Chaffoteaux & Maury Sterling FF Installation And Servicing Instructions

STERLING

Room Sealed Fanned Balanced Flue

Combination Boiler

GAS SAFETY ~INSTALLATION AND USE) REGULATIONS.

It is the law that all gas appliances are installed by a competant person

in accordance with the above regulations

(For use on natural gas only. G20)

G.C. No 47 980 04

from serial number . . . . . . . . . . . .

FF

Installation and

Senrkhg Instructions

(leave these instructions with the user)

Looking Good.Heatfng Better

Page No.

Health and Safety Information

1. INTRODUCTION

1.

1.1.

1.2.

1.3.

1.4.

1.4.1.

1.4.2.

1.4.3.

1.4.4.

1.5.

1.6.

1.6.1.

1.6.2.

1.6.3.

1.6.4.

1.6.5.

1.6.6.

1.6.7.

General Description, Special Features, Guarantee
Dimensions Fig. 1
Technical Data
Ckarances
Wall Thickness
Rear Flue Outlet Fig. 2
Side Flue Outlet Fig. 3, Fig. 3a, Fig. 3b
Other Flue Arrangements, Horizontal Fig. 3c
Vertical Flue Arrangements, Fig. 3d, Fig. 3e, Fig. 3f Fig. 3g
Description of Components and Location Fig. 4
Description of Operation
Central Heating Fig. 5

Hot Water Fig. 6
Gas (also see 2.7)
Functional Flow Diagram Fig. 7

Safety Controls
Functional Flow Wiring Diagram Fig. 8

Illustrated Wiring Diagram Fig. 9

1

2
2
3
3
3
4
4
4
5
6
7
7
7
8
8
8
9

10

2. INSTALLATION REQUIREMENTS

2. 1. General

2.2. Location

2.3.

2.4. Siting the Flue Terminal Fig.

2.5. Air Supply

2.6. Electrical Supply

2.7. Gas Supply

3. SYSTEM

3.1.

3.2

3.3.

3.4.

3.5.

3.6.

3.7.

3.8.

3.9.

3.9.1.

3.9.2.

3.10

3.11

3.12

3.13

3.14

Water Circulation System

GUIDANCE

General

System Controls
Pump Fig. 11
Expansion Vessel

Mains Water Connection
Filling and Recharging

Make up System
Pipework

Domestic Expansion Vessel

Boiler Replacement

Existing Systems

Cylinder

Inhibitors and Water Conditioners

Add on Devices

Heating and Hot Water Systems Fig. 14, Fig. 15,

Shower Application Fig. 17a

Fig. 12, Fig. 13 (page

10

12)

Fig. 16,

Fig. 17

11
11
11
11
12
12
12

12
13
13
13
13
13
13
13
13
14
14

14
14

14

15
16

(4

4. INSTALLING THE BOILER

CONTENTS (cant)

No. Page

General Information

4.1.

4.2.

4.3.

4.4

4.5.

4.6.
47

4.8.

4.9.

4.10.

4.11.

4.12

4.13.

4.14.

Positioning the Boiler Fig. 18
Rear Outlet Flue Fig. 19
Side Outlet Flue Fig. 20
Jig Plate Fig. 21
Gas and Water Connections Fig. 22
Water Connections
Gas Connection
Fitting the Boiler Fig. 23
Fitting the Safety Valve Fig. 24
Fitting the Flue (up to 700 mm long) Fig. 25
Fitting the Flue (over 700 mm long)
Connection the Pressure Switch Fig. 26
Electrical Connections Fig. 27
Vertical Flue Figs. 28.28a, & Fig. 29

5. EXTERNAL CONTROLS

5.1. Programming and Zone Valves

5.2. Honeywell & Satchwell Controlled Zones Fig. 31

5.3. Frost thermostat Fig. 32

5.4. Room Thermostat Fig. 32a

17
17
17
18
18
18
18
18
19
19

19
20
20
20
21

Fig. 30 22

22
22
22

6. COMMISSIONING

6.1.

6.2.

6.3.

6.4.

6.5.

6.6.

6.7.

6.8.

6.9.

6.10.

6.11.

Hot Water Circuits. Filling Fig. 33
Central Heating Circuits, Filling, Fig. 34 G
Lighting the Boiler Fig. 35
Gas Rate Adjustment Fig. 36,37 & Fig. 38
Domestic Hot Water, Flow Rate Adjustment (see also 6.7, Fig. 393)
Adjusting the Heating System By-Pass Fig. 39
Domestic Hot Water. flow Rate Adjustment Fig. 39a
Pump Switching Adjustment Fig. 39b
Central Heating Temperature Differential Setting Adjustment Fig. 39c
Fitting the Casing Fig. 40
Time Clock Operating Instructions

7. ROUTINE SERVICING
General Requirements

7.1.

7.2

7.3

7.4.

7.5.

7.6.

7.7.

To Remove Front Casing Fig.41
To Remove Combustion Chamber Fig.42

To Remove Burner Assembly Fig.43
To Remove Pilot Fig.44
To Clean Heating Return Filter Fig.45
Cleaning and Replacement of Parts
To Check Operation of Safety Valve Fig.46

23
23
23
24
25
25
25
25
26
26

27 & 28

29
29
30

30
30
30
30
30

(ii)

8. REPLACEMENT OF PARTS

iZQNWXG (con0

Page No,

8.1. To Replace Electrodes Fig. 46

8.2.

8.3. To Replace Safety Overheat Thermostat 105°C Fig. 47

8.4.

8.5.

8.6.

8.7.

8.8.

8.9.

8.10. To Replace Pump Head Fig. 55

8.11.

8.12.

8.13. To Replace Air Separator Fig. 59

8.14.

8.15. To Replace Boiler Limit Thermostat Fig. 61

8.16.

8.17. To Replace High Tension Transformer Fig.63

8.18.

8.19. To Replace Solenoids Valves Fig. 66

8.20.

8.21. To Replace Fan Assembly Fig. 68

8.22. To Replace Pressure Switch (Horizontal Flue) Fig. 69

8.23.

8.24. To Re-pressurise Expansion Vessel Fig. 70 .

8.25. To Replace Pressure Gauge Fig. 7 1

8.26.

8.27.

8.28.

8.29.

8.30.

8.31.

8.32. To Replace the Thermometer Fig. 78

8.33.

8.34. To Replace Safety Valve Fig. 80

To Replace Probe Fig. 46a

To Replace Overheat Thermostat 110°C Fig. 48
To Replace Change Over Valve Microswitch Fig. 49
To Replace the Flow Switch Assembly Fig. 50
To Replace Venturi Fig. 5 1
To Replace Primary Heat Exchanger Fig. 52
To Remove Electrical Control Box Fig. 53, Fig. 54

To Replace Change Over Valve Fig. 56 & Fig. 57
To Replace Secondary Heat Exchanger Fig. 58

To Replace Thermistor Fig. 60

To Replace D.H.W. Thermostat Fig. 62
To replace Printed Circuit Board Fig. 64, Electrical box layout Fig. 65

To Replace Heating Body Linings Fig. 67

To Replace Pressure Switch (Vertical Flue) Fig. 69a

To Replace the Domestic Expansion Vessel Fig. 72
To Replace Main Burner Fig. 73
To Replace Burner Manifold Assembly Fig. 74
To Replace Expansion Vessel Fig. 75
To Replace Viewing Window Fig. 76

To Replace Main Gas Valve Body Fig. 77

To Replace the Time Clock Fig. 79

31
31
31
31
32
32
32
33

33
34
34
34
35
35
36
36
38
37
38
38
38

39
39
39

39
40
40
40
41
41
42
42
42
43

9. FAULT FINDING

9.1.

9.2.

9.3. Domestic Hot Water Operation

9.4. Fault Finding Tabular Chart
SHORT SPARE PARTS LIST

Logic Sequence
Central Heating Operation

44
45
46
47

Rear cover

(iii)

CONTROL OF SUBSTANC-RMFUJ, TO w

To comply with the Control of Substances Harmful to Health Regulation 1988 we are required to
provide information on the following substance that is contained in this appliance.

Descriution
platerial
Precautionq

Combustion Chamber Lining
Alumino Silicone Fibre
During servicing, keep the dust generation to a minimum and avoid

inhaling any dust and contact with the skin and eyes. Normal handling
and use will not present any discomfort, although some people with a
history of skin complaints may be susceptible to irritation.

When disposing of the lining ensure that it is securely wrapped and
wash hands after contact.

The STERLING FF is a wall mounted, low water content

fanned balanced flue appliance suitable for central heating
and hot water via a non storage water to water heat
exchanger. The maximum output is 23 kW (78480 Btuih).
The boiler is designed for sealed systems only and included
in the appliance are the expansion vessel, circulating pump,
temperature and pressure gauges, safety valve, electric
connection box, domestic expansion vessel and time clock.

1) The standard flue assembly supplied with the boiler is

100 mm (4 in) dia pipe, can be directed to the rear or to
the lef or right and can be extented to a maximum length
of 3 m, or 1.6 metres horizontally using the available 90”
bend (see sections 1.4.1, 1.4.2 and 1.4.3 figures 2. 3, 3a,
3b, 3~).

2) Vertical flue option (see section 1.4.4.).

Guarantee

The manufacturer’s guarantee on this appliance is for 12 months from the date of purchase. The guarantee is void, if the.
appliance is not installed in accordance with the recommendations made herein.

1.1 DIMENSIONS

Special features include :

-Output to central heating fully range rated between
l/3 and full output.

-High efficiency.

-Special jig plate enabling all pipework to be

installed before installiig appliance.

-Independent control over central heating flow

temperature and hot water.

-Fully adjustable central heating flow temperature.

-regulation between 40” C and 82” C.

-High limit thermostat for both boiler and hot water.

-Water flow switch to protect appliance.

-Suitable for showers with compatible mixer valves.

- 7 day programme time clock.

~\_

B

c ’ --

I\

t-1

---

---- -

2%

_--

-1 -2

r-

‘KI

w

I ;
I ’

1 I

+

LI

1 L

.,- -. ,

X-3

-I

--+

I

REAR OUTLEl

/ -f

~

_-

SIDE OUTLET

1

mm

A

B
C
D
E
F

G

H

J

K
L
M
N
P

R

S
T

820.5

391.0

365.0

100.0

169.5

654.5

43.0

50.0

75.0

260.0

150.0

972.5

13.0

61.0

30.0

152.0

112.0

-7

in

32.3

15.4

14.4
4
61‘1

25.7

1.7

2.0

3.0

10.2

6.0

38.3

0.5

2.4

1.2

6.0

4.4

Fig.1

2

1.2 Technical Data

1.2

1.3

Hot water

Input . .._....................................... 28.90 kW 98612 Btulh

Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.00 kW 78480 Btulh

Water flow raised
45 “C (81
Water iIow raised

35 ‘C (63 “F) .............................. 9.5 Vmin

Water flow raised

30 “C (54 “F). ............................. 11.1 Ymin

Maximum temperature.. ............. 60 T

Maximum pressure.. ................... 10 bar

Minimum working pressure.. ...... .6 bar

Gas rate ...................................... 2.743 m3/h

Burner pressure .......................... 11.8 mbar

Central heating

Maximum input.. ........................ 27.64kW 94313 Btti

Maximum output.. ...................... 22.00 kW 75068 Btti

Gas rate (maximum) ................... 2.63 m3/h 92.98 @lh

.lrner pressure.. ........................ 11.2 mbar 4.5 in wg

.,rinimum input

Minimum output.. ....................... 7.64 kW 26062 Btu/h

Gas rate (minimum)

Burner pressure.. ........................ 1.5 mbar 0.6 in wg

Minimum flow rate

Maximum pressure.. ...................

At the maximum pressrrre loss of the fiue
Temperature of the products of

combustion : . . . . . . . . . . . . . . . . . . . . . . . . . 98 T 208 OF

The CO content of the dry free air

products of combustion : . . . . . . . .

Manifold injectors 14 of . . . . . . . . . 1.28 mm 0.05 in

Gas section restrictors 213 valves

"F)

.............................. 7.4 I/min

...........................

................... 1.0 m3/h

..................... 300 lib 1.1 gal/min

l/3 valve.. .... 2.3 mm 0.09 in

security valve ...... no restricior fitted

10.85 kW 37020 Btuih

2.5 bar 36.5 psi

0.0136%

Natural gas

4.4 mm 0.17 in

1.7 ga.I/min

2.1 gaI/min

2.5 gaI/min
140 OF

150 psi

9 psi

96.87 fi3h

4.7 in wg

35.31 ft3/h

Connections
Gas

..............................................................

Heating flow
Heating return..
Mains cold water inlet..
Hot water outlet..

Electrical supply 240 V - 50 Hz, fused at 3A.

Electrical consumption . . . . . . . . . . . . . . . . . .._.............

