Keston K170 User guide

170,000 Btu/h (50 kW) Model
Fan Powered High Efficiency
Condensing Gas Boiler
Installation And Servicing Instructions
Keston 170 - GC No 41 930 04
CE No : 87AR50
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]
WD51/2/1997 The Keston 170 Condensing Boiler

CONTENTS
Section Description
1 GENERAL INSTRUCTION
1.1 Description
1.2 Boiler Schematic
1.3 Related Documents
1.4 Performance Data
1.5 General Data
2 BOILER LOCATION
2.1 Dimensions & Minimum Clearances
2.2 Service Connections
2.3 Position
2.4 Electrical
2.5 Boiler Size Selection
2.6 Gas Supply
2.7 Water Systems
2.8 Flue System
2.9 Air Supply
2.10 Compartment Installation
2.11 Condensate Drainage
2.12 Radiant Floor Heating
2.13 Low Water Volume Boiler vs. Cast Iron Boiler
2.14 Determine Radiation Needed Room-By-Room
3 INSTALLATION OF THE BOILER
3.1 Wall Mounting Bracket
3.2 Mounting The Boiler
3.3 Assembly Practice
3.4 Installing Flue And Air Pipes
3.5 Condensate Drainage
3.6 Water System
3.7 Gas Supply
3.8 Electrical Supply
3.9 Exchanging A Boiler
4 COMMISSIONING OF THE BOILER
4.1 Initial Flushing
4.2 Gas Supply
4.3 Electrical Installation
4.4 LP Gas Conversion
4.5 Initial Firing
4.6 Hot Flushing
4.7 Checking The Gas Pressure
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4.8 Timing The Gas Meter
4.9 Handing Over To The User
5 FAULT FINDING
5.1 Electrical Control Sequence
5.2 Fault Finding Flow Chart
5.3 Continuity Checking
5.4 Functional Flow Wiring Diagram
5.5 Electrical Wiring Diagram
5.6 Illustrated Wiring Diagram
5.7 Exploded Assembly Diagrams
6 SERVICING
6.1 Pre Service Checks
6.2 Recommended Routine Service
7 REPLACEMENT OF PARTS
7.1 General
7.2 Precautions
7.3 Access
7.4 Electrical
7.5 Gas Orifice
7.6 Spark Ignition/Flame Detection Electrode
7.7 Burner Head & Burner
7.8 Heat Exchanger
7.9 Air Screen
7.10 Condensate Trap
7.11 Pressure Gauge
7.12 Sight Glass
7.13 HT Ignition Lead
7.14 Air Vent
7.15 Air Orifice
8 SPARE PARTS LISTINGS
BENCHMARK INITIATIVE
As part of the industry wide “Benchmark” Initiative all Keston 170 boilers now include a Benchmark
Installation, Commissioning and Service Record Log Book. Please read this carefully and complete all
sections relevant to the appliance installation. The details of the Log Book will be required in the event
of and warranty work being required. There is also a section to be completed after each regular
service visit. The completed Log Book should be left with the customer.
CORGI CONTACT INFORMATION
The boiler should be installed and serviced only by CORGI registered operatives. All CORGI
registered Installers carry a CORGI ID cad, and have a registration number. Both should be
recorded in the Benchmark Log Book. You can call CORGI direct on 01256 372300.
WD51/2/1997 The Keston 170 Condensing Boiler
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1. GENERAL INSTRUCTION
1.1 DESCRIPTION
The Keston Condensing Boiler is unique in its concept and design. While the application
for which the boiler was designed is the same as those which other boilers are used, the
Keston boiler has the added advantage of very high efficiency, and small diameter plastic
flue which can be extended to 15 metres horizontally or vertically.
The Keston uses a high power combustion blower to deliver a pre-mix of gas and air to a
downward firing burner in a high efficiency, single pass heat exchanger. Normally the
combustion temperature of the air gas mixture is around 1800
o
C but the Keston achieves
combustion at an amazing 1000
o
C thereby reducing the NO
x emissions.
The flue system is room sealed and fan powered. The ignition is direct spark and fully
automatic. The boiler housing is not waterproof. The boiler should be installed in a
position where it will always be dry. A small air intake point is incorporated within the
appliance cabinet to ensure that the interior of the cabinet is maintained under a slight
negative pressure. This is a safety feature to ensure no products may leak out of the
cabinet into the installation space.
The boiler is suitable for connection to open vented or, preferably, sealed systems. The
system must be pumped central heating or pumped central heating with combined indirect
sanitary hot water. Gravity circuits must not be used.
Forming part of the boiler is the heat exchanger which is made from a highly corrosion
resistant stainless steel, formed into tightly wound coil. The hot combustion gases from
the central down firing burner pass through this coil imparting heat into the system water.
Head characteristics of the boiler coil must be taken into consideration when calculating
the pump size. The Keston boiler 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. This
feature requires a higher water pumping rate through the boiler otherwise localised boiling
will occur within the boiler. Allow a pressure drop through the boiler of 13.75 ft head and a
water flow of 13.2 gallons (60 litres) per minute.
The boiler selected must be sized relative to the total calculated heat loss of the building.
The boiler rated output should not be greater than the total required to make up the
calculated heat loss plus the heat required to provide sanitary hot water, if the system is
not hot water priority design. If there are special conditions such as excessive sanitary hot
water usage consult the manufacturer.
1.2 BOILER SCHEMATIC
Air is drawn into the boiler through a 50mm muPVC pipe. The air flow is proved by a
differential pressure across the air control orifice. Gas is mixed with combustion air at the
inlet to the fan. The gas flow is regulated by an orifice located in the housing downstream
of the gas valve.
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 coil at the bottom of the heat
exchanger.
Fig. 1.2 - Boiler Schematic
WD51/2/1997 Chapter 1 : General Instruction The Keston 170 Condensing Boiler
Installation & Servicing Instructions Page : 1

