Potterton Envoy Flowsure Installation and maintenance instructions

1
Boiler Module - G.C. No. 41 607 89
20 Litre Tank Module - G.C. No. 114 792
50 Litre Tank Module - G.C. No. 114 793
Installation & Service Instructions
Envoy Flowsure & Envoy Flowsure+
Wall Mounted Fan Powered Balanced Flue Gas Condensing
Combination Boiler and Storage Combination Boiler
EN0025A
THE GAS SAFETY (INSTALLATION AND USE) REGULATIONS 1994.
‘‘ In your own interest, and that of safety, it is law that all gas appliances are installed by competent persons,
in accordance with the above regulations. Failure to install appliances correctly could lead to prosecution.’’
The polythene bags used for packaging are a potential hazard to babies and young children and
MUST BE DISPOSED OF IMMEDIATELY.
Installation must be in accordance with the Installation & Service Instructions and the rules in force.
LEAVE THESE INSTRUCTIONS WITH THE USER FOR USE ON FUTURE CALLS
For Use With Natural Gas
(G20) Only At 20mbar
For Use in GB & IE
IMPORTANT
PLEASE READ THIS BOOK
BEFORE INSTALLING,
OPERATING OR SERVICING
THIS BOILER.

Contents
Publication No. 559779
2
Contents – Page 2
Technical Data........................................................... 3
1Installation Requirements........................................ 5
2Installation............................................................... 12
3Commissioning....................................................... 16
4Boiler Display & Controls....................................... 19
5Servicing & Replacement of Parts ........................ 22
Servicing:
Preparation of the Boiler........................................... 22
Removing Fan........................................................... 23
Removing Combustion Chamber & Flue Hood......... 23
Examination of Flueways & Cleaning ....................... 24
Re-assembly of Boiler............................................... 24
Replacement of Parts
1Fan..................................................................... 25
2Hot Surface Igniter............................................. 25
3Flame Sensor..................................................... 25
4Insulation............................................................25
5Burner.................................................................26
6Syphon...............................................................26
7Flue Hood/Combustion Chamber Seals.............26
8Injector................................................................26
9Gas Valve Assembly..........................................26
10 Sight Glass.........................................................27
11 Water Temperature Sensor................................27
12 Diverter Valve Head...........................................27
13 Case Temperature Sensor.................................27
14 Boiler Control Board...........................................28
15 Boiler Control Board Fuses................................28
16 Water Components ............................................29
Pump..................................................................29
Diverter Valve.....................................................29
Water Pressure Switch.......................................29
Water Pressure Gauge.......................................29
6Fault Finding............................................................30
7Boiler Internal Wiring..............................................35
8Boiler Wiring Layout............................................... 36
9Short List of Spares................................................37
Introduction - Page 2
The Potterton Envoy Flowsure (20l) and Flowsure+ (50l) are
high efficiency, lightweight, automatically controlled wall
hung gas fired condensing combination boilers with Storage
Tanks. The flue system is room sealed and fan powered.
The combination boilers which are designed to provide
domestic hot water and/or central heating must be used on
FULLY PUMPED sealed systems only.
The combination boiler will adjust automatically to provide
central heating outputs between 23.45 kW and 14.8 kW to
suit the system requirements.
Domestic hot water has priority over the central heating
system and is generated within the integral indirect storage
tank.
The combination boilers can be supplied with either of the
following flue systems:-
Horizontal
1 metre, 1.5 metre, 2 metre, 2.5 metre or 3 metre
Vertical
1 metre, 1.5 metre, 2 metre, 2.5 metre or 3 metre
Accessories
The following Potterton Myson controls are
recommended for use with your boiler:-
Electronic Timer
Room Thermostat PRT2 or PRT100
Frost Thermostat PRT100FR
Thermostatic Radiator Valve
Data sheets describing these products are available on
request.
Optional Extras
Part No. 236349 Terminal Wall Plate - where
necessary can be fitted to the
outside face to improve the
appearance, after making good
around the terminal.
Part No. 236591 Terminal Guard.
Part No. 430080 Flat Roof Flashing Kit - for use
with Vertical Flue.
Part No. 430081 Pitched Roof Flashing Kit - for
use with Vertical Flue.
Part No. 236893 Outdoor Weather Compensator