Internally fused, two at 2A (BS 4265)

Weight . . . . . . . . . . ._.._.._........_....... . . . . . . . . . . . . . . . . . . . 42 kg

Water capacity . . . . . . . . . . . . ._.,. . . . . . . . . . . . . . . . . . . . . . . . . 4 Iitres

Ignition - ANSTOSS continuous spark generator
Ignition electrode - SAPCO
Ignition probe - SAPCO

Thermistor - SIEMENS
Boiler fiiit thermostat - SOPAC /JAEGER (85X)
Hot water limit thermostat - SOPAC /JAEGER (57°C + 3°C)

Safety overheat thermostat (TOKOSWHCH - (105°C)

Overheat high- Iiit thermostat (TOKOSWITCH - (1lO’C)

Gas valve - AEMF
Fan motor - SEL
Pressure switch - DUNGS 88 Pa I 49 Pa
Pump head - GRUNDFOS UP 15/60

I

C.H. expansion vessel initial charge pressure - 0.65 bar (9.6 psi)
Domestic expansion vesseI initii charge pressure .

................................................

............................................

................................

.........................................

(manual reset)

(automatic reset) (ELMWOOD - (105’C)

(ELMWOOD

22 mm copper
22 mm copper
22 mm copper

15 mm copper
15 mm copper

195 watts

92.4 lb
7 pints

2 bar (30 psi)

3

1.4

Minimum clearances around Boiler

Top above air duct . . . . . . . . . 50 mm (2 in)

Bottom below case. . . . . . . . . . 150mm (6in)

. . . . . . . . . . . . . . . . . . . . . . 100mm (4in)

Sides

Front. . . . . . . . . . . . . . . . . . . . . . . . . .

6OOmm(24in)

Wall Thicknesses

The standard fIue assembly can accomodate the folrowing thicknesses.

Rear : from 55 mm to 576 mm
Side : from 55 mm to 392 mm
(this allows for a minimum dearance of 100 mm between the appliance and the side wall. As this dimension
increases, so the maximum side waII thickness available decreases).
Extension flue assemblies are available to accomodate waII thicknesses of:

Rear : from 577 mm to 2876 mm
Side : from 393 mm to 2692 mm
See figs. 2 and 3 for details of number of extensions required.
IMPORTANT NOTE : The extension ducts supplied. up to a maximum of 3, wiII in fact permit a greater length than

indicated to be covered. The ducts MUST be cut so that the maximum length from the centre Iine of the flue turret to
the outermost point of the air duct DOES NOT EXCEED 3 metres horizontal. Greater length must not be used.

See sections 1.4.1. 1.4.2. 1.4.3.

3

Rear Flue Outlet Hobontal

should not exceed 1.6 metres

REAR OUTLET ASSEMBLY

To cut flue assembly to length

- Measure wall thickness (T).

- Add 74 mm, tthis will give required lentgh Q.

- Mark plastic air duct for length (L) and cut off
surplus (from plain end).

N.B. If extension sections are used ensure these are
fiily pushed together, see figs. 3b and 3c and a fall of 5
mm per metre length should be provided (see section

- Cut off same amount from aluminium flue duct

Flue extension accessory
Part No. 62823.00

(G.C. 264459)

(1 metre length)

1.4.2

‘ig. 2

Side Flue Outlet Horizontal

Fig. 3

Fig. 3a

SIDE OUTLET ASSEMBLY

PLASTIC AIR DUCT

internal

To cut ffue assembly to length

- Measure from external wall face to centre line of
STERLING FF and substract 37 mm (this will give
required length “L”).

- Cut

off

surplus i?om plastic air duct (plain end).

N.B. If extension sections are used ensure these are
filly pushed together, see figs. 3b and 3c and a fall of 5

- Cut off same amount from

I

Other Flue Arrangements Hotizontal

Fig. 3c

1. Distance from internal comer 300 mm without
kit,107 mm with kit No 76216 (GC No 264 833).

2. Distance below balconies or eaves 200 mm
without kit, 107 mm with kit No 76216 (GC No

264833).

3. Appliance is normally supplied packed with
standard 650 mm staight flue section. Additional
straight extension lengths of 1 metre, part No
62823 (GC No 264 459), can be use up to a total
straight length of 3 metres. It is also possible to
incorporate one bend in the flue using part No
65572 (GC No 264 835). In this case the length
Ll + 12 should not exceed 1.6 metres
horizontally.

4

1.4.4
Vertical Flue Arrangements

a) Straight ffue (fig. 3 d)

1) Adaptor.

2) Extensions (9.5 m maximum).

3) Roof flashing.

4) Terminal.

6) Reducer.

Fig. 3 d

b) Flue with two 45O bends (fig. 3 e)

1) Boiler adaptor.

2) Extensions (8 m maximum).

3) Roof flashing.

4) Terminal.

5) 45’ bend.

6) Reducer.

Fig. 3 e

--I

Fig. 3 g

5

c) Flue with four 45’ bends (fig. 3 f and 3 g)

1) Adaptor.

2) Extensions (6 m maximum) tig. 3 f and 3 g
including horizontal (2 m maximum) fig. 3 f.

3) Roof tlashiig.

4) Terminal.

5) 45’ bends (x 4 maximum) fig. 3 f and 3 g.

6) Reducer.

With the exception of (3) roof fIashing and (4)

terminal, all other fittings are designed for interd
installation only.

N.B. In these two arrangements tigs. 3 f and 3 g, the
total length of straight extensions m not exceed 6
meters with a maximum of 4 x 45” bends.

Horizontal run & not exceed 2 meters.

1.5 Description of Components and Location

1

2

6

3

35

27

-

10

-

2i 22 20 31 19 23 17 18’25

Fig. 4

The appliance is mounted in a steel case which has a
white epoxy resin paint finish.

1. Chassis:
The chassis is a rigid plated mild steel pressing on which
all components are mounted.

2. Flue hood:
Is an aluminium alloy casting onto which the fan is

mounted.

3. Combustion chamber:
This is assembled from a number of components

mounted onto the chassis. The front panel is simply
removed for servicing complete with the expansion vessel,
a hook is fitted below the appliance to accept and retain
the panel during servicing.

4. Expansion vessel:
The expansion vessel has a capacity of 5.4 litres (1.19 gal)

and is sized for a normal system water content where the
load is equivalent to the maximum output of the boiler.

The charge pressure is 0.65 bar.

5. Flame supenrision device (not illustrated).

6. Multigas burner comprising: stainless steel blades (14)
and a manifold with injectors (14).

7. Gas section including two stage solendid valves and
security solendid valve.

6. Secondary heat exchanger :
The secondary heat exchanger is a plate type heat

exchanger. A thermostat is fitted on the pipework limiting
the domestic hot water temperature to a maximum of 57
f3” c.

9. Change over vaIve :
The valve is activated by a demand for domestic hot

water, closes the heating circuits, and directs water to the
secondary heat exchanger.

fO.EIectriciaI box containing :
Mains connection
Fuses
Printed circuit boards
Connections for external controls
Connections for fan, pressure switch and flow switch

Connections for pump
Connections for change over valve and for gas solenoid

valve

Indicator LEES.

.ll. Solenoid valve :

Block on which 4 valves are mounted :

l/3 valve - 1 st stage valve-heating and hot water (blue)
2/3 valve - full output to hot water (black)
2/3 valve - (variable valve) central heating (orange)
Security valve (grey).

12. Grundfos pump motor

13. Air separator and vent directly connected to the pump

inlet (not illustrated).

14. Regtdation screw to adjust output to heating (2/3

valve).

15. Heating body compristig :

Copper finned tube heat exchanger protected with silicone
resin paint. Combustion chamber in aluminium coated
steel. Combustion chamber lining - ceramic fibre panels.

16. High limit thermostat (manual reset).

17. Water service tap (not illustrated).

18. Flow isolating valve - heating (not illustrated).

19. Gas service tap (not illustrated).

20. Domestic hot water outlet with regulator (not
illustrated).

21. Safety valve with drain tap (not illustrated).

22. Heating return isoIating vaIve with filter (not
illustrated).

23. Indicator LEDS.

24. Thermometer indicating boiler flow temperature.

25. Manual lock out reset.

26. Selector switch - hot water or&/OFF/heating and hot
water.

27. Adjustment to regulate heating tlow temperature.

26. Pressure gauge.

29. Pressure switch (not illustrated).

30. Domestic expansion vessel (not illustrated).

31. Water flow switch (not illustrated).

32. Tiie clock.

33. Fuses.

34. Data badge position.

35. Control thermistor.

6

~6 Descdption of Operation

1.6

The STERLING FF a is combination boiler providing
central heating and hot water. Hot water is provided on
a demand basis. For the duration of the demand for
hot water the central heating is interrupted.
The appliance operates in two modes. A hot water only

setting where it operates only on hot water demand
and a hot water + central heating setting providing
central heating and switching to hot water on demand.

1.6.1 Central Heating

The pump (21) circulates water which returns to the

boiler via the return valve (31) which incorporates a

filter (30) Before reaching the pump it passes through

an air separator and air purger (17). The return water

passes through the heat exchanger (2) where it is

heated. It then passes through the change over valve

(19) which in heating mode is in its rest position and

out via the flow valve (27) to the radiator circuits (34).

An expansion vessel (13) is fitted in the primary circuit.

Temperature control is by means of a temperature

sensing thermistor and potentiometer. These signals
are fed to a comparitor.
When the flow approaches the set temperature, the
variable gas valve is closed and the boiler continues to

fire on l/3 soleno?d valve (11). When the set

temperature is reached, the boiler switches off. If

flow temperature reduces, the l/3 solenoid valve

opens followed by the variable solenoid valve (10).

Temperature adjustment is between a minimum of

40°C approx. and a nominal maximum of 82°C.

The boiler is protected by high limit thermostats (4) and

(see fig.

5)

(38) the operation of which interrupts the electrical supply
to the security solendid valve and extinguishes the burner.

1.6.2 Hot Water

When there is a demand water flows in from the cold
mains supply (26) through the water section part (35) of
the change over valve (19). The inclusion of a venturi (24)
produces high pressure under the diaphragm (23) causing
it to rise. This movement is transmitted to the change over
valve closing the heating port and opening the hot water
port, as shown (20). The primary water heated by the
boiler now passes through the water to water heat
exchanger (18) where it flows through alternate plates
indirectly heating the DHW.

The rising of the change over valve spindle causes :

1. The opening of a microswitch stopping the pump.
This circuit is remade by a second microswitch making
when the hot water port is fully open.

2. The by-passing of the boiler thermistor brings the
boiler under control of a fixed temperature thermostat

(32) which operates on the 23 fmed solenoid (12).

The D.H.W. flow rate is adjustable by a restrictor (25) and

a liiiting thermostat (32) reduces the gas rate when the
domestic hot water reaches 57’C by interrupting the
electrical supply to the hot water solenoid (12).

If the primary circuit reaches 85°C the limit thermostat (16)
closes both solendids valves.

A domestic expansion vessel is fitted in the D.H.W. circuit

(see fig. 6)

(36).

Central Heating

17

I ILL

/I----.-.

3, ----lO.ll-

T

16

11 -111

IL 'I IL- I"

L*-l

‘---q ,*

16

Hot water

1

16

30

31

Fig. 5

27

27

Fig. 6

7

1.6.4

1.6.5

Gas

(see figs. 5 and 6)

When the main gas tap (33) is turned to the on position
gas is admitted to the gas section (7).

When there is a demand for heating or hot water, the

security solenoid valve (9) and the l/3 soleno’id valve

open together, which allows gas to pass to the burner.

Srrnultaneously the hight tension transformer is energised
and produces a stream of sparks from the ignition
electrodes (3) whitch light the main burner.

The flame supervision (5) is controled by ionisation

circuit.

r:

FUNCTIONAL FLOW DIAGRAM

Summer

If the main burner is not established after 5 seconds, the
boiler falls safe to lock out and has to be reset manualy.

There are 4 solenoid valves : the right hand (grey) valve
(9) is the security valve, the blue valve (11) fixed at l/3 of
max rated output, the hot water (black) valve (12) fixed at
2/3 of maximum rated output, the left hand central
heating (orange) valve (10) which is variable up top 2/3
maximum rated output.

The gas admitted by the orange valve is varied by adjuster

(6)

(see section 6.4).

D.H.W.

OFF

High
Limit

-+ Stat + Pump --+ Flow

Water

Switch 2

I i-l

(manual reset)

I

Fan ON

113 gas

Security -

5” lockout time

no

I

85°C Limit

Thermostat

105 / 110°C High Limit

Thermostats

2l3 Orange

Solenoid

Thermistor

I+

F

-ig. 7

L

1.6.6 Safety Controls

In addition to the normal safety controls the STERLING FF
incorporates the following feature.

Should the central heating water flow reduce to below 3OC’
Uh (1,l gal/min) the gas supply to the burner is turned 01
via the flow switch (No.31 - page 6). see figs 5 & 6 (37).

8

1.6.7 FUNCTIONAL FLOW WIRING DIAGRAM

1.6.7

PRESSURE

WATER FLOW

BOILER

POTENTIOMETER

HEATING

bk

9e Y

L 3A L

­L-l

LINK or EXTERNAL

-......-,. _I.”

