Benchmark Alpha E-Tec 20NXS User manual

Installation and Servicing
Instructions
E-Tec 20NXS,30NXS and 35NXS
Wall Mounted, Fan Assisted, Room Sealed,
Gas Fired, High Efficiency Condensing System Boiler
Nepicar House, London Road,
Wrotham Heath, Sevenoaks,
Kent TN15 7RS
For Technical help or for Service call ...
ALPHA HELPLINE Tel: [phone]
website: www.alpha-innovation.co.uk
Leave these instructions with the User
These instructions have been carefully prepared but we reserve the right
to alter the specification at any time in the interest of product improvement.
© Alpha Therm Limited 2023.
Part No. 1.046747 rev. ST.006689/000
0223/D450
Alpha E-Tec 20NXS G.C. No. 41 532 53
Alpha E-Tec 30NXS G.C. No. 41 532 54
Alpha E-Tec 35NXS G.C. No. 41 532 55

2Alpha E-Tec 20NXS, 30NXS and 35NXS - Benchmark Scheme
BENCHMARK SCHEME
To comply with Building Regulations Part L1 (Part 6 in Scotland) the boiler should be installed in accordance
with the manufacturer’s instructions. Self-certification that the boiler has been installed to comply with Building
Regulations can be demonstrated by completing and signing the Benchmark Checklist at the back of these
instructions.
Code of Practice
For the installation, commissioning and servicing of domestic heating and hot water products.
Benchmark places responsibilities on both manufacturers and installers*.The purpose is to ensure that customers** are provided
with the correct equipment for their needs, that it is installed, commissioned and serviced in accordance with the manufacturer's
instructions by competent persons and that it meets the requirements of the appropriate Building Regulations. Installers are
required to carry out work in accordance with the following:
Standards of Work
• Be competent and qualified to undertake the work required.
• Install, commission, service and use products in accordance with the manufacturer's instructions provided.
• Ensure that where there is responsibility for design work, the installation is correctly sized and fit for purpose.
• Meet the requirements of the appropriate Building Regulations. Where this involves notifiable work be a member of a
Competent Persons Scheme or confirm that the customer has notified Local Authority Control (LABC), prior to work
commencing.
• Complete all relevant sections of the Benchmark Checklist/Service Record when carrying out commissioning or
servicing of a product or system.
• Ensure that the product or system is left in a safe condition and, where possible, in good working order.
• Highlight to the customer any remedial or improvement work identified during the course of commissioning or servicing work.
• Refer to the manufacturer's helpline where assistance is needed.
• Report product faults and concerns to the manufacturer in a timely manner.
Customer Service
• Show the customer any identity card that is relevant to the work being carried out prior to commencement or on request.
• Give a full and clear explanation/demonstration of the product or system and its operation to the customer.
• Hand over the manufacturer's instructions, including the Benchmark Checklist, to the customer on completion of an installation.
• Obtain the customer's signature on the Benchmark Checklist to confirm satisfactory demonstration and receipt of
manufacturer's instructions.
• Advise the customer that regular product servicing is needed, in line with manufacturers' recommendations, to ensure
that safety and efficiency is maintained.
• Respond promptly to calls from a customer following completion of their work, providing advice and assistance by
phone and, if necessary, visiting the customer.
• Rectify any installation problems at no cost to the customer during the installer's guarantee period.
* The use of the word "installer" is not limited to installation itself and covers those carrying out installation, commissioning and/or servicing of heating and hot water
products, or the use of supporting products (such as water treatment or test equipment).
** Customer includes householders, landlords and tenants.
Benchmark Commissioning and Servicing Section
It is a requirement that the boiler is installed and commissioned to the manufacturers instructions and the data
fields on the commissioning checklist completed in full.
To instigate the boiler guarantee the boiler needs to be registered with the manufacturer within one month of the
installation.
To maintain the boiler guarantee it is essential that the boiler is serviced annually by a Gas Safe registered
engineer who has been trained on the boiler installed. The service details should be recorded on the Benchmark
Service Interval Record and left with the householder.
Useful contact details: Gas Safe Register - 0800 408 5577 - www.gassaferegister.co.uk
Alpha Heating Innovation: General Sales Enquiries - 0344 871 8760
Technical Helpline - 0344 871 8764
www.centralheating.co.uk

