andrews OFS25 User manual

Working towards
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Oil Fired
Installation Guide, Operation and Service Manual
This manual must be kept with the appliance October 2010
Part No E524
Oil Fired Storage Water Heaters
MODELS OFS25, OFS29, OFS63, OFS90, OFS108, OFS163

© Copyright Andrews Water Heaters 2007
Reproduction of any information in this publication by any method is not permitted
unless prior written approval has been obtained from Andrews Water Heaters.
Andrews Storage Water Heaters have been designed and manufactured to comply
with current International standards of safety. In the interests of the health and
safety of personnel and the continued safe, reliable operation of the equipment,
safe working practices must be employed at all times. The attention of U.K. users is
drawn to their responsibilities under the Health and Safety Regulations 1993.
All installation and service on the Andrews Water Heater must be carried out by
properly qualified personnel, and therefore no liability can be accepted for any
damage or malfunction caused as a result of intervention by unauthorised
personnel.
The Andrews Water Heaters policy is one of continuous product improvement, and
therefore the information in this manual, whilst completely up to date at the time of
publication, may be subject to revision without prior notice.
Further information and assistance can be obtained from:
Andrews Water Heaters
Wood Lane, Erdington, Birmingham B24 9QP
Tel: [phone] Fa : 0845 070 1059
Sales: 0845 070 1056
Technical: 0845 070 1057
Service: 0845 070 1058
Email: [email protected]
www.andrewswaterheaters.co.uk
THE ANDREWS WATER HEATERS COVERED IN THIS MANUAL
ARE FOR USE WITH KEROSENE CLASS C2 (BS2869) OR GAS OIL CLASS D (BS2869)

CONTENTS
SECTION 1 GENERAL AND SAFETY INFORMATION
General Information 2
British Standards 2
Health and Safety Regulations 1993 3
Legionellae in Water Heaters 3
SECTION 2 TECHNICAL DATA
All Models 4
SECTION 3 INSTALLATION
Introduction 6
Location 6
Burner Assembly 6
Flue Systems 8
Installation of Flue 8
Terminal Location 8
Common Flue Header 10
Air Supply and Ventilation 11
Water Quality and Treatment 12
Water Connections- Hydrojet System 13
Water Connections - Vented Systems 14
Water Connections - Unvented Systems 16
Electrical Supply 18
Fuel Supply 19
SECTION COMMISSIONING
Combustion Adjustment 20
Air Adjustment 21
Pump Adjustment 21
Instructing the Users 22
Users Safety Guide 22
SECTION 5 OPERATION 23
SECTION 6 SERVICING
Introduction 24
Pre-Service Operations 24
Burner Assembly 24
Flueway 24
Magnesium Anode(s) 25
Cleaning the Storage Vessel - All Models 26
SECTION 7 FAULT FINDING
All Models 27
SECTION 8 PARTS LISTS AND ILLUSTRATIONS
Heater Spares OFS25 28
Burner Spares BTL4 OFS25 29
Heater Spares OFS29 30
Burner Spares BTL4 OFS29 31
Heater Spares OFS63 32
Burner Spares BTL6 OFS63 33
Heater Spares OFS90 34
Burner Spares BTL10 OFS90 35
Heater Spares OFS108 36
Burner Spares BTL10 OFS108 37
Heater Spares OFS163 38
Burner Spares BTL20 OFS163 39
Unvented System Kit OFS25 & OFS29 40
Unvented System Kit OFS63 & OFS90 41
Unvented System Kit OFS108 & OFS163 42
PAGE

GENERAL AND SAFETY INFORMATIONSECTION 1
The Andrews Water Heater has been designed and manufactured to give an efficient,
reliable and long service life.
To ensure the continued, trouble-free operation of your heater at ma imum efficiency,
it is essential that correct installation, commissioning, operation and service procedures
are carried out strictly in accordance with the instructions given in this manual. By law,
installation and commissioning of the heater must be carried out by properly qualified
personnel.
The heater(s) must be installed in accordance with the following requirements;
The current BUILDING REGULATIONS
The Water Supply (WATER FITTINGS) REGULATIONS 1999
Additionally, installation should be performed in accordance with all relevant
requirements of the Local Authority and recommendations of the British Standards and
Codes of Practice detailed below.
BS 5410:Part 1 Installations up to 44kW output capacity for space heating and
hot water supply purposes.
BS 5410:Part 2 Installations of 44kW and above output capacity for space heating
and hot water supply purposes.
GENERAL
INFORMATION
BRITISH
STANDARDS
AND CODES OF
PRACTICE
2