When the return water temperature is below 54
o
C, part of the water vapour in the
combustion products will condense inside the heat exchanger, thus increasing the boiler
efficiency by releasing the latent heat of condensation. This condensate falls to the 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 50mm muPVC pipe to the outside. The temperature of the
flue gases are usually around 10
o
C 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.
The heating level may be controlled by room thermostats, hot water cylinder thermostats,
programmer time clocks and energy management systems.
1.3 RELATED DOCUMENTS
The Keston Condensing Boiler must be installed in accordance with the current issue of
the Gas Safety (Installation and Use) Regulations, current IEE Wiring Regulations,
Building Regulations,Building Standards (Scotland) Consolidation, and the Bye Laws of
the local Water Undertaking.
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
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BS 5440.2 : Air Supply
BS 5482.1 : Domestic Propane & Butane Burning Installations
BS 7074.1 : Expansion Vessels
BS 7593 : Treatment of Water in Hot Water Central Heating
Systems
BS 7671 : Requirments 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'.
1.4 PERFORMANCE DATA
1.5 GENERAL DATA
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Installation & Servicing Instructions Page : 3
Boiler Input (gross) kW 55.0
Btu/h 187,600
Boiler Output To Water kW 49.8
(80
o
C Flow 60
o
C Return) Btu/h 170,000
Boiler Output To Water kW 52.4
(60
o
C Flow 40
o
C Return) Btu/h 179,000
Boiler Output To Water kW 54.5
(50
o
C Flow 30
o
C Return) Btu/h 186,000
Burner Setting Pressure mbar 10.0
(Hot) in wg 3.94
Gas Comsumption After l/s 1.42
10 mins Running Ft
3
/hr 180.73
(CV of Gas - 38.7 MJ/m
3
)
(1038 Btu/Ft
3
)
Max. Operating Flow Temp.
o
C 80.00
Max. Head (Open Systems) m 30.50
Ft 100.0
Max. Press. (Sealed Sys.) Bar 2.70
Min. Head (Open Systems) m 2.5
Ft 8.0
Inlet Gas Pressure mbar 20.0
in wg 8.0
Gas Orifice Size mm 4.5
Air Orifice Size mm 23.0
Recommended Temperature
o
C 10 to 15
Differential
Main Burner Keston Premix
Gas Control White Rogers 36E Series
Combustion Fan Keston
Type LPB 103 220/240
0.6 kW 2900 RPM
Direct Spark RAM ElectronicsIgnition
Ignition Full Sequence Control
Air Press. Switch Tridelta FS6717-1428
Filter Keston Filter
Gas Supply 0.75 inch BSPT Male
Connection (22mm to gas cock)
Flow Connection 35mm Copper
Return Connection 35mm Copper
Power Supply 230V 50Hz
Pwr Consumption 610 W
Ext Fuse Rating 10 Amps
Weight - Full 68 kg (150 lbs)
Weight - Empty 61 kg (134 lbs)
Data Badge Posn Right Hand Panel Inside
Case
Water Content 7.0 litres