3
CONTENTS
1 Introduction........................................3
2 Safety symbols and information ........4
3 Technical data ...................................6
4 General boiler information .................11
5 Installation .........................................18
6 Commissioning..................................29
7 Routine servicing...............................38
8 Component replacement ...................44
9 Wiring diagram ..................................48
10 Error codes and fault finding..............49
11 Short parts list ...................................52
12 Energy classification..........................53
Benchmark Checklist.........................60
Service Record..................................61
The E-Tec 20NXS, 30NXS and 35NXS are wall mounted, room sealed, fan assisted, high efficiency, condensing boilers. The
burner is lit electronically and the heat output is controlled by a modulating fan and gas valve.
The E-Tec 20NXS, 30NXS and 35NXS are boilers that provided central heating only, on a sealed system.
The boiler is supplied with a pump, pressure relief valve, expansion vessel and pressure gauge fully assembled and tested. It
is designed for use with a fully pumped, sealed and pressurised central heating system.
The boiler is approved for operation with Natural Gas (G20), a mixture of Natural Gas and Hydrogen at 20% by volume (G20Y20)
and LPG (G31).
IMPORTANT
Failure to install and commission this appliance in compliance with the manufacturer's instructions may invalidate
the warranty.
It is the law that all gas appliances are installed by a competent person, ie Gas Safe registered personnel, in
accordance with the following recommendations:-
Current Gas Safety (Installation and Use) Regulations
All current Building Regulations issued by the Department of the Environment, i.e. Approved Document L26.
Building Standards (Scotland) (Consolidation) Regulations issued by the Scottish Development Department
UK Water Regulations/Byelaws (Scotland)
Health & Safety Document No. 635 (The Electricity At Work Regulations 1989)
The installation should also be in accordance with the following British Standard Codes of Practice:-
BS 5440-1: 2008........................Flueing and Ventilation Requirements
BS 5440-2: 2009........................Installation and Maintenance of Flues and Ventilation
BS 5546: 2010 ...........................Specification for Water Heating Appliances
BS 6798: 2009 ...........................Specification for Installation gas fired boilers up to 70 kW
BS 6891: 2005 + A2: 2008.........Installation of low pressure Gas Pipework
IGEM/UP/2 ...............................Installation of pipework
IGEM/UP/4 ................................Commissioning of gas fired plant
IGE/UP/10 .................................Installation of Flued gas appliances
IGEM/UP/16 ..............................Design for natural gas installations
IGE/UP/1 and 1B.......................Strength Testing and tightness testing Natural Gas Installations
Reference should also be made to any other standards and requirements relating to the installation depending on the location
and use.
Reference should be made to DEFRA document 'Guide to condensing boiler installation assessment procedures for dwellings'.
If installation is in a timber framed building, refer to the Institute of Gas Engineers document IGE/UP/7.
This appliance meets the requirements of IPX5D, ie degree of protection against moisture.
This appliance contains no asbestos and no substances have been used in the construction process that contravene the
COSHH Regulations (Control of Substances Hazardous to Health).
Failure to install this appliance correctly could lead to prosecution. It is in your own interest and that of safety to ensure that
the law is complied with.
Manufacturer's instructions must NOT be taken in anyway as over-riding statutory obligations.
Notes: 1. Ensure that the Benchmark Checklist has been completed after the boiler has been installed and commissioned.
2. It is the law that all domestic boiler installations are registered by the installer through the Gas Safe Notification
Scheme.
3. The boiler must only be used with Alpha CD condensing flue components.
Propane Gas (LPG) - In addition to the regulations and requirements stated, the boiler must be installed in accordance with
BS 5482:1 - The Installation of Propane Burning Appliances in Permanent Dwellings.
1 INTRODUCTION
Alpha E-Tec 20NXS, 30NXS and 35NXS - Contents/Introduction

4
ELECTRICAL HAZARD
Strictly follow all of the indications next to the symbol. The symbol indicates the appliance’s electrical
components or, in this manual, identifies actions that can cause an electrical hazard.
MOVING PARTS
The symbol indicates the appliance’s moving components that can cause hazards..
HOT SURFACES
The symbol indicates the appliance’s very hot components that can cause burns.
SHARP SURFACES
The symbol indicates the appliance’s components or parts that can cause cuts if touched.
EARTH TERMINAL CONNECTION
The symbol identifies the appliance’s earth terminal connection point.
READ AND UNDERSTAND THE INSTRUCTIONS
Read and understand the appliance’s instructions before performing any operation, carefully following the
indications provided.
RECOVERABLE OR RECYCLABLE MATERIAL
INFORMATION
Indicates useful tips or additional information.
SAFETY GLOVES
SAFETY GOGGLES
SAFETY FOOTWEAR
The user must not dispose of the appliance at the end of its service life as municipal waste, but send it to
appropriate collection centres.
GENERIC HAZARD
Strictly follow all of the indications next to the symbol. Failure to follow the indications can generate hazard
situations resulting in possible harm to the health of the operator and user in general.
Alpha E-Tec 20NXS, 30NXS and 35NXS - Safety Symbols and Information
PERSONAL PROTECTIVE EQUIPMENT
2 SAFETY SYMBOLS and INFORMATION

5
Alpha E-Tec 20NXS, 30NXS and 35NXS - Safety Symbols and Information
2.1 ELECTRICAL SUPPLY
ATTENTION:
The power supply cable must be connected to a 230 V ±10% / 50 Hz mains supply respecting L - N
polarity and earth connection; , this must be connected to a fused 3 A double pole switch with class III overvoltage
category (contact separation of at least 3 mm in both poles) or a fused 3 A 3-pin plug and unswitched shuttered socket outlet
(both complying with BS 1363) in compliance with installation regulations.
The boiler is supplied with a 'Special X' type electrical connection with a PVC <HAR> H05VV-F 3 x 0.75 cable without a plug.
If the power cable is damaged or replaced, it must be replaced with a cable supplied by Alpha or authorized After-Sale
Technical Service. Replacement is recommended using a qualified company in order to prevent any risk.
The boiler must be earthed.
There must only be one common isolator, providing complete electrical isolation, for the boiler and any external controls.
Wiring external to the boiler must be in accordance with the current IEE Wiring Regulations (BS 7671).
Note: If a room thermostat is fitted, it must be suitable for 230 V switching.
If the boiler is locked out and an error code is shown on the display, the RESET button can be pressed to try and clear the fault.
If the fault still occurs after pressing the RESET button, then contact an approved engineer or Alpha service support department.
2.2 PHYSICAL DATA
Boiler flow and return connections mm
Gas connection diameter mm
Boiler dimensions Height mm
Width mm
Depth mm
Clearances for servicing Bottom mm
Bottom (with jig) mm
Top (horizontal flue) mm
Top (vertical flue) mm
Sides mm
Front mm
Recommended hole size for flue pipe mm
Recommended hole size for instalation from inside the building mm
Boiler dry lift weight E-Tec 20NXS kg
E-Tec 30NXS kg
E-Tec 35NXS kg
Boiler operating weight (full of water) approx. E-Tec 20NXS kg
E-Tec 30NXS kg
E-Tec 35NXS kg
Max. total flue length Horizontal m
Max. total flue length Vertical m
Flue system diameter mm
22
22
712
440
253
150
250
240
150
5
450
110
130
30.6
32.8
32.8
33.9
36.2
36.2
12
14
60/100

