bag.
Wall Mounting Bracket Washers 1+1 Inside accessories bag
Wall Bracket Bolt Insulation 1 Inside accessories bag
50 mm muPVC Air/Flue Terminals 2 Inside accessories bag
Air Inlet Spigot (50 mm) 1 Inside accessories bag
Flue Outlet Spigot (50 mm) 1 Inside accessories bag
Air Inlet Spigot Gasket 1 Inside accessories bag
Air Inlet Spigot + Flue Outlet Spigot M6 Screws 4+2 Inside accessories bag
Cabinet Cable Entry Clamps 2 Inside accessories bag
Gas Isolating Cock 1 Inside accessories bag
Condensate Trap 1 Inside accessories bag
Condensate Trap fixing screws 2 Inside accessories bag
Condensate Trap fixing washers 2 Inside accessories bag
Condensate Trap Gasket 1 Inside accessories bag
50 mm muPVC Pipe 2 Inside boiler case
50 mm muPVC Elbow 2 Inside boiler case
Document List
Item Quantity Location
Registration of Purchase 1 In A4 envelope
Installation Template 1 In document bag
Remove the cabinet shell by removing the two retaining screws in the top of the cabinet and
the two retaining screws in the bottom of the cabinet.
0.2 RECOMMENDED HANDLING PROCEDURE
NB : The following lift operation exceeds the recommended weight for a one-man lift as
specified in the Manual Handling Operations 1992 Regulations.
For the carriage of carton it is recommended at least two people perform any lift. Clear the
carriage route of the carton from point of delivery to point of installation. Take care to avoid trip
hazards, slippery or wet surfaces and when climbing steps and stairs. Always use assistance
if required. If a sack truck is used it is recommended the carton is strapped to the truck.
For the unpacking of the appliance from the carton, it is recommended at least two people
perform any lift. It is recommended to cut the base end of carton and open the carton flaps.
Ensure the protective packing over the boiler tappings at the base of the boiler is kept in place,
then tilt the boiler forwards from its back onto its base and remove carton by sliding up over
the boiler. When lifting this appliance the back should be kept straight at all times. Avoid
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twisting at the waist - reposition the feet instead. Avoid upper body bending when holding the
appliance and keep the boiler as close to the body as possible.
Before hanging the appliance on the wall it is best to store the appliance laid on its back with
the casing on. When ready to hang the boiler on the wall remove the casing and place to one
side. At this stage it is assumed that the wall bracket is correctly positioned and secured on
the wall face.
a) Have the wall bracket nut and washers to hand so that they can be accessed whilst
holding the boiler in position on its mounting bracket.
b) The boiler has a dry weight of 43 kg (95 lbs) and will therefore require at least two people
to lift without the use of lifting aids - ensure co-ordinated movements durring lift. Always
use assistance if required.
c) Lift the boiler by gripping at the four corners of the boiler back plate. When lifting this
appliance the back should be kept straight at all times. Avoid twisting at the waist -
reposition the feet instead. Avoid upper body bending when holding the appliance and
keep the boiler as close to the body as possible.
d) Lift the boiler and locate onto the stud and the two pegs of the wall mounting bracket.
e) Place the wall mounting bracket washers over the bracket stud protruding through the
back plate of the boiler.
f) Secure the boiler onto the wall bracket by fixing the wall mounting bracket nut onto the
wall bracket stud. This must be tightened well.
Safety footwear and gloves are recommended PPE when lifting this appliance - to protect
against sharp edges and ensure good grip.
The Qudos 28s and Qudos 28sP boilers can be fitted in compartments with very small
clearances required around the appliance (refer to Section 3.1). Due consideration should
therefore be given to access within the compartment for lifting and positioning.
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1. USER INSTRUCTIONS
1.1 INTRODUCTION
Thank you for choosing this Keston Qudos 28s for your household heating. The boiler is
designed to be very straightforward to operate and has no user serviceable parts inside the
cabinet. The following instructions are to provide you with information on the operation and
maintenance of your Qudos 28s and what to do in the unlikely event of a fault.
These user instructions should be read carefully to ensure safe and economical use of your
Qudos 28s or Qudos 28sP. The Qudos 28s model is for use with natural gas only, the Qudos
28sP model is for use with LPG only.
1.2 MAINTENANCE
Servicing
To ensure continual safe and efficient operation and to maintain product warranties it is a
requirement that the appliance is checked and serviced at least once per year. It is the law
that any servicing must be carried out by a competent person. Removal of the appliance
cabinet by anyone other than a competent person will automatically invalidate the
appliance warranty.
Clearances
If fixtures are to be positioned close to the boiler, the following minimum clearances must be
observed: Top 150mm, Left 5mm, Right 5mm, Base 200mm, Front 10mm. Extended
clearance is required to the front for servicing (300mm).
Cleaning
Normal case cleaning only requires dusting with a dry cloth. To remove more stubborn marks
wipe with a damp cloth and finish with a dry cloth.
1.3 BOILER SETUP & OPERATION
Check that the gas supply from the gas meter is turned on. Switch on the electrical supply to
the boiler. The display will now run through a self check procedure. Set any controls to call for
heat.
To light the boiler
The Qudos 28s features two temperature controls to allow different settings depending on the
source of the demand, ie heating or hot water. Identify the which setting is demanded. Using
the “