Publication No. 559779
Technical Data
3
Technical Data – Page 3
Boiler Details Boiler Details Cont...
Flue Size 100mm Concentric
Heat Input kW 26.86 Water Capacity 3.4 litre
Btu/hr 91,600 ___________________________________________
Heat Output,
NON-CONDENSING kW 23.45 Storage Tank Details - 20 Litre
Btu/hr 80,000
Heat Output, Packed Weight 20kg
CONDENSING kW 25.0 Full Weight 39kg
Btu/hr 85,400
Gas Rate M3/h 2.56 Max. Cold Water
ft3/hr 90.4 Supply Pressure 10 bar
Burner Pressure mb 12.2 Normal Secondary
in/wg 4.9 Operating Pressure Mains Pressure
Injector Size mm 4.2 Water Capacity 17.0 litres primary
Classification I2H. C1. C3. IP20 1.7 litres secondary
Burner Furigas Pre-Mix ____________________________________________
Igniter Norton 401S Hot Surface
Flame Detector Morgon Matroc Storage Tank Details - 50 Litre
Gas Control Valve SIT Nova Mix 1 - 8 Air Gas
Ratio Packed Weight 20kg
Electrical Supply 230V ~ 50Hz Full Weight 65kg
Fuse Rating - External 3A
Packed Weight - Boiler 52kg Max. Cold Water
Gas Supply Connections 15mm Compression Supply Pressure 10 bar
Flow Connections 22mm Compression Normal Secondary
Return Connections 22mm Compression Operating Pressure 3.5 bar
Condense Discharge Secondary Expansion
Connection 21.5mm (¾"Plastic
Compression) Vessel Charge Pressure 3.5 bar
Maximum Flow Water Capacity 2.9 litres primary
Temperature 85°C 41.8 litres secondary
Expansion Vessel 13.5 litre T & P Valve 90°C / 7 bar
(charge pressure 1.0 bar) Pressure Relief Valve 6 bar
Pressure Relief Valve 3 bar
EN0016A
930
815
110
225
450
740 Flowsure
830 Flowsure +
150 177
370 Main Casing
384 Including Door
Boiler Dimensions

Technical Data
Publication No. 559779
4
Technical Data – Page 4
Fig. 2

Publication No. 559779 Installation Requirements
5
1. Installation Requirements – Page 5
General Information
Prior to installation the boiler should be stored as
directed on the carton and in a dry place. Both the user
and manufacturer rely heavily on the installer, whose job
it is to install the boiler and connect it to a correctly
designed heating system. Acquaint yourself with the
British Standards concerning installation requirements. If
you need advice on any points, Potterton Myson’s
Service Operations will be pleased to help
(see back page).
Samples of the Envoy Flowsure and Envoy Flowsure+
have been examined by Gastec, a Netherlands Notified
Body. The range is certified to comply with the essential
requirements of the Gas Appliance Directive
90/396/EEC, the Low Voltage Directive 72/23/EEC and
shows compliance with the Electro Magnetic
Compatibility Directive 89/336/EEC and are therefore
permitted to carry the CE mark.
The appliance has been tested and approved by the
WRc as meeting the requirements of G3 and L of the
Building Regulations.
It is important that no external devices e.g. flue dampers,
economisers etc, be directly connected to this appliance
unless covered by these Installation and Service
Instructions or otherwise recommended by Potterton
Myson Ltd. in writing. If in doubt please enquire.
Any direct connection of a control device not
recommended by Potterton Myson could invalidate the
certificate and normal appliance warranty and could also
infringe the Gas Safety Regulations. Manufacturers
instructions must not be taken in any way as over-riding
statutory obligations.
If the area of installation is recognised as a hard water
area (above 200 p.p.m.), it is recommended that a
suitable water treatment device of an electronic,
magnetic or galvanic type be installed in the mains water
supply.
Codes of Practice
The boiler and tank must be installed in accordance with
the Gas Safety (Installation & Use) Regulations 1994,
and the current issue of:-
I.E.E. Regulations.
Model Water Bye Laws.
Building Regulations.
Building Standards for Scotland.
Health and Safety Document No. 635. (The
Electricity at Work Regulations 1989).
Health and Safety Information for the Installer and
Service Engineer
Under the Consumer Protection Act 1987 and Section 6
of the Health and Safety at Work Act 1974, we are
required to provide information on substances
hazardous to health. Small quantities of adhesives and
sealants used in the product are cured and present no
known hazards. The following substances are also
present.
Insulation and Seals
Material - Ceramic Fibre. Alumino - Silicone Fibre.
Description - Boards, Ropes, Gaskets.
Known Hazards - Some people can suffer reddening
and itching of the skin. Fibre entry into the eye will cause
foreign body irritation. Irritation to respiratory tract.
Precautions - People with a history of skin complaints
may be particularly susceptible to irritation. High dust
levels are only likely to arise following harsh abrasion. In
general, normal handling and use will not present
discomfort, follow good hygiene practices, wash hands
before consuming food, drinking or using the toilet.
First Aid - Medical attention must be sought following
eye contact or prolonged reddening of the skin.
Electricity Supply
A 230 volts ~ 50Hz, single phase electricity supply fused
to 3A, must be provided in accordance with the latest
edition of the IEE Wiring Regulations and any other local
regulations that apply. The current rating of the wiring to
the boiler must exceed 3 A and have a cross sectional
area of at least 0.75mm in accordance with BS 6500,
Table 16.
The supply to the boiler and its associated equipment
should be controlled by an exclusive 3A fused double
pole switch (having at least 3mm contact separation in
both poles) so that complete isolation from the supply
can be achieved to enable servicing work to be carried
out in safety.
Gas Supply
A gas supply pressure of 20mbar is required at the inlet
of the appliance. Performance data is based on use of
reference gas G20. The meter and supply pipes must be
capable of delivering this quantity of gas in addition to
the demand from any other appliances in the house and
must be governed at the meter.