6
3 TECHNICAL DATA
Alpha E-Tec 20NXS, 30NXS and 35NXS - Technical Data
Note: OtherTechnical data is the same as NG data.
3.2 TECHNICAL PERFORMANCE DATA - LPG - PROPANE GAS (Cat I3P 3P - G31 37 mbar)
Heat input gross - DHW kW
Heat input gross - CH kW
Heat input min. gross kW
Gas supply pressure mbar
Gas burner injector mm
CO2 at maximum DHW output %
CO2 at minimum output %
Gas rate at maximum output kg/h (g/s)
SAP/SEDBUK seasonality efficiency 2005 %
SAP/SEDBUK seasonality efficiency 2009 %
CO maximum ppm
31.2
26.6
4.9
37
3.7
10.2 (10.0 to 10.4)
9.7 (9.5 to 9.9)
2.23 (0.62)
91.8
89.7
250
35.5
31.1
5.4
37
4.2
10.3 (10.1 to 10.5)
9.6 (9.4 to 9.8)
2.54 (0.71)
91.7
89.5
250
E-Tec 20 NXS E-Tec 30 NXS
41.3
35.5
6.5
37
4.9
10 (9.4 to 10.3)
9.4 (9.1 to 9.5)
2.95 (0.82)
90.7
89.6
350
E-Tec 35 NXS
3.1 TECHNICAL PERFORMANCE DATA - NATURAL GAS (Cat I2H 2H - G20 20 mbar)
36.3
31.7
32.7
28.6
31.5
27.6
30.4
28
5.6
5.0
4.8
4.8
32
3.46
20 (17)
85
5.7
34.1
19.3
6
9.2 (9.1 to 9.5)
4.4 (3.9 to 4.6)
8.6 (8.3 to 8.7)
5.5 (5.3 to 6.0)
250
0.003
90.2
89.4
94
2.5 (0.25)
0.5 (0.05)
1.0 (0.1)
3.0 (0.3)
8.0
1.0 (0.1)
120
3
73
120
-5 to + 40
53
8
79
57
E-Tec 20 NXS E-Tec 30 NXS
31.9
27.2
28.7
24.5
27.1
23.2
26.1
24.0
5.0
4.5
4.3
4.3
28
3.04
20 (17)
85
4.90
38.8
22
6
9.2 (9.1 to 9.5)
4.4 (3.9 to 4.6)
8.5 (8.3 to 8.7)
5.7 (5.3 to 6.0)
250
0.003
90.2
89.4
94
2.5 (0.25)
0.5 (0.05)
1.0 (0.1)
3.0 (0.3)
8.0
1.0 (0.1)
90
3
79
120
-5 to + 40
46
7
73
58
II 2H3P
C13, C33, C43, C63,C93
E-Tec 35 NXS
42.2
36.3
38
32.7
35
30
34.8
32
6.7
6.0
5.8
5.8
36.9
4.02
20 (17)
85
6.4
27.8
15.8
6
8.7 (8.6 to 9.0)
5.3 (4.8 to 5.5)
8.5 (8.2 to 8.6)
5.7 (5.5 to 6.2)
250
0.003
90.3
89.5
94
2.5 (0.25)
0.5 (0.05)
1.0 (0.1)
3.0 (0.3)
8.0
1.0 (0.1)
130
3
84.4
120
-5 to + 40
64
10
84.4
56
Heat input gross - DHW* kW
Heat input gross - CH kW
Heat input net - DHW* kW
Heat input net - CH kW
Heat input net DHW (G20Y20) kW
Heat input net CH (G20Y20) kW
Heat output condensing (50/30°C) - CH kW
Heat output non condensing (80/60°C) CH kW
Heat input minimum gross kW
Heat input minimum net kW
Heat input net (G20Y20) kW
Heat output minimum - CH kW
Heat output nominal - DHW* kW
Gas rate at maximum output m³/h
Gas supply pressure nominal - (minimum) mbar
Max. CH temperature - Set point °C
Gas burner injector diameter mm
Dry NOx weight (net calorific value) mg/kWh
Dry NOx ppm
NOx Class
Factory set CO2
CO2 at maximum DHW output %
O2 at maximum DHW output %
CO2 at minimum output %
O2 at minimum output %
CO maximum ppm
Maximum CO/CO2 Ratio
SAP/SEDBUK seasonality efficiency 2005 %
SAP/SEDBUK seasonality efficiency 2009 %
ErP Seasonal space heating efficiency %
Maximum primary system pressure bar (MPa)
Minimum primary system pressure bar (MPa)
Recommended system pressure - Cold bar (MPa)
System pressure relief valve setting bar (MPa)
Expansion vessel size litres
Expansion vessel charge pressure bar (MPa)
Electrical power consumption - Max. Watts
Electrical power consumption - Standby Watts
Temp. of combustion products at max. output °C
Maximum flue overheating temperature °C
Ambient operating temperature °C
Flue mass at maximum output Kg/h
Flue mass at minimum output Kg/h
Flue temperature at maximum output °C
Flue temperature at minimum output °C
Category
Type of installation