INTER SWITCH bk

2A 2A
h­Y-

PRINTED CIRCUIT BOARD

,-CHANGE OVER VALVE,. .

MICROSWITCHES :

STAT -

HIGH LIMIT

SECURITY (2)

RESET

SWITCH

N N

k

P

BOILER

THERMISTOR

HEATING

-w w ^C^. .-.-I

rzl

w

r

SkG”Hl I I

SOLENOID

VALVE

IGH RATE

IGNITION ELECTRODES

FLAME
SUPERVISION

1

I

Fig. 8

b = blue
bk = black
br = brown
ge = green
gr = grey
or = orange
r = red
v = violet
w = white
y = yellow

9

1.6.8 ILLUSTRATED WIRING DIAGRAM

FAN

\MESUPERVlSlON 11 , 1

HIGH LIMIT

THERMOSTAT 110”

BOILER THERMISTOR HEATING

240V

50Hz

I

I

L

N

I

Ph

1

EXTERNAL CONTRO

II

ROOM TH

- -

III II II

I

r

UJ

s

II

WATER FLOW SWITCH

I

BOILER POTENTIOMETER

HEATING

---

SELENOID VALVE

-ig. 9

.

HIGH TENSION

II

.,” TRANSFORMER -

ALL CABLES ARE 240V EXEPT WHERE THEY ARE INDICATED 24V

SELECTOR SWITCH t+#-.~ 11

1

tn “AL”q./- ORI!

I-

1111

10

Hki LlMlT
(MANUAL RESET) 105”

SECURll-Y

2

2.1

2.2

INSTALLATION REQUIREMENTS
General

The installation of the boiler must be in accordance

with Gas Safety (Installation and Use) Regulations,

Building Regulations and current Byelaws of the Local
Water Undertaking. It should be in accordance also
with the current BS Codes of Practice and the British

Gas Specifications for Domestic Wet Central Heating

Systems and any relevant requirements of the local

Gas Region and Local Authority Building Standards

(Scotland) Regulations and the Safety document 635

the Electricity at Work Regulation.
Detailed recommendations are stated in the following

British Standard Codes of Practice:
B.S. 6891, B.S. 6798, B.S. 5440 : 1 and 2, B.S. 5449: I,

B.S. 7593, BS 5546B.G.DM2, B.S. 4814. B.S. 7074 1
e 2, B.S. 7671.

Note : Gas Safety Installation and Use Reg. It is the
law that all gas appliances are installed by competant
persons in accordance with the above regulations.
Failure to install appliances correctly could lead to
prosecution. It is in your own interest and that of
safety to ensure compliance wlth the law.

Location

The boiler is not suitable for external installation. The
position chosen for the boiler must permit the
provision of a satisfactory flue termination. The
location must also permit adequate space for servicing
and air circulation around the boiler. The surface on

which the boiler is mounted must be of non

combustible material.

The boiler may be installed in any room or internal

space although particular attention is drawn to the

requirements of the current B.S. 7671 and, in

Scotland, the electrical provisions of the Building

Regulations applicable to Scotland, with respect to the
installation of a heater utilising mains electricity in a
room or internal space containing a bath or shower.
Where the installation of the boiler will be in an
unusual location special procedures may be necessary
and BS 5546 gives detailed guidance on this aspect.
A compartment used to enclose the boiler must be
designed and constructed specifically for this purpose.

An existing cupboard or compartment may be used

provided that it is modified for the purpose.
Details of essential features of cupboard/compart­ment design are given in BS 6798.

2.3

2.4

Water Circulation System

The STERLING FF is suitable for SEALED SYSTEMS
ONLY and should be installed in accordance with the
relevant recommendations given in BS 6798, BS

5449:l (for the smallbore or/and microbore systems)
and the British Gas Specifications for Central Heating
Systems.

Sitfng the Hue Terminal

Refer to section 1.4 for details of wall thicknesses
which can be covered.

Detailed recommendations for flueing are given in BS
5440 Pt 1. The following notes are intended to give
general guidance.

The boiler must be installed so that the ffue terminal is

exposed to external air. The boiler must NOT be
installed so that the terminal discharges into another
room or space e.g. outhouse or closed in lean-to. It is
important that the position of the terminal allows a
free passage of air across at all times. The miniium

acceptable clearances from the terminal to
obstructions and ventilation openings are specified
below (fig. 10).

Horizontal Flue
Terminal positions
A - Directly below an opening, windowsetc

or adjacent to an opening . . . . . . . . . . . . . . . . . . . .

B - Below gutters soil pipes or drain pipes . . .

C - Below eaves . . . . . . . . . . . . . . . . . . . . . . . . ..200

D - Below balconies or car port roof . . . . . . . . . . . . 200 mm*

E - From a vertical drain pipe or soil pipe . . . .

F - From an internal or external corner _....... 300 mm*

G - Above ground roof or bs.lcony level . . . . . . . 300 mm

H - From a surface facing the terminal. . . . . . . . 600 mm

J - From an opening in the car port

(e.g. door or window) into dwelling . . . . . . . . 1200 mm

K - Vertically from a terminal on the same

wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1500

L - Horizontally from a terminal on the

same wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

* ( 107 mm) minimum clearance using
kit No. 76216.CK)(G.C.264833)(seesect.h 14.3,fig.3c)

Vertical Ffae
Terminal positions

M - Above intersection with Roof . . . . . . . . . . . . . . . .

Mii clearances

300 mm

75 mm

mm*

75 mm

mm

300 mm

Min clearances

150 mm

Fig. 10

L

11

BUILDING REGULATIONS excerpt.
Approved document J Part B 1.4 (C) (D).

C) Protect with a terminal guard fitted centralIy over
the terminal if it could come in contact with people
near the building or be subjected to damage.

D) Designed so as to prevent the entry of any matter
which might restrict the ffue.
(A terminal guard G.C. No 381 782 is available from).

Quinnel Barret & Quinnel Wiieworks
Old Kent Road
London SE15 INL Tel. [phone]

The air inlet/outlet duct and the terminal of the
appliance must not be closer than 25 mm (1 in) to
any combustible material . Detailed recommendations
on the protection of combustiable material are given
inBS5440Pt 1.

IMPORTANT NOTICE : TIMBER FRAMED HOUSES
IF THE APPLIANCE IS TO BE FITTED IN A TIMBER

FRAMED BUILDING IT SHOULD BE FITTED IN

ACCORDANCE WITH THE BRITISH GAS

PUBLICATION - “GUIDE FOR GAS INSTALIATIONS IN

TIMBER FRAMED HOUSING” reference DM2. IF IN

DOUBT, ADVICE MUST BE SOUGHT FROM THE
LOCAL REGION OF BRITISH GAS OR C.O.R.G.I.

2.5 Air Supply

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
and low level air vents must communicate with the
same space.

Position of vents Air fivm room Air direct fivm outside

High level
Low level

2.6

Elect&al Supply

- This appliance must be earthed.

- All wiring externaI to the appliance must conform to
the current B.S. 767 1.

- The STERLING FF requires a 240 V - 50 Hz supply.

- Connection of the appliance and any system controls
to the mains supply must be through a common
isolator and must be fused at 3A maximum.
This should preferably be an unswitched shuttered
socket outlet and 3 pin plug to BS 1363. AltemativeIy,
a double pole isolating switch may be used, provided
it has a minimum contact separation of 3 mm in both
poles. The isolator should be clearly marked showing
its purpose, preferably positioned close to the
appliance.

-Fuse the supply at 3A.

-The suppIy cord must be 0.75 mm2 (24 x 0.2 mm)
three core to BS 6500 Table 16.

261 cm2 (40 in2)

261 cm2 (40 in2) 130 cm2 (20 In2)

130 cm2 (20 in2)

2.7 Gas Supply

The STERLING FF requires:

2.743 m3fh (96.87 A3/h) gas Ilow.
The meter and supply pipes should be capable of

delivering this quantity of gas in addition to the
demand from any other appliances in the house.

The complete Installation must be tested for

soundness as described in BS 689 1.

3

SYSTEM GUIDANCE

3.1 General

The low water content STERLING FF boiler indudes

the expansion vessels. safety overheat thermostat,
temperature and pressure gauges, and safety valve.

The flow temperature is adjustable and gives a

nominal 82 ‘C (180’ F) on its maximum setting.

When the appliance is connected to a vertical flue. the

temperature adjustment must not be set below the
midway position.

Detailed recommendations for water circulation are
given In BS 5546. Whilst the boiler provides hot
water, there may be occasions when a cylinder wiU be
used, for instance, if the property has two bathrooms.
Detailed recommendations of this application are
given in sections 3.13. Thermostatic control should be
used in the heating circuits and the cylinder if one is
fitted.

It must be remembered that a combination appliance
has a limited volume of hot water that can be
supplied at any one time for a given temperature.
Indeed in most respects it is equivalent to a multipoint
water heater and many of the contraints associated
with multipoints apply equally to combination boilers.

The appliance has two separate functions, to provide
heating and hot water on demand. It can have a third
which is to supply hot water high demand through the
use of an Indirect cylinder, where there is more than
one bathroom or if the standard and appointments of
the property, such as basins in all bedrooms and a
large kitchen indicate a high usage of hot water.

Hot water produced IndiiectIy through a cylinder can
be used to satisfy high simultaneous demand outlets ­bathrooms etc, whilst the benefits of high effciency in
generally small quantities of hot water, can be fully
utilised in kitchens, cloakrooms and so on.

Separate time and temperature control over hot water
generated in this way can be achieved by the use

either of two port valves or three port valves of a flow
share or priority pattern.

It is also possible, where the occupation of the house
is variable, to provide either for a small or large load.

This is best achieved with a taII, small diameter cylinder.

See section 5 for possible wiring arrangements.

A domestic expansion vessel is fitted to the boiler with

a capacity of 0.16 litres. prior to the secondary heat
exchanger which enables the boiler to be connected
to a cold main water supply containing a non-return
valve or any device containing a non-return valve.

12

IF THE MAINS COLD WATER SUPPLY IS IN
EXCESS OF 10 BAR (150 PSI) A PRESSURE
LIMITER MUST BE FITTED TO AVOID EXCESSIVE
PRESSURE BEING APPLIED TO THE BOILER.

When replacing an existing cylinder storage system

with STERLING FF it is essential that all redundant
pipework is removed and dead legs eliminated,

In properties where there are multiple draw-off Points
on different levels consideration should be given to
the use of non-return valves in the secondary hot
water system to avoid “active dead legs”. No non­return valve should be less than 1 m (3 It) above the
top of the appliance and ideaIIy should be as close as
possible to the hot water outlet.

3.2 System controls

The boiler is electricaky controlled and is suitable for
most control schemes currently available including
thermostatic radiator valves and motorised valves.

When using motorised valves the controls should be
arranged to switch off the boiler when circuits are

satistield. The boiler requires a mink-num flow rate of
300 L/h (1.1 gaI/min) and consequently, if
thermostatic radiator valves are fitted to alI radiators, a
by pass will be necessary. This will ensure that the
boiler will operate correctly when all TRVs are closed.

(see fig. 17).

3.3 Pump

The boiler is fitted with a Grundfos UP.15160 pump

head. The graph (fig. 11) indicates the residual head

available for the system.

flow rate in g.p.m.

6

At the design flow temperature and the initial system
pressures quoted the maximum allowable system
volume is 75 Iitres.If the water volume is not known

and cannot be accurately assessed from

manufacturers data the following volumes may be

used to give a conservative estimate of the system

volume.

Boiler.. . . . . . . . . . . . . . . . . . . . . . . . . . . ..,.... . . . . . . . . . . 4 litres

Small bore pipework . . . . . . . . . . . .._.__... 0.3 litres (0.07 gals)

Microbore pipework. . . . . . . . . . . . . . . . . . . . . . . . . .7

Steel panel radiators

per 0.292 kW (1000 Btu/h) of system output

Hot water cylinder . . . . . . . . . . . . . . . _.. .2

If the volume exceeds 75 Iitres an additional vessel
wilI be required fitted In the flow from the appliances.
Refer to BS 7074 Pt. 1 or BS 5449 for details of sizing.

3.5

Mains water connection

There shall be no permanent connection to the
Heating System Pipework for filling or replenishing
without the approval of the Local Water Authority (see
Byelaw No.14 and figs. 12 and 13).

3.6

Fdlhg point

Filling and recharging can be done :

1) Through a temporary hose connection to mains

water.
A stop-valve should be fitted to the service main outlet

and a double check valve assembly and stop-valve

should be fitted to the system side of the temporary

hose (see fig. 12).

2) A cistern used for no other purpose connected to

the mains water. The static head provided by the

cistern m be sufticient to satisfy the designed Initial
system pressure. The supply pipe from the cistern
should include the double check valve assembIy and
stopcock (see tig. 13).

