BENSON HEATING LTD GUH100, User Instruction

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GUH RANGE PROPANE GAS FIRED UNIT HEATERS
Page 27 of 41
Injectors and Manifold
With the pilot bracket assembly removed and the burner tray either fully withdrawn or pulled forward by
at least 100mm the manifold and injectors can be removed by using the following procedure. Release the
union between the gas valve and the flange, remove the four flange fixing screws. Rotate the manifold so
that the injectors are aligned with the keyhole and carefully withdraw the manifold complete with the
injectors through the right hand side panel.
Check that the manifold is straight, the injectors are correctly aligned, and that they are clean, and that
there are no contaminates restricting the orifices, if necessary clean carefully with compressed air and or
lint free cloth and acetone.
Caution
The injector orifice is precision machined to fine tolerances, do not clean with hard sharp or abrasive
instruments. If the injectors have been removed from the manifold, when they are replaced, the copper
washers must be refitted, and care should be taken not to overtighten.
Ensure all joints are gas tight.
Fan and Motor
Check that the fan is secure and rotates freely without excessive play in the shaft. The fan blades and
motor should be cleaned using a soft brush. The fan and motor assembly can be removed from the heater
by first disconnecting the leads from the terminal block and by removing the strain relief bush. The four
screws securing the fan and motor assembly to the rear of the plenum can be removed, and the assembly
complete with guard can then be removed from the heater.
Fan and Limit Thermostats
Lower the right hand panel, on twin fan units the left hand side panel will also have to be lowered, so as
to gain access. Remove securing screw from cover, remove cover plate and disconnect the cables.
Remove the screws which secure the unit to the side of the heater and withdraw the thermostat complete
from the heater.
Check that the bi metal coil and its housing are secure clean as necessary with a soft brush .
Flue System
Check that the flue is in good condition, that it is adequately supported, that there are no blockages or
restrictions, and that there is a positive draw . Check that any joints are properly sealed preventing an
escape of products of combustion. Check condensate drain if fitted . Check for signs of water ingress and
any resultant damage.
Test
Test and re-commission as per sections 3.0 to 3.4 inclusive.
Automatic Controls
Automatic control is by way of a Satronic controller (with automatic gas valve replacing the manual
standing pilot valve) used in conjunction with a Satronic spark generator (which replaces the piezo
igniter as fitted to manual units) , giving a maximum pilot sequence of 15 seconds.
Flame supervision is via a flame sensor rod . instead of the thermocouple as fitted to the manual units.
Check the flame sensor rod for signs of pitting or corrosion, ensure that the ceramic insulation material is
not damaged or cracked. Check connections are secure.