Glow-worm Micron 40FF User Manual

Instructions for Use

Installation and Servicing

To be left with the user

221911E.04.05

Micron

40FF

G.C. No. 41-047-47

Fanned Flue Boiler

This is a Cat I2H Appliance

Reference in these instructions to British Standards and Statutory

Regulations/Requirements apply only to the United Kingdom.

For Ireland the current edition of I.S.813

"Domestic Gas Installations" must be used.

The instructions consist of three parts, User, Installation and Servicing Instructions.
The instructions are an integral part of the appliance and must, to comply with the current issue of the
Gas Safety (Installation and Use) Regulations, be handed to the user on completion of the installation.

7319

Guarantee Registration

Thank you for installing a new Glow-worm appliance in your home.

Glow-worm appliances' are manufactured to the very highest standard so we are pleased

to offer our customers' a Comprehensive First Year Guarantee.

We recommend you complete and return your Guarantee Registration Card as soon as possible.

If this card is missing you can obtain a copy or record your registration by telephoning Glow-worm's own service

Our Guarantee gives you peace of mind plus valuable protection against breakdown by covering the cost of:

✔

All replacement parts

❏

✔

All labour charges

❏

All call-out charges

✔

❏

organisation on 01773 828100.

REGISTER YOUR GLOW-WORM APPLIANCE

FOR 1ST YEAR GUARANTEE PROTECTION

CALL 0800 073 2142

Glow-worm

Tel: [phone]

Fax: [phone]

Nottingham Road, Belper, Derbyshire. DE56 1JT

General/Sales enquiries:

Tel: [phone] Fax: [phone]

www.glow-worm.co.uk

Important Information

TESTING AND CERTIFICATION

This boiler is tested and certificated to EN483 for safety and performance. It is therefore important that no alteration is made to the
boiler, without permission, in writing, from Glow-worm.

Any alteration not approved by Glow-worm, could invalidate the certification, boiler warranty and may also infringe the current issue
of the Statutory Requirements.

CE MARK

This boiler meets the requirements of Statutory Instrument No. 3083 The boiler (Efficiency) Regulations, and therefore is deemed
to meet the requirements of Directive 92/42/EEC on the efficiency requirements for new hot water boilers fired with liquid or gaseous
fuels.

Type test for purposes of Regulation 5 certified by: Notified body 0086.

Product/production certified by: Notified body 0086.

The CE mark on this appliance shows compliance with:

1. Directive 90/396/EEC on the approximation of the Laws of the Member States relating to appliances burning gaseous fuels.

2. Directive 73/23/EEC on the harmonization of the Laws of the Member States relating to the electrical equipment designed
for use within certain voltage limits.

3. Directive 89/336/EEC on the approximation of the Laws of the Member States relating to electromagnetic compatibility.

INFORMATION FOR THE INSTALLER AND SERVICE ENGINEER.

Under Section 6 of The Health and Safety at Work Act 1974, we are required to provide information on substances hazardous to
health.

Insulation Pads, Glass yarn.

These can cause irritation to skin, eyes and the respiratory tract. If you have a history of skin complaint you may be susceptible to
irritation. High dust levels are usual only if the material is broken. Normal handling should not cause discomfort, but follow normal
good hygiene and wash your hands before eating, drinking or going to the lavatory. If you do suffer irritation of the eyes or severe
irritation to the skin seek medical attention.

SPARE PARTS

REMEMBER: When replacing a part on this appliance, use only spare parts that you can be assured conform to the safety and

performance specification that we require. Do not use reconditioned or copy parts that have not been clearly authorised by
Glow-worm.

CONTENTS DESCRIPTION SECTION PAGE No.

INSTRUCTIONS

FOR USE

INSTALLATION

INSTRUCTIONS

General Information 3
Lighting the Boiler 3

General Data 1 4
Flue and Ventilation 2 7
Water Systems 3 8
Flue and Appliance Preparation 4 10
Boiler Installation 5 13
Commissioning 6 17
Instructions to the User 7 19

SERVICING

INSTRUCTIONS

221911E

Servicing 8 20
Fault Finding 9 21
Replacement Parts 10 25
Spare Parts 11 28

2

Instructions for Use

Introduction

Please read these instructions and follow them carefully for the
safe and economical use of your boiler.