3.7

. . . . . . . . . . . . . . . . . . . . . . 2.3 litres

(see

Bs

5449)

litres (0.44 gals)

Make up system

(0,8 gals)

per 0.292 kW

(1.5 gals)

litres

(0.5 gals)

Fig. 11

flow rate in litres/hour

3.4 Expansion vessel

The expansion vessel which is fitted on the front of
the combustion chamber accomodates system water
expansion. The vessel has a capacity of 5.4 litres

(1.19 gals) and is charged to a pressure of 0.65 bar
(9.7 p.s.i.).

THE CONNECTION IN THE CENTRE OF THE
EXPANSION VESSEL IS A CHARGING AND NOT A
VENT POINT.

13

Provision must be made for replacing water lost from
the system indicated by a reduction in pressure
shown on the pressure gauge. Recharge through the
ftiing point (see section 3.6).

3.8
Pipework

Pipework can be of copper or suitable plastic, small
bore or microbore with capillary or compression

jointing to a high standard. Leak sealant must not be

used in the system.

3.9
Domestic expandon vessel

The expansion vessel which is fitted on the cold water

supply to the secondary heat exchanger accomodates
domestic hot water expansion. The vessel has a
capacity of 0.16 litres (0.035 gals) and is charged to a
pressure of 2 bars (30 p.s.i.) ; it has a maximum

working pressure of 10 bars with an allowable

pressure peak of 14 bars.

Air inlet

valve

Fig.

12

Double check
valve assembly

valve

Test cock

(a) Non-automatic filling and make-up. Temporary hose filling loop avaible, Pt.No.CHL.112

Hose

pion;y-++ zE

@+P

j j

jj

I’
\~-zd!

Te;irgw

Overflow

%o be located

above highest
point in the
system and
satisfy the
designed initial
system pressure

SUPPlY

Mains

(b) Automatic filling and make-up.

Fig. 13

3.9.1 Boiler replacement (retrofit)

In an old system where the boiler is being replaced,
we recommend the use of p strainer, fitted with a

drain tap on the heating return, designed to retain

scale particles and other solid debris It is good practice
to use a chemical cleaner with a floctuating agent,
used as recommended by the cleanser manufacturer,

to clean the system before the old boiler is removed.

(see BS 7593).

3.9.2 Extsting systems

Valves and joints should be carefulIy checked for leaks

and the appropriate action should be taken either as a

repair or replacement. The old open system has

probabfy only been subjected to a pressure of 0.4 bar

or less. When you change to a sealed system where

the charge pressure will be 1.0 bar and the running

pressure exceeding .1.5 bar, consideration should be

given to the replacement of radiator valves with a

pattern capable of sealing at the higher pressures.

3.10 Cylinder

Where a domestic hot water cylinder is used with the

STERLING FF it MUST be of the indirect and high

recovery type to BS 1566 Pt 1 Single feed cyIinders

are not suitable for use with this appliance. Flow and

return pipework to the cylinder should be in 22 mm

pipe.

3.11 Inhibitors and water conditioners

(see BS 7593)

Chaffoteaux et Maury generalIy recommend the use

3.12

of inhibitors in systems using the STERL-ING FF boiIer.
The following are the appliance manufacturer’s

recommendations :

1) Use or@ a British Gas or sImiIar approved inhibitor.
These manufacturers can assist with the selection.

Grace Dearbon Ltd - WIdnes - Cheshire WA8 8 UD

Telz 051424 5351.

Fernox Manufacturing Company Limited Britannica

Works, Clavering, Essex CBI1 4Qz

Tel: [phone].

2) Use only the quantities specified by the inhibitor
manufacturer.

3) Cleanse the system as required by the inhibitor
manufacturer.

4) Add inhibitor only after flushing when fmally re­filling the system.

5) In-line water conditioners both of chemical and
magnetic type are suitabIe for use with the S?TIRUNG FF.

Add-on devices

It is important that no external control devices e.g.
economisers be directIy fitted to this appliance unless
covered by these installation instructions or agreed
with the manufacturer in writing. Any direct
connection of a control device not approved by the
manufacturer could make the guarantee void and also
infringe the Gas Safety (InstaIlation & Use) Regulations.

14

STERLING FF

instant hot

water low

demand

outlets

Heating & stored hot
water - spring return

valves onlv

3.13 Heating and hot water systems

Figs. 14, 15. 16 and 17 indicate various layouts for
the production of hot water. It is recommended that
only a high recovery indirect cylinder is used and
circumstances may from time to time dictate that a
special saturated heat exchanger in an indirect
cylinder may be desirable.

stat.

When replacing an exisiting cylinder storage system
with an instantaneous type system it is essential that
all redundant pipework is removed and dead legs
elimiialed.

Fig. 14

ins&t hot

water low

demand

outlets

I

‘ig. 15

STERLING FF

STERLING FF

I I

Heating & stored hot

water using flow share

relay required

The consideration of heating systems using
thermostatic valves should ensure that the minimum

ffow rate through the appliance is maintained at all
times and in this conneclion the remote by-pass is
preferred (see fig. 17).

in

hot

Fig. 16

STERLING FF

n

fJ 77

instant AA

hot water

Remote by-pass

L 1r

remote by pass

with US valve

I

15

3.14

Shower Applfcatfon

The appliance can be used to supply hot water to separate shower draw-off. It & not be used to supply more than
one shower mixing valve.

The recommended pipework arrangement for a shower is shown below and the hot supply to the mixing valve should
be the first draw off.

STERLING FF ~

HOT WATER

HOT

COLD 4-1

Fig. 17a

It is important to select a compatible shower for the STERLING FF The following manufacturers can assist with the
selection

New Team Ltd

Brunell Road
Earlstree Industrial Estate
Corby
Northants NN17 2LF

Tel.No.0536-62822

Aqualisa Products Ltd

Hortons Way
London Road

Westerham

Kent TN1 6 1 BT

Tel.No.0959-63240

Meynell Valves Ltd

Shaw Road
Bushbury
Wolverhampton
West Midlands WV1 0 9LB

Tel.No.0902-28621

Barking Grohe

1 River Road
Barking
Essex IG11 OHD

Tel.No.081-594-8898

COLD WATER

Do not use the appliance with push on hand showers that tit over hot and cold taps.

16

4

4.

INSTALLING THE BOILER

A vertical flat area is required for the boiIer: 1122 mm high x 591 mm wide (44 in x 23.25 in). The surface on which the

boiler is mounted must be of a non reverberating and of a non combustible material. The appliance is supplied in a single
carton which contains :

1) The chassis with all functional parts attached.

2) casing comprisblg : 2 side panels
1 front panel
1 controls fascia cover
1 glass door complete with hinges

4.1

3) Mounting bracket compr3s3ng :

4) Plastic bag containing :

5) Box containing :

6) Box containing :

7) Flue assembly :

6) Plastic bag containing :

N.B. (i) Flue accessories are not supplied as standard, and must be ordered to suit (see section 1.4)

gas and water connections inc.4 above.

control knobs
safety valve
wall plugs

saews and fixings.
flue turret with pressure differential switch and 1st flue duct section
plastic wall liner with terminal
flue duct
plastic turret cover
2nd flue section

flue lockiig ring
‘0’ ring
2 gaskets - one cork and one rubber
4 mounting screws with washers for flue turret

flueguide
top support plate
spacing strip
bottom support plate
plastic jig plate connection

gas filter/washer

Positioning the boiler
a) Select the location for the boiler referring to the

dimensions shown in 1.1 and 1.3 terminal location
positions (2.4 - tig. 10). b) Check flue length (see 1.4 ­figs. 2 and 3).

c) Check clearance on external wall for flue terminal

position (see table 2.4 - fig. 10)

d) Assemble the mounting bracket made up from 4

pieces (fig. 18) using 4 thread forming saews.

e) If for rear flue installation, remember to include the flue

guide plate E, using 2 thread forming screws.

4.2

Tg.

18

‘ig. 19

Rear outlet ffue
a) Mark vertical centre line for boiler on wall.
b) Mark horizontal centre lie for 107 mm (4.2 in) dia

wall opening and one for upper bracket tixing saews

(A).

c) Using bracket as template mark 4 fixing points (A) and

03.
d) Mark wall for flue opening using flue guide plate.
e) Drill the wall for the flue opening using a 107 mm (4.2

in) core drill.

fJ Drill 4 fixing holes (A) and (B) 7.9 mm (5116 in) and

Plug.

g) Fii bracket to wall using 6 mm x 50 mm wood saews

provided.

N.B. Ensure bracket is square and plumb to vertical
centre line before tightening

17

4.3

4.4

Slope 5 mm. per metre

@I’

Side

Dmm Amm

300
400
500

700
1200
1700
2200
2700
2900

N.B. Dimension (A) decreases as dimension (D)

Fig. 20 mm per metre.

increases due to the required decline of flue of 5

166

167.5
167

1E

16i

158.5
E

Fig. 21

D (295 mm minimum)

Y

Sfde outlet fhe

I

a) Mark vertical centre line for boiler on wall (see fig. 20).
b) Using bracket as a template mark 4 fixing slots (A) and

(B).

c) Mark horizontal line through the fling slots (A) and

project to side waII.

d) Mark vertical axis of flue opening 112 mm (4.4 in) Born

comer of wall.

e) Mark waII for centre of flue opening 169.5 mm above

the horizontal on side wall.

f) DriII the waII for the flue opening using a 110 mm (4.3

in) core drill.

g) Drill 4 f&g holes (for (A) top of slot) and (for (B)

. 6) Fii bracket to wall using 6 mm x 50 mm wood screws

provided.
N.B. Ensure bracket is square and plumb to vertical centre
line before tightening.

Jig plate

N.B. By using the plastic jig plate the piping system can bc
completed before the boiler is mounted.

a) Attach plastic jig plate to bottom bracket using 4.6 mn
x 10 hexagonal screws provided (fig. 21).

6) Fit copper tails and washers to jig plate, the maim
water inlet tail (M) is the shorter of the two 15 mm tails
c) All connections can either come from above or belou
using the standard tails provided.
N.B. IF THE GAS CONNECTION IS FROM ABOVE THE
PIPE WILL HAVE TO BE SET AROUND THE FLUE
OUTLET, IF THE OUTLET IS TO THE REAR.

4.5

4.6

4.7

Tabe dimeter

22 mm

15 mm

22 mm

15mm

22 mm

Fig. 22

‘I ‘I

pttt

K L M N

Gas and water
connections

J) Heating return

K) Hot water outlet domestic
L) Gas inlet
M) Mains water inlet domestic
N) Heating flow

Pipework

a) Copper tails are 22 mm and 15 mm to accep

staight connectors.

Water connections

a) Make connections to copper tails using either solder capillary fittings or compression type.

Gas connection

a) The gas connection is 22 mm diameter.
b) Make the gas connection using solder capillary fittings.

N.B. The gas supply pipe must not be less than 22 mm diameter

IMPORTANT NOTE :

At this stage the pipework can be completed and tested before the boiler is positioned. Having completed a satisfactory

test on the pipework the boiler can now be fitted or retained for fitting at a later date.

18

4.8

:ig. 23

-ig. 24

ounted below the

b) Fit safety valve and secure with grub
screw provided.
c) Fit support bracket (A).

Fitting the boiler

a)

Remove plastic jig plate from bracket and retain

screws.

6) Hang boiler on mounting bracket, ensure that it is
properly located.

c) Fit two screws through the lower part of the support

bracket and into the rear spacers on the boiler.

N.B. Insert washer into union nut and offer assembly to
boiler. Use the plain black 3/4 and 112 diameter graphited
fibre washers for water unions, and the white 314
filter/washer for the gas union.
d) Connect water union using plain washers, working

from left to right.

e) Connect the gas union using the filter/washer packed

separately either way round.

N.B. As an alternative to using the plastic jig plate the tails
can be fitted to the boiler before mounting, then
connected

to the services.

d) Fit 14 mm tail drain bend using washer provided.
N.B. The drain must be 22 mm and the 14 mm drain
bend from the safety valve must be installed so that
discharge of water is readily visible. A tundish
arrangement is acceptable. The connection must NOT be
made by a capilary or compression fitting directly
between the 14 mm drain bend and the 22 mm
discharge pipe without an 2 mm air gap. see fig. 24.

THE 22 MM DISCHARGE PIPE MUST DISCHARGE TO THE
OUTSIDE OF THE BUILDING WHERE POSSIBLE OVER A
DRAIN. THE DISCHARGE MUST BE SUCH THAT
NOT BE HAZiRDOUS TO OCCUPANTS OR CAUSE DAMAGE
TO EXTERNAL ELECTRICAL COMPONENTS
PIPE SHOULD BE DIRECTED DOWNWARDS. IT MUST NOT
DISCHARGE ABOVE AN ENTRANCE OR WINDOW OR ANY
TYPE OF PUBLIC ACCESS AS THE TEMF’ERATURJZ OF THE

WATER BEING DISCHARGED MAY REACH 100” C.