Installation Requirements
Publication No. 559779
6
Installation Requirements – Page 6
Condensate Drain
The condensate outlet on the boiler is designed to
accept 21.5mm plastic overflow pipe, which if possible
should discharge into the household drainage system
and have an internal termination. If this is not practical,
discharge into an outside gully or soak away is
acceptable. To avoid blockage of this pipe due to
freezing it should be routed internally where possible
and have sufficient fall over its entire length to dispose of
condensate quickly. See British Gas ‘Guidance Notes for
the 'Installation of Domestic Gas Condensing Boilers’.
Location of Boiler and Tank
These boilers and tanks are not suitable for external
installation and should not be fitted directly above a
cooking appliance. The boiler and tank may be installed
in any room, although particular attention is drawn to the
requirements of the current IEE Wiring Regulations and
in Scotland, the electrical provisions of the Building
Standards applicable in Scotland with the respect to the
installation of the appliance in a room 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.
Where the installation of the boiler will be in an unusual
position, special procedures may be necessary and
BS6798 and BS5546 give detailed guidance on this
aspect.
It should be noted that due to the high efficiency of this
boiler a white plume of condensate will be emitted from
the flue terminal, therefore care should be taken when
selecting the terminal position.
Boiler Mounting Surface
The boiler and tank must be mounted on a flat wall,
which may be of combustible material and must be
sufficiently robust to take the weight of the boiler. The
requirements of the Local Authorities and the Building
Regulations must be adhered to.
Timber Framed Houses
If the boiler is to be installed in a timber framed building
it should be fitted in accordance with the British Gas
publication- Part 19 - Building and Kitchen Work. If in
doubt advice must be sought from the local region of
British Gas or from Potterton Myson.
Clearances around the Boiler and Tank
The following minimum clearances must be maintained
after installation for correct operation and servicing of
the boiler and tank.
Front: 15mm (610mm for servicing)
Sides: 5mm each side
Top: 140mm (from top of boiler case)
Bottom: 120mm
Ventilation
The room in which the boiler is installed does not require
a purpose provided air vent.
If the boiler is installed in a cupboard or compartment,
permanent air vents are required in the cupboard or
compartment, one at high level and one at low level,
either direct to the outside air or to a room. Both high
level and low level air vents must communicate with the
same room or must be on the same wall to outside air.
Both the high level and low level vent must each have a
free area as stated below. The free area of each vent
may be halved if the ventilation is provided directly from
outside.
High and Low air vent areas: 277 cm²
If the boiler is installed in a cupboard or compartment
with a door, allow at least 15 mm clearance between the
front of the boiler and the door for air movement.
Flue Terminal and Ducting
The Standard Horizontal Flue system (Part No.
236346) is suitable for installations up to 1030mm,
measured from the centre line of the boiler outlet to the
outside face of the wall.
0.5 & 1 Metre Flue Extension kits (0.5m - Part No.
430092, 1m - Part No. 430085) are available to extend
horizontal flues to a maximum length of 2920mm. The
siting positions for horizontal flue terminals are shown in
Fig. 3.
A Concentric Vertical Flue system is available (Part
No. 236348) when used in conjunction with the One
Metre Flue Extension kits is suitable for flue heights up
to 3 metres to terminate through a roof.
The siting of the flue terminal through a roof is shown in
Fig. 3.
Only the flue systems shown here can be fitted to the
Envoy Flowsure and Flowsure+ boilers.
If the terminal is fitted less than 2m (6.6 ft) above a
balcony, above ground or above a flat roof to which
people have access then a suitable terminal guard must
be provided and fitted.