” on the left of the display, select the setpoint you wish to adjust, generally the one
indicated by a radiator symbol with a “1” to the left. Set the required temperature using the “+”
or “-” buttons associated with the heating zones or hot water temperature. After the selection
of the desired tempreatures press ENTER and then preset “RESET” to return to the normal
display.
If the actual temperature is less than the desired temperature the boiler will fire and, after a
few seconds, a “flame” will appear on the display to show that the boiler is alight.
NB: Where the demand is via 0-10VDC or Opentherm the boiler setpoint is set using the
external controller in use.
Normal Operation
During normal operation the digital display will show the current boiler temperature and will
show relevant operational symbols to confirm what action the boiler is taking. If the the
“radiator”, or “z
zz
z” symbol is shown on the display the boiler is receiving a demand for that
function.
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Installation & Servicing Instructions Page : 1

Fault Modes
In the event that the boiler detects a situation which it considers to be a fault the display will
change to show a flashing fault code starting with an “E” and then a two digit number. The
table below explains these codes and the action you should take.
The cabinet has overheated - consult your Service Engineer before operating the boiler
further - SERVICE RESET REQUIRED
E70
Water pressure too high - check that the system water pressure top-up valve has not
been left open or consult your installer to check the expansion vessel.
E62
The flue temperature is too high. Consult your Service Engineer - SERVICE RESET
REQUIRED
E52
The boiler temperature is rising too fast - ask your Service Engineer to check for
system blockage or pump failure.
E25
The system water pressure is too low. Check the system has water in and, for sealed
systems, top up the system water pressure to restore a pressure of between 1 and 2
bar. (Consult your installer for instruction how to top up water pressure - repeated need
for restoration of water pressure indicates a system leak which should be investigated)
E26 or
E67
Flow overheat - the boiler has exceeded it maximum water temperature. Check that any
by-pass is open and the controls are operating correctly
E12
Flame failure whilst running - the boiler is having difficulty maintaining the flame.
Consult your Service Engineer and check for flue, gas supply or condensate drainage
obstruction
E04
Ignition lockout - the boiler has attempted to light five times and not succeeded - check
the gas supply is on.
E02
Description of faultDisplay
The above is an abbreviated list of possible error codes. If the code is not in the list above
consult a CORGI registered engineer. A full list of codes can be found in Chapter 6 of this
manual. If a code appears and you feel the original cause has been rectified and it has not
been designated as requiring a “Service Reset”, press the “Reset” button to resume boiler
operation. Otherwise, or if the code persists consult a CORGI registered engineer.
Raise up the system pressure until error E67 or E26 disappears from display (the boiler will
enter in standby mode or will start to fire up if a heat demand exists). To check the system
pressure press the “

” button repeatedly until the display shows the water pressure, indicated
by the word “bar” to the right of the number. To return to main screen press the RESET
button.
Precautions
Care must be taken at all times to ensure that no blockage or obstruction is present in the
condensate drainage line. In addition, the air intake and flue exhaust terminals must be free
from obstruction at all times.
Care should be taken not to damage the condensate trap protruding from the base of the
boiler. Any sign of leakage of this part should be reported to a CORGI registered engineer
immediately. If the part becomes broken the boiler should be turned off and a CORGI
registered engineer contacted to make a repair.
Any indication of leakage from the boiler cabinet should be investigates by a CORGI engineer.
Frost Protection
The Qudos 28s has an integral frost protection function. However, care should also be taken
that any exposed pipework is adequately insulated to prevent freezing.
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Installation & Servicing Instructions Page : 2

1.4 SAFETY INFORMATION
IF YOU SUSPECT A GAS LEAK TURN OFF THE APPLIANCE IMMEDIATELY, TURN OFF
THE GAS TAP TO THE APPLIANCE (LOCATED UNDERNEATH) AND CONTACT YOUR
GAS SUPPLIER WITHOUT DELAY.
Benchmark Initiative
As part of the industry wide “Benchmark” initiative Qudos 28 boiler manual includes Gas
Boiler Commissioning Checklist (Chapter 10). This form should be completed by your
installer at the end of the installation and commissioning process. The details of the Checklist
will be required in the event of any warranty work being required. There is also Service
Interval Record (Chapter 10) to be completed after each annual service visit.
These forms (Chapter 10) should be kept in a safe place for the life of the boiler.
The boiler should be installed and serviced only by CORGI registered operatives. All CORGI
registered Installers carry a CORGI ID card and have a registration number. Both should be
recorded in your boiler manual (Chapter 10: GAS BOILER COMMISSIONING
CHECKLIST). You can check your installer by calling CORGI direct on 01256 372300.
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Installation & Servicing Instructions Page : 3