OR

IT

WILL

WIRING. THE

Fig. 25

Rtttng the flue up to
a)

Cut

plastic

dimension (L).
b) Cut same amount from aluminium flue duct (H).
N.B. In very cold weather the plastic air duct becomes brittle,

warm before cutting.

c) Remove plastic turret cover (D) from flue turret (B)

700 mm long

duct

(G) to length

required, see fig. 2 or 3

held by two screws.

d)

Peel off protective paper from adhesive side of cork

gasket (A) place on mating side of flue turret (B) Iiniig

up with four clearance holes, press together.
e) Assemble second part of flue duct (H), push fit.
f) Slide locking ring (C) and ‘0’ ring over plastic air duct.
g) Slide air duct over flue duct, engage end of flue duct

into terminal and locate air duct into turret (B).
h) Slide ‘0’ ring along air duct (C), to contact with the face

of the turret (B). Locate lugs on locking ring (C)

between lugs on flue turret (B). Push together and

turn to lock.

j) Position square channelled rubber gasket (E) on the

flue hood outlet of the boiler. channel facing

downwards.
k) Pass the lIue assembly through the waII and seat turret

(B), onto the flue outlet, secure with 4 screws
provided.

N.B.

The terminal must extend 13 mm (0.5 in) past the
surface of the externa1 wall (see figs 2 and 3).
I) Fit waII plate (F) provided with mastic sealing ring over

air duct to structure.

m) Make good internal waII face where the air/flue duct

assemblies exit the room.

n) Do not fit plastic turret cover ‘D’ until electrical

connections to the pressure switch have been made
(see fig.26).

19

4.11

Fitting the flue over 700 mm long
a) Assembly is precisely as detailed in section 4.10 using

the requisite number of extension flue and air ducts. In
particular note the following.

b) The standard flue duct is always used (both sections)

at the appliance end (uncut).

c) The standard air duct is always used at the terminal

end (uncut).

d) When cutting, always cut one extension flue duct and

the same amount from one extension air duct Always
cut the plain end NOT the socket end.

e) Full details of dimensions and assembly are given in

figs. 2 or 3 as applicable.

fJ If internal futures prevent the assembled ducts being

passed through the wall from the inside, the ducts

may be pushed through from outside (remove the

Iockiig ring (C) and 0 ring first).

N.B. see also section 4.3

4.12

4.13

Fig. 26

Fig. 27

Connection to the pressure switch
a) The 3 wires on the harness must be connected.
b) Push spade terminals onto tags COM (P) No (1) and

No

(2)

c) Fit turret cover (D) (fig.25) ensuring that both the air

tube and cables are not trapped.
Ensure that the cable retaining clip is positionned
inside of the cover as shown, (see fig. 26).

Making the electrical connection
N.B. See Section 2.6 for electrical supply requirements
THIS APPLHNCE MUST BE EARTHED.
a) PuII out fuses (A).
c) Open door to left hand side of electrical box.
d) Cut the cable entries to the size of the cable being used

which should not be less than 0.75 mm2
e) Remove cable clamp.
f) Connect permanent live to L terminal (1) and neutral to

N terminal (2).
g) Connect earth to earth tag with the spade connector

provided.

6) Connect external controls - room thermostat etc. across

terminals 3, 4 and 5, (see section 5.).

j) Secure cables with cable clamp and locate flex into clip

on boiler chassis.
k) Close door
I) Replace fuses.

N.B. The length of the earth wire between the cable
clamp and the terminal must be such that the live and
neutral wires become taut before the earth wire if the
supply cord is pulled.

In the event of an electrical fault after installation preliminary electrical system checks must be carried out. Checks to

ensure electrical safety should be carried out by a competent Person i.e earth continuity, polarity and resistance to earth.
USE ONLY VOLTAGE FREE EXTERNAL CONTROL SWITCHING. NO SUPPLY VOLTAGE SHOULD BE CONNECTED

TO TERMINALS 3,4 OR 5.

20

Fig. 28

COMBUSTION

A

Q

flue adaptor

i

Positioning the boiler
a) Select the location for the boiler refering to the

dimensions shown in 1.1 and 1.3.

b) Select the flue configuration (see section 1.44).

C)

Assemble the mounting bracket made up from 4
pieces using 4 thread forming saews (do not tit rear
outlet guide plate).

d) Mark vertical centre line for boiler on wall.
e) Mark horizontal lie for upper bracket fixing screws.
f) Using bracket as template mark 4 ftig points (A) and

(B).

g) Drill 4 f&g holes (A) and (B) and plug.
h) Fii bracket to wall using 6 mm x 50 mm wood saews

provided (see fig. 28).

Fitting the flue adaptor to the boiler
a) Peel off potective paper from the adhesive side of the cork

gasket (A) and place on the mating side of the flue adaptor.

b) Position the square channelled rubber gasket (E) on the flue

hood outlet of the boiler channel facing downwards into
the boiler.

c) Seat the flue adaptor on top of the boiler making sure that

both gaskets are in place and secure the adaptor to the

boiler by the 4 screws provided, utikzing the 2 right hand

screws to fjx the pressure switch support (D).

d) Connect the small silicon tube between the adaptor

connection (C) and the low pressure connection on the

pressure switch (D) (see fg. 28 a).

e) Connect the 3 wires to the pressure switch (see section

4.11 f$j. 26).
Corn P (red)
No. 1 (white)
No. 2 (black)

Installing the boiler

The connection are made in the usual manner, see sections

4.4 and 4.5 and the bok can now be titted, see section 4.8.
Fittii the condensation draia

Fit the retainiig clip by removing the bottom left hand screw
from the combustion chamber, placing it through the faring
hole in the bracket and replacing the saew with the bracket
located (F).
Place the condensation trap (J) into the bracket and connect
the large silicon tube between the adaptor connection (G) and
the trap conn~on 0.
The remaining silicon tube is

co~ected

to the condensation
trap bottom connection (I) and must be fitted to suitable
plastic pipework to ensure that the discharge is over a drain
(see tig. 29). Fii condensation trap with water prior to use.

Fitting the ffue
The flue can now be fitted into the adaptor via the reducer,

making sure that all sections are tightly secured by pushing
them tirmly into position. All sections must be supported to
ensure sfakdity and no excessive weight put on the boiler (see

section 1.4.4).

Important
fhefi~m~st~v~aminimmnd.SmetersbeEore
a bend is fitted. It must only be installed in the manner

shown in section 1.44.
Ensure that all joints are fitted with “0” ring and lightly
lubri~ted with silicone grease.
It is appreciated that in some instances it may be necessary to
install the flue prior to the Wing of the boiler. If this is the case,
if is important to remember that the measurement between

the horizontal tXng line for the template to the start of the flue

is 245 mm.

21

5.

EXTERNAL CONTROL5

Programmer and zone valves

External programmer

240 V - 50 Hz supply

‘ig. 30

i.2.

Honeywell Y plan, Satchwelf

ffow chart or Satchweff
mini valves to control zones.

Refer to controls manufacturers
literature. Lie to relay coil is the wire
in their literature which carries the
signal to the boiler.

relay

5.3

kOSt

block

thermostat

N.B. Boiler time control
must be set on constant

5.4 Room thermostat

Room thermostat

boiler terminal block

Fig. 31

Fig. 32

22

boiler terminal block

Fig. 32

a

6.

COMMISSIONING

6.1

6.2

Fig. 33

Fig. 34

Central heating circuits - fdling

1) Ensure that the isolating valves are open (B and C) (fig.

34).

N.B. Valve (C) must be turned anti-clockwise by the

knurled shaft until it dislocates from the thread and
then pulled out horizontally to its extremity

(approximately 30 mm (1 114 ins)).

2) Fill system to charge condition, see section 3.

3) Vent radiators and any high points.

4) Vent air separator by loosening screw (E) (fig. 34) and
purging until no air is apparent
N.B. : ensure screw E is tightened.

Hot water circuits - f&g

1) Check that stop cocks up stream of appliance are of a
fixed jumper type.

2) Open mains cold water inlet valve (fig. 33) (A).

2) Vent installation by opening taps and closing.

4) Check that “dead legs’ have been eliminated.

5) Check for water soundness and rectify if necessary.

6) Set D.H.W. flow rate as required by adjusting screw
(D) increase (anticlockwise) decrease (clockwise), see
section 6.7.

5) Set system charge Pressure to design cold pressure.
For a new installation we suggest 1.0 bar. For an old
system see section (3, 9, 2) set to system static head
or 0.8 bar which ever is the greater.

6) Check for water soundness and rectify any leaks.

7) Switch on electrical supply.

8) Manually check pump is free to rotate. Remove cap

(D) (fig. 35).

Insert small electrical screwdriver (3 mm blade), locate

in slot in pump shaft, rotate clockwise to ensure that
pump is free replace cap (D).

9) Switch to HOT WATER + CENTRAL HEATING on
selector switch (A) (fi

10) Allow pump to run
OFF.

11) Isolate water supply and drain boiler by
disconnecting fill system and opening the drain valve
(F). This is incorporated in the safety valve and is
achieved by screwing down the head until the valve
lifts. Open all low level drain cocks.

12) Remove filter in the return isolating valve (C) and
inspect for any installation debris. see section (7.4) to
clean and replace.

13) Refill system as above.
N.B. It is recommended that this is repeated after the
system has been operated up to temperature to ‘hot
flush’ to remove fluxes and remaining debris.

. 35) switch position ,@# . .

or further lo-15 minutes. Switch

8

6.3

Fig. 35

Remove protective fXm f&m case.
Lighting the boiler

1) Purge gas supply. Switch on electrical supply

2) Turn the lever on the gas service tap (fig. 34) (G) to the

left. In the open position.

3) Temporarily locate the temperature control ‘knob - and

turn to maximum setting.

4) Switch to HOT WATER + CENTRAL HEATING tt El# m on

the selector switch (A).
Ensure that any ancillary controls are in the demand
position the boiler will now fire automatically.

5) Check for gas soundness using leak detection ffuid or

gas detector.

6) Check and adjust gas pressure/gas rate, see Section

6.4.

7) L.E.D. display sequence.

Green : electrical supply on

Yellow : run

Red : lock-out
and if boiler locks out. reset and repeat.

23

6.4

Fig.

36

Gas rate atjjustment
N.B. Before adjustment check gas pressure on the inlet to

the appliance, with the appliance working - this should be
20 mbar (8 in wg) for natural gas (G 20).
The maximum gas rate on hot water is fared and is a
function of the restrictor size. The central heating variable
adjuster is factory set at 75 % i.e for an output of approx

16.5 kW (56248 Btu/h).

1) Switch boiler to the off (0) central position, see section

6.3 (fig. 35).

2) Remove the pressure test point screw - (B) and
connect a suitable pressure gauge.

3) Remove the hexagonal cap from gas rate adjuster
exposing the adjusting screw (C).

4) Switch the boiler to hot water and central heating ‘q!# Y
and check that any fitted external controls are calling
for heat.

5) Adjust. Setting pressures are given in graph figs. 37
and 38. The pressure will be reduced by clockwise

movement of screw, increased by anticlockwise
movement. Now select hot water only, adjust hot
water regulator, see fig. 4 (20). to miniium and open

the largest volume draw-off tap. The gas pressure
should now be the maximum as indicated in Technical
Data.

6) Switch boiler off aOn. Remove pressure gauge and
replace test point screw and gas rate adiuster hexagon
cap. Check for gas soundness around saew.

7) Mark the data badge, located on the front of the
combustion chamber below the sight glass to indicate
output to heating system.

Output I Burner pressure
Output kV$

15 20

25

Input / Burner pressure
Input ft3$

14

12

10

6

6s

2

4!!

3
I

OutputJOBtuk :I

03

2:

t
E

50

60

70 60

90

z

E

Ii

/

1.00 1.25

Input m3/h

Fig. 37 Fig. 38

50 60 70 60

1.50 1.75 2.00 2 25

90 100

I I I*Ic

2.50 2.75

t

2

24

6.5

D.H.W ffow rate amstment
This is set by the installer during commissioning.
See section 6.1 and 6.7.

6.6

6.7

S RLING FF

I

Remote by-pass

remote by. pass remote by. pass

with US valve with US valve

Adjusting the heating system by-pass
Where a by-pass is fitted, see section 3.2, it is necessary

to adjust to obtain the boiler miniium flow requirement

of3OOVh(l.l gal/min).

1) Set boiler thermostat to maximum, switch boiler to
HOT WATER + CENTRAL. HEATING << l%i ,.

2) Open all radiators and close the by-pass. Check the
temperature rise accross the boiler which should not
be greater than 20’ C (36 “F).

3) Adjust system to miniium load. This is normally done

by closing valves on all but two radiators.

4) Open by-pass gradually until the boiler operates

quietly and the temperature rise is maintained.
N.B. The by-pass valve should be of the lock shield
pattern. The flow switch operates at approx 300 I/h (1.1
gallmin) .

