BENSON OUHA 100 Guide

BENSON OIL UNIT HEATER
1
BENSON
OIL UNIT HEATER2
RANGE
I N S T A L L A T I O N C O M M I S S I O N I N G
S E R V I C I N G
U S E R I N S T R U C T I O N S
Issue 3
October 2007
PART NO 33-65-190
THIS MANUAL SHOULD BE LEFT WITH THE END USER .
TO ENSURE SERVICE AND MAINTENANCE INFORMATION IS AVAILABLE ON SITE
BENSON

BENSON OIL UNIT HEATER
2
Section Contents Page No
1.0 Compliance Notices 3
1.1 Certificates of Conformity 4
1.2 General product Information 4
1.3 General Requirements 4
1.4 Delivery & Pre-installation Checks 4
1.5 Warranty 5
2.0 Installation 6
2.1 Installation Clearances and Mounting Heights 6
2.2 Heater Mounting 7
2.3 Warm Air Circulation 7
2.4 Air Supply 7
3.0 Fuel Installation 9
4.0 Flue Installation 11
5.0 Electrical Installation 12
6.0 Commissioning 12
6.1 Ignition Sequence 13
7.0 Servicing 15
7.1 Servicing Procedure 15
8.0 Fault Diagnosis 16
9.0 Wiring Diagrams 19
10.0 Technical Data 27
11.0 Parts Listing 28
12.0 Dimensions 29

BENSON OIL UNIT HEATER
3
1.0 Compliance notices
The following information is relevant to the
Benson Oil Fired Unit Heater range (OUHA)
and (OUHC) manufactured by Benson
These heaters are manufactured within a
strictly controlled quality environment within
the parameters of
ISO 9001:2000.
The Benson OUHA (C) Heater range has
been tested and assessed for compliance
with the following European Directives.
Machinery Directive (89/392/EEC)
Low Voltage Directive (73/23/EEC & 93/68/
EEC)
Electromagnetic Compatibility Directive
(89/336/EEC & 91/31/EEC)
Product Liability Directive (65/374/EEC)
The manufacturer has taken reasonable and
practical steps to ensure that Benson Unit
Heaters are safe and without risk when
properly used. These heaters should
therefore only be used in the manner and
purpose for which they were intended, and in
accordance with the recommendations
detailed herewith.
The heaters have been designed,
manufactured, assembled, inspected, and
tested, with safety and quality in mind, there
are certain basic precautions which the
installer and user should be aware of, and
they are strongly advised to read the
appropriate sections of the information pack
accompanying the heater, prior to installation
or use.
Benson Heating supports all new products
being supplied to their customers with a
comprehensive information pack; this clearly
defines mandatory instructions for the safe
installation, use, and maintenance, of the
appliance (s).
Where proprietary items are incorporated
into Benson Heating products, detailed
information and instructions are also
provided as part of the information pack.
It is the responsibility of the installer, owner,
user, or hirer, of such products supplied by
Benson Heating, to ensure that they are
familiar with the appropriate information
manuals, supplied by the manufacturer, and
that they are suitably aware of the purpose of
the manuals and the safety instructions. In
addition, operators must be suitably trained
in the use of the appliance so as to ensure its
continued safe and efficient use.
Benson Heating has a commitment to
continuous improvement, and therefore
reserves the right to amend or change the
specification of the Unit Heater range subject
to compliance with the appropriate
European, National, and Local Regulations.
Contained within the text of the manual, the
words 'Caution' and 'Warning' are used to
highlight certain points.
Caution is used when failure to follow or
implement the instruction (s) can lead to
premature failure or damage to the heater or
its component parts.
Warning is used when failure to heed or
implement the instruction (s) can lead to not
only component damage, but also to a
hazardous situation being created where
there is a risk of personal injury.
The Benson OUHA ( C ) Range conform to
the following harmonized standards;
BS EN ISO 12100-1: 2003 &
BS EN ISO 12100-2: 2003
Safety of Machinery - Basic Concepts,
General Principles for Design
Technical principles and specifications
Part 1 & Part 2
BS EN 60204 - Part 1 : 1993
Safety of Machinery - Electrical Equipment
for Machines
Specification for General Requirements
BS EN 60335 - Part 1 : 1988
Safety of Household and Similar Electrical
Appliances General Requirements
BS EN 55014 - 1993
Limits and methods of
measurement of radio disturbance
characteristics of electrical motor-operated
and thermal appliances for household and

