Riello Vokera Mynute 20 VHE Release note

Installation
& Servicing
Instructions
THESE INSTRUCTIONS
TO BE RETAINED
BY USER
Mynute VHE
High efciency open vent boiler
Vokèra is a licensed member of the Benchmark scheme
which aims to improve the standards of installation and
commissioning of domestic hot water systems in the UK.
G.C. N° 41 094 70

2
Contents
Design principles & operating sequence Page
1.1 Principle components 3
1.2 Mode of operation (at rest) 3
1.3 Mode of operation 3
1.4 Safety devices 3
Technical data Page
2.1 Central heating 4
2.2 Gas pressures 4
2.3 Dimensions 4
2.4 Clearances 4
2.5 Connections 4
2.6 Electrical 4
2.7 Flue details (concentric) 4
2.7A Flue details (twin pipes) 4
2.7B Flue details (80/125) 4
2.8 Efciency 4
2.9 Emissions 4
General requirements (UK) Page
3.1 Related documents 6
3.2 Location of appliance 6
3.3 Gas supply 6
3.4 Flue system 6
3.5 Air supply 6
3.6 Water circulation 6
3.7 Electrical supply 7
3.8 Mounting on a combustible surface 7
3.9 Timber framed buildings 7
3.10 Inhibitors 7
3.11 Appliance pipework conguration 7
General requirements (EIRE) Page
3A.1 Related documents 9
3A.2 Location of appliance 9
3A.3 Gas supply 9
3A.4 Flue system 9
3A.5 Air supply 9
3A.6 Water circulation 9
3A.7 Electrical supply 10
3A.8 Mounting on a combustible surface 10
3A.9 Timber framed buildings 10
3A.10 Inhibitors 10
3A.11 Appliance pipework conguration 10
3A.12 Declaration of conformity 10
Installation Page
4.1 Delivery 11
4.2 Contents 11
4.3 Unpacking 11
4.4 Preparation for mounting the appliance 11
4.5 Fitting the ue 11
4.6 Connecting the gas & water 15
4.7 Electrical connections 15
Commissioning Page
5.1 Gas supply installation 16
5.2 The heating system 16
5.3 Initial lling of the system 16
5.4 Initial ushing of the system 16
5.5 Pre-operation checks 17
5.6 Initial lighting 17
5.7 Checking gas pressure & combustion analysis 17
5.8 Final ushing of the heating system 17
5.9 Setting the boiler operating temperature 17
5.10 Regulating the central heating system 17
5.11 Final checks 17
5.12 Instructing the user 17
Servicing Page
6.1 General 18
6.2 Routine annual servicing 18
6.3 Replacement of components 18
6.4 Component removal procedure 18
6.5 Automatic air release valve 18
6.6 Primary thermistor 18
6.7 Return thermistor 18
6.8 Printed circuit board 18
6.9 Gas valve 19
6.10 Injectors 19
6.11 Electrodes and condense sensor 19
6.12 Flue fan & mixer 19
6.13 Burner 20
6.14 Main heat exchanger 20
6.15 Condense trap removal 20
6.16 Flue collector removal 20
Checks, adjustments and fault nding Page
7.1 Checking appliance operation 21
7.2 Appliance modes of operation 21
7.3 Appliance fan speeds 21
7.4 Checking the CO2& adjusting the valve 22
7.5 Combustion analysis test 22
7.6 External faults 22
7.7 Electrical checks 23
7.8 Fault nding 23
7.9 Component values & characteristics 23
7.10 Fault codes 23
Wiring diagrams Page
8.1 External wiring 24
8.2 Typical control applications 24
8.3 Other devices 24
L.P.G. instructions Page
9.1 Related documents 27
9.2 Technical data 27
9.3 Converting the appliance gas type 27
9.4 Gas supply 27
9.5 Gas supply installation 27
9.6 Adjusting the gas valve 27
9.7 Appliance fan speeds 28
Commissioning checklist 29
Benchmark 30-32

1
The Mynute VHE is a high-efciency boiler for open
vent system.
These appliances – by design – incorporate premix
combustion and a radial aluminium heat exchanger.