The Micron series are fanned flue boilers designed to provide
central heating and indirect domestic hot water.

The boiler is fully automatic in operation having only one user
control, the temperature control.

WARNING: It is important that the case is not disturbed or
removed other than for servicing by a competent person.

Gas Leak or Fault

Turn off the gas emergency control valve immediately. Eliminate
all sources of ignition, i.e. smoking, blowlamps, hot air guns etc.
Do not operate electrical lights or switches either on or off. Open
all doors and windows, ventilate the area.

Electrical Supply Failure

Failure of the electrical supply will cause the burner to go out.
Should this occur, operation of the appliance will normally
resume after the electrical supply is restored.

NOTE: If the boiler is switched OFF, manually, wait at least 30
seconds before switching on again.

Safety Temperature Limiter

If the overheat Safety Temperature Limiter operates as indicated
by illuminated reset light, open the controls cover and turn
temperature control to “0” (anticlockwise) and then back to
original position, refer to diagram 9.1. If the overheat operates
again, turn the appliance off and contact your installation/
servicing company.

Protection Against Freezing.

If the boiler is to be out of use for any long period of time during
severe weather conditions we recommend that the whole of the
system, including the boiler, be drained off to avoid the risk of
freezing up. Make sure that, if fitted, the immersion heater in the
cylinder is switched off. Alternatively, there is a built-in frost
protection which will cause the boiler when it is switched off at
the control knob to operate in the event of the water temperature
in the boiler dropping to 6
again when the temperature of the water in the boiler reaches
about 15oC. This will only protect the central heating system if
the external controls are set so that the pump runs continuously,
that is they are calling for heat.

NOTE: The frost protection will not operate if the electrical
supply is turned off.

o

C or 7oC. The boiler will switch off

All CORGI Registered Installers carry a CORGI ID card, and
have a registration number. Both should be recorded in your
boiler Logbook. You can check your installer is CORGI registered
by calling CORGI direct on :- 01256 372300.

Cleaning

WARNING: This appliance contains metal parts (components)

and care should be taken when handling and cleaning, with
particular regard to edges.

Clean the casing occasionally by wiping it over with a damp
cloth or dry polishing duster.

Do not use an abrasive cleaner.

To Turn the Boiler On

Do not operate the boiler wthout water.

SEALED SYSTEMS (only)

The pressure gauge should show at least 0.7bar, anything less
than this figure could indicate a leak and you MUST contact your
installation/servicing company.

ALL SYSTEMS

Turn the electrical supply on to the boiler and check that all
remote controls are calling for heat.

Open the controls cover, see diagram 9.1.

Check also that the programmer (if fitted) is in the “ON” mode.

Turn the control knob clockwise to any position between "O"
and MAX. The maximum temperature setting is approx. 82
(180OF), see diagram 9.1.

The boiler lighting operation is now automatic as follows:

The fan will operate for a short period prior to the start of the
ignition sparks. The gas valve solenoids will open and the
burner will light. This is shown by the "Burner Lit" LED on the
control panel lighting up.

The burner will remain alight until switched off by the control
thermostat, any remote control or the programmer.

NOTE: If the boiler is switched OFF, by hand, wait at least 30
seconds before switching on again.

When the boiler switches off, the boiler will go out.

The automatic lighting sequence will operate again when heat
is required.

Shut the controls cover.

It should be noted that this is a fan flue appliance and fan
operation may be heard.

O

C

Maintenance

To ensure the continued efficient and safe operation of the
boiler it is recommended that it is checked and serviced as
necessary at regular intervals. The frequency of servicing will
depend upon the particular installation conditions and usage,
but in general once a year should be enough.

If this appliance is installed in a rented property in the UK there
is a duty of care imposed on the owner of the property by the
current issue of The Gas Safety (Installation and Use)
Regulations, Section 35.

It is the law that any servicing is carried out by a competent

person.

To obtain service, please call your installer or Glow-worm’s own
Service Organisation using the telephone number given on the
front cover of these instructions.

Please be advised that the ‘Benchmark’ logbook should be
completed by the installation engineer on completion of
commissioning and servicing.