2. GENERAL INSTRUCTION
2.1 DESCRIPTION
The KESTON Qudos 28s and Qudos 28sP boilers utilize the latest in condensing
technology to produce a high efficiency boiler with SEDBUK A rated efficiency plus
advance controls to maximize operational efficiency.
The Qudos 28s is unique in concept and design. It comprises a high efficiency stainless
steel heat exchanger coupled with a low emissions burner to deliver ultra high efficiency
condensing mode operation within a compact wall hung cabinet. The unit automatically
adjusts gas and air rate according to demand to give a heating input in the range of 7.8kW
to 29.4kW (GCV). The integral pump assembly, in the Qudos 28s, is automatically speed
controlled to best match water flow rate to heat output & further increase appliance
efficiency.
The Qudos 28s has been developed to embrace the concept of advanced controls to
ensure the ultra high performance burner and heat exchanger system is run to optimum
performance levels whilst provided or exceeding the comfort levels demanded. As a result
the boilers feature a host of additional connections for:
- an optional outside sensor to enable the boilers inbuilt weather compensation
option which delivers enhanced user comfort levels with peak operating efficiency
due to the lower flow temperatures involved.
- an optional “Opentherm” connection point for the Keston Room Control module
which provides further advanced user control for room temperature compensation
and optimum start.
- optional 0-10VDC input where temperature control is provided by external 3rd
party intelligent controls
- optional connection of a DHW thermistor to enable modulated reheat of DHW and
optional legionella prevention function
Further, the Qudos 28s is developed with the concept that the gas boiler in the modern
home is often supplemented by alternative or renewable energy sources. As a result the
Qudos 28s features:
- optional connection of a solar thermal system, pump, panel and DHW sensor, for
direct control of solar thermal system from the boiler. Other additional energy
source systems, such as Ground Source Heat Pump, will be accommodated
soon.
The boilers have the added advantage of very high efficiency, and small diameter muPVC
plastic flue which can be extended up to 20 metres horizontally or vertically. The boilers
also feature an optional remove fascia panel so the boiler can be controlled from within
the house where the boiler is located outside the house or in the loft.
The Keston Qudos 28s uses a variable speed combustion blower to deliver a premix of
gas and air to a downward firing burner in a high efficiency, single pass heat exchanger.
The flue system is room sealed and fan powered. The ignition is direct spark and fully
automatic. The boiler housing is not waterproof and should be installed in a position
where it will always be dry. Combustion air is drawn from the cabinet which is connected
to outside atmosphere via a small diameter plastic intake pipe. The cabinet therefore
remains under negative pressure at all times the boiler is operating.
These boilers are designed for use as part of a sealed water central heating system with
fully pumped circulation. The pump, an 8l expansion vessel and associated safety devices
are all fitted within the Qudos 28s boiler. However, consideration should be given to
additional expansion vessels on larger systems where 8 litres may be inadequate.
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The boiler heat exchanger is made from highly corrosion resistant stainless steel in
corrugated pipe form which provides massive surface area within a compact dimension.
The hot combustion gases from the down firing burner pass around the stainless steel
pipes imparting heat into the system water. On the Qudos 28s integral variable speed
pump within the appliance cabinet ensures the heat exchanger receives correct water flow
when firing. The Qudos 28s is not a high water content boiler and does not contain the
metal mass, or water volume, of a cast iron or steel boiler. This boiler is of low mass and
low water content and therefore responds faster when there is a call for heat. The Qudos
28 features full user diagnostics, integral frost protection function, automatic pump and
fan exercise in periods of inactivity, anti cycle control and dry fire protection.
2.2 BOILER SCHEMATIC
Air is drawn into the boiler through a 50 mm muPVC (BS5255 and/or BSEN1566-1 and
BSEN1329) plastic pipe or, alternatively, via a 75mm Keston composite plastic pipe. Gas
is mixed with combustion air at the inlet to the fan. The gas flow is automatically regulated
by the gas valve according to the air flow generated by the fan. The gas and air are
thoroughly mixed in the blower and fed into the burner located at the top end of the heat
exchanger module. The gas and air mixture is ignited by a direct spark ignition control
system and burns with a blue flame just off the surface of the burner. As the hot products
of combustion pass downwards, they are cooled by exchanging heat with the circulating
water which enters the heat exchanger at the bottom of the heat exchanger. The optimum
heat input is detected by monitoring flow and return temperatures and is adjusted by
controlling the speed of the fan. The optimum pump speed is also detected and
automatically selected by the boiler.
When the return water temperature is below 55oC, part of the water vapour in the
combustion products will condense inside the heat exchanger, thus increasing the boiler
efficiency further by releasing the latent heat of condensation. This condensate falls to the
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ENTER RESET