BENSON OIL UNIT HEATER
4
similar purposes, electrical tools and similar
electric apparatus
BS EN 50165 - 1997 Electrical
Equipment of non-electric heating appliances
for household and similar purposes, safety
requirements
1.1 Certificates of conformity
Certificates are available from the Quality
Control Department at Benson Heating
1.2 General product information
The unit heater models have an output range
from 100,000 Btu to 350,000 Btu.
Each heater must be connected to its own
individual open flue.
Each heater is fitted with a forced draught
burner which has been test fired and pre-set
prior to despatch. The safety functions of the
burner are by way of a fully sequential
control box fitted to the burner.
Note
Neither asbestos nor soft soldered joints are
used in the construction or manufacture of
the Benson range of Unit Heaters. The
materials selected for use can withstand the
mechanical, chemical, and thermal stresses
which they will be subject to during foreseen
normal use when installed in accordance
with the manufacturers recommendations.
1.3 General requirements
Caution
Ensure that the fuel supply is in accordance
with the manufacturer's recommendations
and is as stated on the appliance data plate.
Installation, commissioning, and servicing
must only be carried out by appropriately
qualified and competent persons.
Warning
Unauthorised modifications to the appliance,
or departure from the manufacturers
guidance on intended use, or, installation
contrary to the manufacturers
recommendations may constitute a hazard.
Note
To ignore the warning and caution notices,
and to ignore the advice from the
manufacturer on installation, commissioning,
servicing, or use, will jeopardise any
applicable warranty, moreover, such a
situation could also compromise the safe and
efficient running of the appliance itself, and
thereby constitute a hazard. The installation
of the appliance must meet all the relevant
European, National, and Local Regulation
criteria.
Prior to installation the following points
should be considered;
a) The position of the heater for the efficient
distribution and circulation of warm air
b) The position of the heater relative to the
route of the flue
c) The position of the heater relative to the
supply of fuel
d) The position of the heater relative to the
electrical services, and if appropriate, any
additional controls.
e) The position of the heater relative to the
supply of fresh air
f) The position of the heater relative to
service and maintenance requirements
Caution
The heater must not be installed within an
area where the conditions are unsuitable,
e.g. where the atmosphere is highly
corrosive, has a high degree of salinity, or
where high wind velocities may affect burner
operation. Suitable protection should be
provided for the appliance when it is located
in a position where it may be susceptible to
external mechanical damage from; for
example, fork lift trucks, overhead cranes
etc.
1.4 Delivery and pre-installation
checks
The heater is supplied wrapped in heavy
duty protective polythene. On receipt of the
heater, the following checks should be
carried out;

BENSON OIL UNIT HEATER
5
(a Model is as per order
(b That it is undamaged
(c That it is suitable for the fuel supply
(d That it is suitable for the electrical supply
If any of the points are not satisfied then
contact should be made with the sales office
at Benson Heating as soon as possible by
telephoning 01547 528534. in the case of
claims for damage, this must be reported in
writing within 24 hours of delivery, in order to
comply with insurance criteria.
THE WARRANTY REGISTRATION CARD
SUPPLIED WITH THE HEATER MUST BE
COMPLETED AND RETURNED IN THE
PRE PAID ENVELOPE TO BENSON
HEATING ON COMPLETION OF
COMMISSIONING
Warranty claims made without this
condition being fulfilled will not be
processed
1.5 Warranty
The heater is supplied with a 2 year warranty
comprising of the following :-
1 year parts and labour
1 year parts only.
In addition to this there is also a 10 year time
related warranty on the combustion chamber.
The warranty commences from the date of
dispatch from the manufacturer, and is
subject to the terms detailed within the
Benson Heating 'conditions of business'.
The warranty may be invalidated if -
a) The warranty registration and
commissioning card has not been completed
and returned to Benson Heating
b) The installation is not in accordance with
the general requirements of this manual
c) The flue arrangement and air supply for
the heater are not in accordance with the
manufacturers recommendations, codes of
practice, or similar standards
d) Air flow through the heater is not in
accordance with the manufacturers technical
specifications
e) Internal wiring on the heater has been
tampered with or Unauthorised service/
repairs undertaken
f) The main electrical supply input to the
heater has been interrupted during the
heating mode
g) The heater has been subject to and
affected by the ingress of water in any form
h) The heater is not operated at the rating’s
laid down in the manufacturers technical
specifications
i) The heater has not been operated or used
within the normal scope of its intended
application
j) The manufacturer's recommended
minimum service requirements have not
been complied with
All warranty claims must contain the
following information to enable
processing to take place;
(1) Heater model
(2) Heater serial number
(3) Order reference/date of order, together
with full installation details (name and
address)
(4) Details or symptoms of fault
(5) Installers name and address.
Faulty parts must be returned to the Benson
Heating Spares Department, the address of
which is provided at the back of this manual.
Any such parts will undergo inspection to
verify the claim. Replacement parts supplied
prior to this may be charged, and a credit
supplied upon subsequent validation of the
warranty claim.
Consumable items are specifically not
included within the scope of the warranty.
Notification is required immediately a fault is
suspected.
The manufacturer will not accept
responsibility for any additional damage that
has been caused, expense incurred, or
consequential loss resulting from any failure
of the heater (s)