Hot water adjustment

A flow restrictor (A) is fitted on the domestic hot water

outlet. Adjustment of this restrictor enables regulation of
the fIow rate of the D.H.W. to suit individual installation
conditions and requirements.
Adjustment is made by either turning the screw in a
clockwise direction to reduce the flow rate and increase
the temperature or by turning the saew anti-clockwise to
increase the flow rate and decrease the temperature.

6.8

Fig. 39 a

/

PUMP @

I

0

.a0

\

\

Fig. 39 b ’

25

Pump switching adjustment
The pump is set to turn ON/OFF via the room thermostai
along with the burner, when the central heating mode is
selected.
It is possible if required, to have the pump running conti­nuously by turning the switch 0 anti-clockwise, (see tig,

39b). the room thermostat then only switching the burner
on and off.

Pump and

burner

switched

4%

Burner only

switched

6.9

Central heating temperatwe diierential setting
adjrrstment (1)
The applance is set to give a temperature of differential
setting of 12’C on the termistor control (AT2 position).
For largers systems, to increase the mean temperature, it
is possible to decrease the temperature differential to 7°C
by removing the plug Q from AT2 position and inserting it

into AT 1 position.
For smaller systems, to minimise cycling a temperature
differential of 20 “C be achieved by removing the plug
from AT2 position and inserting it into AT3 position, see

r=

6.10

Fig. 39~

Fitting the casing

1) Take from the carton the controls cover (H). the glass
door (J) the top front panel (K) the side panels (A) an
the rubber grommets (I).

2) Remove control knobs used during testing ant
commissioning and tit the four grommets into the hole:
at the top of each side panel (I).

3) Fit side panels (A) and secure with screws at botton
rear(B).

4) Put the control cover (H) in position and secure win

five screws.

5) Fit the front top panel over the pins at the top of the
boiler (C) and secure with two screws at the bottom (D)

6) Fit the central heating control knob.

7) To tit the glass door proceed as follows :
N.B. THE TIE ROD (G) MUST BE USED

a) Remove the nuts from the machine saews securing the

tie rod to the hinges.

b) Offer the door up vertically. Engage part (E) in the

profile of the right hand side panel Fii assembly with
screw from beneath (F).

c) Pivot the left hand hinge and engage into profile of the

IeA hand side panel. Fix assembly with screw frorr
beneath.

Fig. 40

26

p.11 Time Clock Operating Instructions

LCD display-unit

The display contains a large number of elements to clearly
;how the various data and information.

1st example :

narker

Days of the week

/

I I

A

\

(Current time)

I

2nd example Days of the week

Hours and

- minutes dis­play

(switching

time)

3nd example

r:rlj’lJlj

CH1 ON

Days

of the week

n l-l , l-l l-l

9.

w order to enter the current time of day.

8

+ Day

8

+ h+O

8

+ m+

he relevant keys are only pressed individually for aII further
ntries or to check the programmed switching time.

CH 1

Day

h+ For entering the hours for switching times.
m+ For entering the minutes for switching

T\l

To select the standard display (current
status)

To select the relevant memory locations for

ON or OFF when programming and

entering in the memory.
For selecting the relevant day of the week

for switching times.

times.
For manually advancing the switching state

+[ @--~;j+[O~+[OFF]+

to enter the current day of the
week

to enter the time (hours)
to enter the time (minutes)

M3luVIElHRSAsu

Tie marker

Switching preselection ON

Data admMstration ii&de the time

a) Blocks
The time switch is designed as a 7-day clock but can, of tour

se. also be used in 24-hour mode if, for example. all sevei
days of the week are allocated to particular switching times.

If you wish switching to take place at the same time on variou
days, this can IX done with the following weekday blocks :

Monday - Sunday (MO . . . SU)

Monday- Friday (MO . . . . FR)

Saturday+ Sunday (SA + SU)

Single-day programming is, of course, possible.
b) Memory locations

The memory capacity is designed for 16 locations, 8 switchii

pairs being available (8 ON and 8 OFF).
c) Implementation of the switching commands

Whenever the program or time is changed (e. g. summer time

winter time switchover), aII memory locations are “interroge
ted” and the processor creates the switching state which COI
responds to the “current status” according to the program.

swkh

Keypad description - functions

The relevant keys must be pressed in combination with the ke

1.1

+lh

Res. To delete all stored switching times in the

Means constant operation (fix)
To select summer time or winter time

memory and the current time in
the display.

5nten’ng the current time

: must be assumed that the battery of the time switch is
lischarged until the appliance is put into operation. It can take
up to 2 minutes until the various segments in the display light
up (battery charging procedure).

Jse a pencil or a similar object to press the “Res” key. This setr
he electronics to “neutral”. AII segments in the display are
isible for approximately 5 seconds.

tlhmlumlHRsAsu

I

)n pressing the re-set button the n\o
lisplay will show thus :

RX ; CH1 ONOff IIf1

Aum m-l,l-ll-l

Later 5 seconds,
he following the appears :

<outine start :
‘ress the 0 button once. MO (Monday) appears in the

iisplay and the clock starts at 20:O0.
be 8 key mast be constar@ pressed in order to enter the

urrent time.
Iny sequence of entry is possible.

o lJylJr,r

; tH1

; RX

27

IIf the current time is entered during the summer time periode,]

the time may be advanced by one hour with the “+ lh” ke
The additional “+ 1 h” identifier appears in the display.

Example :

I

16:20

Thursday

If the h+ and m+ keys are pressed for longer than 2 second
roll mode occurs.

Release the key. Make a time check, e.g. radio/television/teI
phone speaking clock. A colon flashes between the hours ar
minutes display in the display.

Keys :
Keep 6 pressed ,$

Day
h+, m+

Display :

,

P

r CH1

I

H

I!: I jrI

IlJ’l lj

Pmgramming swkhing times

Entering switch-on and switch-off times is started and compl
ted (stored) with thr CH 1 key.

When this key is pressed, the memory locations for an 0

command and then for an OFF command are alternately talk
up.

After the individual switching times have been entered, the

are also entered into the memory with the CH 1 or 8 key.
Example :

MO, Tu, We,
6:oO ON

The time switch is now ready to accept the fast switch/off tim
Corresponding switch-off times are programmed in the san
way.
If the relevant programming procedure is interrupted for long
than approximately 1 - 2 minutes, the display contents chanI
back to the current time.
Partial entries, e.g. only hours, are recorded in the memory b
are not effective as a switching command. See point 10 c.

To return the clock to its normal mode press the 8 key.

33-1, Fr

Keys :

CH 1 - caII up
memory location

for ON command,
then press day until
M.T.W.T.F. appear, then
press h+, m+ until correct
switch/off time is display I
\

This switching command is then stored

by pressing CH 1 again.

Display :

IHl ON

7

Read - change - delete

1) Read
The programmed switching times are “read” step-by-step with

he “CH 1” key. Every display content corresponds to a memo­y location.

1) Change
3 command called up with key CH 1 key can be changed (cor-

.ected) in the display - simply overwrite displayed data - but is
lot recorded in the memory until “CH 1” key is pressed.

The 8 key is also used to transfer the new-value into the
nemory.

fhe time switch is now in the current mode of operation.
:) Delete

:f you want to cancel one of the entered switching times, it is
sufficient to “deleted” part of the entry. E.g. 06:-- ; or --:30 ;
x --:--.
The entire contents of the memory, including the time, are
deleted with the “Res” key.

Manual actuation of the switching output

fhe switching output can be influenced as follows with the n
‘ey 1.

Starting position
n Press once

1”\

\ Press again

Y

\ Press again -

F\

\ Press again

back to automatic mode)
?Jotes :

9 manually changed switching state % ON or n OFF is can
:eIIed again by the next automatic switching time, i.e. the nex
programming step is carried out again automaticaIIy.

[t is onIy possible to return to automatic mode from the func
tions FIX ON and FIX OFF by pressing the \

T

keys.

I

HAND OVER THE USERS INSTRUCTIONS AND EXPLAIN THE BASIC FUNCTIONS OF OPERATING THE APPLIANCE. LEAVE
THE INSTALLATION AND SERVICING INSTRUCTIONS WITH THE USER.

28

1.

7.

ROUTINE SERVICING

To ensure continued efficient and safe operation of the appliance it is recommended that it is checked and serviced as
necessary at regular intervals. The frequency of servicing will depend upon the particular installation condition and
usage, but in general once a year should be adequate.
It is the law that any service work must be carried out by a competant person, such as British Gas, other C.O.R.G.I.
registered personnel or your local Chaffoteaux Service Centre, in accordance with the Gas Safety (Installation and Use)
Regulations. This routine service will normally be confmed to :

1) Cleaning the burner.

2) Cleaning the heat exchanger.

3) Checking the gas controls.

4) Cleaning water filter, hoses and heating filter.

5) Check operation of safety valve and pressure in heating system.
The foIIowing schedules are recommended :
a) Check the function of appliance, burner pressure, gas flow rate and soundness.
b) Observe ilame picture and undertake combustion test.

c) Check, clean or replace components as necessary.
N.B. Before commencing any work turn off gas at the gas inlet tap (fig. 34) item (G) and ensure that the electricity
supply is disconnected. Isolate water supply and drain appliance if required.

7.1

7.2

Fig. 41

‘ig. 42

-I-

-

- MEI II I

To remove fimnt casing
a) Remove two screws (A) bottom rear of boiler.

6) Remove screw (B) centre of lower front panel.
c) Remove thermostat knob.
d) Remove case by easing forward at bottom and Wing

off lugs at top. If necessary, remove the lower control
cover (4 screws) and lift off the upper front panel before
removing case.

To remove sealed chamber front panel and combastton
chamber front panel to expose heat exchanger

W-q)

a) Remove four screws (A) securing the combustion
chamber front panel, and unclip wiring harness to
pressure switch.

b) Lift off front panel complete with expansion vessel and
hang on hooks provided below boiIer through matching
holes on top folded edge.

N.B. Alternatively support on worktop or Boor to avoid
damage to ikaxible tube.

- Remove 2 screws (Fl) and remove closure plate (see
section 7.3).

c) Remove 8 screws (C) and Iii off heating body front

panel with access panel (B).
d) Clean the heat exchanger after removing the burner.

(see section 7.5).

- Replace in reverse order.

29

Fig. 43

Remove burner assembly
a) Remove two screws (Fl) and remove closure plate by

wlthdrawlng forward.

b) Remove two screws (F2) and remove burner by

withdrawing forwards, taking care not to trap ignition
electrode lead.

c) Remove gasket and retain in safe place, or if adhered

to one surface, leave alone as removal may damage
the gasket. Replace gasket if necessaq.

d) To clean burner (see section 7.5).

To dean heating retam klfter
a) Close heating flow and return valves (B and C) and

drain through safety valve (F) (see section 6.2).

b) Using spanner remove return valve spindle guide

assembly (D).
c) Lift filter (E) off assembly.
d) Clean in warm water.
e) Replace in reverse order. Replace all components

removed in reverse order.

r

Fig. 44

I

Cleaning and replacement of parts
a) The burner can be cleaned by inverting and brushing

with a soft brush, Inspect injectors, ensure they are

clear.
b) The heat exchanger flueways can be cleaned by

thoroughly brushing the finned surface . After brushing

inspect to ensure that the flueways are completely

clear.
c) Examine electrode and clean, the tip. If the tip appears

damaged replace electrode and lead assembly - (see

section 8.1).
d) Replace all components in reverse order ensuring that

the gasket between the gas section and the manifold is

correctly positioned upon reassembly.
e) Open all isolation valves and repressurise system if

necessary.
f) Recommission and check controls.
g) After the boiler is lit, check all gas connections for

soundess .

6) Allow the boiler to warm up thoroughly, then check

the burner pressure and adjust as necessary to that

given in the table for required output (see section 6.4).

1) Restore any sytem controls and clocks to their original

setting.

7.6

drain bend

Fia. 45

To check operation of safety valve
Turn off the appliance by selecting the 0 position on the
Summer and Winter switch.
Engage the knurled ring (A) to the thread and turn it
clockwise until water can be seen to discharge from the
outlet (B). Turn the knurled ring (A) anti-clockwise until it
disengage from the thread.
Ensure that the pressure has not decreased below 1 bar
and repressurise if necessary. (see section 6.2).
N.B. If the water does not discharge replace valve (see
section 8.33).

30

d.

8.

REPLACEMENT OF PARTS

N.B. 8efore commencing ensure gas and electricity supplies are isolated, and drain appliance if necessary.

8.1

‘-2

Fig.

46

‘I? replace electrodes
a) Remove front case (see section 7.1).
b) Remove outer front panel and combustion chambe

front panel (see section 7.2),

c) Disconnect from electrical box by pulling off elect&c

lead from the hight voltage transformer.

d) Feed cable up through gas section (H) removing

grommet (J) (see fig. 46),
e) Disconnect probe (see section 8.2).
fj Remove burner (see section 7.3).
g) Remove screws securing electrodes,

6) RepIace in reverse order.