bottom of the heat exchanger where it is separated from the flue gases and exits from the
boiler through the condensate drain. Any condensate formed in the flue runs back down
the flueway and is drained at the base of the flue connection to the heat exchanger or
drain points within the flue.
The condensate is very slightly acidic (about the same acidity as vinegar) and should be
piped in a plastic pipe. It is not harmful to the waste disposal system and may be disposed
of as normal waste water.
The flue gases are piped in a 50 mm muPVC (BS5255 and/or and BSEN1329) plastic or,
alternatively, 75mm Keston composite plastic pipe to outside. The temperature of the flue
gases are usually around 5oC to 10oC above the temperature of the return water. The flue
pipe should be terminated outside the building from where they cannot re-enter the
building or any other adjacent building. It should also be terminated such that flue
products cannot be drawn into the boiler air intake terminal.
The heating level may be controlled by room thermostats, programmer time clocks and
compatible energy management systems. An optional Keston room controller can be
connected which will provide enhanced controls such as room compensation to further
increase efficiency and comfort levels. However, this is only recommended for heating
only applications. Once the controls are set the boiler operates automatically. Further, a
Keston outside sensor can be connected to the boiler which will automatically invoke
weather compensated heating which further boosts user comfort and boiler efficiency.
In the event of the
boiler overheating the
safety devices will
cause a safety
shutdown. A safety
discharge valve and
discharge pipe is fitted
to the boiler.
The Qudos 28s
features an integral
frost protection
function which will
operate the pump,
regardless of the
external controls,
should the boiler
temperature fall below
10oC. In the event the
boiler temperature
falls below 5oC the
boiler will also fire.
This is to avoid
damage to the boiler
through freezing of
boiler water. The
boiler will turn off
when the flow
temperature exceeds
15oC.
The Qudos 28s
features an integral
pump exercise
function which will run
the pump, without
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Installation & Servicing Instructions Page : 6

firing the boiler, for 10 seconds in the event the boiler is on standby for in excess of 24
hours without firing. This is to help prevent seizing of the pump due to long periods of
inactivity.
2.3 RELATED DOCUMENTS
The Keston Qudos 28s and Qudos 28sP Condensing Boilers must be installed in
accordance with the current issue of the Gas Safety (Installation and Use) Regulations
1996, current IEE Wiring Regulations, Building Regulations,Building Standards (Scotland)
Consolidation, and the Bye Laws of the local Water Undertaking. It is the law that ALL
gas appliances are installed by a competent person in accordance with the above
regulations.
In addition, due account must be taken to the following Codes Of Practice:
BS 6891 : Gas Supplies
BS 6798 : Installation Central Heating Boilers
BS 5449 : Installation Pumped Central Heating
BS 5546 : Installation Domestic Hot Water
BS 5440.1 : Flues
BS 5440.2 : Air Supply
BS 5482.1 : Domestic Propane and Butane Burning
Installations
BS 7074.1 : Expansion Vessels
BS 7593 : Treatment of Water in Hot Water Central
Heating Systems
BS 7671 : Requirements for Electrical Installations. IEE
Wiring Regulations 16th Edition.
For Timber Framed Buildings, British Gas Publications DM2. Also British Gas
Publications 'Guidance Notes For The Installation Of Domestic Gas Condensing
Boilers' and 'Specification For Domestic Wet Central Heating Systems'.
In IE, the installation must be carried out by a competent person and installed in
accordance with the current edition of IS813 “Domestic Gas Installations”, the current
Building Regulation and reference should be made to the current ETC1 rules for electrical
installations.
No alterations should be made to the boiler without written permission from Keston Boilers
Ltd. Any unauthorised modification will invalidate the warranty and may affect the safe and
efficient operation of the boiler.
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Installation & Servicing Instructions Page : 7