7
Alpha E-Tec 20NXS, 30NXS and 35NXS - Technical Data
3.3 FLUE LENGTHS
A 500 mm or 1000 mm Easy-Flue terminal kit with 90° bend or horizontal terminal is available.
CD 750 mm and 1000 mm flue extensions are available.
Length of Flue Required:-
Rear Flue = wall thickness + 180 mm (includes terminal).
Side Flue = wall thickness + distance between wall and side of boiler + 265 mm (includes terminal).
Vertical Flue = distance from top of boiler side panel to required roof position minus 1000 mm for vertical terminal assembly.
Maximum horizontal flue length = 12 m.
Maximum vertical flue length including terminal is 14 m.
Each additional CD 90° Bend is equivalent to 1.3 m of flue length.
Each CD 45° Bend is equivalent to 0.9 m of flue length.
The CD Vertical Flue terminal assembly is equivalent to 1 m of flue length.
3.4 PUMP
The boiler is equipped with a variable speed low power consumption pump.
During the DHW mode, the pump always runs at the maximum speed.
During the CH mode, three different functioning modes of the pump are available, Proportional, Fixed and Constant )T.
Proportional - The pump speed is controlled automatically in order to give a proportional pump head, the pump speed
varies based on the heat output supplied by the burner - the greater the heat output the higher the pump
speed. See parameter A3 in Section 6.13.
It is possible to adjust the pump speed range in the boiler parameter menu.
Fixed - The pump runs at a constant speed by setting the same minimum and maximum speeds. See parameters
A1 and A2 in Section 6.13.
Constant - The pump speed is controlled to give a set )T. See parameter A3 in Section 6.13.
The boiler is factory set to Constant - to achieve a )T of 15°C (parameter A3 is set to 15)
By-pass Regulation - The boiler leaves the factory with the by-pass open.
If necessary, the by-pass can be adjusted to the system requirements from maximum (by-pass open) to minimum
(by-pass closed). Adjust using a flat head screwdriver, turn anticlockwise to close the by-pass, and clockwise to open.
With the by-pass in the closed position the system must have a continuous open circuit.
If zone valves are used in the system an external by-pass must be fitted.
When the pump is running, the symbol flashes with green light.
When the pump power supply on, the symbol is steady with green light.
If the pump detects an alarm, the symbol is steady with red light.

8
Fig. 3.1
Fig. 3.2
3.5.1 E-Tec 20NXS Available Pump Head and Power Consumption
3.5.2 E-Tec 30NXS and E-Tec 35NXS Available Pump Head and Power Consumption
Alpha E-Tec 20NXS, 30NXS and 35NXS - Technical Data
A+B = Head available with by-pass closed
B = Head available with by-pass open
C+D= Power consumed by the pump with by-pass open (dotted area)
D = Power consumed by the pump with by-pass closed (dotted area)
Pump electrical consumption (W)
Flow rate (l/h)
Head (m water)
1400 1500 1600 1700 1800
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300
Speed 9
Speed 9
Speed 6
A
C
B
D
Speed 6
A+B = Head available with by-pass closed
B = Head available with by-pass open
C+D= Power consumed by the pump with by-pass open (dotted area)
D = Power consumed by the pump with by-pass closed (dotted area)
Pump electrical consumption (W)
Flow rate (l/h)
Head (m water)
1400 1500 1600 1700 1800
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300
Speed 9
Speed 9
Speed 6
CD
B
A
Speed 6

9
Alpha E-Tec 20NXS, 30NXS and 35NXS - Technical Data
Note: This Appliance Must Be Earthed
Optional integral single channel controls are available if required.
Note: Only use the Alpha two channel controls. Do not fit any single channel controls*.
Fig. 3.3 shows the Internal two channel clock option for S or Y plan. Alternatively bring a Switched Live from external controls
to terminal 1.
DO Not connect an Alpha Climatic control when the proprogrammer clock is connected.
3.6 ELECTRICAL CONNECTIONS
Fig. 3.3
3.7 DATA BADGE ANNOTATION
Md
Sr No
Type
Q
nw /Q n min.
PMS
NO
x Class
Q
nw /Q n max.
PMW
Cod. Md
Cod. PIN
P
n min.
D
P
n max.
TM
CONDENSING
Md.............................Model
Cod. Md ....................Model code
Sr No.........................Serial number
CHK..........................Check
Cod. PIN ...................PIN code
Type..........................Type of installation (ref. CEN TR 1749)
Qnw min. .....................DHW minimum heat input
Qn min. .......................CH minimum heat input
Qnw max. ....................DHW maximum heat input
Qn max. ......................CH maximum heat input
Pn min. .......................Minimum heat output
Pn max........................Maximum heat output
PMS..........................Maximum system pressure
PMW.........................Maximum DHW pressure
D...............................Specific flow rate
TM ............................Maximum operating
temperature
NOxClass.................NOxClass
CONDENSING .........Condensing boiler
NOTE: Technical data is provided on the boiler data label and in Section 3.1.
* If the boiler is used for heating only a single
channel control can be fitted.
Fit the clock or receiver as normal and connect
a link between terminals A and 3 on the boiler.
J2 on PCB
J2 on PCB
J1 on PCB
X4 on PCB
Colour Code
Bk Black
Bl Blue
Br Brown
G Green
Gy Grey
G/Y Green/Yellow
Or Orange
R Red
W White
YYellow
B4 External sensor (optional)
B9 Cylinder sensor (optional) - Remove
cylinder resistor R8 when connecting
cylinder sensor
R8 Cylinder resistor
Programmer clock
(optional)
Remove link to
connect clock
Remove link
to connect 230 V
room thermostat
Room thermostat (optional) When an Alpha Climatic control
is connected to terminals 40 and 41
remove the links between terminal
blocks 1 and 2
Bk
Bk
Bk
Bl
Br
Br
Gy
W
W
R
R
Gy
BlBk
Bl
Br G/Y G/Y
Mains Supply
230 V ~ 50 Hz
Br Bl G/Y
G/Y
LNAB56124
3
Y
Y
Alpha
Climatic Control
(optional)
B4
B9
R8
ROr Y
Bk Or Y
44
40
41 38 39 38 48
2
1
34
5
Ch 1
Ch 2
Bl
R
Bl
DHW ON
DHW OFF
CH ON
Alpha Diverter Valve option to be used with
Alpha Climatic Control
Configurable relay Parameter P3=5
CH ON contact closed CH OFF contact open
6=Neutral 5=Live (CH ON)
L
LNNFor testing
only
R
Bk