To Turn the Boiler Off

For short periods, turn the control knob anti-clockwise to “0” Off.
To relight, turn the control knob to any position between “0” and
“MAX”.

For longer periods, turn the control knob fully anti-clockwise to
“0” Off and switch off the electrical supply to the boiler.

To relight follow the lighting sequence given above.

Optional Programmer

A programmer is available, which will automatically switch your
central heating system on and off once or twice a day at
whatever times you choose.

3

221911E

Installation - 1 General

6784

A

J

H

B

PUMPED

FLOW

PUMPED

RETURN

K

C

WATER CONNECTIONS

GAS CONNECTION

F

Q

D

E

M

R

TOP / SIDE
FLUE OPTION

C

REAR

G

FLUE OPTION

P

N

MODEL A B C D E F G H J K L M N P Q R

40FF 262 75 102 360 139 500 68 85 115 115 126 156 100 104 23 40 35 108

STD/EXD. EASYFIT STD/EXD. EASYFIT

Diagram 1.1All dimensions are given in millimetres

IMPORTANT NOTICE

This boiler is for use on Natural Gas (G20) as distributed in the
United Kingdom and Ireland and cannot be used on any other
gas. This boiler must be installed by a competent person

ONLY.

This boiler can be used on open vented or sealed water
systems.

Domestic hot water must be provided by pumped circulation.

Wherever possible, all materials, appliances and components
used shall comply with the requirements of applicable British or
Irish Standards.

Where no Standards exists, materials and equipment should be
fit for their purpose and of suitable quality and workmanship.

Sealed Components

Under no circumstances must the User interfere with or adjust
sealed parts.

In IE, the installation must be carried out by a competent
person and installed in accordance with the current edition of
I.S.813 "Domestic Gas Installations", the current Building
Regulations and reference should be made to the current ETCI
rules for Electrical Installation.

In GB the following Codes of Practice apply:

BS4814, BS6798, BS5440 Part 1 and 2, BS5546 Part 1,
BS5449, BS6891, BS6700, BS7074 Part 1 and 2, BS7593,
BS7671.

In IE: I.S.813, BS5546, BS 5449, BS 7074, BS 7593.

Manufacturer’s instructions must not be taken as overriding
statutory requirements.

NOTE: For further information, see the current issue of the
Building Regulations, approved document L1 ( in the UK) and
the references:

1) GIL 59, 2000: Central heating system specification (CheSS)
and

2) GPG 302, 2001: Controls for domestic central heating system
and hot water. BRECSU.

Sheet Metal Parts

WARNING: When installing or servicing this boiler care should

be taken when handling sheet metal parts, to avoid any possibility
of personal injury.

1.1 Statutory Requirements

In GB the installation of the boiler must be carried out by a
competent person as described in the following regulations:

The manufacturer’s instructions supplied.

The Gas Safety (Installation and Use) Regulations.

The appropriate Buildings Regulations either The Building
Regulations, The Building Regulations (Scotland),The Building
Regulations (Northern Ireland).

The Water Fittings Regulations or Water byelaws in Scotland.

The Health and Safety at Work Act, Control of Substances
Hazardous to Health (COSHH).

The Current I.E.E. Wiring Regulations.

Where no specific instructions are given, reference should be
made to the relevant British Standard Code of Practice.

1.2 Data

See diagrams 1.1,1.2 and Table 1.

All dimensions are given in millimetres (except as noted).

The Seasonal Efficiency Domestic Boilers UK (SEDBUK) is

78.6%.

The value is used in the UK Government’s Standard Assessment
Procedure (SAP) for energy rating of dwellings. The test data
from which it has been calculated have been certified by B.S.I.

1.3 Range Rating

This boiler is range rated and may be adjusted to suit individual
system requirements, refer to diagram 1.2 for data label position,
ratings and settings.

L

221911E

4

1 General

1.4 Gas Supply

The gas installation shall be in accordance with the relevant
standards.

In GB this is BS6891.

In IE this is the current edition of I.S.813 "Domestic Gas
Installations".

The supply from the governed meter must be of adequate size
to provide a steady inlet working pressure of 20mbar (8in wg)
at the boiler.

On completion test the gas installation for soundness using the
pressure drop method, purge in accordance with the above
standard.