GENERAL AND SAFETY INFORMATION SECTION 1
It is the duty of manufacturers and suppliers of products for use at work to ensure, so far
as is practicable, that such products are safe and without risk to health when properly
used and to make available to users, adequate information about their safe and proper
operation.
Andrews Water Heaters should only be used in the manner and purpose for which they
were intended and in accordance with the instructions in this manual. Although the
heaters have been manufactured with paramount consideration to safety, certain basic
precautions specified in this manual must be taken by the user.
It is imperative that all users of the heater must be provided with all the information and
instruction necessary to ensure correct and safe operation.
Water systems in buildings have been associated with outbreaks of Legionnaires' Disease,
particularly in health care facilities where occupants are significantly more susceptible to
infection.
In recognition of the risks in hospitals, a Code of Practice for the Control of Legionellae
in Health Care premises has been issued by the Department of Health (1991). Codes of
Practice applicable to other premises have been published by other organisations,
principally the Health and Safety E ecutive (HS)(G70) and the Chartered Institute of
Building Services Engineers (CIBSE, TM13).
All Codes of Practice draw attention to the design and operation of water systems with
reference to avoidance of factors that favour colonisation by Legionellae bacteria. These
factors include stagnation, lukewarm conditions (20ºC to 45ºC) and the accumulation of
debris, scale and corrosion in the base of tanks and calorifiers.
Andrews Water Heaters has commissioned an independent evaluation of their products
to investigate their resistance to build-up of legionellae bacteria.
E periments were conducted to determine whether, following a substantial challenge by
legionellae pneumophilia, after overnight and stagnation conditions, the system was
rendered free from viable recoverable legionellae. It was found that at 61ºC, following a
challenge of appro imately 107 organisms per litre, within one hour, more than 99.999%
of organisms had been killed. After a subsequent stagnation period, sampling did not
reveal any residual contamination. The design of the base of the water heater precludes
legionellae colonisation, even after build-up of debris. The burner positioning ensures
that the water at the bottom of the heater reaches the same, or higher temperature as in
the rest of the heater.
Based on data obtained through e periment, the Andrews Water Heater can be described
as legionellae resistant as it is considered unlikely that, at the temperature tested, the
organism would colonise the water heater and present a possible health risk.
HEALTH AND
SAFETY
REGULATIONS
1993
EFFECTIVENESS
IN COMBATING
LEGIONELLAE
3

TECHNICAL DATASECTION 2
4
Storage Cap Ltrs 192 265 146 146 378 306
Storage Cap Galls 42 58 32 32 83 67
Rec Thro 44c L/H 491 577 1227 1759 2110 3166
Rec Thro 44c GPH 108 127 269 386 463 694
Rec Thro 56c L/H 390 443 975 1398 1677 2516
Rec Thro 56c GPH 86 97 214 307 368 552
Heat Input kW 30.8 34.9 71.8 102.6 123.1 184.6
Heat Output kW 25.2 28.6 63 90.3 108.3 162.5
Heat Input Btu/Hr 105,000 119,000 245,000 350,000 420,000 630,000
Heat Output Btu/Hr 86,000 97,580 215,600 308,000 369,600 554,400
Efficiency % 82 82 88 88 88 88
Fuel BS2869 Kerosene Class C2
Fuel BS2869 Gas Oil Class D
Burner Type EOGB BTL4 BTL4 BTL6 BTL10 BTL10 BTL20
Elec. Data V 220/240 220/240 220/240 220/240 220/240 220/240
Frequency Hz 50 50 50 50 50 50
Power Cons. Watt 110 110 110 110 110 185
Start Current Amp 2.2 2.2 2.2 2.2 2.2 2.0
Run Current Amp 0.87 0.87 0.87 0.87 0.87 1.28
Fuse Amp 5 5 5 5 5 5
Nozzle fitted Kero 0.75 80s 0.85 80s 1.65 80s 2.50 80s 3.00 80s 4.50 80s
Pressure PSI 113 110 127 113 113 113
Pressure Bar 7.8 7.6 8.6 7.8 7.8 7.8
Nozzle Supplied Gas Oil 0.55 80s 0.60 80s 1.25 80s 1.75 80s 2.25 80s 3.50 80s
Pressure PSI 195 211 206 214 187 174
Pressure Bar 13.5 14.5 14.2 14.8 12.9 12
Smoke No. 0 0 0 0 0 0
Flue Gas Temp ºC 380 380 260 260 260 260
CO2% 11.5 11.5 11.5 11.5 11.5 11.5
O2% 5.5 5.5 5.5 5.5 5.5 5.5
Flue Size mm 150 150 200 200 200 200
(Secondary) Ins 6 6 8 8 8 8
ANDREWS MODEL NO OFS25 OFS29 OFS63 OFS90 OFS108 OFS163