2.4 PHYSICAL DATA - Qudos 28s & Qudos 28sP
Cabinet Height mm 700
Cabinet Width mm 435
Cabinet Depth mm 280
Top Clearance mm 150
Side Clearance mm 5
Base Clearance mm 200
Front Clearance (for servicing) mm 300
Weight - Full kg / (lbs) 47/(104)
Weight - Empty kg / (lbs) 43/(95)
Flow and Return Connection G3/4
Gas Connection G1/2
Condensate Connection overflow 22mm plastic
Safety Valve Connection discharge 15mm copper
IP Rating IP20 (IPX0)
Flue and Air Intake Material 50mm muPVC (BS5255 and/or BSEN1566-1 and BSEN1329)
Flue Pipe Size (nominal bore) mm / (in) 50 / (2)
Air Intake Pipe Size (nominal bore) mm / (in) 50 / (2)
Max. Air Intake Length m 39
Max. Flue Outlet Length m 20
Max. Total Flue Outlet and Air Intake Length m 40
Flue and Air Intake Material 75mm Keston Composite
Flue Pipe Size (nominal bore) mm / (in) 75 / (3)
Air Intake Pipe Size (nominal bore) mm / (in) 75 / (3)
Max. Air Intake Length m 117
Max. Flue Outlet Length m 60
Max. Total Flue Outlet and Air Intake Length m 120
2.5 OPTIONAL ACCESSORIES
A range of accessories are available from Keston Boilers Ltd to compliment an installation.
Terminal wall sealing collars are available to make good the external all face whilst working from
the inside of the building using 50mm muPVC (BS5255 and/or BSEN1566-1 and BSEN1329)
pipe. Stand-off frames are available to leave a 50mm gap behind the boiler to allow routing of
pipes behind the boiler.
Description Part Number
Flue Terminal Wall Sealing Collar (50mm) C.08.0.00.07.0
Air Terminal Wall Sealing Collar (50mm) C.08.0.00.07.0
50/75mm Flue Adapter C.17.2.00.60.0
Flue Outlet Terminal (75mm) C.17.2.26.00.0
Air Inlet Terminal (75mm) C.17.2.26.00.0
Stand Off Back Plate Q.10S.0.01.00.0
Outside Temperature Sensor C.10C.0.09.00.0
Keston Chronotherm Room Controller C.17.4.21.00.0
Remote Fascia Kit Q.10S.0.03.00.0
DHW Tank Sensor Q.10S.0.04.00.0
Solar Sensors Kit (Panel sensor and 2 x DHW Tank Sensors) Q.10S.0.05.00.0
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Installation & Servicing Instructions Page : 8

2.6 PERFORMANCE DATA - Qudos 28s & Qudos 28sP
Seasonal Efficiency (SEDBUK) = 91.1 (Qudos 28s) & 92.9 (Qudos 28sP)
This value is used in the UK Government's Standard Assessment Procedure (SAP) for
energy rating of dwellings. The test data from which it has been calculated have been
certified by Advantica Technologies Ltd
Keston Boilers Ltd declare that there are no substances harmful to health within the
appliance or used during the production of the appliance.
The Qudos 28s is intended for domestic and commercial EMC environments and on a
governed G20 meter supply.
The Qudos 28sP is intended for domestic and commercial EMC environments and on a
governed G31 supply.
This boiler meets the requirements of SI 3083 The Boiler (Efficiency) Regulations and is therefore
deemed to meet the requirements of Directive 92/42/EEC. The CE mark on the appliance shows
compliance with Directives 90/396/EEC, 73/23/EEC and 89/336/EEC.
IMPORTANT
This product contains ceramic fibre boards, which although not regarded as a risk, contain
ceramic fibre which may cause temporary irritation to eyes, skin and respiratory tract. The
fibres are held in place by inorganic binders. Therefore as long as the boards are not
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Installation & Servicing Instructions Page : 9
Qudos 28s Qudos 28sP
Nat. Gas (G20) LPG (G31)
Min. Input (Gross CV) kW/(Btu/h) 7.8/(26,600) 7.6/(26,000)
Max. Input (Gross CV) kW/(Btu/h) 29.4/(100,300) 28.8/(98,300)
Max. Output To Water
(80/60oC Flow/Return) kW/(Btu/h) 26.4(90,500) 26.4/(90,500)
(50/30oC Flow/Return) kW/(Btu/h) 28.4/(96,900) 28.4/(96,900)
Min. Output To Water
(80/60oC Flow/Return) kW/(Btu/h) 7.0/(24,900) 7.0/(24,900)
(50/30oC Flow/Return) kW/(Btu/h) 7.8/(26,600) 7.6/(26,000)
Max. Burner Press.-Hot (Factory Preset) mbar/(in w.g) 0/(0) 0/(0)
Max. Gas Cons. After 10 mins (DHW) l/s / (Ft3/hr) 0.76/(96.6) 0.35/(45.0)
Max. Operating Flow Temp. oC 82 82
Max. Press. (Sealed System) bar 2.50 2.50
Inlet Gas Pressure mbar/(in w.g) 20.0 / (8.0) 37.0/(14.8)
Recommended Temp Diff. oC 8 to 20 8 to 20
Electrical Supply 230V 50Hz 230V 50Hz
Power Consumption (Max) W 150 150
Power Consumption (Standby) W 7 7
Type of Gas G20 Natural Gas G31 LPG
Optimum Flue Gas CO2Level (at max CH rate, case on) 9.1 10.5
Expected CO/CO2 Ratio (at max CH rate, case on) 0.0007 0.001
Destination Countries GB/IE GB/IE
SEDBUK Efficiency 91.0 93.0
NOx Class 5 5
Safety Valve bar / (lbf/sq in) 3 / (43.5) 3 / (43.5)
Expansion Vessel Capacity litre 8 8
SEDBUK Rating A (91.1%) A (92.9%)
[NB: For larger systems an additional expansion vessel may be required]
Expansion Vessel Charge Pressure bar / (lbf/sq in) 1.0 / (14.5)
Heating System Minimum Pressure bar / (lbf/sq in) 0.6 / ( 8.7)

