BENSON MH300, User Instructions

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In ducted applications the ductwork must be
designed so as to give a static pressure within the
limits stated in section 8 of this manual.
It should be noted that if the static pressure is too
high, nuisance shut-down will occur when the
heater goes out on the overheat limit thermostat, if
the static pressure is too low, then damage can be
caused to the fan motor.
Warm air outlets on ducted applications must be
such that they cannot be closed or become
blocked, which again would lead to an increase in
static pressure and nuisance shut-down.
The outlets must not be sited so that warm air can
be discharged onto combustible materials, if
necessary, guard rails should be used to ensure
that effected areas are kept clear.
Return air intakes must not be located so that
potentially harmful or hazardous contaminated air
can be drawn into the system.
2.11 Flue system
Warning
Each heater must have its own separate flue, with a
flue diameter of not less than
225mm The minimum
vertical length of flue must not be less than 1m.
The flue should rise vertically, and 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.
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.
3.0 Installation
3.1 Electrical Installation/Connection
Benson MH 300 cabinet heaters are
415V 50Hz 3PH NEUTRAL & EARTH
It is recommended that reference is made to the
wiring diagrams contained within section 7 of this
manual prior to installation or connection to the
supply.
The electrical supply must be as specified and
suitable for the heater, and must be run within
conduit to a point adjacent to the heater, and be
terminated to provide an isolation point that will
prevent remote or inadvertent activation.
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.
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 dispatched.
Warning
Always isolate from mains electrical supply before
commencing work on the heater.
Always ensure that the appropriate personal
protective equipment is used.
3.2 Air Distribution Installation
The materials selected must be of low heat
capacity, and it is preferable that all warm air
ductwork is thermally insulated.
Where ducting may be subject to deterioration from
exposure to moisture or high humidity material
selection and insulation are prime considerations.
Joints and seams must be airtight and fastened
securely and designed to remain so, even when
operating at high temperatures.
Adequate support must be designed into the layout
of the ductwork to ensure that the integrity of the
seams and joints is maintained.
The support must be independent and separate