TECHNICAL DATA SECTION 2
5
Fle ible Hose
Connection Size G 0.25 0.25 0.25 0.25 0.25 0.25
Fuel Cons. Kero L/H 3.2 3.7 7.5 10.8 12.9 19.4
Fuel Cons. Kero GPH 0.70 0.81 1.65 2.4 2.8 4.3
Fuel Cons. Gas Oil L/H 3.1 3.5 7.2 10.3 12.4 18.6
Fuel Cons. Gas Oil GPH 0.68 0.77 1.60 2.3 2.7 4.1
Cold Inlet Top BSP 0.75 1 1.5
Cold Inlet Front BSP 1.5 1.5 1.5 1.5
Cold Inlet Rear BSP 1.5 1.5 2 2
Hot Outlet Top BSP 0.75 1 1.5
Hot Outlet Front BSP 1.5 1.5 1.5 1.5
Hot Outlet Rear BSP 1.5 1.5 2 2
Drain Port BSP 0.75 0.75 0.75 0.75 0.75 0.75
Ma Work Press PSI 150 150 150 150 150 150
Ma Work Press Bar 10.3 10.3 10.3 10.3 10.3 10.3
Ma Test Press PSI 300 300 300 300 300 300
Ma Test Press Bar 20.6 20.6 20.6 20.6 20.6 20.6
Weight Empty Kg 118.5 143.5 195 195 345 395
inc Burner
Weight Empty Lbs 260 315 429 429 761 871
inc Burner
Weight Full Kg 309 406 340 340 722 699
inc Burner
Weight Full Lbs 680 895 749 749 1591 1541
inc Burner
Shipping Height mm 1645 1740 1530 1530 2434 2134
Shipping Width mm 686 737 991 991 965 965
Shipping Depth mm 737 775 883 888 1073 1073
ANDREWS MODEL NO OFS25 OFS29 OFS63 OFS90 OFS108 OFS163

BURNER
ASSEMBLY
INSTALLATIONSECTION 3
THE LAW REQUIRES THAT INSTALLATION IS CARRIED OUT BY A
PROPERLY QUALIFIED PERSON
Installations must be carried out in accordance with current Building Regulations, The
Water Supply (Water Fittings) Regulations 1999 and any requirements of the Local
Authority, Water and Fire Authorities and the current British Standards and Codes of
Practice listed in Section 1.
The location selected for installation of the heater must allow the provision of a
satisfactory flue, adequate air supply, drain facilities and must be well illuminated.
A purpose built boiler room or compartment is strongly recommended. If a purpose built
boiler room is not available, measures should be taken to protect the heater from
damage and prevent any e traneous matter from being stored on or around the heater.
There must be easy access to the boiler room and heater at all times.
The heater must not be installed in a room which contains a bath or shower and must
not be installed in a bedroom or bedsitting room.
We recommend that adequate clearance is left around the heater for fitting and servicing
purposes with no obstruction at the front of the heater to allow easy access to the
burner. Service clearance above all the heaters e cept heater models OFS25 should be
1270mm for removal of the flue baffle. Heater model OFS25 flue baffle is hinged for low
ceiling removal. It is very important that heater models OFS108 & OFS163 have at least
600mm clearance at the rear for the installation and removal of the T/P valve if fitted.
We will supply magnesium articulated anodes part No.C333 as a service replacement for
all heater models this will be beneficial where lack of head room is a problem.
The floor on which the heater is installed must be non combustible, level and of sufficient
strength to withstand the heater weight when filled with water. Any combustible material
adjacent to the heater must be placed or shielded as to ensure that its temperature does
not e ceed 65oC (150oF).
Every Andrews oil fired water heater is supplied with a purpose matched burner
assembly. The burner is supplied complete with nozzle factory fitted for use with
kerosene-class C2only. If the appliance is to be used with gas oil-class D1the nozzle must
be changed before the burner is fitted to the water heater. The correct nozzle specified
for use with gas oil is supplied in the nozzle burner bo . It is the responsibility of the
installer to ensure that the correct nozzle is fitted to suit the fuel to be used with this
appliance.
INTRODUCTION
LOCATION
6