Publication No. 559779 Installation Requirements
7
Installation Requirements – Page 7
A protective guard is available from the Potterton Myson
Sales Office whose address and telephone number are
shown on the rear cover. The guard (Part No 236591)
must be securely fitted to the wall and centrally located
over the flue terminal.
Where a flue terminal is installed less than one metre
from a plastic, or painted gutter, or 500mm from painted
eaves, an aluminium shield one metre long, should be
fitted to the underside of the gutter or painted surface. A
suitable wall plate should be fitted to the painted wall
surface of a mobile home.
It is absolutely ESSENTIAL to ensure that products of
combustion discharging from the terminal cannot re-
enter the building, or any other adjacent building,
through ventilators, windows, doors, natural air
infiltration, or forced ventilation/air conditioning. If
products of combustion are found to be re-entering
any building, the appliance MUST be turned OFF
IMMEDIATELY.
G
A
A
B,C
B,C
C
E
FGGG
G
K
LL
K
K
F F
EN0006A
Horizontal Flues
Vertical Flues
Flue Terminals
Facing Terminal
or Wall
A
P
R
Q
Q
S
N
N
N
H,I
Fig. 3
Terminal position Minimum spacing
A – Directly below an openable window, air vent or any other ventilation opening 300 mm
B – Below gutters, soil pipes or drain pipes 75 mm
C – Below eaves (Horizontal Flue Only) 200 mm
* – Below balconies/Carport Roof Not Recommended
E – From vertical soil pipes or drain pipes 75 mm
F – From an internal or external corner 300 mm
G – Above adjacent ground or balcony level 300 mm
H – From a surface facing the terminal 2000 mm
I – From a terminal facing the terminal 2000 mm
* – From opening (Door/Window) in carport into dwelling Not recommended
K – Vertically from a terminal on the same wall 1500 mm
L – Horizontally form a terminal on the same wall 300 mm
M – Adjacent to opening 300 mm
N – Above roof level (to base of terminal) 300 mm
P – From adjacent wall to flue 300 mm
Q – From internal corner to flue 400 mm
* – Below eaves or balcony (Vertical flue) Not Recommended
S – From facing terminal 2000

Installation Requirements
Publication No. 559779
8
Installation Requirements – Page 8
EN0033A
Filling
Point
Boiler
Cold
DHW
By - Pass
Balancing Valve
The System
The Envoy Flowsure and Flowsure+ have an aluminium
alloy heat exchanger, therefore all systems need to be
thoroughly cleansed and the correct treatment added to
the system water.
The only system additives recommended by Potterton
Myson Ltd. are FERNOX-COPAL or GRACE
DEARBORN - SENTINEL X 100 and should be used in
accordance with the manufacturers instructions. This will
include use of the appropriate system cleanser.
To ensure sufficient pump head is available to overcome
system resistance, a system differential of 14° should be
allowed for.
Where all radiators may be controlled by thermostatic
radiator valves a by-pass should be fitted as far away
from the boiler as possible.
Drain off taps should be fitted in the pipework close to
the boiler and at all low points of the system.
Note: Although the system can be emptied using the
drain off taps installed in the pipework around the
system, to empty the boiler it is necessary to remove
the drain off cap positioned within the boiler case.
Installation
The installation must comply with the requirements
of BS 6798: 1987 and BS 5449: Pt 1. The British
Gas publication "British Gas Specification for
Domestic Wet Central Heating Systems" should also
be consulted.
The following components are incorporated within
the appliance.
a) Circulating pump.
b) Diverter valve.
c) Pressure Relief valve with a non-adjustable pre-
set lift pressure of 3 bar (45 psi).
d) Pressure gauge covering the range 0-4 bar (0-60
psi).
e) 13.5 litre expansion vessel with initial charge
pressure of 1.0 bar (14 psi).
The domestic hot water system must be in
accordance