To

replace

probe
a) Remove front case (see section 7. l),
b) Remove outer front panel and combustion chamber

front panel (see section 7.2)

c) Disconnect from electrical box by pulling off probe lead

at lower left hand rear.

d) Feed cable up through gas section (H) removing

grommet (J) (see fig. 46a),

e) Disconnect electrodes (see section 8.1).

9) Remove burner (see section 7.3).
g) Remove screw securing probe
h) Replace in reverse order.

8.3

8.4

Fig. 46a

Fig. 47

Fig. 46

To replace safety overheat thermostat 105°C
a) Remove front case (see section 7.1)

B

-

b) Remove two screws securing high limit thermostat to
bracket (B).
c) Remove high limit stat.
d) Replace in reverse order. Use heat sink grease
between high limit stat and bracket (B).

To replace overheat thermostat 1lO’C
a) Remove front case (see section 7. l),
b) Remove outer front panel.
c) Remove left side panel.
d) Remove two screws securing high Iimit thermostat to

bracket.
e) Remove high limit stat.

f) Replace in reverse order. Use heat sink grease between

high limit stat and bracket.

31

8.5

To replace change over valve microsw3tch
a) Remove front case (see section 7.1).
b) Undo screw (A) and remove microswitch box cover.
N.B. Upper microswitch operates for D, H, W mode.
Lower microswitch operates for C H mode.
c) LIA spring (B) and pull operating lever off mounting
pins.
d) Remove respective microswitch from mounting pins.
e) Note colour code and pull off electrical tags.
fJ Replace in reverse order. When replacing box cover,
ensure that the lugs on the connector block are clamped
inside the box.
N.B. Refer to fig. 9 for colour codes.

Fig. 49

8.6

To replace the flow switch assy.
a) Remove air separator (see section 8.13).
b) Disconnect high pressure tube at union A.
c) Disconnect low pressure tube at union B.
d) Replace reverse order.
e) Check for leaks

To replace vent&

a) Remove front case (see section 7.1).

b) Isolate from cold mains water supply (A), open an hot
water outlet and drain down from valve (E).
c) Remove plug (C) from left hand side of change over
valve.
d) Use small screw driver to gently push out venturi
ensure screw driver does not enter throat of venturi.
e) Replace in reverse order.
0 Ensure that valve E is closed, restore cold mains water

supply, check for leaks.

32

8.9

Fig. 52

To replace primary heat exchanger
a) Remove front case (see section 7.1).
b) Isolate appliance from system by closing heating flow

and return valves (B and C), see (fig. 34).

c) Drain boiler (primary side) through safety valve (F) (fig.

34).

d) Remove four screws securing the sealed chamber

kont panel and remove (see section 7.2).

e) Remove left and right hand side on chamber Panels by

pulling them carefully towards you.

f) Remove combustion chamber front panel, see section

7.2.

g) Remove burner. (see section 7.3).
h) Remove overheat thermostat (C).

1) Remove four screws (A) securing heating body panels
to chassis.

j) Undo flow and return pipe unions (E), remove pipes

and slide primary heat exchanger forwards.

j) Replace in reverse order.

Fig. 53

To remove

a) Remove front casing (see section 71).
b) Remove fuses by pulling fuse carrier (B) from electrical

electrical control

box

box (see fig. 54).

c) Remove 3 screws (C) lift electrical box cover away and

unplug from PCB.

d) Pull off plug from solenoid valves at PCB.
e) Unplug pump connector at PCB and earth wire.
f) Unplug connector to change over valve at PCB.
g) Unplug connector from fan at PCB.
h) Remove one screw (D) and two screws (E). (Electrical

box support bracket to lower chassis) (see fig. 53).

ti

E

1) Carefully ease electrical box forward to allow access to
tlow switch lead, also to electrode at bottom rear of

bOX.

j) Disconnect lead from flow switch at connector.

k) Disconnect electrode from rear of electrical box.
I) Disconnect the two time clock plugs from the electrical

bOX.

m) Carefully move the electrical box away from the

appliance and to the right whilst straightening the
capillary tube from boiler limit thermostat and
domestic hot water thermostat.

n) Continue moving electrical box until bottom support

bracket can be positioned on hook at bottom of
appliance. To remove the electrical box completely,
continue in the following manner.

o) Isolate appliance from the system by closing valve A

(see Section 6.2) (Fig. 34).

p) f;in secondary side by opening drain plug (H) (fig.

?g. 54

33

q) Remove clip and phial from DHW thermostat pocket.
r) Unclip and remove limit boiler thermostat phiil.

s) Remove box completely.

To replace electrical box in reverse order note :

a)

Hang box on hook.

b) CapiIlaries must be routed behind any pipework .

8.10

To replace pump head
a) Remove front case (see section 7.1).
b) Isolate boiler from system by closing fIow and return

valves see section 8.11 (B and C, fig. 57).

c) Drain boiler (primary side) through safety valve (see

section 8.11 (F, fig. 57).
d) Remove four hexagon headed screws (A).
e) Remove pump head noting orientation.

f) Take off electrical connection cover by removing screw

03.

g) Remove lead and transfer to new pump head.
h) Replace in reverse order.

j) Open flow and return valves Top up system if

necessary.

N.B. For the STERLING FF the pump is a Grundfos UF’

15-60

8.11

‘ig. 56

C

:ig. 57

F

-

To replace change over valve (C, 0, V)
a) Remove front case (see section 7.1).
b) Remove the 3 electrical box ftig screws (D) and (E)

(see tig. 53) and carefully pull the electrical box towards

you, taking care not to damage any capillaries or

disconnect wiring.
c) Turn off main water at vaIve (see section 6.2 (A)).
d) Turn off central heating flow and return valves (see

section 6 (B)).
e) Drain secondary side by opening drain plug on bottom

of change over valve (H).

f) Remove safety overheat thermostat from tube and

carefully position to one side.

g) Remove front tube (1) from change over valve unclip

thermometer sensor, unclip high limit thermostat.

h) Remove flow pressure tube (2) from C, 0, V, to ffow

switch.

N.B. Swing microswitch box to give access to union nuts.

j) Remove rear tube (4) from C, 0, V, to secondary heat

exchanger.
k) Unscrew union nut (5) of mains water inlet to C, 0, V.
I) Unscrew heating flow tube nut (6) from C, 0, V.
m) Unscrew union nut (7) of C, 0, V, to secondary heat

exchanger.
n) Remove C, 0. V.
o) To inspect diaphragm remove height screws (E)

securing valve to water section.
N.B. To service the C, 0, V, piston remove spring clips,
remove piston, clean and grease.
p) Clean or replace diaphragm.
q) Flush out water section.
r) Replace in reverse order.
s) Open flow and return valves. Top up system if

necessary

8.12

:ig. 58

To replace secondaxy heat exchanger

a) Remove front cash (see section 7.1).
b) Disconnect and remove electrical box, (see section 8.9)
c) Remove change over valve (see section 8.11).
d) Unscrew union nut (8) at top of secondary heat

exchanger.

e) Unscrew bottom Ieft hand union nut (9) of secondary

heat exchanger.
f) Slacken top screw (A) of heat exchanger to chassis.
g) Remove bottom screw (B) and spacer.
h) Remove secondary heat exchanger.
i) Replace in reverse order.
N.B. Do not unscrew the four tie rods in the secondary

heat exchanger.

34

8.13

To replace air separator
a) Remove front case (see section 7.1).
c) Close heating flow and return valves (B & C) (see

section 8.11 (tig. 57))

d) Drain boiler down through safety valve (F) (see section

7.6 (fig. 45)).

Remove electrical box (see 8.11) and disconnect
pump.

e) Disconnect flow switch pipe union from pump volute

(EL

f) Disconnect manual vent tube (B) be careful1 not to

loose black washer.
g) PuII out spring dip (A) with pliers.
h) Disconnect pump connection at union (D) at pump

outlet.

j) Pull pump complete with volute forwards and remove.

k) Disconnect union nut at base of air separator (F).
m) Ease air separator forward and disengage integral peg

from chassis bracket,

q) Replace in reverse order, Ensure that washer is

replaced in lower union of separator.

r) Open flow and return valves. Re-pressurise system if

necessary.

Fig. 59

8.14

To replace themistor
a) Remove front case (see section 7.1).
b) Disconnect the spade connectors.
c) Unscrew the knurled ring (A) (fig. 60) retaining

thermistor.
d) Remove the thermistor by gently pulling.
e) Replace in reverse order using heat sink grease on

thermistor.

Fig. 60

-

35

8.15

Fig. 61

To replace boiler limit thermostat
a) Remove front case (see section 7.1).
b) Remove electrical box (see section 8.11).
N.B. Thermostat (B) is situated to right bottom of

electrical box, sensor on flow pipe, on right hand

lower side.
c) Remove from flow pipe (A).
d) This thermostat is located on moulded pins - ease

forward and remove spade connectors.
e) Feed capillary through the control box having removed

the split grommet.
f) Replace in reverse order (polarity immaterial).

I

8.16

Fig. 62

To replace domestic hot water thermostat
a) Remove front case (see section 7.1).
b) Isolate mains water supply - drain t?om valve beneath

the change over valve (see section 8.11 fig. 56 (H)).
c) Remove clip which retains phial in wet pocket.
d) Remove phial from pocket.
e) Remove electrical box front cover (see section 8.11, c).
f) Ease thermostat (C) off moulded pegs and pull of

spade connections.
g) Feed capillary through the control box, having

removed the split grommet.

h) Replace in reverse order. Polarity immaterial.

I

To replace high tension transformer (spark generator)

a)

Remove front case (see section 7.1).

b) Remove the 3 screws (A).

A

-

c) Unplug electrical connection to the pump.
d) Carefully pull the control box forward and angle to give

access to the transformer (see section 8.9.).

e) Remove screw from transformer and disconnect from

amp tags.

f) Replace in reverse order.

36

Fig. 64

To replace printed circuit boards (PCBs)
a) Remove front case (see section 7.1).
b) Remove electrical box front cover (see section 8.9 (C)).
c) Unplug LED printed circuit board to replace new LED

printed circuit board.
Remove aII plug in connectors.

d) Disconnect mains input cable at terminals 1 and 2 but

not the earth.

e) Disconnect external controls, if fitted, from terminals 3,

4 and 5.
f) Remove two screws (A).
g) Slide PCB slight@ upwards to disengage guide.
h) PuII PC B forward.
i) Replace in reverse order.

Vn

Fig. 65

17 18 9 1 11 6

Summer/winter Switch

1

Pump

2

Earth

3

LEDS

4

CH. Limit Thermostat

5

Water Flow Switch

6

ELECTRICAL BOX SHOWING POSITION OF COMPONENTS

13 8

7 D.H.W. Thermostat

Capillary
8 Change Over Valve
9 Time clock

10 Solenoid Gas Valve
11 Fan connection
12 240 V-50 Hz connection

WITH LAYOUT OF PLUGS AND WIRING.

13 Igniter

14

15 Boiler Thermistor
16 Limit Thermostat

17

18 Room thermostat

37

D.H.W. Thermostat

Fuse

connection

8.19

To replace solenoid valves
a) Remove front case (see section 7.1).

b) Withdraw plugs - colour coded - from solenoids (B).
c) Remove six screws (A) securing valve mounting plate.
d) Remove mounting plate and solenoids - take care not

to misplace valve springs and plungers.

e) Replace in reverse order using a NEW GASKET.

8.20

8.21

Fig. 66

Fig. 67

Rear lining-

To replace heating body finings
a) Remove case (see section 7.1).
b) Remove combustion chamber front panel with

expansion vessel (see section 7.2 (A, B, C and D)).

c) Remove burner (see section 7.3 d)) First slide out side

linings followed by rear which is removed by easing
upwards and sliding out from bottom.

e) Replace in reverse order.

To replace fan assembly
a) Remove case (see section 7.1).
b) Remove outer front panel (see section 7 2).
c) Remove right hand side sealed chamber panel (see

section 8.8).
e) PuII off 3 spade connections from fan.
r) Remove 2 screws on ffue hood (A).
g) Turn anti-clockwise 10” to disengage lug from rear and

withdraw assembIy.

6) Replace in reverse order using new gasket,
N.B. Ensure correct location of fan connections and that
the lug at the rear is located correctly.
(0) : Red
(1) : Brown

(E) : Yellow/Green
(2) : Not used.

Fig. 68

38

8.22

Fig. 69

sampling tube

To replace pressure switch (Horizontal Ffcre)

a)

Remove two screws (A) retaining plastic turret cover
and remove terminal cover.

b) Note position of spade connectors and remove (COM-

P, No 1 and No 2).

c) Disconnect pressure sampling tube by pulling off

nipple.
d) Remove two screws retaining pressure switch (B) .
e) Replace in reverse order.

N.B. Ensure ‘0’ ring is position on rear of pressure

switch to seal pressure switch - high pressure sample

joint. Transfer 4 mm support screw (C) and nut onto

the new switch if not supplied.