INSTALLATION SECTION 3
The burners are supplied complete with pre-wired control thermostat loom to a harness
plug with connects to the harness socket on the burner. The burners are supplied with
the flange fitted to the burner blast tube in the correct position. A gasket is also supplied
loose in the burner carton. See below for correct burner fitting to the heater.
Heater Models: OFS256, OFS63, OFS90 & OFS108
Locate the burner gasket on the two fi ing studs fitted on the heater mounting flange.
Push the burner into the heater combustion chamber and locate the burner flange on the
two fi ing studs fitted on the heater mounting flange and tighten the two fi ing bolts
supplied with the heater.
Heater Model: OFS29
Because of the reduced height of the combustion chamber entry position it is necessary
to locate the burner onto the heater as the diagram below shows. The pump has been
rotated thro 180oso that the solenoid is positioned above the vertical to ensure correct
operation.
The burner is fitted to the heater in the same way as heater models shown above.
Heater Model: OFS163
The burner used on this heater is considerably bigger and heavier therefore a different
fi ing method is required. (See below).
Locate the burner adaptor flange on the two fi ing studs fitted on the heater mounting
flange and tighten the two fi ing bolts supplied with the heater. Ne t locate both the
mating plate and the gasket onto the burner adaptor flange using the four locating studs.
Finally push the burner into the heater combustion chamber and located the burner
flange onto four locating studs and tighten the four fi ing bolts supplied.
BURNER
ASSEMBLY
7
Burner Flange
Heater
Mounting
Bracket
2 Locating Studs
Gasket
Burner Flange
Burner Flange
Heater
Mounting
Bracket
Heater
Mounting
Bracket
2 Locating Studs
2 Locating Studs
Gasket
Mating
Plate
4 Locating
Studs
Gasket Adaptor
Flange

INSTALLATIONSECTION 3
Detailed recommendations for flue installation are given in BS5410 PT 1 and
BS5410 PT 2
The Building Regulations allow the use of stainless steel under the term “Deemed to
Satisfy” but the minimum thickness must be 0.71mm (22swg).
We recommend that Selkirk SMW Flue System is used to the following specification:
Twin Wall, Insulated, Stainless Steel.
The flue route should be as vertical as possible avoiding sharp bends and horizontal runs.
It is recommended that each heater should be fitted with its own individual flue.
It is essential that separate flues are used for equipment using oil and equipment using
solid fuel.
A draught stabiliser is fitted to ensure burner flame stability.
If a common flue header is to be used see page 10.
Notes: 1. Draught stabiliser to be fitted to appliance (see page 9).
2. Male flue spigots to point downwards inside building to keep flue clean.
3. Use changeover section going through roof so that male spigots point
upwards outside the building to assist weatherproofing.
4. The flue should be kept a safe distance from any combustible material
especially when going through the roof (joists etc).
This must be at a height at least level with the highest point of the building roof and not
subject to down draught. Ideally the flue should terminate 1m higher than the highest
point of the roof, or at least 1m higher than the section of roof through which it projects.
FLUE SYSTEMS
INSTALLATION
OF FLUE
TERMINAL
LOCATION
8
Fig. 1

INSTALLATION SECTION 3
Assembly of Draught Stabiliser Approx Height
Flue kit 6”
E013
OFS25 = 1949mm
OFS29 = 2000mm
Tee with draught stabiliser
fitted
Spigot Adaptor
Heater Outlet Spigot
Crimped Adaptor
9
Fig. 2
Fig. 3
FLUE
SYSTEMS
Assembly of Draught Stabiliser Approx Height
Flue kit 8”
C916
OFS63 = 1739mm
OFS90 = 1739mm
OFS108 = 2307mm
OFS163 = 2307mm
Tee with draught stabiliser
fitted
Spigot Adaptor
Heater Outlet Spigot
Crimped Adaptor
The flue should provide a negative pressure at the base of the flue between -1.1mm
(0.03”w.g) and -2.00mm (0.06”w.g.). The flue route should be as vertical as possible.
A draught stabiliser is supplied with the heater (see Figs. 2 & 3).
Fit the flue tee c/w draught stabiliser to the outlet spigot of the water heater
(see Figs. 2 & 3).