10
3.8 BOILER SCHEMATIC
Fig. 3.4
Alpha E-Tec 20NXS, 30NXS and 35NXS - Technical Data
1 Gas valve
2 Gas injector
3 Condensate trap
4 Expansion vessel
5 Venturi positive pressure point (+)
6 Pressure signal vent fitting
7 Venturi
8 Primary flow temperature sensor
9 Ignition/sensing electrode
10 Air supply pipe
11 Flue temperature sensor
12 Flue test point (pressure point +)
13 Air test point (pressure point -)
14 Burner
15 Primary return sensor
16 Fan
17 Automatic air vent
18 Boiler pump
19 Primary pressure switch
20 By-pass
21 Drain point
22 3 bar safety valve
23 Safety valve indicator
24 Heating flow isolation valve
25 Heating return isolation valve
26 Air vent drain valve
27 Gas isolation valve
28 Primary heat exchanger
Gas Condensate discharge
and expansion relief
Primary
Heating
return Primary
Heating flow
1
2
3
4
5
6
7
8
9
10
27
26
25 24
23
22
21
20
19
18
11
12
13
14
15
16
17
A(-) F(+)
28

11
4.1 GAS SUPPLY
The meter and supply pipes must be capable of delivering the required quantity of gas in addition to the demand
from any other appliances connected to the same gas supply.
Refer to Technical performance data in Section 3.1 and 3.2.
The complete installation, including the meter, must be tested for gas tightness and purged as described in BS 6891.
4.2 AIR SUPPLY
The boiler does not require any air vents for cooling in the room in which it is installed or when installed in a
cupboard or compartment. The minimum clearances for servicing must always be maintained.
Note: A cupboard or compartment used to enclose the boiler must be designed and constructed specifically for the purpose,
i.e. comply with the Building Regulations.
4.3 FLUE SYSTEM - Figs. 4.1, 4.2
The flue system must be installed in accordance with BS 5440:1.
With configuration C6:
• In case of windy conditions the permitted recirculation level must be lower than 10%.
• Installation on opposite walls of the building is not allowed.
• The maximum permitted pressure loss of the flue system is 160 Pa for E-Tec 20NXS, 210 Pa for E-Tec 30NXS and 310
Pa for the E-Tec 35NXS .
• The flue system must be suitable to work up 120°C.
Configuration C4 is allowed with natural draught flue chimney only.
With configuration C9, the dimensions of the shaft must ensure a minimum gap between the outer wall of the flue duct and
the inner wall of the shaft: 30 mm for circular section shaft or 20 mm for square section shaft.
When using a horizontal flue kit ensure that the flue outer duct is installed horizontally (please note that the flue inner duct
already has a pre-determined slope towards the boiler for condensate to run back towards the boiler).
When additional flue extensions are used, ensure the flue slopes downwards towards the boiler by a minimum of 30 mm per
metre of flue. For extended flue runs a fall of 50 mm per metre is recommended.
Horizontal and vertical flue assemblies should be supported every metre with access provided to the joints.
All joints between flue sections should be connected using the clamps provided. It is not required to add additional screws
through the clamps and into the flue sections.
Additional flue components are available as follows:-
CD EasyFlue 500 mm telescopic terminal - Part No. 6.12000510.
CD EasyFlue 1000 mm telescopic terminal - Part No. 6.12001010.
CD 750 mm flue extension - Part No. 6.2000750.
CD 1000 mm flue extension - Part No. 6.2001050.
CD 100 mm flue support brackets (pack of 5) - Part No. 6.1000355.
CD 90° bend - Part No. 6.2000590.
CD 45° bend - Part No. 6.2000545.
CD Vertical flue terminal kit - Part No. 6.2000520. Refer to the separate installation instructions supplied with the kit.
Flue support brackets - Part No. 6.1000355.
Terminal guard - Part No. 6.2000570.
Additional flue accessories and plume management are also available.
Note: 1. If an extra 90° bend is used, this reduces the maximum flue length by 1.3 m. Each 45° bend used reduces the
maximum flue length by 0.9 m.
2. Under no circumstances must the flue length (including allowances for extra bends) exceed 12 metres horizontally
and only 14 metres vertically.
3. Failure to use Alpha flue components with the boiler will invalidate the boilers CE approval, guarantee and may be
unsafe.
4 GENERAL BOILER INFORMATION
Alpha E-Tec 20NXS, 30NXS and 35NXS - General Boiler Information