1.5 Electrical Supply

WARNING: This boiler must be earthed.

All system components shall be of an approved type and shall
be connected in accordance with the current issue of BS7671
and any applicable local regulations.

External wiring must be correctly earthed, polarised and in
accordance with the relevant standards.

In GB this is BS 6891.

In IE this is the current edition of I.S.813 "Domestic Gas
Installations".

Connection of the boiler and system controls to the mains
supply must be through a common isolator and must be fused
3A, maximum. This method of connection must be by a fused
double pole isolating switch, with a minimum contact separation
of 3mm on both poles. The switch should be readily accessible
and preferably adjacent to the appliance. It should supply the
appliance only and be easily identifiable as so doing.

Alternatively, an unswitched shuttered socket outlet and 3A
fused 3 pin plug, both to the current issue of BS1363 may be
used provided that they are not used in a room containing a bath
or shower.

Wiring to the boiler must be PVC 85
than 0.75mm

2

(24/0.20mm).

0

C insulated cable, not less

1.9 Safety Valve

A safety valve need not be fitted to an open vented system.

PMS = 3.0 bar, is: Maximum water-side operating pressure.

The appliance flue type is a C
concentric or twin flue where the fan is downstream of the heat

exchanger. The C12 is a horizontal flue termination, the C
shared duct system (Seduct), the C32 is a vertical flue termination and

the C

has separate ducts to two terminals that may terminate in

52

zones of different pressure.

, C

12

, C

and C52. This refers to a

22

32

is a

22

9441

7316

1.6 Contents of Packaging

The boiler is delivered in one pack with the flue system packed
separately.

1.8 Water System

This boiler may be fitted to an open vented or a sealed water
system.

1.8 Draining Tap

System

A draining tap must be provided at the lowest points of the
system which will allow the entire system and hot water cylinder
to be drained.

Draining taps should be to the current issue of BS2879.

Boiler

A draining point is fitted at the bottom right hand side of the heat
exchanger.

When draining is required cover the controls to avoid water
damage.

If required remove the combustion chamber front cover to
improve access.

DATA
LABEL

TABLE 1.

TOTAL DRY WEIGHT
(Including Terminal)

LIFT WEIGHT

WATER CONTENT

GAS CONNECTION

ELECTRICITY RATING

WATER CONNECTION

ELECTRICITY SUPPLY

DATA LABEL

Diagram 1.2

36.4 kg (80lb)

29.7 kg (65.34lb)

2.2 litre (0.48 gallon)

1

/2in.

Rc

66W Internal fuse Type T3.15A

2x22mm copper pipes from

back of case

230V~50Hz,fused 3A

Top left hand inside of case

5

221911E

1 General

190mm with Easyfit top flue fitted,

*

160mm with standard/extended top flue fitted,

*

20mm without top flue fitted
Increased top clearance is required if flow pipe enters from
below to permit access to air vent.

MINIMUM CLEARANCES FROM WALLS, CEILING, FLOOR,
CUPBOARD, WORKTOPS AND INFLAMMABLE MATERIALS

7064

Diagram 1.3

1.10 Location

This boiler is not suitable for outdoor installation.

The boiler may be installed in any room, although particular
attention is drawn to the requirements of BS7671 with respect
to the installation of a boiler in a room containing a bath or
shower. Any electrical switch should be so positioned that it
cannot be touched by a person using the bath or shower. The
electrical provisions of the Building Standards (Scotland)
Regulations apply to such installations in Scotland.

This boiler is suitable for installation in bathroom zones 2 and 3.

In GB this is the current I.E.E. WIRING REGULATIONS and
BUILDING REGULATIONS.

In IE reference should be made to the current edition of I.S.813
"Domestic Gas Installations" and the current ETCI rules.

The boiler must be mounted on a flat wall which is sufficiently
robust to take its total weight.

The boiler may be fitted to a wall made of combustible material.

1.11 Boiler Clearances

Refer to diagram 1.3.

This boiler must be positioned so that at least the minimum
operational and servicing clearances are provided.

Additional clearances may be required for installation.

If fixtures are positioned next to the boiler ensure access is
provided for pipework installation.

At least a minimum clearance of 300mm from a permanently
fixed surface must be left in front of the boiler for servicing, see
diagram 1.3.

