Glow-worm Inset BBU50 User Manual

221723B.10.00

Installation & Servicing Instructions

To be left with the user

INSET BBU 50

G.C. No. 44 047 02

For Use Only With Specially Designed Fire Fronts

8023

One Contact Local Service

This is a Cat I2H Appliance

Customer Services:
Tel: [phone]
Fax: [phone]

Nottingham Road, Belper, Derbyshire. DE56 1JT

Tel: [phone] Fax: [phone]

Hepworth Heating Ltd.,

General/Sales enquiries:

Important Information

B.S.I Certification

It is important that no alteration is made to the boiler without permission, in writing, from Hepworth Heating Ltd.
Any alteration that is not approved by Hepworth Heating Ltd., could invalidate the B.S.I. Certification, the boiler warranty and could

also infringe the current issue of the Statutory Requirements, see Section 1.1.

CE Mark

The 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 for Regulation 5 certified by: Notified body 0086.
Product/production certified by: Notified by 0086.

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 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.

The adhesives and sealants used in this appliance are cured and give no known hazard in this state.

RADIANTS, FUELBEDS, ARTIFICIAL FUEL

After handling wash hands thoroughly.

INSULATION PADS/CERAMIC FIBRE, GLASSYARN, MINERAL WOOL

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 to the eyes or severe irritation to the skin seek medical attention.

THERMOSTATS

These contain very small amounts of trichlorofluoromethane in the sealed phial and capillary. If broken, under normal circumstances
the fluid does not cause a problem, but it can, in exceptional cases cause freeze burns.

If there is skin burn or irritation to the eyes or skin seek medical attention.
These contain very small amounts of xylene in the sealed phial and capillary. If broken, under normal circumstances the fluid does

not cause a problem, but in cases of skin contact, wash with cold water.
If swallowed drink plenty of water and seek medical attention.

CUT-OFF DEVICES

These contain a very small amount of ethylene glycol and methanol in the capillary. If broken, under normal circumstances the fluid
does not cause a problem, but in cases of skin or eye contact, wash with cold water.

If swallowed drink plenty of water and seek medical attention.

CONTENTS DESCRIPTION SECTION PAGE No.

General Data 1 3
Types of Installation 2 6

INSTALLATION

INSTRUCTIONS

Flue and Ventilation 3 7
Installation 4 8
Electrical Wiring 5 13
Commissioning 6 16
Fire Installation 7 18

SERVICING

INSTRUCTIONS

221723B

Servicing 8 18
Fault Finding 9 22
Replacement Parts 10 24
Spare Parts 11 28

2

1 General

1 General

References in these instructions to British Standards, Statutory
Regulations and Requirements apply only to the United Kingdom.

For Ireland the rules in force must be used.
The instructions consist of three parts, Installation and Servicing

Instructions for the Back Boiler Unit, Installation and Servicing
Instructions for the specified Fire Front and Instructions for Use
and the Guarantee Registration Card. 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.

The Glow-worm Inset 50 Back Boiler Unit, GC No. 44 047 02 is
for use only with the Glow-worm Inset Fire Fronts.

1 General Notes and Information

IMPORTANT NOTICE
This boiler is for use only on G20 gas.
The back boiler unit is fitted with a flue blockage safety device

which will shut it down if there is a lack of oxygen resulting from
a build up of combustion products, the flame on the pilot light will
become unstable and lift up off the thermocouple. This will
deactivate the mag unit in the gas control valve, cutting off the
gas supply.

If the back boiler unit shuts down frequently for no apparent
reason the first things to check are the chimney and air inlets
into the room. Any problems found must be put right, by a
competent person, and a full operational test carried out before
the fire is used again.

The flue blockage safety device incorporates the electrode,
thermocouple and pilot assemblies.

The flue blockage safety device MUST NOT be adjusted or
disconnected. It must be serviced strictly in accordance
with the instructions in this book. Any unauthorised
interference could result in the device failing to operate,
creating a potentially dangerous situation. If replacing, use
only the correct and approved parts.

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

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

This boiler, together with its fire can be used on a precast flue,
see Section 3.4.

Sheet Metal Parts

WARNING. When installing or servicing this back boiler care
should be taken when handling the edges of sheet metal parts
to avoid any possibility of personal injury.

1.1 Statutory Requirements

The installation of this back boiler unit must be carried out by a
competent person in accordance with the current issue and
relevant requirements of:

Manufacturer’s instructions, supplied.
The Gas Safety (Installation and Use) Regulations, The Building

Regulations, The Building Standards (Scotland) Regulations,
applicable in Scotland, Local Gas Undertaking, Bye-laws of the
Local Water Company, The Health and Safety at Work Act,
Control of Substances Hazardous to Health, The Electricity at
Work Regulations and any applicable local regulations.