INSTALLATIONSECTION 3
It is recommended that individual flues are used for each heater. However if a common
flue header is to be used the following guidelines must be used.
1. The cross - sectional area of the common flue header must be adequate for the
combined output of both heaters. Contact the flue manufacturer or flue e pert for
further information.
2. Each heater shall be fitted with draught stabiliser and shall have its own flue pipe to
the flue header.
3. The entry into the flue header shall be inclined towards the direction of the flue gases.
(See fig. 4).
4. The common flue header must have a vertical discharge. Its is preferable to run the
flue inside the building to avoid unnecessary heat losses and minimize the risk of
condensation within the flue.
COMMON FLUE
HEADER
10
Fig.
Draught
Stabiliser
Must have vertical flue
discharge
Draught
Stabiliser

INSTALLATION SECTION 3
AIR SUPPLY
AND
VENTILATION
11
The following notes are intended to give general guidance:
Where the heater is to be installed in a room or internal space the heater requires the
room or internal space containing it to have a permanent air vent. The vent must be
either direct to outside air or to an adjacent room or internal space which must itself have
a permanent vent of at least the same size direct to outside air. The minimum effective
area of the permanent air vent(s) required is as follows:
Air supply requirements for appliances up to 44kW
Where the appliance is to be installed in a room.
High level 550mm2per kW of appliance rating over 5kW.
Where the appliance is to be installed in a compartment. Air supply direct to outside.
High level 550mm2per kW of appliance rating over 5kW.
Low level 1100mm2per kW of appliance rating over 5kW.
Where the appliance is to be installed in a compartment. Air supply into a room.
High level 1100mm2per kW of appliance rating over 5kW.
Low level 1650mm2per kW of appliance rating over 5kW.
The room itself must have permanent ventilation direct to outside.
High level 550mm2per kW of appliance rating over 5kW.
Draught Stabilisers
When an appliance with draught stabiliser is fitted in a room, add 550mm2per kW to the
free air of the combustion air inlet. When an appliance with a draught stabiliser is fitted
in a compartment which is vented as above, no additional allowance is required.
Air supply requirements for appliances of 44kW and above
High level 0.1m2per 300kW of appliance rating.
Low level 0.2m2per 300kW of appliance rating.
Typical e ample for heater model OFS63
Heat input 71.8kW/300kW = 0.24kW
High level 0.24kW 0.1m2= 0.024m2
Low level 0.24kW 0.2m2= 0.048m2
Some halogen containing compounds can cause rapid corrosion of the Burner
and Storage Vessel if drawn into the combustion air.
Therefore, if heaters are to be installed in any of the following locations or in any
applications where the above compounds are present they should be sealed off from
atmospheres which may contain these compounds, and all ventilation air must be taken
completely from outside.
i) Hairdressing salons and adjoining rooms or basement.
ii) Establishments where dry-cleaning solutions are used.
iii) Industrial use near chemical de-greasing processes or where solvents are used or
stored.
iv) Installations where refrigerant gases are used or stored.
v) Environments with dust laden atmosphere.