BENSON OIL UNIT HEATER
6
2.0 Installation
Note
It is a requirement that only qualified and
competent personnel may undertake
installation commissioning and servicing of
OUHA ( C ) Range Heaters.
Warning
All of the basic criteria must be satisfied prior
to commencing installation and
commissioning, additionally, the Unit Heater
must be positioned and installed so as to
comply with all the relevant standards and
guide lines as well as meeting national and
local fire regulations and insurance criteria,
especially if it is proposed that the heater is
to be installed within a special risk area (e.g.
proximity to where petrol engined vehicles
are stored or parked, where cellulose
spraying takes place, where woodworking
machinery is operated, etc,).
Indirect fired heaters must not be located in
hazardous areas, however, it is permissible
for the heater to supply air to such areas.
The heater must not be installed within an
environment where there is a high
concentration of chlorides, fluorides, salts, or
other aggressive or volatile chemicals /
compounds.
Nor should the heater be positioned where
the burner could be adversely affected by
high winds or draughts.
The heater must be installed so that it is
level. Supports for the heater must be
sufficiently robust to withstand the weight of
the heater and any ancillary equipment. Any
combustible material adjacent to the heater
or flue system must be so placed or shielded
so that its surface temperature does not
exceed 65C
The location chosen for the heater must
allow for the fitting of an effective flue
system.
The location must also allow for adequate
clearance for the air supply, return air
circulation, oil supply, electrical supply, whilst
also providing good and safe working
access.
Suspended free blowing Unit Heaters are at
their most effective when located as close to
the working area as possible. However care
should be exercised to avoid directing the
discharged air directly onto the occupants of
the area to be heated.
Where the passage of cold air causes
problems (e.g by entrances, loading bays
etc) it is considered favourable if the heater
is positioned so as to discharge towards or
across the cold air source from a distance
from 1.5m - 6m dependent upon the size of
the entrance and the air throw characteristics
of the heater. On exposed walls heaters
should be positioned so as to discharge
towards, or along the length of the exposed
wall. In areas where it is proposed that more
than one heater is to be installed, a general
scheme of circulation should be drawn up
and maintained, thereby offering the best
heat distribution.
Air pressure within the area heated and the
outside air pressure must remain the same,
factors influencing this would be the
presence of extraction systems, ventilation
systems, and various types of process plant.
OUHA 200-350 models can be installed to
allow the fans to work in opposite directions .
This enables the heater to be installed
centrally in the area to be heated and allows
warm air to be discharged to both the front
and rear of the heater
2.1 Installation Mounting Heights
OUHA models
The Heater must be installed within the
mounting heights indicated below in metres
Model OUHA 100 140 200
Min 2.0 2.0 2.4
Max 2.7 2.7 3.0
Model OUHA 250 300 350
Min 2.4 2.4 2.4
Max 3.5 3.5 3.5

BENSON OIL UNIT HEATER
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The following clearances in mms must be
observed
*when suspended
2.2 Heater Mounting
The heater and flue must be adequately
supported by one of the following methods ;
a) Suspension by steel drop rods or straps
from the M10 fixing points located on top of
the heater
These must be of sufficient strength to
safely carry the weight of the unit and
ancillary equipment. The straps may only
drop vertically to eyebolts, if used; I.E. They
must not be joined to the eyebolt at an angle
to the vertical, and eyebolts if used should be
of an approved type.
b) OUH heaters can be mounted on
specifically designed cantilever wall or
vertical stanchion brackets which locate
directly to the four M10 fixings on the heater
casing.
Alternatively OUHA or OUHC units can be
mounted on cantilever type wall brackets
however consideration must be given to
ensure that the bracket is large enough to
support the heater whilst providing the
necessary clearances
In either case the installer should ensure that
the wall wall fixings or other support medium
is capable of supporting the weight
c ) On a level non-combustible surface
capable of adequately supporting the weight
of the unit and ancillary equipment .
2.3 Warm Air Circulation
The air heater should be positioned to enable
maximum circulation of discharged warm air
within the area to be heated, whilst taking
account of personnel within the area,
sources of cold air ingress , and obstructions.
Ensure louvres are adjusted outwards
and ensure blades are not resonating
The air temperature rise on passing the heat
exchanger is typically around 340 C
A full and unobstructed return air path to the
air heater must be provided
(see 2.4 Air Supply).
Where the heater is positioned to deliver
blown air through an opening in a wall, return
air intakes should be located so that they
cannot become blocked. Similarly these
intakes must be positioned so as not to draw
in odours, fumes, hazardous vapours or
particles.
2.4 Air Supply
Provision must be made for the existence of
an air supply in order to satisfy both
combustion and ventilation criteria.
It is a requirement that the area where the air
heater is located must have a permanent air
vent of negligible resistance direct to the
outside air.
Such air vents must be positioned so as not
to become blocked or flooded, nor should
they be placed so as to introduce
undesirable matter (e.g. flammable, volatile,
or aggressive chemicals/compounds or
potentially hazardous or harmful substances)
either direct from the outside, or through their
proximity to an adjacent extraction system.
Note
It is strongly recommended that BS 6230 :
2005 is referred to for further information
concerning ventilation requirements
Where mechanical ventilation is used it is a
requirement that the inlet is of the
mechanical type, and the outlet is either
mechanical or natural.
Model 100 140 200 250 300 350
Above 300 300 300 300 300 300
Below * 300 300 300 300 300 300
R Hand 680 680 680 680 810 810
L Hand 250 250 250 250 250 250
Rear Axial 400 500 560 560 560 560
Rear Cent 200 200 200 200 200 200