The Mynute VHE range are produced as room sealed,
category II2H3P appliances, suitable for internal wall
mounting applications only. Each appliance is provided
with a fan powered ue outlet with an annular co-axial
combustion air intake that can be rotated – horizontally
– through 360 degrees for various horizontal or vertical
applications.
The Mynute VHE can also be used with the Vokera
twin ue system.
These appliances are designed for use with an open-
vent system; consequently they are not intended for use
on sealed or pressurised systems. Please contact the
Vokera technical helpline for advice should you wish to
use the Mynute VHE on a sealed/pressurised system.
This booklet is an integral part of the appliance. It
is therefore necessary to ensure that the booklet is
handed to the person responsible for the property in
which the appliance is located/installed. A replacement
copy can be obtained from the Vokèra website - www.
vokera.co.uk.
The Mynute VHE is approved for use with C13 & C33
type ue appliacations
Mynute VHE boiler complies with basic requirements
of the following Directives:
- Regulation (EU) 2016/426;
- Yield directive: Article 7(2) and Annex III of directive
92/42/EEC;
- Electromagnetic compatibility directive 2014/30/EU;
- Low-voltage directive 2014/35/EU;
- Directive 2009/125/EC Ecodesign for energy-using
appliances;
- Regulation (EU) 2017/1369 Energy labeling;
- Delegated Regulation (EU) No. 811/2013;
- Delegated Regulation (EU) No. 813/2013.
At the end of its life, the product should be not
be disposed of as solid urban waste, but rather it
should be handed over to a differentiated waste
collection centre.
All installers are asked to follow the Benchmark
Scheme by adhering to the Code of Practise, which
can be obtained from www.centralheating.co.uk.
INTRODUCTION
Fig. 1 G FR
General layout (g. 1)
1 Gas valve
2 Condense trap
3 Vacuum detection pipe
4 Air pressure switch
5 Top AAV pipe
6 Return sensor
7 Fume thermostat
8 Flue gas analysis test point
9 Flue outlet & air intake
10 Ignition transformer
11 Top AAV
12 Flow sensor
13 High limit thermostat
14 Sensing Electrode
15 Spark Electrode
16 Condensate level sensor
17 Cylindric Burner
18 Main heat exchanger
19 Air intake pipe
20 Fan assembly
21 Mixer
22 Condensing drain
RHeating return connection
FHeating ow connection
GGas connection

2
Fig. 1A
Boiler at reset/standby Select this position if/when the boiler requires to be reset
Boiler switched OFF Select this position if you want the boiler to remain OFF (this will over-ride
any heating/hot water request from the time-clock/programmer)
Boiler switched ON Select this position when you want the boiler to respond to a heating/hot
water request from the time-clock/programmer
Temperature selector Move the temperature selector clockwise to increase the boiler outlet
temperatu- re, or counter-clockwise to reduce the outlet ow temperature
2-digit LED display Displays the current outlet temperature of the boiler. During a fault
condition, the appropriate fault code will be displayed (refer to the users
handbook for in structions regarding fault codes)
Green LED lit Boiler is working/responding to a heating/hot water request
Red LED lit Boiler has identied a fault and has failed-safe. Refer to users handbook for
instructions on how to reset
MODE SELECTOR
SWITCH
RED LED
GREEN LED TEMPERATURE SELECTOR
2-digit LED
display


3
1.1 PRINCIPLE COMPONENTS
● A fully integrated electronic control board featuring
electronic temperature control, anti-cycle control,
pump over-run, self-diagnostic fault indicator, full
air/gas modulation
●Radial aluminium heat exchanger
●Electronic ignition with ame supervision
●Fan
●Condensate level sensor
1.2 MODE OF OPERATION (at rest)
When the appliance is at rest and there are no requests
for heating or hot water, the following functions are active:
● 2-stage frost-protection system – the frost-protection
system protects the appliance against the risk of
frost damage. The rst stage enables activation of
the pump should the temperature of the appliance
fall to 6oC. Should the rst stage become active, the
appliance will function on minimum +25% power until
it reaches 35oC.
●Anti-block function – the anti-block function enables
the pump to be energised for short periods, when the
appliance has been inactive for more than 24-hours.
