BENSON MH300, User Instructions

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have resulted from incorrect wiring or the incorrect
use of the heater.
2.9 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 : 1991 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.
2.9.1 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 4.7m
3
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 4.7m
3
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 cm
2
per kW of heat input
For heaters with a rated input of more than 60 kW
— 270 cm
2
plus for each kW of rated input over the
60 kW threshold an additional 4.5 cm
2
Or by mechanical input (
not extract ) ventilation in
association with either mechanical or natural extract
and with a ventilation flow rate of 1.08m
3
/h per kW
of total rated input
Where mechanical extract is used to complement
the above then the extract rate shall be 2.16m
3
/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.
2.9.2
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 cm
2
per kW of heat input
For heaters with a rated input of more than 60 kW
— 270 cm
2
plus for each kW of rated input over the
60 kW threshold an additional 2.25 cm
2