INSTALLATIONSECTION 3
Where e treme conditions of water hardness e ist, scale can form in any water heating
equipment, especially when the heater is working under conditions of constant heavy
demand and at high temperatures.
Each water heater is fitted with one or more magnesium anode(s) which protect the tank
from corrosion caused by electrolytic action. Magnesium anodes are sacrificial in that
they erode as they protect. When the anode has eroded to less than 50% of it's original
diameter, it may not offer protection.The anodes should be inspected annually and
replaced as necessary. Frequency of anode replacement will vary dependent on water
quality.
Andrews Water Heaters offer Corre TM UP powered anodes as an alternative to the
standard magnesium anodes. These anodes do not need maintenance or replacement.
The potentiostat which regulates the current to the Corre TM anode, features an indicator
light which shows green to indicate correct function and red to indicate malfunction.
An additional Corre TM BEMS version is available, which provides a remote
warning signal.
These anodes are available as an optional e tra on all Andrews Water Heaters.
In hard water areas, scale formation can occur in hot water systems and hot water
heaters and the higher the temperature and volume of water used, the more problematic
the scale build-up can be. Water treatment is normally recommended when the hardness
reaches 100 - 150ppm (7 - 10 degrees Clark) and above. This problem can be minimised
by reducing the water temperature in the heater and by fitting suitable water pre-
treatment equipment.
When installing Andrews Water Heaters in hard water areas we would recommend
that a water treatment specialist is consulted
The following companies have supplied water treatment equipment in the UK for a
number of years to various establishments including those where Andrews water heaters
have been installed.
WATER
QUALITY AND
TREATMENT
12
WATER TECHNOLOGY LTD
Powke Lane Ind. Estate
Blackheath
Birmingham
B65 0AH
Contact
Gareth Morris
Tel: [phone]
Fa : 0121 561 4184
WATERMATIC
Reddicap Trading Estate
Sutton Coldfield
West Midlands
B75 7BY
Contact
Mike Potter
Tel: [phone]
Fa : 0121 311 1427

INSTALLATION SECTION 3
WATER
CONNECTIONS
13
Hydrojet System
Top Cold Inlet
Connection
The upper “jet
ports” direct the
flow outward to
begin the dynamic
mixing action.
The lower “jet
ports” direct the
flow inward to
increase the
turbulence.
Mini
Hydrojet Inlet Nipple
(Side Cold Inlet
Connection)
The heater is fitted with the Hydrojet Total Performance System incorporated in the cold
inlet dip tube. The tube is designed to increase turbulence and reduce sediment build up,
reduce thermal stacking and increase delivery.
All models now incorporate the
new Mini Hydrojet system on
cold inlet side connections.
This system ensures water is
directed onto the tank base
which minimises sediment build
up from day one of installation.
Heater Casing
Tank

The water heater must be supplied from a cold water feed cistern and the hot water
supply pipe must be fitted with an open vent pipe in accordance with BS 5546 and
BS 6644.
The Water Supply (Water Fittings) Regulations 1999 must be observed when installing
the system.
The cold water feed cistern must have an actual capacity greater than the hourly
recovery rate of the heater or heaters to which it is fitted, the minimum actual capacity
allowed for a feed cistern being 227 litres (50 gallons).
The actual cistern capacity is the capacity to the normal water line of the cistern.
All cisterns should be manufactured to the relevant British Standard.
The distance from the normal water line to the top of the cistern should comply with that
specified by the Water Authorities.
The cold water inlet and hot water outlet connection nipples are identified in Fig. 5.
Connect the cold water feed and hot water outlet to these nipples with union adaptors
for ease of servicing.
CAUTION!
DO NOT APPLY HEAT TO THESE NIPPLES IF MAKING CAPILLARY SOLDERED
JOINTS AS THEY ARE FITTED WITH PLASTIC INSERTS MAKE THE CAPILLARY
JOINTS TO THE PIPES BEFORE CONNECTING TO THE HEATER A DRAIN COCK IS
SUPPLIED WITH THE HEATER AND THIS SHOULD BE FITTED TO THE APPROPRIATE
BOSS AS SHOWN IN FIG 5
After installation of the water system, open the main water supply valve, flush the system
and fill the heater.
Open the hot taps to allow air to escape from the system.
When the water is free of air, close the taps and check for leaks at the gas control
thermostat, drain cock and the pipe connections at the top of the heater.
Typical water service layout for single heater vented system is shown in Fig 6
INSTALLATIONSECTION 3
WATER
CONNECTIONS
VENTED SYSTEMS
14

INSTALLATION SECTION 3
WATER
CONNECTIONS
15
Fig. 5
Fig. 6
All connection sizes are
shown on page 5
Front
Cold Inlet/Hot Outlet
OFS63
OFS90
OFS108
OFS163
Drain &
Secondary Return
Tapping
Front/Rear Entry Models
OFS63
OFS90
OFS108
OFS163
Optional Rear
Cold Inlet/Hot Outlet
OFS63
OFS90
OFS108
OFS163
T & P Valve Tapping
Cold Inlet/Hot Outlet
on models
OFS25
OFS29
OFS108
1.0m (40”)
Open Vent
Overflow
Top Entry Models
OFS25
OFS29
OFS108