BENSON OIL UNIT HEATER
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2.4.1 Heaters installed within the
heated space
Where heaters are installed within the space
to be heated (e.g. not a plant room separate
room, or compartment then Combustion and
general ventilation is not required if
The combustion air intake is ducted to
atmosphere (i.e. Room Sealed Appliance)
OR
The design air change rate of the building is
more than 0.5 air changes per hour and the
volume of the space is greater than 4.7m3
per kilowatt of the total rated heat input
Combustion and general ventilation
is required if
The appliance is not provided with
combustion ductwork e.g. the air for
combustion is taken from the space being
heated
And
The building design air change rate is less
than 0.5 air changes per hour and the
volume of the space is greater than 4.7m3
per kilowatt then low level ventilation is
required
Where combustion air ventilation is required
as dictated by the previous criteria then that
ventilation can be via permanent ventilation
openings / grilles situated at low level (I.e.
below the flue takeoff spigot ) and with the
free area of such grilles as :-
For heaters with a rated input of less than
60 kW — 4.5 cm2 per kW of heat input
For heaters with a rated input of more than
60 kW — 270 cm2 plus for each kW of rated
input over the 60 kW threshold an additional
4.5 cm2
Or by mechanical input (not extract)
ventilation in association with either
mechanical or natural extract and with a
ventilation flow rate of 1.08m3/h per kW of
total rated input
Where mechanical extract is used to
complement the above then the extract rate
shall be 2.16m3/h per kW of rated heat input
Mechanical ventilation systems where fitted
must be provided with safety interlocks to
prevent heater operation in the event of
airflow failure.
2.4.2
Heaters installed Within a Plant Room
Where the heater is installed within a plant
room ,separate room or compartment then
combustion and general ventilation
is always required
Where the combustion air intake is ducted to
atmosphere (i.e. Room Sealed Appliances)
Then that ventilation can be via a permanent
ventilation / grille situated at both low level
(inlet) and high level (outlet) and with the free
area of such grilles as :-
Low level (Inlet)
For heaters with a rated input of less than
60 kW — 4.5 cm2 per kW of heat input
For heaters with a rated input of more than
60 kW — 270 cm2 plus for each kW of rated
input over the 60 kW threshold an additional
2.25 cm2
High Level (Outlet)
For heaters with a rated input of less than
60 kW — 4.5 cm2 per kW of heat input
For heaters with a rated input of more than
60 kW — 270 cm2 plus for each kW of rated
input over the 60 kW threshold an additional
2.25 cm2
Alternatively mechanical input (not extract)
ventilation may be used in association with
either mechanical or natural extract and with
a ventilation flow rate of 2.16m3/h per kW of
total rated input.
Mechanical ventilation systems where fitted
must be provided with safety interlocks to
prevent heater operation in case of air flow
failure
Where the combustion air intake is not
ducted to atmosphere heater installed in
flue only configuration then ventilation can
be via a permanent ventilation opening /
grille situated at both Low level (Inlet) and
high Level (Outlet) and with the free area of
such grilles as :-
Low level (Inlet)
For heaters with a rated input of less than
60 kW — 9.0 cm2 per kW of heat input