1.3 MODE OF OPERATION
When there is a request for heat and/or hot water, via the
programmer/time clock and/or any external control, the
pump and fan are started, the fan speed will modulate
until the correct signal voltage is received at the control
PCB. At this point an ignition sequence is enabled.
Ignition is sensed by the electronic circuitry to ensure
ame stability at the burner. Once successful ignition
has been achieved, the electronic circuit increases the
gas rate to 75% for a period of 15 minutes. Thereafter,
the boiler’s output will either be increase to maximum
or modulate to suit the set requirement.
When the appliance reaches the desired temperature
the burner will shut down and the boiler will perform a
5-minute anti-cycle (timer delay).
When the request for heat has been satised the pump
and fan may continue to operate to dissipate any residual
heat within the appliance.
NOTE
●The pump must be connected directly to the desig-
nated terminals within the appliance controls panel.
●When power is restored to the PCB and/or the PCB
is powered for the rst time, the appliance will enter
a 2-minute purge cycle whereby only the pump will
run for 15-seconds then off for 15-seconds.
1.4 SAFETY DEVICES
When the appliance is in use, safe operation is en-
sured by:
●Fan speed sensor and pressure differential mecha-
nism to ensure safe operation of the burner.
●A high limit thermostat that over-rides the temperature
control circuit to prevent or interrupt the operation
of the burner.
●Flame sensor that will shut down the burner when
no ame signal is detected.
●A sensor that interrupts the operation of the appli-
ance if the condense pipe becomes blocked.
SECTION 1 DESIGN PRINCIPLES AND OPERATING SEQUENCE
Fig. 2
CH
return
CH
ow
return tem-
perature
sensor
main heat
exchanger
ow temper-
ature sensor
top
AAV
drain
valve

4
SECTION 2 TECHNICAL DATA
Ref. Condition 15 °C, 1013,25 mbar, dry gas
NOTE: L.P.G. data refer to section 9
*The system should be so designed and balanced to ensure
a minimum and maximum temperatute differential of 10 °C
and 20 °C respectively, when the appliance is operating at
maximum output.
2.1 Central Heating Mynute 20 VHE
Heat input (kW) 20.00
Maximum heat output (kW) 60/80°C 19.52
Minimum heat output (kW) 60/80°C 4.83
Maximum heat output (kW) 30/50°C 20.80
Minimum heat output (kW) 30/50°C 5.35
Minimum working pressure 0.1 bar
Maximum working pressure 3.0 bar
Minimum ow rate 850 l/h*
2.2 Gas Pressures
Inlet pressure (G20) 20.0 mbar
Maximum gas rate (m3/hr) 2.12
Minimum gas rate (m3/hr) 0.53
Injector size 3.65 mm
2.3 Dimensions
Height 740 mm
Width 400 mm
Depth 342 mm
Dry weight 29 kg
2.4 Clearances
Sides 12mm
Top 150mm from casing or 25mm above ue elbow (whichever is applicable)
Bottom 150mm
Front 600mm
2.5 Connections
Flow & return 22mm
Gas 15mm
Condense 21mm
2.6 Electrical
Power consumption (Watts) 54
Supply (V/Hz) 230/50
Internal fuse 3.15A T (for PCB) - 3.15A F (for connections block)
External fuse 3A
2.7 Flue Details (concentric - 60/100)
Maximum horizontal ue length (60/100mm) 7.8m
Maximum vertical ue length (60/100mm) 8.8m
2.7A Flue Details (concentric 80/125mm)
Maximum horizontal ue length (80/125mm) 25m
2.7B Flue Details (twin pipes)
Maximum horizontal ue length (80mm/80mm) 40m/40m
Maximum vertical ue length (80mm/80mm) 40m/40m
2.8 E󰀩ciency
SEDBUK (%) 90.17 - Band ‘A’
2.9 Emissions
CO2@ maximum output (%) 9.0
CO2@ minimum output (%) 9.0
CO @ maximum output (p.p.m.) 120
CO @ minimum output (p.p.m.) 20
NOx @ maximum output (p.p.m.) 50
NOx @ minimum output (p.p.m.) 30
NOx rating class 6

5
Fig. 3
Key Location Minimum distance
A Below an opening (window, air-brick, etc.) 300 mm
B Above an opening (window, air-brick, etc.) 300 mm
C To the side of an opening (window, air-brick, etc.) 300 mm
D Below gutter, drain-pipe, etc. 25 mm
E Below eaves 25 mm
F Below balcony, car-port roof, etc. 25 mm
G To the side of a soil/drain-pipe, etc. 25 mm
