BENSON GUHA, User Instructions

The recommended maximum and minimum 
mounting heights in metres are as follows 
 

MODEL     50      75       100       125       165          

Max           2.73   2.73    3.03      3.33      3.64 
Min            1.82   1.82    2.12      2.42      2.73  

 
MODEL   205     250       285     325   400    480

Max        

3.94   3.94   4.24     4.24   4.24     4.24         

Min         

2.73   2.73    2.73    2.73    2.73    2.73   

Any combustible material adjacent to the air 
heater and / or flue system must be so 
placed or shielded so as to ensure that its 
temperature does not exceed 65

0

 C 

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  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)  On specifically designed cantilever 
brackets mounted from a non-combustible 
wall. 
c)  On a level non-combustible surface 
capable of adequately supporting the weight 
of the unit and ancillary equipment . Under 
these circumstances approved mounting feet 
must be fitted. 
 

Note

GUH (C) Models cannot be supported on 
cantilever brackets. 
 

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,  

Ensure louvres are adjusted outwards 
and ensure blades are not resonating 

sources of cold air ingress , and obstructions. 
The air temperature rise on passing the heat 

exchanger is typically around 34

0 

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.  
Barrier rails should be provided to eliminate 
the risk of combustible materials being 
placed within 1 metre of the warm air outlet. 
 

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. 
 

The criteria necessary for establishing the 

minimum size of natural vents is detailed as 
follows; 

Position of vent        Area of vent 

direct to outside

 INLET  

Low level (<60kW)   9.0cm

2

 per kW 

Low level (>60kW)  540cm

2 

+ 4,5cm

2

 per kW

          of rated input per heater  

 
OUTLET 

High level (<60kW)   4.5cm

2

per kW  

High level (>60kW) 270cm

2

+ 2,25cm

2

 per kW 

of rated input per heater