disturbed they will not be released. Since the boards are non-servicable parts there should
be no risk. Under no circumstances should the user interfere with any sealed parts.
To ensure that the release of fibres from these RCF articles is kept to a minimum, during
installation and servicing we recommend that you use a HEPA filtered vacuum to remove
any dust accumulated in and around the appliance before and after working on the appli-
ance. When replacing these articles we recommend that the replaced items are not broken
up, but are sealed within heavy duty polythene bags, and clearly labelled as RCF waste.
RCF waste is classed as a stable, non-reactive hazardous waste and may be disposed at a
landfill licensed to accept such waste. Protective clothing is not required when handling
these articles, but we recommend you follow the normal hygiene rules of not smoking,
eating or drinking in the work area and always wash your hands before eating or drinking.
Benchmark Initiative
As part of the industry wide “Benchmark” initiative Qudos 28S boiler manual includes Gas Boiler
Commissioning Checklist (Chapter 10). This form should be completed by your installer at the
end of the installation and commissioning process. The details of the Checklist will be required in
the event of any warranty work being required. There is also Service Interval Record (Chapter
10) to be completed after each annual service visit.
These forms (Chapter 10) should be kept in a safe place for the life of the boiler.
The boiler should be installed and serviced only by CORGI registered operatives. All CORGI regis-
tered Installers carry a CORGI ID card and have a registration number. Both should be recorded
in your boiler manual (Chapter 10: GAS BOILER COMMISSIONING CHECKLIST). You can
check your installer by calling CORGI direct on 01256 372300.
WD420/3/2007 Chapter 2 : General Instruction The Keston Qudos 28s & Qudos 28sP Boilers
Installation & Servicing Instructions Page : 10
IN THE EVENT OF A GAS LEAK
Turn off the gas isolation valve to the property immediately. Extinguish
all naked flames or other sources of ignition. Do not operate electrical
switches on or off. Open all doors and windows to ventilate the area.

3. BOILER LOCATION
3.1 DIMENSIONS AND MINIMUM
CLEARANCES
The boiler must be installed in minimum
clearances shown to allow subsequent
servicing, and safe operation. However, larger
clearances may be required during installation.
3.2 SERVICE CONNECTIONS
Gas, water, air and flue pipe, condensation,
and electrical connections are as shown in the
diagram below. Gas : 15mm compression.
Flow/Return 0.75 inch BSP male, Gas 0.5 inch
BSP male, PRV 15mm copper pipe and
Condensate 21.3mm plastic pipe .
An optional stand-off frame (part number
Q.28S.0.01.00.0) is also available which
mounts behind the boiler to leave a 50mm
deep space behind the boiler. This is to
permit pipe routing behind the boiler if
required. See Section 2.5 - Optional
Accessories.
3.3 POSITION
The Qudos 28s and Qudos 28sP are not
suitable for external installation. The boiler
may be installed in any room or internal
space, although particular attention is drawn
to the requirements of the current IEE 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.
Where a room-sealed appliance is installed
in a room containing a bath or shower, any
electrical switch or appliance control, utilising
mains electricity, should be so situated that it
cannot be touched by a person using the
bath or shower. The Qudos 28S and Qudos 28SP are classified as IP20 (IPX0) and are
therefore suitable for installation in Zone 3 areas, unless subject to hose down.
WD420/3/2007 Chapter 3 - Boiler Location The Keston Qudos 28s & Qudos 28sP Boilers
Installation & Servicing Instructions Page : 11
All dimensions in mm.
150
300 When servicing appliance
200
Figure 3.1.1
Minimum Clearances
55
10 When appliance is operating
All dimensions in mm.
435
280
Figure 3.1.2
Dimensions
Flue Exhaust
Air Intake
700
mm