H From internal/external corner or boundary 300 mm
I Above ground, roof, or balcony level 300 mm
J From a surface or boundary facing the terminal 1200 mm
K From a terminal facing a terminal 1200 mm
L From an opening in the car-port into the building 1200 mm
M Vertically from a terminal on the same wall 1500 mm
N Horizontally from a terminal on the same wall 300 mm
P From a structure to the side of the vertical terminal 500 mm
Q From the top of the vertical terminal to the roof ashing As determined by the xed collar
of the vertical terminal
Seasonal space heating energy e󰀩ciency
class AWater heating energy e󰀩ciency class -
Parameter Symbol Value Unit Parameter Symbol Value Unit
Rated heat output Prated 20 kW Seasonal space heating energy
e󰀩ciency ηs 92 %
For boiler space heaters and boiler combination heaters:
useful heat output
For boiler space heaters and boiler combination heaters:
useful e󰀩ciency
At rated heat output and high-
temperature regime (*) P4 19,5 kW At rated heat output and high- temperature regime (*) η4 87,9 %
At 30% of rated heat output and
low-temperature regime (**) P1 6,5 kW At 30% of rated heat output and low-temperature regime (**) η1 97,3 %
Auxiliary electricity consumption Other parameters
At full load elmax 30 W Stand-by heat loss P󰀬by 34,0 W
At part load elmin 14,0 W Pilot ame energy consumption Pign - W
In Stand-by mode PSB 4,0 W Annual energy consumption QHE 38 GJ
Sound power level, indoors LWA 50 dB
Emissions of nitrogen oxides NOx 34 mg/kWh
For combination heaters:
Declared load prole -Water heating energy e󰀩ciency ηwh - %
Daily electricity consumption Qelec - kWh Daily fuel consumption Qfuel - kWh
Annual electricity consumption AEC - kWh Annual fuel consumption AFC - GJ
(*) High-temperature regime means 60 °C return temperature at heater inlet and 80 °C feed temperature at heater outlet.
(**) Low temperature means for condensing boilers 30 °C, for low-temperature boilers 37 °C and for other heaters 50 °C return
temperature (at heater inlet).

6
SECTION 3 GENERAL REQUIREMENTS (UK)
This appliance must be installed by a competent per-
son in accordance with the Gas Safety (Installation &
Use) Regulations.
3.1 RELATED DOCUMENTS
The installation of this boiler must be in accordance with
the relevant requirements of the Gas Safety (Installation
& Use) Regulations, the local building regulations, the
current I.E.E. wiring regulations, the bylaws of the local
water undertaking, the Building Standards (Scotland)
Regulation, and Building Standards (Northern Ireland)
Regulations.
It should be in accordance also with any relevant
requirements of the local authority and the relevant
recommendations of the following British Standard
Codes of Practice.
ATTENTION
The use of PPE (Personal Protective Equipment) such
as but not limited to gloves, mask, safety glasses, etc.
is strongly recommended whenever carrying out the
installation, repair, or maintenance of this appliance –
please pay particular attention to:
• Sharp edges that may be encountered when:- han-
dling or lifting the appliance, removing parts, etc.
during installation and maintenance.
• Airborne particles that may be released and/or
disturbed when cleaning or removing components
during maintenance.
• Water treatment chemicals that could have been
added to the system water may spill from the appli-
ance and or components during maintenance.
Please refer to an appropriate Health and Safety docu-
ment such as HSE L23 (UK) or S.I. 299 (Ireland), for
more detailed advice on safe working practices and
procedures.
3.2 LOCATION OF APPLIANCE
The appliance may be installed in any room or internal
space, although particular attention is drawn to the
requirements of the current I.E.E. wiring regulations,
and in Scotland, the electrical provisions of the Build-
ing Regulations, with respect to the installation of the
appliance in a room or internal space containing a
bath or shower.