To replace pressure switch (Vertical Fke)
a) Note position of spade connectors and remove (COM-

P. No 1 and No 2).
b) Disconnect pressure sampling tube

nipple.
c) Remove two screws retaining pressure switch (B).
d) Replace in reverse order.

by

pulling off

8.24

8.25

Fig. 69a

To re-pressurise expansion vessel
a) Remove case (see section 7.1).
b) Close heating flow and return valves and drain boiler

through safety valve (see section 6.2 fig. 34 (F)).

c) Remove protective cap and check pressure on

Schroeder valve with gauge.

N.B. The setting pressure is 0.65 bar (9.5 psi).
d) To re-pressurise use car foot pump or bicycle pump

with adaptor.

e) Close safety valve.
f) Open heating flow and return valves.
g) Refill and commission boiler.
N.B. Do not me a high pressure air line.

Fig. 70

To replace pressure gauge
a) Remove case (see section 7.1).
b) Close heating flow and return valves and drain boiler

through safety valve, see section (6.2 fig. 34 (F)).
d) Undo union nut (A) on pressure tube at rear of gauge.
e) Withdraw gauge.
r) Replace in reverse order.
g) Open tIow and return valves. Re-pressurise system if

necessary.

Fig. 71

39

8.26

8.27

To replace the domestic expansZon vessel
a) Isolate cold water mains supply (see section 6.2).
b) Drain from valve (E) beneath the change over valve

(see section 8.7) (fig. 51).
c) Remove electrical control box (see section 8.11, b).
d) Undo connection +- and remove domestic expansion

vessel.
Replace in reverse order.
Check for leaks.

Fig. 72

To replace main burner
a) Remove case (see section 7.1).
b) Remove outer t?ont panel, (see section 7.2).
c) Remove burner (see section 7.3).
d) Replace in reverse order ensuring that the gasket is

correctly positioned between the injector cover plate

and the manifold.

8.28

Fig. 73

To replace the bumer manifold assembly
a) Remove the front case (see section 7.1).
b) Remove the combustion chamber front panel to

expose the burner manifold (see section 7.2 (a to c.)).
c) Remove the two screws Fl and remove the closure

plate .
N.B. When replacing the manifold it is advisable to

replace the gasket at the same time.
d) Remove the two screws F2 and lift off from Burner

base.
e) Replace in reverse order.

‘ig. 74

40

8.29

To replace expansion vessel
a) Remove front case (see section 7.1).
b) Isolate appliance from system by closing flow and

return valves (see section 6.2 fig. 34 (B et C)).

c) Drain boiler (primary side) through safety valve fig. 34

(F) and vent expansion vessel at (C).
d) Remove flexible pipe from expansion vessel, at (A).
e) Loosen upper securing screw (B) support and loosen

lower screw. Slide out expansion vessel.
Q Replace in reverse order, engaging the thread of the

ffexible pipe before screwing fully home screws (B).

The vessel must be central on the front panel.
g) Re-pressurise expansion vessel (see section 8.23).
h) Open flow and return valves. If necessary, repressurise

system.

(See section 6.2).

Fig. 75

8.30

Fig. 76

A

,B

To replace viewing window
a) Remove front case (see section 7.1).
b) Remove combustion chamber front panel (A) (see

section 7.2).

c) Remove the screws (B) securing the sight glass bracket

(C). Take care not to loose the two nuts (D).

d) Replace in reverse order referring to diagram opposite.

41

8.31

To replace the main gas valve body

a) Remove front case (see section 7.1).
b) Remove sealed chamber front panel (see section 7.2).
c) Remove burner assembly (see section 7.3).
d) Remove electrical control box (see section 8.11, b).
e) Disconnect electrodes probe and solendids.
f) Remove two screws (P) retaining bracket to gas section

and ease bracket down to clear gas section.

g) Slacken and undo the gas supply union (D) beneath

gas section.

h) Remove two screws (R) retaining gas section to

combustion chamber base.

i) Remove gas section by pulling forward.

j) Reassemble in reverse order and check for gas

soundness.

Fig. 77

8.32

To replace the thermometer
a) Remove the front case (see section 7.1).

6) Unclip and remove thermometer sensor from flow
pipe (A) (see fig. 78).
c) Withdraw gauge (B).
d) Replace in reverse order.

Fig. 78

8.33

Fig. 79

42

To replace time clock

a)

Remove front case (see section 7.1).

b) Remove 2 screws tixing the time clock support (A)

(see fig. 79).
c) Withdraw “amp tags” noting position.
d) Remove 4 screws (D) ftig the time clock to the

support.

e) Replace in reverse order.

To replace safety vahre
a) Remove case (see section 7.1).
b) Close heating flow and return valves and drain the
appliance through safety valve (see section 6.2 fig. 34 (0
and section 7.6).
c) Ensure that the boiler is completely drained and the
pressure gauge is reading zero (0).
d) Undo the grub screw (A) and remove the complete
assembly by carefuly pulling it in a downwards direction.
e) Replace in reverse order.
r) Ensure that the valve is in the close position and

repressurise system (see section 6.2).
g) Open heating flow and return valves.
h) Check for leaks.

43

FAULT FINDING

3.1 Logic sequence

1 electrici supply 1

change over valve

No

position

D.H.W.

summer

Yes

No

switch position

summer / winter

i

b

v

water flow

switch

Ye:

l

D.H.W.

winter

change over valve

position
heating

A

link

L - - - - - - - - -

heating

Yes

(5) -

red lead

manual reset

energised

‘-

security solenoid open

1 st stage solenoid open

high tension transformer energised

J

1 stream of sparks 1

l!!&,

1 time delay; sec. maxi. 1

2nd stage solenoid open

Yes

D.H.W.

high tension transformer energised

I

9

stream of sparks

2nd stage solenoid open

44

No

NO

T>5s

t

t

Yes

FAULT FINDING

CENTRAL HEATING OPERATION

SEQUENTIAL FLOW CHART 1

READ IN CONJUNCTION WITH SECTIONS (9.1 & 9.3)

START

Chedc
i) System water pressure - 1 bar
ii) Gas co& open - gas lines purged

iii) Electrical supply switched on.

Set selector swtch to central heatmg

.,,,,,.,LCI

t

END

45

i) Vent at air separator
if) Isolating valves open and all ra-

diators valves open

RMtif~.

I

t

Remove plugs from board and chedc
continuity across following :
a) Black and orame wires to change
o;ervahw ­b) Water flow switch (black leads)
c) CH limit stat (Made leads)
d) CH control SM (red and Ma&

Is there continuity aaoss all
components.

I

1

a.3

FAULT FINDING

DOMESTIC HOT WATER OPERATION

SEQUENTIAL FLOW CHART 2

READ IN CONJUNCTION WITH SECTIONS (9.1 & 9.2)

START

t

END

4-1

domestic hot water thermostat ?

YES

t

+I*

connection from printed circuit
board.
Is there continuity across

jbla&andblwlsads? 1 , f ,

Chedc venturi for blockage.

Ensure all isolating valves and
stop co& open.

I

Replace if necessary.

No

t

46

9.4 FAULT FINDING TABULAR CHART

PROBLEM CAUSE REMEDY

) Explosive ignition

!) Unstable burner

Poor sparks

i)

ii) Blocked gas filter 2) Clean

l/3 valve not operating

iii)

a) 24 volts supply to valve 3a) Replace solenoids, see section 8.19
b) No voltage at solenoid 3b) Check plugs on printed circuit board,

iv) Crosslighting strip - missing/incorrectly 4) Replace or reposition, see section 8.26

positioned

Incorrect injectors 1) Replace manifold 1.28 mm injectors

i)

ii) Gas pressure at manifold

a) Too high 2a) Adjust, see section 6.4

a) Too low 2b) Check restrictors and inlet pressure,

iii) Terminal incorrectly positioned 3) See section 2.4

iv) Incorrectly assembled flue duct 4) Check and reassemble,

Fan incorrectly located 5) Remove and refit correctly,

VI

vi) Combustion chamber front cover not sealing 6a) Tighten

vii) Heat exchanger fins blocked 7) Clean, see section 7.5

viii) Neoprene gasket in turret not crrectly fitted 8) Fit or refit, see section 4.10

or missing

1) Check electrodes and HT transformer
replace if necessary

see sections 8.17 and 8.1

see section 8.18

3c) Replace printed circuit board,

see section 8.18

for natural gas, see section 8.27

see section 1.2

see section 4.10, 1.4.4

see section 8.21

6b) Replace sealing strip

5) Central heating
low flow

temperature

i) Boiler thermistor out of calibration

ii) Insufficient gas pressure 2) Check pressure at meter and pipe

iii) 113 blue or 2/3 orange gas valve not opening

a) 24 volts at solenoid 3a) Replace solenoid, see section 8.19

b) No voltage at solenoid 3b) Replace print circuit board,

Hot water valve in change over valve assembly

iv)

sticking
a) Dead leg on hot water system 4a) Eliminate

b) Bent spindle in valve

v) By-pass, if fitted, incorrectly adjusted

vi) Pressure switch hunting

47

1) Replace, see section 8.14

sizing, see sections 1.2, 2.1 and 2.7

see section 8.18

4b) Replace, see section 8.11

5) Adjust, see section 6.6

6) Replace, see section 8.22

PROBLEM

CAUSE

REMEDY

I) Boiler noisy

i) Hot water does not

operate over
temperature range

i) On heating only

a) Low flow rate as result of system resistance

b) Air in system

ii) On hot water and central heating

a) Low pressure in sealed system

b) Pump not running
iii) Blocked filter on heating return or blocked pump hose
iv) Gas filter fitted to heating flow or return pipes

Heat exchanger scaled

VI

vi) Overgassed

/ii)) isolating valves not fully open

Change-over valve sticking

9

Low inlet water pressure

ii)

Incorrect venturi fitted

iii)

iv) Hot water limit stat out of calibration

v) Solenoids not operating

Pressure switch hunting

vi)

vii) Low inlet gas pressure

I a) Check and if omitted fit by-pass

see section 6.6

lb) Purge by venting radiators

!a) Repressurise to 1 bar cold

see section 3.6

!b) Replace pump head, see section 8.10

3) Clean and replace see section 7.5

4) Remove and reposition see section 4.5
ia) Descale
ib) Replace, see section 8.8

ia) Check gas pressure and adjust, see

section 6.4

ib) Check restrictors, see section 1.2

7) Open fully see section 6.2

1) Lubricate or replace
see section 8.11

2) Ensure all down stream stop cocks
open

3) Replace with 5.4 mm diameter,
see section

4) Replace, see section 8.7

5) See section 8.19

6) Replace, see section 8.22

7) See section 1.2

i) No main burner

3 Safety valve

discharges

5) Pump noisy

Lack of water flow

1)

ii) Pump jammed
iii) No water
iv) Flow switch not operating

Fan pressure switch not operating

VI

i) System pressure too high

ii) Not isolated from mains

iii) Vessel lost air charge

Secondary heat exchanger (water to water)

iv)

internal water leak

i) Air in system

ii) Air in separator

iii) Debris in pump
iv) Water filter blocked

1) Checks valves are open
see section 6.2

2) Manually check, see section 3.3

3) Fill system, see section 6.2

4) Replace switch, see section 8.6

5) Replace, see section 8.21

1) Adjust 1 bar cold

2) Remove filling loop

3) Recharge 0.65 bar, see section 8.23

4) Replace, see section 8.12

1) Vent radiators

2) Open vent on air separator and purge,

see section 6.2

3) Clean and replace, see section 8.10

4) Clean and replace, see section 7.5

I

48

PROBLEM

CAUSE

9) Excessive
temperature

rise across boiler

10) Rapid cycling
high/low or

high/low/off

11) Fan on
continuously

12) Loss of pressure

i) Return filter blocked

ii) Low water flow rate

a) Pump defective
b) High system resistance
c) Gas filter inadvertantly fitted in flow

of return connection

iii) Gas rate too high

Low water flow rate

i)

ii) Thermistor out of calibration
iii) By-pass, if fitted, not regulated
iv) Blocked heat exchanger

Temperature differential setting incorrect

VI

i) Defective printed circuit board

Leak on system

1)

ii) Leak on appliance

1) Clean and replace, see section 7.5

2a) Replace, see section 8.10

2b) Fit by-pass, see section 6.6

2c) Remove and refit,

see section 4.4

3) Adjust, see section 1.2

1) See ‘System guidance’ section 3.13

2) Replace, see section 8.14

3) Adjust, see section 6.6

4) Clean or replace, see section 8.8

5) Adjust. see section 6.9

1) Replace, see section 8.18

1) Locate and rectify

2) Locate and rectify

I-

13) Gain in pressure
shown on gauge

Filling loop still fitted and letting by

0

ii) Blockage in expansion chamber flexible hose

iii) Secondary heat exchanger (water to water)

internal water leak

1) Close stop cocks and remove

2) Clear blockage

3) Replace, see section 8.12

49

Chaffoteaux et Mauty Limited,

Trench Lock, Trench, Telford, Shropshire TFI 4SZ

Telephone: [phone] Fax: [phone]

Looking Good. Heating

Better

~fl(01939)232.796~

ESPOI 5