12
L = A + B = 12m max.
Alpha E-Tec 20NXS, 30NXS and 35NXS - General Boiler Information
L = A + B + (90° bend = 1.3 metre)
L = A + (2 x 45° bends = 1.8 metre)
Fig. 4.2
VERTICAL FLUE OPTIONS
Hmax = 14 m Hmax = 12.2 m (14 m - 1.8 m)
12 m
B
A
A
B
A
HORIZONTAL FLUE OPTIONS - Lmax - 12 metres
Not less than
300 mm
H
Not less than
300 mm
H
Fig. 4.1

13
4.4 FLUE TERMINAL LOCATION - Figs. 4.3 and 4.4
Notes:
1. In addition, the terminal should not be nearer than 150 mm to the framework of an opening into the building, i.e. a
window surround or door surround.
2. This clearance may be reduced to 25 mm without effecting the performance of the boiler. However, to ensure the
condensate plume does not affect adjacent surfaces a clearance of 300 mm is preferable.
3. These clearances may be reduced to 25 mm without effecting the performance of the boiler. However, to ensure the
condensate plume does not affect adjacent surfaces the terminal can be extended beyond gutters, pipes, eaves,
balconies etc. by upto 500 mm. If the flue is extended more than 500 mm outside, it should be boxed and insulated.
4. To reduce the possibility of nuisance to neighbouring buildings etc. it is recommended the terminal should not be less
than 2500 mm from car parking spaces, building boundary walls, fences etc.
5. A terminal must not be sited under a car port roof.
6. In certain weather conditions the terminal will emit a plume of steam. If possible avoid positioning the terminal where
this may cause a nuisance, i.e. positions A, D, G, H, J or M.
7. The flue terminal must be exposed to the external air and the position must allow the free passage of air across it at all times.
8. The flue terminal must be positioned where products of combustion will freely disperse and not cause a nuisance.
9. Where a terminal is sited below 2 m from the ground or floor level, the terminal must be protected by a terminal guard.
In these situations, consideration should also be given to prevent nuisance plume and fumes in areas such as access
routes, passageways, patios, balconies etc.
Alpha E-Tec 20NXS, 30NXS and 35NXS - General Boiler Information
A Directly below an opening, air brick, windows, etc.
B Below gutters, soil pipes or drain pipes
C Below eaves
D Below balconies
E From a vertical drain pipe or soil pipe
F From an internal or external corner
G Above ground, roof or balcony level
H From a surface or boundary facing the terminal
I From a terminal facing the terminal
J Above an opening, air brick, window etc.
K Vertically from a terminal on the same wall
L Horizontally from a terminal on the same wall
M Horizontally from an opening, air brick, window etc.
N Minimum protrusion through a roof
O From a vertical obstruction
P From an openable window
Q From an adjacent vertical terminal
Min. distance (mm)Terminal position
300 (See Note 1)
75 (See Note 3)
200 (See Note 3)
200 (See Note 3)
150 (See Note 3)
300 (See Note 2)
300 (See Note 9)
600 (See Note 4)
1200 mm
300 (See Note 1)
1500 mm
300 mm
300 mm (See Note 1)
300 mm
300 mm
600 mm
600 mm
J
D
G
HI
Q
Boundary
OP
N
Fig. 4.3

14
Proximity of flue duct outlets to boundaries
The flue duct shall be sited so that it is at least 600 mm (see Fig. 4.4) from the boundary line when facing it and at least 300
mm from the boundary line when running parallel to it.
Fig. 4.4
600 mm
2000 mm
600 mm
300 mm
300 mm
Terminal facing the boundary
Terminal facing an opening
in adjacent building
Terminal at an angle to the boundary
Terminal parallel to the boundary
Boundary
Boundary
Boundary
Boundary
Terminal
Terminal
Terminal
Terminal
Building Building
Building
Building
Adjacent building Window
4.5 BOILER LOCATION
The boiler is not suitable for external installation unless it is installed within a purpose designed weatherproof
building.
The boiler must be installed on a flat vertical wall which is capable of supporting the weight of the boiler. The boiler can be fitted
to or adjacent to a wall comprising of a combustible material without the need for a special thermal insulation barrier.
If the boiler is to be fitted in a timber framed building, it should be fitted in accordance with the Institute of Gas Engineers
'Guide for Gas Installations in Timber Frame Housing', reference IGE/UP/7.
The boiler may be installed in any room or internal space, although particular attention is drawn to the requirements of the
current IEE Wiring (BS 7671) 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 boiler is installed in a room containing a bath or shower, it must not be possible for a person using the bath or shower
to touch any electrical switch or boiler control utilising mains electricity.
The boiler may be installed in a cupboard or compartment, provided it is correctly designed for that purpose, i.e. complies
with the Building Regulations and the requirements of BS 6798.
Alpha E-Tec 20NXS, 30NXS and 35NXS - General Boiler Information