Detailed recommendations are contained in the current issue of
the following British Standard codes of practice,

BS1251, BS5440 Part 1 and 2, BS5449, BS5546, BS5871,
BS6798, BS6891, BS7593, BS7671.

Manufacturer’s notes must not be taken as overriding statutory
obligations.

1.2 Data BBU 50

Gas connection Rc1/
(1/2inBSPT)
Water connection Supplied in fittings pack
Electrical supply 230V~50Hz fused 3A
Weight, about 40kg
(81.6lb)
Water content 3.11Litres
(0.68gall)
Injector 3.5mm
Dimensions, except as noted, shown on diagrams are in

millimetres.
Data Label: On the base of the boiler next to the electrical

control box.
The Seasonal Efficiency Domestic Boilers UK (SEDBUK)

is 76.8%.
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.

2

1.3 Gas Supply

The gas installation must be in accordance with the current
issue of BS6891.

The supply from the governed gas 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 and suitable leak detection fluid, purge
in accordance with the above standard.

1.4 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.

Connection of the boiler and system controls to the mains
supply should be through a common isolator , a double pole
isolating switch, fused 3A, should be used, having a minimum
contact separation of 3mm in both poles.

Alternatively, a fused 3A 3pin plug and unswitched shuttered
socket both to the current issue of BS1363 may be used.

Wiring to the boiler must be PVC (85
current issue of BS6500 Table 9, not less than 0.75mm

0.20mm).

o

C) insulated type to the

2

(24/

3 221723B

1 General

FIRE FIXING WALL FACE

C

L

FLUE

D

P

M

E

F

L

6173

B

G

WATER
CONNECTIONS

C

L of Flue

R

N

C

J

H

H

A

K

22mm COPPER PIPE

GAS CONNECTION
RC (1/2 in BSPT)

SIDE ELEVATION

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

50 / BBU 550 400 337 245 130 164 146 193 174 39 348 65 530 80 50

OVERALL DIMENSIONS

(RIGHT HAND WATER CONNECTION SHOWN)

TABLE 1

INSET BBU 50

RANGE RATING

FRONT ELEVATION

350mm
MIN

Diagram 1.1

560mm MIN

590mm MAX

6302

221723B

405mm MIN
500mm MAX

PREPARED
BASE

4

Diagram 1.2

1 General

1.5 Contents of Packaging

The boiler is delivered in one pack which contains all the parts
required for installation.

1.6 Site Requirements

For all types of installation a standard 16inch builder’s opening
is required, see diagram 1.2.

Note: The depth of the fire opening is IMPORTANT, it MUST
therefore conform to the dimensions given in diagram 1.2.

Any larger opening will need to be reduced, with non-combustible
material to conform to this requirement.

It is important that the opening is cleared of debris and mortar
etc.

The prepared base for the back boiler must be level.
Refer to diagram 1.3 for dimensions of the fire fixing wall face

which MUST be true.

1.7 Water System - Open Vented

This boiler can be used on an unrestricted open vented system
with the water supply taken from a feed and expansion cistern,
having a head between 1m (3ft 3in) minimum and 27m (90ft)
maximum.

Diagrammatic layouts of systems are shown in diagram 1.4 and

1.5.

Sealed Water System

A Kit and instructions, Part No. 459033, is available to enable
the back boiler to be used on a sealed water system.

Please give the serial number of the back boiler unit when
ordering the kit.

1.8 Hot Water Cylinder

The back boiler is suitable for open vented systems using an
indirect cylinder (including single feed self priming type). The
cylinder must be fitted to the manufacturer’s recommendations
and the system must conform to the requirements of the current
issue of BS5449.

It is recommended that the cylinder be fitted with some form of
temperature control.

1.9 Frost Protection

If the position of the boiler is such that it may be vulnerable to
freezing it should be protected as specified in the current issue
of BS5422.

It is also recommended that a frost thermostat is fitted.

Minimum flat area and fixture or
surround protection clearance

690

C

L

800 MIN WIDE FRAME

PREPARED BASE

28mm

FIXED
DIMENSION

FLOW

RETURN

INDIRECT

CYLINDER

DISTRIBUTOR
TUBE IN RETURN
CONNECTION

22mm
CENTRAL
HEATING
RETURN

BOILER

22mm
CENTRAL
HEATING
FLOW

Diagram 1.3

C

L

MAXIMUM

27 METRES

PUMPED HEATING & GRAVITY DOMESTIC HOT
WATER (DIAGRAMMATIC)

Diagram 1.4

5506

780 MIN STANDARD FRAME

6242

6243

1.10 Draining Tap

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

Draining taps shall be to the current issue of BS2879.