When an appliance is installed in a room or internal
space containing a bath or shower, the appliance or
any control pertaining to it must not be within reach
of a person using the bath or shower.
The location chosen for the appliance must permit the
provision of a safe and satisfactory ue and termination.
The location must also permit an adequate air supply
for combustion purposes and an adequate space for
servicing and air circulation around the appliance.
Where the installation of the appliance will be in an
unusual location special procedures may be neces-
sary, BS 6798 gives detailed guidance on this aspect.
A compartment used to enclose the appliance must be
designed and constructed specically for this purpose.
An existing compartment/cupboard may be utilised
provided that it is modied to suit.
Details of essential features of compartment/cupboard
design including airing cupboard installations are given
in BS 6798. This appliance is not suitable for external
installation.
3.3 GAS SUPPLY
The gas meter – as supplied by the gas supplier – must
be checked to ensure that it is of adequate size to deal
with the maximum rated input of all the appliances that
it serves. Installation pipes must be tted in accord-
ance with BS 6891.
Pipe work from the meter to the appliance must be
of adequate size. Pipes of a smaller size than the ap-
pliance gas inlet connection must not be used. The
installation must be tested for soundness in accord-
ance with BS6891.
If the gas supply serves more than one appliance, it
must be ensured that an adequate supply is main-
tained to each appliance when they are in use at the
same time.
3.4 FLUE SYSTEM
The terminal should be located where the dispersal
of combustion products is not impeded and with due
regard for the damage and discoloration that may occur
to building products located nearby. The terminal must
not be located in a place where it is likely to cause a
nuisance (see g. 4).
In cold and/or humid weather, water vapour will con-
dense on leaving the terminal; the effect of such pluming
must be considered.
If installed less than 2m above a pavement or platform
to which people have access (including balconies or
at roofs) the terminal must be protected by a guard
of durable material. The guard must be tted centrally
over the terminal. Refer to BS 5440 Part 1, when the
terminal is 0.5 metres (or less) below plastic guttering
or 1 metre (or less) below painted eaves.
3.5 AIR SUPPLY
The following notes are intended for general guidance
only.
This appliance is a room-sealed, fan-ued boiler, con-
sequently it does not require a
Permanent air vent for combustion air supply.
When installed in a cupboard or compartment, ventila-
tion for cooling purposes is also not required.
3.6 WATER CIRCULATION
Detailed recommendations are given in BS 5449 Part
1 and BS 6798. The following notes are for general
guidance only.
3.6.1 PIPEWORK
It is recommended that copper tubing to BS 2871 Part
1 is used in conjunction with soldered capillary joints.
Where possible pipes should have a gradient to ensure
air is carried naturally to air release points and that
water ows naturally to drain cocks.
BS 5440 PART 1 FLUES
BS 5440 PART 2 FLUES & VENTILATION
BS 5449 PART 1 FORCED CIRCULATION HOT WATER SYSTEMS
BS 6798 INSTALLATION OF BOILERS OF RATED INPUT NOT EXCEEDING 60kW
BS 6891 LOW PRESSURE INSTALLATION PIPES

7
Except where providing useful heat, pipes should be
insulated to avoid heat loss and in particular to avoid
the possibility of freezing. Particular attention should
be paid to pipes passing through ventilated areas such
as under oors, loft space, and void areas.
3.6.2 AUTOMATIC BY-PASS
Vokera recommend that an automatic bypass is installed
to ensure the required minimum ow-rate is achieved at
all times. Additionally, the design of the system and its
controls should ensure that an adequate temperature
differential is met, and should be such that it prevents
boiler ‘cycling’.
3.6.3 DRAIN COCKS
These must be located in accessible positions to fa-
cilitate draining of the appliance and all water pipes
connected to the appliance. The drain cocks must be
manufactured in accordance with BS 2879.
3.6.4 AIR RELEASE POINTS
These must be positioned at the highest points in the
system where air is likely to be trapped. They should
be used to expel trapped air and allow complete lling
of the system.