15
4.6 CENTRAL HEATING SYSTEM - Fig. 4.5
The boiler is designed for use in a sealed central heating system in accordance with the requirements of BS EN 12828 and BS 6798.
The system should be designed to operate with flow temperatures of up to 90°C. When designing the system, the pump
head, expansion vessel size, mean radiator temperature, etc. must all be taken into account. Refer to the pump performance
table for guidelines.
System volume - The expansion vessel incorporated into the boiler is suitable for a sealed heating system with a
maximum water content of 80 litres (18 gal). Above 80 litres, consideration should be given to fitting an additional
expansion vessel fitted in the position shown in Fig. 4.5. To check correct operation of the expansion vessel(s)
the system pressure should not be more than 2.5 bar when the system is at maximum operating temperature (for
further guidance refer to BS 7074:1).
The boiler is supplied with the following components built in:-
Pressure gauge - To indicate the system pressure to be maintained.
Expansion vessel - Conforming to EN 13831 with a capacity of 8 litres and pre-charged with air to a pressure of 1.0 bar.
By-pass - The boiler incorporates an automatic by-pass, an automatic by-pass is required for the system when
zone valves are used.
4.7 FILLING THE CENTRAL HEATING SYSTEM - Fig. 4.6
The system design pressure (cold) should be set to 1.0 bar. This pressure is equivalent to a static head (see Fig. 4.5) of 10.2
metres of water.
Provision must be made for filling the system. This is done by the use of a filling loop. See Fig. 4.6. A filling loop is not
supplied with this boiler.
Filling of the system must be carried out in a manner approved by the local Water Undertaking. Where allowed, the system
may be filled via a temporary connection as shown in Fig. 4.6. After filling, always disconnect the flexible hose of the filling
loop.
All fittings used in the system must be able to withstand pressures up to 3 bar. Drain taps (to BS 2879) must be used to allow
the system to be completely drained.
Fig. 4.5
Fig. 4.6
Alpha E-Tec 20NXS, 30NXS and 35NXS - General Boiler Information
Filling loop
temporarily connected
Heating circuit
return Mains
water
supply
Stop
valve
Hose
unions
Stop
valve
Double check
valve assembly
Test cock
Automatic
air vent
Additional expansion
vessel (if required)
Filling point
Static head of system
Heating return
System
drain tap
Heating flow
Note: A drain tap should be installed at the lowest
point of the heating circuit and beneath the appliance.
Boiler

16
4.8 FLUSHING THE HEATING SYSTEM
It is essential that the central heating system is thoroughly cleaned and flushed before fitting an Alpha E-Tec
NXS boiler. Failure to do so will invalidate the warranty. The primary condensing heat exchanger is constructed in
stainless steel and therefore is compatible with most materials used in a heating system.
Where possible, the heating system should be cleaned before installing the boiler. A proprietary cleaner should
be used following the product manufacturers' instructions. After installation the system should then be filled and
flushed before final filling. A corrosion inhibitor approved by Alpha must be added to ensure that the heating system
operates effectively and efficiently, it is important to maintain the correct level of corrosion inhibition at all times.
The corrosion inhibitor should be checked annually at the time of the boiler service, and topped up if necessary. A further
dose of corrosion inhibitor should be added to the system every five years.
It is important to ensure that the correct level of inhibitor has been added, and that any cleaner residues have been
adequately removed to maintain the operation of the boiler and heating system. Failure to correctly clean and treat the
system will invalidate the boiler warranty.
If it is not possible to clean the system before fitting the new boiler, the system should be cleaned using a proprietary cleaner
and a magnetic filter connected in the return before the boiler as this is the most effective method of ensuring that any
magnetite and rust particles are prevented from entering and damaging the boiler.
Once the system condition has been restored, an effective magnetic filter and strainer should be fitted permanently to the
system as a method of collecting any magnetite and rust from the system during operation.
4.9 DISPOSAL OF CONDENSATE
Provision must be made for the safe disposal of condensate produced by the flue gases of the Alpha boilers and
reference should be made to BS 6798 for the requirements on the disposal of condensate.
The boilers incorporate a condensate trap which has a seal of greater than 75 mm, therefore no additional trap is required.
The condensate should ideally be discharged internally into an internal waste pipe (washing machine/sink waste) or soil pipe
to avoid the possible risk of freezing. The pipework must be in 22 mm pipe (minimum).
External pipe runs should be avoided, but if it is necessary, the pipework should be protected from the risk of freezing with
waterproof insulation and the length should be kept to a maximum of 3 m and the condensate pipework should be increased
to a minimum of 32 mm diameter. Termination should be into an external gulley or soakaway as shown in Figs. 4.7 and 4.8.
Note: All pipework must have a continuous fall (see Figs. 4.7 and 4.8) from the boiler and must be of an acid resistant
material such as plastic waste pipe. (copper or steel is not suitable).
The condensate pipe is combined with the expansion relief discharge. The flexible condensate hose supplied meets the
requirements for use with both condensate and expansion relief. This should be connected to a suitable waste pipe and
fittings with approval for hot and cold water, i.e. BS EN1451-1PP Waste piping, BS EN1455-1 ABS piping or BS EN 1566-1
MUPVC piping.
The condensate and discharge should be connected to a drain for sewage and foul waste or a dedicated soak away with
neutraliser added.
It should be noted that the connection of a condensate pipe to a drain may be subject to local building control requirements.
If the condensate is connected to a gutter or drain down pipe where there is a risk of water blocking and rising back towards
the boiler, a suitable air gap / tundish must be fitted to the condensate pipe.
Alpha E-Tec 20NXS, 30NXS and 35NXS - General Boiler Information
Fig. 4.7 - External gully
Open end of pipe
diverted into gully
below grid but above
water level
Use waterproof
pipework insulation
in very exposed
positions
Ensure pipe is
adequately supported
Plastic pipe
(minimum 32 mm)
Minimum gradient 2½°

17
Fig. 4.8 - External soakaway
Alpha E-Tec 20NXS, 30NXS and 35NXS - General Boiler Information
Ground level (either/or)
22mm termination from boiler, increase to 32 mm if external
2½ fall
O
25mm
300mm
Two rows of 3 x 12mm
holes at 25mm centres,
50mm from the bottom
of the tube. Holes to face
away from house.
Cement mortar sealing
100mm plastic tube
Bottom of tube sealed
Soakaway depth 400mm
filled with limestone chippings
500 mm min.