1.11 Safety Valve

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

1.12 Boiler Location

This back boiler unit MUST NOT be installed in a private garage
or in a room containing a bath or shower or a room used or
intended to be used as sleeping accommodation.

INDIRECT
CYLINDER

1 METRE MIN

27 METRE MAX

TO HEATING
CIRCUIT

PUMP

C

BOILER

FLOW

RETURN

L

FULLY PUMPED SYSTEM
(DIAGRAMMATIC)

5 221723B

Diagram 1.5

2 Types of Installation

2.1 Hearth

In ALL cases there MUST be a non-combustible hearth under
the fire front.

For minimum dimensions of a hearth see diagram 2.1.
Carpet or similar floor covering must not be placed on the

hearth.
If the boiler is to be mounted above the prepared hearth the

hearth must still conform to the instructions above and the
dimensions given in diagram 2.1.

2.2 Fire Surround

The combined thickness of the surround and the lintel must be
checked, to ensure that the back boiler can be positioned within
the opening to allow easy connection of the flue into the boiler
flue socket, see diagram 2.2.

For fireplaces where the wall is not plastered and not covered
by BS1251 it is important that such installations comply with the
current issue of The Building Regulations.

Any combustible material, for example, blown vinyl wall coverings,
on the fire fixing face area of the surround must be removed, see
diagram 1.3.

50mm MIN

165mm
MAX

650mm

PREPARED
BOILER
BASE

HEARTH

300mm

FIRE WALL FACE

5423

2.3 Without Fire Surround

The builder’s opening, with lintel must have minimum dimensions
as shown in diagrams 1.2 and 2.2.

350mm
MIN

350mm MIN

FLUE
PIPE

*165mm
MAX

PREPARED BASE

TOPS OF HEARTH
MUST NOT BE
ABOVE PREPARED
BASE

13mm MIN
NON-COMBUSTIBLE
MATERIAL

Diagram 2.1

FIRE FIXING
WALL FACE

*NOTE
This dimension can
be increased up to
190mm if builder’s
opening depth is at
least 375mm deep

50mm
MIN

6196

221723B

Diagram 2.2

6

3 Flue and Ventilation

3.1 General

The general recommendations of the current issue of BS5440
Part 1 should be followed.

In all cases the flue should be lined, preferably with a flexible
liner.

It is essential that the flue has an equivalent height of at least

2.5m (8.2ft) measured from the flue connection on the appliance.
The first 600mm, at least, above the draught diverter must be
vertical.

Where the installation is new it is essential to make sure that the
annular space between the boiler flue liner and the chimney is
sealed at the base and at the top of the chimney, as shown in
diagram 3.2.

The flue socket is designed to take flue pipe to BS567. If flue
pipe conforming to a different standard is used a suitable
adapter must be fitted and secured to the flue socket. A flexible
flue liner may be used, with connection to the back boiler flue
socket, see diagram 3.1.

The existing flue may not be completely sound. Therefore, to
prevent the possibility of leakage to an adjacent flue, additional
sealing MUST be carried out between the base of the chimney
and the flue liner.

The end of the flue liner at the chimney top must be adequately
sealed and clamped, using proprietary fittings suitable for the
flue liner used, see diagram 3.2.

The flue should, preferably, end above ridge height but at the
least above the eaves of a pitched roof. Use a certificated
terminal.

If the flue is to pass through or near any combustible material it
should be installed in accordance with the current issue of
BS5440 Part 1. If in doubt seek advice from the local gas
undertaking or Hepworth Heating Ltd.

If a specially built compartment is constructed for the back
boiler, it must conform to the requirements of the current issue
of BS5440 Part 1 and BS5871.

The flue should, preferably, end above ridge height but at least
above the eaves of a pitched roof. Use a certificated terminal.

RIGID
FLUE

1593

LINER

FLEXIBLE
LINER

APPROVED
SEAL

BACK BOILER

Diagram 3.1

SEALING AND
CLAMPING
PLATE

6197

3.2 Existing Chimney

An existing brick chimney must be thoroughly swept and all
debris cleared away before lining.

Remove any damper or register plate. Alternatively it may be
locked in the open position,

A flexible flue liner is preferred but a rigid liner may be used, with
connection to the back boiler flue socket made with a short
vertical piece of flexible liner, see diagram 3.1.

Any air supply that enters the builder’s opening other than by the
front opening, that is underdraught openings and the like must
be completely sealed off.

The sealing plate also prevents debris falling and gives the flue
better insulation, reducing the possibility of condensation, see
diagram 3.2.