Publication No. 559779 Installation Requirements
9
Installation Requirements – Page 9
with the relevant recommendations of BS 5546. Copper
tubing to BS 2871:1 is recommended for water carrying
pipework and MUST be used for pipework carrying
potable water. All capillary joints in the D.H.W pipework
must be joined with a lead free solder.
Ancillary pipework, not forming part of the useful heating
surface, should be lagged to prevent heat loss and any
possible freezing, particularly where pipes run through
roof spaces and ventilated under-floor spaces.
The expansion vessel on this appliance is suitable for
central heating systems up to 135 litres. For systems
greater than this, an additional expansion vessel will be
required.
Mains Water Feed: Central Heating
A connection must be incorporated into the central
heating system to facilitate filling. There must be no
direct connection to the mains water supply, even
through a non-return valve, without the approval of the
Local Water Authority.
Permissible Methods of Filling
(1) Direct Method (Fig. 5)
A detachable flexible hose is connected to a stop valve
fitted to an outlet on the service main. The other end of
the hose is connected to a second stop valve and a
double check valve. The double check valve is fitted to
an inlet connection on the central heating return pipe
under the appliance. The hose should be disconnected
after filling. Where the mains pressure is excessive a
pressure reducing valve could be used to make filling
easier. The following fittings shall form a permanent part
of the system and shall be fitted in the order stated.
a) A stop valve complying with the requirements of BS
1010 Part 2, (the temporary hose from the draw off
tap shall be connected to this fitting).
b) Double check valve of an accepted type.
comprising a cistern, pressure booster pump and if
necessary, an automatic pressure-reducing valve or
flow restrictor.
The pressure booster pump must be capable of
pressurising the system to a minimum of 1.0 bar (14
p.s.i.) measured at the appliance.
The cistern should be supplied through a temporary
connection from a service pipe or cold water distributing
pipe. The unit may remain permanently connected to
the heating system to provide limited water make-up.
Provisions for make up water
Provision should be made for replacing water loss from
the system by re-pressurisation of the system. See
section on Methods of Filling.
Reference should be made to British Gas Publications
"Material and Installation Specifications for Domestic
Central Heating and Hot Water".
Note: The pre-charge pressure of the expansion vessel
is set at 1 bar, therefore, the cold fill pressure should be
1 bar.
Installation to an Existing Central Heating System
The boilers are designed to operate on a sealed system
only, therefore if the existing system is of the open type
it will have to be modified to comply with BS 6798.
Before installing a new boiler to an existing system
flush out the old system with a recommended descaling
/ flushing agent at least twice.
Also check pipework and renew any corroded pipework
or fittings. Valve glands must be re-packed or replaced
wherever necessary and any defective controls
replaced.
Central Heating Range Rate
Double
Check
Valve
Temporary
Connecting
Pipe
Stop
Valve
Pressure
Reducing
Valve
Service
Pipe
Fig. 5
For most installations the boiler will automatically adjust
the central heating output to match your heating system
requirement.
Pump
When set on maximum the circulating pump fitted within
the appliance should be capable of satisfying most
system requirements. Fig. 6 indicates the amount of
pump head available for the system. The boiler
resistance is already taken into account in this curve.
(2) Booster Pump Method
The system may be filled through a self contained unit

Installation Requirements
Publication No. 559779
10
Installation Requirements – Page 10
0
0
0.10.20.30.40.5
1.0
2.0
3.0
4.0
5.0
CP63
Litres / Sec
M / Head
80,000
DIFFFLOW
RATE
10°c0.56
14°c0.40
16°c0.35
18°c0.31
20°c0.28
EN0017A
To ensure sufficient pump head is available to overcome system resistance,
a system differential of 14° should be allowed for.
Domestic Hot Water - 20 Litre Tank
The 20 litre tank is a primary store which is designed to
be kept heated to meet instantaneous hot water
demands. It is a compact unit designed to supply instant
hot water at a flow rate of approximately 6.5 litres/min at
a 50°C rise.
Domestic hot water always takes priority over central
heating.
If domestic hot water is drawn off while the central
heating is operating the boiler will automatically transfer
the boiler output to the domestic hot water supply.
The tank is provided with all the necessary equipment to
ensure correct operation, except when a water meter
and/or water softener have been fitted in the system. In
such cases, an external secondary mini expansion
vessel (Part No. 430029) will need to be fitted on the
mains inlet to the tank.
Domestic Hot Water - 50 Litre Tank
The 50 litre tank is a secondary store which is designed
to be kept heated to meet instantaneous hot water
demands that require intermittently higher flow rates.
At a flow rate of approximately 12 litres/min, hot water
will be delivered for around 4 minutes at a 50°C rise
reducing thereafter. The tank will fully recover after a
few minutes to again deliver 12 litres/min at a 50°C rise.
Domestic hot water always takes priority over central
heating.
If domestic hot water is drawn off while the central
heating is operating the boiler will automatically transfer
the boiler output to the domestic hot water supply.
A secondary water expansion vessel is supplied with the
tank and must be connected to the appropriate tapping
on the controls assembly.
Important
No valves should be fitted between the expansion vessel and the storage cylinder.
DHW Store Temperature both tanks
Water is stored in the tank at approximately 73C. To ensure a safe delivery temperature a thermostatic mixing valve is fitted
in the hot water outlet and should be adjusted to produce a hot water delivery temperature of 60C.