Compartment installation is permitted - such compartments must be constructed in
accordance with BS 6798.
The wall on which the boiler is mounted must be of suitable load bearing capacity and
must be non-combustible.
The Keston Qudos 28s can be located virtually anywhere desired provided that all
regulations are complied with. Because of the boiler's compact size and venting flexibility,
the installation is not limited to a boiler room setting. Before locating the boiler near a living
space consider whether the sounds generated by the boiler will be objectionable. The
boiler may be located within a cupboard enclosure to reduce noise levels if located within
a living space. LPG boilers must not be installed in a cellar.
3.4 ELECTRICAL
3.4.1 Electrical Connections
The boiler must be connected to a permanent 230V ~ 50Hz supply, fused at 3A.
The boiler can be wired to a single switched live 230VAC signal input.
However, the boiler has TWO thermostats, and will therefore accept up to
TWO switched live 230VAC signal inputs, such as heating and hot water or
radiators and underfloor heating zones. Alternatively, a Keston Room
Controller can be connected directly, via two core low voltage cable, to the
terminals marked “OT”. The Keston Room Controller will then provide fully
room compensated control to ensure the boiler output is matched to the
rooms requirements at optimum boiler efficiency. This is only
recommended for heating only applications. The boiler can also be driven
by an external 0-10VDC input.
Wiring external to the boiler must be in accordance with current I.E.E wiring
regulations and local regulations.
The method of connection to the mains electricity supply must facilitate complete
electrical isolation of the boiler, preferably by the use of a fused, unswitched three
pin plug and a shuttered socket-outlet, both complying with the requirements of
WD420/3/2007 Chapter 3 - Boiler Location The Keston Qudos 28s & Qudos 28sP Boilers
Installation & Servicing Instructions Page : 12
Chimneys not used for
venting any other
appliance may be used.
Figure 3.3
Secure air & flue pipes at
chimney outlet.
[NB: Refer to
Section 3.8.3]

BS 1363. There must be only one common method of isolation for the boiler and
its control system.
The appliance must be connected to the 3A supply via a fused double-pole switch
having at least 3 mm (1/8 inch) contact separation in both poles, serving only the
boiler and the system controls.
The connection point to the mains supply should be readily accessible and
adjacent to the boiler, except for rooms containing a bath or a shower. Refer to
section 3.3 Position.
3.4.2 External Wiring & Controls
1. The boiler is designed so that all control wiring is external to the boiler.
2. Heating control signal inputs must be 230VAC "switched live" type unless
using a Keston Room Controller (see below) or 0-10VDC input.
3.4.2.1 Enhanced Control Options
The Qudos 28s can be wired into a conventional heating installation using only
permanent and switched live connections.
However, the Qudos 28s features a wide range of OPTIONAL control features
normally associated with commercial boilers installations at additional cost. These
are provided as standard in the Qudos 28s and require low costs sensors to be
added to activate them. The features provided are detailed below. Refer to
Chapter 4.8 for further wiring detail.
Room Compensation (Opentherm)
A Keston Room Controller may be used to provide room compensated
control to ensure the boiler output is matched to the rooms requirements
at optimum boiler efficiency. This is only recommended for heating only
applications
Weather Compensation (Ext Sensor)
A Keston outside temperature sensor may be connected as an option.
The boiler will automatically detect this connection and will operate on a
"weather compensation" basis when receiving a heating demand signal
from the SL terminal or from a Keston Room Controller. Screened cable
(80% density) must be used to connect the outside temperature sensor.
Solar Control
Where a solar thermal system is in use, with a twin coil cylinder such as
the Kesotn SpaTwin, the Qudos 28s will control operation of the solar
pump in conjunction with the boiler. The boiler requires connection to the
solar tank sensor, solar panel sensor and solar pump
Modulating DHW Reheat
The Qudos 28s can provide direct modulation to maximise the re-heat
performance of the DHW cylinder. A DHW cylinder sensor can be
connected directly to the Qudos 28. A DHW demand input can also be
provided to control DHW reheat activity, perhaps in conjunction with Solar
Thermal. With this facility connected an automatic anti-legionnella facility
can also be provided.
Analog Demand (0-10VDC)
Where external control panels are used, in boiler room applications, a
0-10VDC input can be connected to the boiler, in place of the SL1
switched live demand. The 0-10VDC signal will drive the first setpoint at
1VDC = 10C setpoint (NB: <0.5VDC is off, >8.0 VDC is 80C)
External Lockout Signal
Where remote monitoring and/or alarms are installed the boiler offers a
volt-free lockout signal output. The boiler will provide a closed circuit
across the two output points when the boiler is in lockout.
WD420/3/2007 Chapter 3 - Boiler Location The Keston Qudos 28s & Qudos 28sP Boilers
Installation & Servicing Instructions Page : 13