BENSON OIL UNIT HEATER
9
For heaters with a rated input of more than
60 kW — 540 cm2 plus for each kW of rated
input over the 60 kW threshold an additional
4.5 cm2
High Level (Outlet)
For heaters with a rated input of less than
60 kW — 4.5 cm2 per kW of heat input
For heaters with a rated input of more than
60 kW — 270 cm2 plus for each kW of rated
input over the 60 kW threshold an additional
2.25 cm2
Alternatively mechanical input (not extract)
ventilation may be used in association with
either mechanical or natural extract , and
with a ventilation flow rate of 3.24m3/h per
kW of total rated input
Where mechanical extract is used to
complement the above then the extract rate
shall be 2.06m3/h per kW of rated heat input
Mechanical ventilation systems where fitted
must be provided with safety interlocks to
prevent heater operation in case of air flow
failure
2.4.3 Ventilation Openings and Grilles
Ventilation openings and grilles must
communicate directly with the outside air, be
of negligible resistance and shall be sited so
that they cannot easily be blocked of flooded
3.0 Fuel
The heaters are set for single pipe operation
The bypass plug is provided separate with
the burner for conversion to two pipe see
Riello manual
Three methods of fuel supply can be used to
supply fuel to the heaters
(a) Two pipe system
(b) Gravity Feed
(c) Pressurised ring main
Two pipe system
This is used where the oil storage tank is
lower than the pump.
Access for the fuel feed to the burner should
be via a suitable tapping made in the top of
the tank, and the fuel feed pipe should
extend to not less than 100mm above the
bottom of the tank. A non return valve with a
metal to metal seat should be fitted,
especially if the return pipe work is
terminated at a level above the draw off tube.
The non- return valve must be removable for
service and maintenance purposes, and the
return pipe from the pump must therefore be
extended down into the tank to the same
level as the suction pipe. The use of a Fuel
Deaerator in this type of installation will
reduce the need of a return pipe back to the
tank
Caution
The Deareator must be fitted the burner
side of the inlet fuel filter
Maximum lift should not exceed 3.5 metres,
and the vacuum should not exceed 0.4 bar.
Each heater must have a separate fuel
supply.
Note
It is strongly recommended that the separate
manual concerning the operational details of
the burner supplied with the heater as part of
the information package is studied prior to
installation
Gravity feed system
For installations where the oil tank is 200mm
or more above the level of the fuel pump the
principle of gravity feed may be used.
The draw off point for the supply to the
burner must not be positioned any lower than
100mm above the bottom of the tank.
Where a return valve is fitted this must be
tamper proof to prevent inadvertent
operation.
Each heater must have a separate fuel
supply
Pressurised ring main system
This system is used to supply a number of
units from a common storage tank.
A booster pump is used to provide the
pressure to push the oil around the ring main
and back to the tank. Pressure reducing
valves should be fitted on the delivery pipe to
each heater to ensure that the delivery
pressure at the heater is less than 6 psi.

BENSON OIL UNIT HEATER
10
BURNER
H
m
0
0.5
1.0
1.5
2.0
3.0
3.5
I.D.
8mm
35.0
30.0
25.0
20.0
15.0
8.0
6.0
I.D.
10mm
100.0
100.0
100.0
90.0
70.0
30.0
20.0
Maximum
4 metres
H
H
Priming the pump: Start the burner and await priming.
Should lock-out occur prior to arrival of the fuel, wait at least 20 seconds
before repeating the operation.
This solution, however, is less safe than the previous one, due to
possibility of leakage of the valve.
Should, however, the return line terminate over the fuel level,
a non return valve is essential.
The return line should terminate within the oil tank at the same level
as the suction line; in this case a non return valve is not required.
The pump suction should not exceed a maximum of 4 metres.
Beyond this limit gas is released from the oil.
BURNER
H
The pump suction must not exceed 4 metres;
beyond this value the pump becomes noisy.
The return valve must terminate at the same level
as the foot valve, otherwise the pump may
become air locked.
1 GATE VALVE
2 IN-LINE FILTER
3 PUMP
4 RELIEF VALVE
5 PRESSURE GAUGE
6 PRESSURE REDUCING VALVE
7 RETURN TO TANK
1 2
3
4 5
66
7
Typical Fuel layout

BENSON OIL UNIT HEATER
11
Caution
The internal by-pass plug must be removed
from the burner pump when used in a
pressurised ring main application .
3.1 Pipe work and fittings
Caution
Galvanised pipe work and fittings must not be
used.
All joints must be sealed properly, if necessary
using PTFE tape or other approved sealing
media. The pipe work must be effectively
sealed so as to prevent the ingress of air. It is
advisable to check all pipe work prior to
installation to ensure that there is no loose
debris or scale present.
Black iron pipes can be hammered to assist in
the removal of these contaminants
A Capillary type fire valve is supplied loose
with the heater for installation by the fitter on
site.
The capillary should be inserted through the
grommet at the rear of the heater burner
compartment and secured via the P clips
mounted above the burner.
The fire valve can now be secured to the oil
installation pipe work .
Note
Any waste oil or sludge must be disposed
of correctly.
Never dispose of it by dumping or tipping
it down drains or into watercourses where
ground water can become polluted and
environmental damage caused.
4.0 Flue system
Warning
It is essential that the products of combustion
are flued to the outside of the building.
Each heater must have its own separate flue,
with a flue diameter of not less than is
detailed in this manual. The minimum vertical
length of flue must not be less than 1m. The
number of bends should be kept to a
minimum. It is strongly advised that BS 5854;
1980, and BS 5440; parts 1 and 2, are used
as consultative documents when considering
flue requirements.
Care should be taken to ensure that the flue
terminal is not situated in a high-pressure
area, the proximity of buildings and other
obstacles which will influence this must be
taken into account, preferably at the design
stage.
Provision must be made for the disconnection
of the flue for inspection and service
requirements, and it is strongly advised that
where bends are fitted inspection covers are
included.
Flue should be supported at intervals not
exceeding 1.8 mtrs
The materials from which the flue is
constructed must be non-combustible,
resistant to internal and external corrosion,
and be capable of withstanding the stresses
and loadings associated with normal use.
When designing the flue system the
prevention of the formation and entrapment of
condensation must be a key consideration.
Twin wall or insulated systems are
recommended, as they tend to inhibit the
formation of condensates.
Where condensation is unavoidable traps
should be included to encourage the
condensates to flow freely to a point from
which they may be released, preferably into a
gully. The condensate pipe from the flue to the
disposal point must be made from corrosion
resistant pipe of not less than the internal
diameter of the drain pipe.
If the flue passes through a wall, ceiling, or
roof made from combustible material then it
has to be sleeved so as to provide a minimum
of a 25mm void between the exterior of the
flue and the internal wall of the sleeve. The
maximum permitted temperature of any
adjacent combustible material is 65o C.
The position of the flue and its terminal should
be such that it does not impair the combustion
process. It should terminate in an exposed
position so as to allow the escape and
dissipation of flue gases without risk of their
re-entering the property through windows,
ventilation ports, etc.
The flue should extend to at least 1m above
the height of any object within 3.5m of the
terminal.