3.7 ELECTRICAL SUPPLY
The appliance is supplied for operation on 230V @
50Hz electrical supply; it must be protected with a
3-amp fuse. The method of connection to the mains
electricity supply must allow for complete isolation
from the supply. The preferred method is by using a
double-pole switch with a contact separation of at least
3,5mm (3° high-voltage category). The switch must only
supply the appliance and its corresponding controls,
i.e. time clock, room thermostat, etc. Alternatively an
un-switched shuttered socket with a fused 3-pin plug
both complying with BS 1363 is acceptable.
3.8 MOUNTING ON A COMBUSTIBLE SURFACE
If the appliance is to be tted on a wall of combustible
material, a sheet of reproof material must protect
the wall.
3.9 TIMBER FRAMED BUILDINGS
If the appliance is to be tted in a timber framed build-
ing, it should be tted in accordance with the Institute
of Gas Engineers publication (IGE/UP/7) ‘Guide for Gas
Installations in Timber Frame Buildings’.
3.10 INHIBITORS
Vokera recommend that an inhibitor - suitable for use
with aluminium heat exchangers - is used to protect
the boiler and system from the effects of corrosion
and/or electrolytic action. The inhibitor must be ad-
ministered in strict accordance with the manufacturers
instructions*.
*Water treatment of the complete heating system -
including the boiler - should be carried out in accord-
ance with BS 7593 and the Domestic Water Treatment
Association’s (DWTA) code of practice.
3.11 APPLIANCE PIPEWORK CONFIGURATION (g.4)
The appliance ‘ow’ and ‘return’ connections can be
congured to suit the following:
1. Top outlet connection
2. Bottom outlet connection
3. Top (ow), bottom (return) connection
4. Top (return) bottom (ow) connection.
3.11.1 FEED & VENT PIPEWORK
The feed and vent pipe work from the boiler to the
F&E (Feed & Expansion) tank should be congured as
shown in g. 4A using a 22 mm combined feed and
vent pipe.
NOTE
●The combined feed and vent pipe must rise continu-
ously and be unrestricted.
●The diameter of the combined feed and vent pipe
shall be 22mm.
●The minimum distance from the top of the boiler
to the bottom of the F&E tank shall be no less than
1-metre, whilst the maximum distance shall be no
greater than 30-metres.
The supply of water to the F&E tank should be taken
from the mains water supply via a suitable oat oper-
ated valve, whilst the supply from the F&E tank to the
boiler/heating circuit (via the combined feed and vent
pipe) shall be unrestricted.
Fig. 4
Fig. 4A

8
Fig. 4C
Fig. 4B
Fig. 4D
3.11.2 ALTERNATIVE CLOSE-COUPLED
ARRANGEMENT
If necessary or if preferred, a close-coupled arrangement
for the feed and expansion pipe work can be used as
an alternative to a combined feed and vent pipe. The
conguration of the close-coupled pipe work shall be
as shown in gure 4B.
NOTE
●The distance between the cold feed pipe and the
safety vent pipe shall be no more than 150mm
●The cold feed pipe must be inverted as shown in
gure 4B
●The safety vent pipe must be 22mm in diameter
●The cold feed pipe must be 15mm diameter
●The cold feed pipe and safety vent pipe must both
rise continuously and be unrestricted.
●The minimum distance from the top of the boiler
to the bottom of the F&E tank shall be no less than
1-metre, whilst the maximum distance shall be no
greater than 30-metres.
●The distance between the bottom of the F&E tank
and the highest point of the safety vent pipe must
be no less than 500mm.
The supply of water to the F&E tank should be taken
from the mains water supply via a suitable oat oper-
ated valve, whilst the supply from the F&E tank to the
boiler/heating circuit (via the cold feed pipe) shall be
unrestricted.
3.11.3 REMOTE CONNECTION
It’s permissible to connect the feed and vent pipe work
remote from the boiler, providing it’s connected to the
primary heating pipe work as shown in gures 4C/4D.
NOTE
The instructions for a combined feed and vent instal-
lation (3.11.1) or close-coupled arrangement (3.11.2)
still apply when connecting the feed and vent pipe
work remote from the appliance.