1.13 Boilers in a Compartment

Where the installation of the boiler will be in an unusual position,
the current issue of BS6798 gives detailed guidance on these
requirements.

An existing cupboard or compartment modified for the purpose
may be used, providing minimum clearances are maintained.
Details of essential requirements for cupboard or compartment
design are given in the current issue of BS6798.

The doorway opening should be of sufficient size to allow for
easy removal of the boiler.

Where the boiler is fitted in a cupboard or compartment,
permanent ventilation is not required.

1.14 Timber Frame Building

If the boiler is to be installed in a timber frame building it should
be fitted in accordance with the Institute of Gas Engineers
document IGE/UP/7/1998. If in doubt seek advice from the local
gas undertaking or Glow-worm.

1.15 Anti-theft Kits

Anti-theft kits are available for these appliances, contact
Glow-worm. for further information.

1.12 Room Ventilation

The boiler is room sealed and does not require the room or
space containing it to have permanent air vents.

221911E

6

2 Flue and Ventilation

The flue must be installed in accordance with the rules in force
in the countries of destination.

2.1 Terminal Position

The minimum acceptable siting dimensions for the terminal
from obstructions, other terminals and ventilation openings are
shown in diagram 2.1. For Ireland the minimum distances for
flue terminal positioning must be those detailed in I.S.813
"Domestic Gas Installations".

The terminal must be exposed to the external air, the position
allowing free passage of air across it at all times.

Car ports or similar extensions of a roof only, or a roof and one
wall, require special consideration with respect to any openings,
doors, vents or windows under the roof. Care is required to
protect the roof if it is made of plastic sheeting. If the car port
consists of a roof and two or more walls, seek advice from the
local gas company before installing the boiler.

If the terminal is fitted within 600mm below plastic guttering or
painted soffit an aluminium shield 1500mm long should be fitted
immediately beneath the guttering or eaves. If the terminal is
fitted within 450mm below painted eaves or a painted gutter, an
aluminium shield 750mm long should be fitted immediately
beneath the guttering or eaves.

N

A

P

Q

E

L

F

UNDER CAR PORT etc.

C

B,C

G

A

H,I

B,C

K

F

G

J

M

11508

D

F

K

2.2 Flue Options

There are various flue systems to choose from, as follows:

Standard Top Outlet Flue Pack - Pt.No. 230483

Easyfit Top Outlet Flue Pack - Pt. No. 232057

Standard Rear Outlet Flue Pack - Pt. No. 230482

Extended Top Outlet Flue Pack - Pt. No. 230487

1 Metre Extension Kit - Pt. No. 230484
A flue system up to 3 metres in length can be made by
connecting 1 metre flue extension kits together.

Optional Wall Liner Kit No. 900862

A Flue Bend Kit or Vertical Flue Kit up to 4 metres can be
supplied, see Glow-worm's "Flue Options Guide" for
configurations available.

o

Flue Bend Pack - Pt. No. 230485

45

90o Flue Bend Pack - Pt. No. 230486

In Line Flue Adapter Kit - Pt. No. 230488

Vertical Flue Kit No. 458115

MINIMUM SITING DIMENSIONS FOR
FANNED FLUE TERMINALS POSITION MM

HORIZONTAL FLUES

A DIRECTLY BELOW, ABOVE OR

HORIZONTALLY TO AN OPENING, AIR BRICK,
OPENING WINDOW, AIR VENT, OR ANY

OTHER VENTILATION OPENING 300
B BELOW GUTTER, DRAIN/SOIL PIPE 25
C BELOW EAVES 25
D BELOW A BALCONY OR CAR PORT 25
E FROM VERTICAL DRAIN PIPES AND

SOIL PIPES 25
F FROM INTERNAL/EXTERNAL CORNERS

OR TO A BOUNDARY ALONGSIDE THE

TERMINAL 25
G ABOVE ADJACENT GROUND OR

BALCONY LEVEL 300
H FROM SURFACE OR A BOUNDARY

FACING THE TERMINAL 600
I FACING TERMINALS 1200
J FROM OPENING (DOOR/WINDOW)

IN CAR PORT INTO DWELLING 1200
K VERTICAL FROM A TERMINAL 1500
L HORIZONTALLY FROM A TERMINAL 300

VERTICAL FLUES

M FROM ADJACENT WALL TO FLUE 300
N FROM ANOTHER TERMINAL 600
P FROM ADJACENT OPENING WINDOW 1000
Q ABOVE ROOF LEVEL 300

Diagram 3.3

7

221911E

2 Flue and Ventilation

2.3 Terminal Guard

A terminal guard is required if persons could come into contact
with the terminal or the terminal could be subject to damage.