INSTALLATIONSECTION 3
WATER
CONNECTIONS
UNVENTED
SYSTEMS
16
Unvented Systems should be fitted by an Approved Installer
When used in an unvented system, the Andrews water Heater will supply hot water at a
pressure of 3.5bar (51lbf/in2), provided that this pressure is available at the mains feed.
During conditions of no-flow, system pressure may rise to a ma imum of 6bar (87lbf/in2)
whilst the burner is operating. When testing the system, it is recommended that a
ma imum test pressure of 8.6bar (125 lbf/in2)is employed.
The heater can be used on unvented hot water storage systems, with the addition of an
Unvented Systems Kit, these are available from Andrews Water Heaters.
See Parts List Pages 40 - 42. The Wall mounting assembly is available as an optional e tra.
Item C5 must be fitted into C6 and fitted on the hot water outlet nipple located at the
rear of heater models OFS108 & OFS163.
When assembling items C1 and C2, ensure that the flow arrows marked on the
components are pointing in the direction of flow, i.e. towards the water heater.
The cold water for services may be drawn from the 22mm compression port on item
C1(a). The water pressure at this point will be similar to that available at the hot water
outlet of the water heater. If port (a) is not used, it should be sealed with the blanking
plug supplied.
C4
E pansion Vessel
C8
Wall bracket Assembly
C7
Hose Assembly
C6
2” Sq Tee
Cold Water
Inlet of
Water Heater
C2 Check Valve/
C3 E pansion Valve
(a)
Balance Cold Water
Take-off
(if required)
C1 Pressure Reducing
Valve / Strainer
Cold Water Inlet
NB Tees, elbows, stop valves and
pipework not supplied
OPTIONAL PARTS
C7 Tundish
C5
Temperature/
Pressure
Relief Valve

INSTALLATION SECTION 3
WATER
CONNECTIONS
17
Fig. 7.
If higher flow rates are required for the cold water services, a suitable tee fitting should
be fitted to the pipework, upstream of item C1.
The pipework fitted to the tundish outlet should be one size larger than the outlet pipe of
the safety device and should be terminated at a suitable drain (see Building Regulations
1991 Approved Document G3).
All fittings and materials must be suitable for use with drinking water and listed in the
current Water Research Centre "Materials and Fittings Directory".
Installation of unvented hot storage water systems must comply with Part G of
Schedule 1 of the Building Regulations 1991.
Typical water service layout for single heater unvented system is shown in Fig 7
Note: On heater models OFS108 & OFS163 the 2” T/P is located at the rear via a
2” Sq Tee.
Front Rear Entry
Models
OFS63
OFS90
OFS108
OFS163
Top Entry Models
OFS25
OFS29
OFS108
See Note

INSTALLATIONSECTION 3
ELECTRICAL
SUPPLY
18
Fig. 8.
2
M
L1
X2 V1
220/240V
50Hz
Time Clock and/or
Switch if fitted
220/240V
50Hz
Stat 2o (max)
Limit 93o C
Brown
Black
TLSC stat
TC2 stat
TLSC thermostat
N T1 T2 S3 B4
T
PE
X1 3 1 10 9 6 4 11 12
L1 N
AL H1
NL
L
L
N
N
N
N
T1 T2 S3 B4
Key to diagram
M Motor
PE Photocell
T Ignition transformer
V1 Oil Valve
X1 LMO/LOA 2.. control
X2 7 pole connector
H1 Remote burner run signal
AL Remote lockout signal
Wiring e ternal to the water heater must be installed in accordance with the I.E.E.
Regulations for the wiring of buildings and to any local regulations that may apply.
The heaters are designed to run off 220/240V 1 Ph 50 Hz supply and the fuse rating is
5 Amp See pages 4 & 5.
The method of connection to the mains electricity supply should facilitate complete
electrical isolation of the appliance preferably by use of an unswitched shuttered socket
outlet in conjunction with a fused three pin plug both complying with the requirements
of BS 1363/A.
Alternatively, a fused double pole switch of fused spur bo serving only the heater may
be used.
The point of connection to the mains should be readily accessible and adjacent to the
appliance.
Connect electrical supply to the harness plug/socket (see Fig. 8 Wiring Diagram) Mains
input cable should be connected to the mains supply as detailed above.