Check the flue system efficiency before installing the back
boiler.

3.3 New Chimney

A newly built chimney can be lined with a moisture resistant
lining, such as salt glazed pipe, of an appropriate diameter as
specified in the Building Regulations

In the case of a salt glazed lined flue, it is recommended that a
short vertical length of flue pipe, preferably flexible metallic be
used. Fix and seal it to the back boiler flue socket, make good
with approved packing and parge with fire cement, see diagram

3.1.
If a flue and false chimney breast are to be constructed all

openings for pipework to upper floors etc., must be sealed. The
only opening for the back boiler must be at the front, being of the
dimensions as shown in diagram 1.2.

AIR
SPACE

150mm (6in) plug of Mineral Wool or similar

SEALING
PLATE

600mm

BACK

BOILER

UNIT

Diagram 3.2

7 221723B

3 Flue and Ventilation

3.4 Precast Flue

The appliance is suitable for fitting to a properly constructed
non-impeded precast flue.

Note: It is not recommended that this boiler is fitted to a pre-cast
flue where plaster/rendering has been applied directly on to the
face of the flue block as this could lead to high surface temperature
and cracking of the plaster.

There must be a minimum vertical effective height of 3metres.
The flue cross sectional area must not be less than

198mmx97mm.
It is essential that the correct recess blocks, cover block and

offset blocks suitable for back boiler units have been used.
A sealed connection must always be made between the boiler

socket and the precast flue.
Note: It is possible, if this is a replacement, that the previous

appliance may have been more tolerant in respect of flue
requirements.

It is essential, therefore, as for ALL installations to make sure
that there is no spillage of the products of combustion from this
new appliance.

3.5 Ventilation - Back Boiler and Fire

The room in which the back boiler unit is installed must have
adequate air inlets to ensure correct operation as specified in
the current issue of BS5440 Part 2.

2

Ventilation requirement for the BBU 50 is 84cm
This ventilation area takes into account the total requirement of

the back boiler unit and fire.

(13in2).

The ventilation openings may be direct to the outside air or with
an internal room or space (such as a hall) which itself has a
permanent air vent of the same effective area. The permanent
air vent should be in a position which will cause the least
nuisance to occupants, due to draughts.

This vent MUST NOT be placed in the builder’s opening.
If the appliance is to be installed in a room already containing

another fuel burning unit, the air supply required for this other
unit MUST be added to the figure above.

Any air vent taken through a cavity wall must be ducted.

3.6 Extract Fans

If an extract fan is fitted in the premises, there is a possibility that
if adequate air inlet openings are not provided spillage of the
products of combustion could occur.

When openings are fitted in accordance with the
recommendations of the current issue of BS5440 Part 2, extract
fans should not cause spillage.

Where such a fan installation is found, a clearance of products
test must be conducted as described in the fire front Installation
Instructions, Section 4.5.

This test must be carried out with the back boiler fitted with its
fire front.

See also Section 6.3 of these instructions.
Note: Refer again to Section 1.7 and diagram 1.2 and make

sure that there is sufficient depth for the back boiler unit.

4 Installation

4.1 Preparation

Remove draught diverter, flueway baffles and fittings pack from
carton.

Check contents of fittings pack against packed list.
Remove back boiler body assembly from carton.

4.2 Water Connections

IT IS EXTREMELY IMPORTANT THAT NO SERVICE PIPES
ARE ROUTED IN FRONT OF THE BOILER. If the builder’s
opening was previously used for solid fuel all pipework within
should be protected with PVC tape or equal. Pipework passing
through walls of the opening should be sleeved and made good.

The two heat exchanger connections are supplied in the fittings
pack and MUST be used, see diagram 4.1.

IMPORTANT: Make sure that the return pipe assembly is
fitted the correct way, that is, the brazed joint must be
positioned downward into the heat exchanger - remove
label before fitting - see diagrams 4.1 and 4.4.

NOTE: Take care when soldering the copper connections not to
damage the fibre washers.

4.3 Pumped Heating with Gravity Domestic
Hot Water

NOTE: The draught diverter and capillaries are shown to aid
plumbing, but would not be fitted at this stage.

All pipework must comply with the current issue of BS5546.
The domestic hot water flow and return pipes must be 28mm.
Refer to diagram 1.4 for a diagrammatic layout.

If it is necessary to route pipework from both sides of the
builder’s opening, it is recommended that the heat exchanger is
positioned on the combustion chamber so that the gravity
circuits exit on the same side as the boiler connections.