18
5.3 PREPARE THE WALL - Fig. 5.2
1. Decide upon the position of the boiler taking into account the clearances required
for servicing and the flue terminal position.
2. Tape the template to the wall (ensure it is level and the right
way up) and mark the position of the holes for the boiler
mounting bracket. If rear exit flue is used, mark the position of
the hole for the flue.
3. Side exit flue - Continue the horizontal centre line of the flue
across the wall to the side wall, then along the side wall 135 mm
(ensure the lines are horizontal).This will give the position of the
centre of the hole for the flue.
4. Cut the 110 mm diameter hole (or use a 107 mm core drill) in
the wall for the flue.
Notes: 1. Ensure the hole is horizontal.
2. For internal fitting of the flue, using the flue sealing
collar supplied, cut a 130 mm dia. flue hole using a
127 mm core drill.
5. Drill the fixing holes (10 mm dia.) to accept the No.10 plugs
supplied. Using the screws supplied, fit the mounting bracket.
5 INSTALLATION
Fig. 5.1
Alpha E-Tec 20NXS, 30NXS and 35NXS - Installation
5.1 UNPACKING
1. The boiler carton also contains the following:-
Flue turret, seals and screws (loose)
Connection kit (union bends, washers and valves)
Mounting bracket plus screws and wall plugs
Condensate discharge pipe
Literature pack and Wall template
A suitable Alpha flue system must be selected to use with the boiler.
Notes: a. All flues must be suitable for Alpha condensing boilers.
b. CD 750 mm and 1000 mm flue extensions are available, if required.
Damaged products must not be used.
2. Unpack boiler and remove the loose items, packs and mounting bracket.
Note: The boiler can be stood in an upright position (only while the valves and union bends are not
fitted).
It is recommended that two persons lift the boiler.
5.2 CLEARANCES REQUIRED - Fig. 5.1
Fig. 5.2
==
Template
Outline of
boiler
135 mm
Ensure line is level
Rear exit hole
110 mm dia.
Position of
110 mm hole
to be cut for
side exit flue
149 mm
Fixing holes
if wall jig used
Fixing holes
if mounting
bracket used
Minimum clearances
5 mm 5 mm
150 mm
240 mm - Can be reduced to
150 mm when using a
vertical flue
440 mm
712 mm
Minimum
clearance
of 450 mm
from front
of boiler
253 mm
bar

19
Alpha E-Tec 20NXS, 30NXS and 35NXS - Installation
5.4 FIT THE BOILER - Refer to Figs. 5.2 and 5.3
Lift the boiler and locate it on the mounting bracket - the
boiler should be lifted by two persons.
Note: When handling or lifting always use safe techniques
- keep your back straight, bend your knees, don't twist -
move your feet, avoid bending forwards and sideways and
keep the load as close to your body as possible.
Where possible transport the boiler using a sack truck or
other suitable trolley.
Always grip the boiler firmly, and before lifting feel where
the weight is concentrated to establish the centre of gravity,
repositioning yourself as necessary.
5.5 CONNECT THE PIPEWORK - Fig. 5.4
1. Thoroughly flush out all the water pipework. Refer to Section 4.9.
2. Fit the valves to the boiler connections as shown in Fig. 5.4, using the gaskets
supplied.
3. Connect the system pipework to the union fittings on the valves just fitted.
Note: When soldering bends, ensure they are not connected to the valves, otherwise the internal seals may be
damaged.
One metre of copper pipe must be fitted to the boiler before connecting to any plastic pipework conforming to
BS 7291.
4. Connect the flexible condensate pipe to the rubber connector as shown in Fig. 5.4. Using the adaptor supplied, connect
the flexible pipe to the condensate drain.
Ensure that the condensate discharge pipe is as required in Section 4.9.
5. Ensure that all the valves are closed (operating lever at right angle to valve) and do not turn on the water or gas supplies
at this stage.
Fig. 5.4
A- Gas inlet - (22 mm)
B- Heating return - (22 mm)
C- Heating flow - (22 mm)
Fig. 5.3 - rear of boiler
Location for
wall mounting
bracket on
rear of boiler
Pour water into flue duct
(to fill condensate trap)
ABC
65 4570260
30
Condensate discharge pipe
Heating drain point
Gas service cock (yellow)
Heating return valve
Safety valve operation indicator
Heating flow valve
Electrical connection 120
Automatic air vent outlet
(do not block)

20
Gasket protruding rib
facing downwards
Flue turret
Four fixing screws
Fig. 5.5
5.6 FIT THE FLUE TURRET - Figs. 5.5 and 5.6
1. Remove flue turret, flat concentric gasket and four screws from the accessory pack.
2. Place the flat concentric gasket onto the boiler, ensuring the protruding 60mm rib is facing downwards and located
correctly. See Figs. 5.5 and 5.6.
3. Fit the turret on top of the flat concentric gasket and secure with the four screws provided.
4. Check the 60mm and 100mm double lip seal gaskets are fitted with the lips facing downwards. See Fig. 5.6.
Flue seal ribs
must face downwards
Flue turret gasket
must be located
as shown
Fig. 5.6
Alpha E-Tec 20NXS, 30NXS and 35NXS - Installation