Remote Fascia Panel
For installations where the boiler is located outside of the living area, such as the loft or an
out-house, a remote fascia control can be fitted within the living area. This will allow full
functionality normally access via the boiler fascia panel.
3.5 BOILER SIZE SELECTION
The Qudos 28s will automatically adjust heat output and pump speed to match the system
requirements at any given time. Efficiency and combustion levels are maintained at
optimum levels throughout the possible output range. The Qudos 28s is therefore suitable
for all systems with a total heat load within the maximum range of the boiler.
3.6 GAS SUPPLY
A gas meter should be connected to the service pipe by the local gas region or their
contractor. An existing meter should be checked preferably by the gas region to ensure
that the meter is adequate to deal with the rate of gas supply required. Installation pipes
should be fitted in accordance with BS 6891.
Minimum/Maximum Gas Pressure:
Natural gas pressure before the gas valve must be maintained at between 18 mbar (7.2 in
WG) and 22 mbar (8.8 in) while the boiler is running.
LPG pressure must be maintained between 31.5 mbar (12.4 in w.g) and 37.6 mbar (14.8
in w.g) while the boiler is running.
Gas pressures above or below these levels will lead to problems associated with the gas
valve's internal pressure regulator.
Supply pipes to the boiler must not be sized less than the boiler inlet connection
(15 mm). Due consideration must be given to the supply pressure to other gas
appliances in the premises. Reduction in dynamic gas supply pressure will result in
intermittent ignition failures. Ensure gas supply pipe work is adequately sized for
the length of run from the meter to the boiler at a supply rate of 28.4kW (i.e. a natural
gas supply should be considered to be a minimum of 22mm diameter, reducing to 15mm
at the boiler. If gas runs greater than 12m, including the allowance for bends, are involved
the pipe size should be increased further).
3.7 WATER SYSTEMS
All piping must be installed in accordance with all applicable local and Water Supply
Bylaws for forced hot water heating systems.
Consideration must be given to pipe capabilities and pressure drop through the piping
when selecting pipe sizes. The primary pipe connections to the boiler must be sized
according to the system load, not dictated by the boiler connection sizes.
Water treatment must be carried out to BS 7593 : Treatment of Water in Hot Water
Central Heating Systems.
In IE the requirements given in the current edition of IS813 and the current Building
Regulations must be followed.
a The Keston Qudos 28s is designed for installation on sealed water systems only.
With fully pumped water circulation. The pump, an 8l expansion vessel and
associated safety devices are fitted within the boiler.
b Any system must be thoroughly flushed clean of grease, dirt and debris, prior to
connection with the boiler. A trap may be installed in the flow line to collect any
solder, or other debris, from the installation.
c All water systems must be constructed to comply with requirements of the Local
Water Authority.
d Always use a system complying with the requirements of BS 5449 and BS 6798.
e System design must ensure an open circuit is always available to ensure
circulation when the pump overrun function is operating after boiler shutdown.
f Isolation valves must be fitted on the flow and the return to enable isolation when
maintaining the boiler.
WD420/3/2007 Chapter 3 - Boiler Location The Keston Qudos 28s & Qudos 28sP Boilers
Installation & Servicing Instructions Page : 14

g Copper tubing to BS 2871 Part 1 or barrier plastic pipe suitable to 110 oC, such as
Unipipe, is recommended.
h Jointing should be either with capillary, threaded or compression fittings. Pipes
should have a gradient to ensure air is passed easily to vent points and water
flows readily to drain points.
i Draining taps must be located in accessible positions which permit the draining of
the boiler. Draining taps should be at least 22 mm in nominal size and be in
accordance with BS 2879.
AIR VENT POINTS
j These must be fitted at all high points where air will naturally collect and must be
sited to allow complete draining of the system.
Table 3.7 Additional Expansion Vessel Selection
13.6
125 litres
10.9
100 litres
8.2
75 litres
5.4
50 litres
2.7
25 litres
Vessel
Volume
Total Water Content of system in
excess of 125 litres
1.0 bar
Vessel charge & initial system
pressure.
3.0 bar
Safety Valve Setting
k. The boiler is supplied with an integral expansion vessel of 8l capacity. This is
suitable for systems of up to 125 litres system volume. Table 3.7 Expansion
Vessel Selection provides guidance for the correct additional expansion vessel
size to use for systems with a water content larger than 125 litres. Any additional
vessel must be fitted on the boiler primary return.
l A filling point must be fitted, in accordance with local water authority
requirements.
WD420/3/2007 Chapter 3 - Boiler Location The Keston Qudos 28s & Qudos 28sP Boilers
Installation & Servicing Instructions Page : 15
Stop Tap
BS 1010:2
Cock
Test
bib tap
Hose Union
after filling)
(disconnected
Hosepipe
Connector
Hose
Dbl Check Valve
L/S
ir Vent
RETURN
Vessel
Expansion
(if required)
HEATING CIRCUIT
Qudos 28s
KESTON
By-pass
Cock
Drain
Figure 3.7 : Sealed Systems Diagram
FLOW
Additional