If the heat exchanger connections are opposite hand to that
required, the heat exchanger can be turned, as follows, remove
the four screws securing the heat exchanger to combustion
chamber, see diagram 4.2. Turn heat exchanger, refit the four
screws.

It is recommended that pumped heating connections are pre­piped as in diagram 4.4.

IMPORTANT: Make sure that the return pipe assembly is
fitted the correct way, that is, the brazed joint must be
positioned downward into the heat exchanger - remove
label before fitting - see diagrams 4.1 and 4.4.

Note: The diagram 4.4 shows two methods “A” and “B” of
plumbing the flow pipe.

The central heating return must have the injector fitted on both
methods “A” and “B”, see diagram 4.4 for fitting the injector.

4.4 Pumped Heating and Hot Water

NOTE: The draught diverter and capillaries are shown to aid
plumbing, but would not be fitted at this stage.

Refer to diagram 1.5 for a diagrammatic layout.
If it is necessary to route pipework from both sides of the

builder’s opening it is recommended that the heat exchanger is
positioned on the combustion chamber such that the flow pipe
exits on the same side as the boiler connections.

It is recommended that the pumped return is pre-piped as in
diagram 4.3.

221723B

8

4 Installation

If the heat exchanger connections are opposite hand to that
required, turn in the same manner as described in Section 4.3
paragraph 5.

4.5 Heat Shield Assembly

If the boiler electrical supply cable has to be routed down the left
hand side of the combustion chamber you must fit the heat
shield assembly supplied in the fittings pack. Refer to Section

5.1 and diagrams 5.2 and 5.3.

4.6 Circulating Pump

Isolating valves, integral if possible, must be fitted each side of
the circulating pump.

4.7 Gas Supply

The gas installation must be fitted in accordance with the
recommendations of the current issue of BS6891.

1

Do not use pipe of a smaller diameter than Rc
or 15mm, see diagram 1.1 for position of gas connection.

The gas meter must be capable of passing natural gas at the
following rates: 49.5ft

This rate is in addition to all other natural gas appliances
supplied from the same meter.

It is recommended that the gas supply enters the builder’s
opening on the right hand side.

If the gas supply enters from the left hand side it will be
necessary to route the pipe behind the combustion chamber
before final fixing.

3

/h to 82.1ft3/h (1.40m3/h to 2.32m3/h).

/2 (1/2BSP) inlet

22mm COPPER PIPE
SUPPLIED WITH APPLIANCE

(Do not cut)

INJECTOR

22mm RETURN
PIPE ASSEMBLY
SUPPLIED WITH
APPLIANCE

(Do not cut)

BRAZED JOINT

LABEL

SEALING WASHERS

HEAT EXCHANGER

6254

UNEQUAL
TEE PIECE

Diagram 4.1

6175

4.8 Positioning the Back Boiler

To position the back boiler lift by the heat exchanger casting and
place centrally in the builder’s opening. The installation centre
line is indicated on the base by a notch on the front of the plate
and the fire fixing wall face positioning line by the front corner
edges of the base, see diagram 4.5.

The back boiler must be positioned so that a line across the
opening of the fire fixing wall face coincides with the fire fixing
wall face positioning line, see diagram 4.5. Use a straight edge
across the fire fixing wall face to make sure that the back boiler
is square to it.

Check that the back boiler is level. If packing is required to
adjust the level of the back boiler, use metal shims and pack
under the full width of the base.

Mark through the three fixing holes on the floor protection plate,
see diagram 4.6. Remove the back boiler unit. Drill three holes
using a 5mm masonry drill bit to accept the plugs and fixings
provided.

4.9 Positioning the Back Boiler - continued

Fit the flueway baffles, ensuring that they are positioned centrally
in the flueways, see diagram 4.7.

NOTE: The front flueway does not have a baffle.
NOTE: If the heat exchanger has been turned the baffles must

still be fitted into the back and middle flue ways only.
Fit the draught diverter onto the heat exchanger with the two

securing screws supplied in the fittings pack, see diagram 4.8.
Push fit the sensing tube onto the flue blockage safety device

and draught diverter. Secure the sensing tube assembly with
the securing screw, see diagram 4.9.

3

Where a flexible flue liner is being used, fully fit the No8x
tapping screw provided into the rear of the flue socket as in
diagram 4.10.

/8in self

SECURING
SCREWS
(4)

COMBUSTION
CHAMBER

22mm COPPER PIPE SUPPLIED
WITH APPLIANCE (Do not cut)

22mm COPPER
PIPE SUPPLIED
WITH APPLIANCE

(Do not cut)

Pumped Heating and Hot Water

Diagram 4.2

8024

22mm
RETURN

22mm
FLOW

Diagram 4.3

9 221723B