If a terminal guard is required, it must be positioned to provide
a minimum of 50mm clearance from any part of the terminal and
be central over the terminal, see diagram 2.2.

A suitable guard, reference Type “K3”, can be obtained from:

Tower Flue Components Ltd.,

Morley Road, Tonbridge,

Kent. TN9 1RA

3 Water Systems

7056

Diagram 2.2

The installation of the boiler must comply with the requirements
of the current issue of BS6798, in Ireland, refer also to the
current edition of I.S.813 "Domestic Gas Installations".

In GB it is necessary to comply with the Water Supply (Water
Fittings) Regulations 1999 (for Scotland, the Water Byelaws
2000, Scotland).

To comply with the Water regulations your attention is drawn to:
The Water Regulations guide published by the Water Regulations
Advisory Service (WRAS) gives full details of the requirements.

In IE the requirements given in the current edition of I.S.813
"Domestic Gas Installations" and the current Building Regulations
must be followed.

3.1 Frost Protection

There is a built-in frost stat in this boiler. See Protection Against
Freezing in Instructions for Use. Where other parts of the
system are vulnerable this should also be considered as specified
in the current issue of BS5422.

3.2 Pump

The pump, with integral valves, should be fitted in the heating
flow pipework from the boiler, it should be set to produce a
temperature difference of 11

O

C (20OF), between the flow and
return, with the boiler thermostat set at “MAX”, which is about
82OC (180OF).

The pressure loss of the boiler at 11.5 litre/minute giving 11

O

temperature difference is 150mm head of water.

High resistance microbore systems may require a higher duty
pump.

3.3 Bypass

A bypass is unnecessary, unless thermostatic radiator valves
are fitted to all radiators.

If required, a 15mm bypass must be fitted at least 2m away from
the boiler and adjusted such that there is a temperature difference
no greater than 20

O

C between flow and return.

3.4 Water System

For an open vented system the boiler must be supplied from an
unrestricted water supply taken from a feed and expansion
cistern fitted at a maximum height of 27 metres above the boiler.

The cold feed must be 15mm minimum size.

It is important that the relative positions of the pump, cold feed
and open vent are as shown in diagram 3.1.

The unrestricted open vent from the boiler must rise continuously
to discharge over the feed and expansion cistern.

OPEN VENTED FULLY PUMPED WATER SYSTEM
RECOMMENDED RELATIONSHIP BETWEEN
PUMP COLD FEED AND VENT

22mm VENT
450mm
MIN.
HEIGHT

FEED AND
EXPANSION
CISTERN

1METRE
MIN.

There must
always be a cold
water path to the
return connection

C

of the boiler.

BOILER

(MIN.)

15mm (MINIMUM)
COLD FEED

RETURN

PUMP

150mm
MAX.

IF REQUIRED
15mm (MINIMUM)
BY-PASS WITH
LOCKSHIELD VALVE

3.5 Domestic Hot Water System

General - All domestic hot water circuits, connections, fittings

must be in accordance with the relevant standards and water
supply regulations.

For GB: Guidance G17 to G24 and recommendation R17 to
R24 of the Water Regulations Guide.

For IE: The current edition of I.S.813 "Domestic Gas Installations".

3.6 Cylinder

For all systems supplying domestic hot water the cylinder must
be indirect. It is recommended that the cylinder be fitted with
some form of temperature control.

3.7 Open Vented Fully Pumped Heating and
Domestic Hot Water

The connections for the system MUST be as shown in diagrams

3.1 and 3.2.

Plastic pipes should not be connected directly to the boiler. An
intermediate metallic pipe of 1m in length should be fitted
between the boiler and the plastic pipe system. Plastic pipes
should be type S to BS7291.