2. BOILER LOCATION
2.1 DIMENSIONS AND MINIMUM
CLEARANCES
The boiler must be installed in minimum
clearances shown to allow subsequent
servicing, and safe operation.
2.2 SERVICE CONNECTIONS
Gas, water, air and flue pipe,
condensation, and electrical
connections are as shown. Gas :7 0.5
inch BSP male. Flow/Return 35 mm
copper.
2.3 POSITION
The Keston is 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
WD51/2/1997 Chapter 2 - Boiler Connections The Keston 170 Condensing Boiler
Installation & Servicing Instructions Page : 4
All dimensions in mm.
254
305
127 Figure2.1.1
MinimumClearances
1
1
All dimensions in mm.
500
327
Figure 2.1.2
Dimensions
AirIntake
Flue
Flow
Return
50
113
Condense Gas
890
30 44
97
BaseView
ServiceConnectionLocations All dimensions are in mm.
190
405
Top View
65
50
263
244
37
85
152
50
35

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.
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.
Important : It is not recommended to install the boiler on a studded wall or similar - it is
possible that the vibration from the fan would be amplified and transmitted to other parts
of the property.
Chimneys notusedfor
venting anyother
appliancemaybe used.
Figure2.3
Condensatedrain
Secure air & fluepipes at
chimneyoutlet.
[NB: Refer to
Section 2.8.3]
The Keston 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.
2.4 ELECTRICAL
2.4.1 Electrical Connections
The boiler must be connected to a 230V ~ 50Hz supply, fused at 10A. All
external controls and wiring must be suitable for mains voltage. 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,
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Installation & Servicing Instructions Page : 5

unswitched three pin plug and a shuttered socket-outlet, both complying with the
requirements of BS 1363.
The appliance must be connected to the supply via a fused double pole switch
having at least 3mm (1/8 inch) contact separation in both poles, serving only the
boiler and the system.
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 2.3 Position.
2.4.2 External Wiring & Controls
1. The boiler is deisgned so that all control wiring is external to the boiler.
Hence, any programmers or room thermostats etc must act by switching
the 230V supply to the boiler.
2. System designs which allow the boiler to fire when there is no pumped
circulation must NOT be used.
3. A programmer may be used with zone valves to give independent control
of central heating and hot water.
2.5 BOILER SIZE SELECTION
The size of the boiler to be used is determined by the total calculated heat loss of the
building. Match the calculated heat loss with the boilers rated output. If a boiler is installed
with an output rating greatly exceeding the total capacity of the distribution system the
efficiency of the boiler will be reduced.
2.6 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 Natural Gas Pressure:
Natural gas pressure before the gas valve must be maintained at 20 mbar (8 in WG) while
the boiler is running.Gas pressures above or below this level 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 (22 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.
A gas cock is supplied loose with the boiler. This cock should be fitted in the gas line to
the boiler as close to the boiler as possible so that it is easily identified as the cock to
isolate the boiler.
2.7 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.
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Installation & Servicing Instructions Page : 6

Water treatment must be carried out to BS 7593 : Treatment of Water in Hot Water
Central Heating Systems.
Pump isolating valves must be positioned as close to the pump as possible.
a The Keston 170 is suitable for use on open vented water systems with combined
feed and vent.
b It is preferable for use on sealed water systems, provided the appropriate
components required (see Section 2.7.2 Sealed Systems) are included in the
system.
c Any system must be thoroughly flushed clean of grease, dirt and debris, prior to
connection with the boiler. A trap should be installed in the flow line to collect any
solder, or other debris, from the installation.
d All water systems must be constructed to comply with requirements of the Local
Water Authority.
e Only fully pumped systems can be used - gravity systems are strictly not suitable.
f Always use a system complying with the requirements of BS 5449 and BS 6798.
g The system must be so arranged that there shall always be a minimum flow of
13.2 gpm (60 litres/min) when the boiler is firing.
This can be via a specially
installed by-pass arrangement.
h Copper tubing to BS 2871 Part 1 is recommended.
i 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.
j Draining taps must be located in accessible positions which permit the draining of
the boiler and hot water storage vessel. Draining taps should be at least 22 mm in
nominal size and be in accordance with BS 2879.
AIR VENT POINTS
k These must be fitted at all high points where air will naturally collect and must be
sited to allow complete draining of the system.
2.7.1 Open Vented Systems
A typical system is shown in Figure 2.7.1 which includes a combined feed and
vent. Note there must be no valve between the boiler flow and the open vent.
Note that the minimum static head required is 9 ft at the boiler flow pipe. If the
cold feed/vent is not brought to the flow pipe as shown, then the pressure loss
across the heat exchanger may have to be taken into account when estimating
the static pressure.
Although suitable for open vented systems with combined feed and vent
arrangements, the Keston is a low water content boiler. As such, any air
entrainement within the system water will produce boiler “kettling”. It is
therefore recommended, if in any doubt, to consider the use of sealed
systems where possible.
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