BENSON OIL UNIT HEATER
12
Flue terminals should be fitted on all flues, the
terminal must be of the approved type, and
have outlet grilles on all sides giving a total
free area of at least double that of the flue.
Caution
It is imperative that the flue should be properly
sealed where it passes through the roof, this
can best be achieved by using the approved
method of roof flashing plate and cravat.
Note
It should be noted that claims made under
warranty and attributed to the ingress of water
may not be considered especially if an
approved method of sealing has not been
used, or if the design of the flue has not made
provision for possible condensation problems.
5.0 Electrical supply
Wiring external to the unit heater must be
installed in accordance with any Local,
National, and European regulations, as well
as meeting the appropriate requirements of
IEE regulations.
The means of connection to the main
electrical supply must allow for complete
electrical isolation of the heater, the supply
should only be used to serve the heater itself
and no other plant or equipment. The position
of the isolation switch must be such that it is
adjacent to the heater and easily accessible at
all times. In addition, the isolator itself must
have a contact separation of not less than
3mm. (as per BS5991 clause 20.2).
All connections must be checked to ensure
that they are secure, and free from corrosion.
Terminals and connections should also be
checked to ensure that no stray strands are
bridging terminals.
Electrical continuity should also be checked
Cables, conduit, and fittings that are used to
make the connection between the isolator and
the heater must conform to the appropriate
IEE regulations.
All heaters are supplied fused and pre-wired,
all must be earthed.
The Control fuse ratings are detailed on the
appliance data plate.
Warning
Ensure that the electric and oil supplies are
turned off before any electrical work is carried
out on the heater. Ensure that wiring cannot
make contact with any surfaces liable to be
subject to high temperatures or where the
insulation of the wiring could be impaired as a
result of such contact.
Final connections for any additional external
controls must be completed on site, and must
be carried out according to IEE regulations.
Separate user information is provided for the
time control unit and the burner, and forms
part of the product information pack which
accompanies every heater when despatched.
Caution
The main electrical supply must not be
switched off or disconnected as a method for
stopping the heater ,the exception to this is in
an emergency,
or during servicing when the controls must be
completed on site and the heat exchanger has
been allowed to cool sufficiently to prevent
any damage from occurring , Claims will not
be considered if they have resulted from
incorrect wiring or the incorrect use of the
heater
Always ensure that the appropriate
personal protective equipment is used.
6.0 Commissioning – Pre test
Check to ensure electrical safety, and inspect
and check the oil installation, testing for leaks.
(a) Ensure that the electrical supply is turned
off.
(b) Ensure that the oil supply is turned off.
(c) Check that all panels and fasteners are
secure and in place.
(d) Check that the heater is installed correctly
and that the support is adequate.
(e) Ensure that warm air delivery outlets are
open.
(f) Check that fan is free to rotate and the
guards are in place.
(g) Ensure that the flue is secure, adequately
supported, and that the various joints are
properly sealed.