7065

FLOW

CYLINDER

FLOW

HEATING

RET.

Diagram 3.1

221911E

8

3 Water Systems

3.8 Inhibitor

Attention is drawn to the current issue of BS5449 and BS7593
on the use of inhibitors in central heating systems.

When installing in an existing system take special care to drain
the entire system, including radiators, then thoroughly cleaning
out before installing the boiler whether or not adding an inhibitor.

3.9 Sealed Water Systems

The installation should comply with the appropriate requirements
of the current issue of BS4814, BS5449, BS6759, BS6798 and
BS7074 Part 1 and 2.

3.10 Safety Valve

A safety valve must be fitted to a sealed water system.

It shall be preset, nonadjustable with a lift pressure of 3bar,
incorporating seating of a resilient material, a test device and a
connection for drain.

The drain from the safety valve must be routed clear of any
electrical fittings and positioned so that any discharge can be
seen.

3.11 Expansion Vessel - Sealed Systems Only

A diaphragm type expansion vessel, conforming to the current
issue of BS4814 (see also BS7074 Part 1 and 2) must be
connected at a point close to the inlet side of the circulating
pump, unless laid down differently by the manufacturer.

The expansion vessel volume depends upon the total water
system volume and the initial system design pressure. For any
system an accurate calculation of the vessel size is given in the
current issue of BS7074 Part 1.

Example: For an initial system design pressure of 0.7bar the
minimum total vessel volume required is 0.063 x Total System
volume.

NOTE: A higher initial design pressure requires a larger volume
expansion vessel.

Guidance on vessel sizing is also given in the current issue of
BS5449 and BS7074 Part 1, for IE refer to the current edition of
I.S.813 "Domestic Gas Installations".

The charge pressure must not be less than the static head of the
system, that is, the height of the highest point of the system
above the expansion vessel.

The water content of the boiler is given in Table 1.

3.15 Filling a Sealed Water System

Provision for filling the system at low level must be made.

The installation should comply with the appropriate requirements
of the current issue of BS 5449.

3.16 Water Makeup

Provision must be made for replacing water lost from the
system. A make up vessel mounted above the highest point of
the system and connected through a non-return valve to the
system on the return side of either the hot water cylinder or
heating system.

PUMPED
FLOW

22mm
PIPE

22mm
PIPE

22mm VENT & 15mm COLD FEED TO BE FITTED
IN ACCORDANCE WITH BS5449

1metre Min.

27 metres

Max.

IF REQUIRED
BYPASS 15mm
MIN WITH
LOCKSHIELD
VALVE

FULLY PUMPED CIRCULATION
BYPASS (DIAGRAMMATIC)

PUMPED
RETURN

22mm
PIPE

22mm
PIPE

7067

INDIRECT
CYLINDER

ALTERNATIVE
SYSTEM
CONTROL
VALVES

HEATING
SYSTEM

PUMP

6770

3.12 Pressure Gauge - Sealed Systems Only

A pressure gauge with a set pointer and covering at least the
range of 0 to 4bar (0 to 60lb/in
the system in a position where it can be seen when filling the
system.

2

) shall be permanently fitted to

3.13 Domestic Hot Water Cylinder

SINGLE FEED INDIRECT CYLINDERS ARE NOT SUITABLE.

The domestic hot water cylinder must be of the indirect coil type.
It must be suitable for working at a gauge pressure of 0.35bar
above the safety valve setting.

3.14 Domestic Hot Water System - Unvented

Where a storage system will not have a vent to atmosphere the
installation must comply with Building Regulations and local
Water Company Bye-laws, see also the current issue of BS6700.

If fitting into an existing system the local authority must also be
advised.

22mm FOR COMBINED FEED & VENT TO BE FITTED
IN ACCORDANCE WITH BS5449

INDIRECT
CYLINDER

1metre Min.

27 metres

Max.

IF REQUIRED
BYPASS 15mm
MIN WITH
LOCKSHIELD
VALVE

PUMP

ALTERNATIVE
SYSTEM
CONTROL
VALVES

FULLY PUMPED CIRCULATION
BYPASS (DIAGRAMMATIC)

9

HEATING
SYSTEM

Diagram 3.2

221911E