BENSON OIL UNIT HEATER
13
(h) Check that there is provision for flue gas
sampling and that this sample point can be
plugged and sealed after commissioning.
(i) Remove cover from fan limit stat check
that fan limit stat settings have not been
disturbed and are as follows
Fan Off 30º C
Fan On 50º C
Overheat Limit is preset at 100º C
check that overheat reset button is reset
(j) Ensure that the burner is securely
attached to the heater.
(k) Test for electrical earth continuity
between the heater, oil pipe work, and mains
supply.
(l) Turn on main electrical supply, select the
following switch settings on CP2
On/Standby - Standby
Heat/Ventilation - Ventilation
The fan will start enabling fan direction etc to
be verified. Reset on/standby switch to off
position.
If CP4 supplied press Fan and enter to
operate fan, Repeat operation to switch off
fan
(m) Set CP4 controller as per customer
requirements
(n) Set override to on (1) and put in override
time and enter
6.1 Commissioning - Ignition
It is strongly recommended that the separate
manual concerning the operational details of
the burner supplied with the heater as part of
the information package is studied prior to
commissioning.
Time intervals within the ignition sequence
will vary slightly from one model to another.
Warning
Do not proceed with commissioning unless
all the criteria detailed have been satisfied.
(a) Ensure that the electrical supply is turned
off.
(b) Ensure that the oil supply is turned off.
(c) If CP2 supplied Select the following
switch settings on the control for the heater
On/Standby - Standby
Heat/Ventilation - Heat
(d) Turn on main electrical supply.
(e) Select 'on' position for heater on/standby
switch.
(f) Check for the following burner sequence
Interval Operation
5s Combustion air damper
actuated burner fan motor
initiates purge cycle
15s Solenoid valve opens
ignition transformer
provides spark for burner
ignition
-------------- EITHER-------------------
15s Ignition failure caused by
fuel starvation resulting in
burner lockout/shutdown
(g) Set heater on/standby switch to standby
position
(h) Attach oil manifold bleed screw and
gauge)
(i) Open oil supply valves and bleed air from
pipe work and adjust burner oil pressure as
per detailed in burner manual
(j) Repeat steps c,e,f.
----------------OR--------------
15s Burner ignition - flame
detection
20s Burner ignition cycle
complete

BENSON OIL UNIT HEATER
14
Warning
If burner ignition is not satisfactorily
accomplished, commissioning must not
proceed until the reason or fault has been
identified and rectified, if necessary by
reference to the separate burner information
supplied with heater.
(k) Repeat steps 4.2 c,a,
(l) Repeat steps 4.2 d,e,f, allowing the heater
to reach thermal equilibrium.
(m) Adjust room thermostat to its highest
setting, and allow the heater to continue to fire
(n) Gradually reduce the temperature setting
on the room thermostat until the burner shuts
down, (@ < ambient and then gradually
increase the temperature setting on the .
thermostat until heat is called for,
(@ > ambient) and the burner automatically
re-fires.
(o) Re-set time clock to a minimum off period,
checking that the burner shuts down, and then
automatically re-lights once the minimum off
period has elapsed (Separate information on
the time clock is contained within the
information package supplied with the heater)
(p) Check limit stat by isolating fan control
circuit
The time between the fan stopping and burner
shut down should be noted,
If the time interval between fan stop and
burner shut down is greater than 2 minutes
Check settings on fan and limit stat are
correct,
(q) Undertake flue gas analysis using
approved and calibrated analysing equipment
recording data on the commissioning card, ie,
CO, CO2, net and gross flue temperatures.
Record burner oil pump pressure, ambient
temperature, barometric pressure, and smoke
reading (0 - 1 Baccarach scale).
Note
The burner air and oil pressure settings should
be only very finely adjusted to achieve a CO2
reading of 12.5% (+/- 0.5%).
All Unit Heaters are test fired and pre-
commissioned as part of the manufacturing
process, if however, during on site
commissioning the data are found to be not in
accordance with the manufacturers data, then
the following action is recommended.
* Re-check all readings and calculations.
* Adjust burner as per manufacturers
instructions.
* Consult Benson Heating Technical
Department.
(r) Complete commissioning card and provide
operating instructions for the user, high-light
the fact that the manufacturer recommends
that in the interests of safety and efficiency the
heater is serviced on a regular basis only by
qualified and competent persons.
The completed commissioning card must be
returned to Benson Heating Service
Department immediately after the satisfactory
completion of commissioning, failure to do so
can invalidate any subsequent warranty claim.
(s) Set all controls to the requirements of the
user.
(t) Set override on CP4 to Off
Final adjustment for the direction of the air
flow from the heater should be made,
Caution
On ducted applications it is necessary that the
system is balanced in order to \the efficiency
of the heater and the air distribution and
delivery system Failure to balance the system
can result in fan motor overloading and
premature component failure, it can also result
in an inefficient heating/ventilation system.
(a) Check that the amount of fan produced air
volume is in accordance with the heater
specification, if the volume is too great the fan
can be overloaded.
Ensure that the running current is as per that
stated on the heater data plate.
Alternatively, the static pressure should be
measured at the start of the ductwork to
confirm that it is within the permissible
tolerance.

BENSON OIL UNIT HEATER
15
(b) If the current drawn is greater than the
stated running current, in most probability this
will be caused by insufficient static
pressure within the ductwork, in which case
system resistance should be increased
through the introduction of a damper placed as
close to the start of the ductwork as possible,
thereby resulting in a reduction in drawn
current.
The damper should be adjusted until the
current is in accordance with that stated on the
data plate.
(c) If the current drawn is too low the duct
outlet grilles will require opening to reduce
static pressure and increase air volume, if this
is not the case overheat cut outs can be
caused
7.0 Servicing
Warning
Servicing must be carried out on a regular
basis, the maximum interval between services
being 1 year.
In certain applications the frequency of
servicing will have to be increased , this to a
large extent is governed by the working
environment.
It is a requirement that only suitably qualified
and competent persons are allowed to
undertake servicing.
Before any maintenance or servicing work
is carried out the heater must be shut
down and allowed to cool, and have the oil
and electric supplies to it turned off at the
supply valve and isolator
respectively.
Caution
Certain component parts are factory sealed
and are designed so as to be tamper proof.
Usually such items do not require servicing,
and therefore should not be tampered with.
Failure to comply with this can invalidate any
warranty, and can also lead to premature
failure. The following parts fall within this
category: room thermostat, time clock, frost
thermostat, controller, and fan motor
assembly .
Additionally, the fan and limit stat has been
factory set, and must not be re-set without
formal consent from the manufacturer.
Reference should be made to the separate
information covering the operational details of
the burner and remote controllers.
Only approved spare/replacement parts can
be fitted, failure to comply with this can
compromise the safe and efficient running of
the heater, and can also invalidate any
warranty claim
7.1 Planned Servicing
In order to maintain the efficient operation of
the heater it is recommended that the
following planned servicing and preventative
maintenance programme is adopted by the
user.
Quarterly Inspection
(a) Visual inspection of the burner
(b) Clean and check spark electrode
(c) Clean and check photocell
(d) Check overheat safety is operational
Bi-Annual Inspection
(a) As per quarterly inspection, plus...
(b) Combustion check
(c) Smoke test
Annual Inspection
(a) As per half year inspection, plus...
(b) Heat exchanger and cleaning
(c) Electrical connections
(d) Main fan motor assembly
(e) Oil supply including filter
(f) Burner
(g) Air delivery system
(h) Flue
Turbulator positions 100-250
Turbulator positions 300-350

BENSON OIL UNIT HEATER
16
8.0 Fault Finding
Burner
fails to
Run
No Power
No
Demand
Check Isolator Check Fuses
Check
Controls
Burner Lockout
Fan / Limit
Thermostat
Room
Thermostat
Timer
Heat / Ventilate
Switch
On / Off Switch
Burner
starts
Ignition
sequence
but fails to
light and
Lockout
Occurs
Fuel Feed
Incorrect
Check that the
Oil Pressure is
correct
Check that Head
of Gravity is
Sufficient
Check that the
suction Lift is not
too great (two
pipe system)
Check that the
Bypass Plug is
Present
Fuel / Air
Problem
Check Burner
Air Setting
Bleed System
Air in System
Restricted Fuel
Feed
No Spark
Check
Electrode
Possible Fuel
Contamination
Check Valves,
Fuel Feed, Filter
Nozzle for
Blockages or
Restrictions
Check Control

BENSON OIL UNIT HEATER
17
Burner gives a
sparky flame
Too Much Air
Air / Fuel Mix Ratio
Incorrect
Fuel Feed
Restricted
Adjust Air
Damper
Check for Air in
Fuel Line
Check Fuel
Pressure
Check Nozzle
Check Filter
Check Fuel
Line
s
Check Valves
Burner
gives a
smokey
flame
Poor
Combustion
Insufficient
Combustion Air
Inadequate Flue
Draught
Check Oil
Pressure
Check Air Damper
Check Nozzles
Check if Correctly
fitted
Check if Correct
size
Check if Damaged
or Worn
Check Flue

BENSON OIL UNIT HEATER
18
Fan and
Lim it
regularl
y go
to lockout
W arm Air
Short Circuit
Adjust W arm Air
Discharge and
Cool Air Inlet
Accordingly
Check for High
Resistance
Check Outlet
Grilles are not
shut or
restricted
Insufficient Air
Flow over the
Heat Exchanger
Check Fan and
Motor
Assembly
Check for no
Loose
Contacts
Limit Control
Incorrectly Set Reset to 100C
Check Fan and
Motor are
Secure
Check that
Fan is not
Blocked or
Check that
Impellor is not
Slipping
Burner
giving
excessive
noise
Check Burner
Fan Motor
Suction Lift to
Great
Check Burner
Oil Pump
Foreign Matter in
Fan
Worn / Dry
Bearing
Insecure Burner
Fan
Water in Fuel
Line
Fuel Feed
Restriction

BENSON OIL UNIT HEATER
19
9.0 Wiring Diagram OUHA 100 - OUHA 140 ON / OFF 33-65-100

BENSON OIL UNIT HEATER
20
Wiring Diagram OUHA 200 - OUHA 350 ON / OFF 33-65-106