MGN 2800N HP 16
SKP75 Combustion Chamber Impulse Connection
The impulse connection to the combustion chamber is not required in the majority of applications and
is therefore not supplied as part of the burner package. This is because the resistance of the
combustion chamber / flue assembly is assumed to remain constant and that the pressure within this
chamber will change in proportion to the burner gas and combustion air pressure. (As the burner
output changes).
If however, the pressure in the combustion chamber does not change in proportion to the burner gas
or air pressure, i.e. the plant is fitted with a flue gas fan, continuously operating flue gas damper, or
the chamber pressure changes from negative to positive whilst moving from Low to High flame, then
a compensating circuit is required. This means that the pressure in the combustion chamber must be
connected to the SKP75 so that the controller can automatically offset the pressure changes.
This compensating circuit should also be used if pressure shocks and vibrations, which adversely
affect the burner start-up, develop in the combustion chamber during the start-up phase.
Naturally, it must always be taken into consideration that the burner output decreases as the pressure
in the combustion chamber increases, and visa-versa.
Installation of the Combustion Chamber Impulse Pipe
A minimum inside pipe diameter of 8mm is recommended. The impulse pipe should be as short as
possible so as to allow the controller to respond quickly to sudden burner output changes. It must be
installed such that the gases will cool down in the area of the impulse pipe and condensing gases will
not enter the controller but run back into the combustion chamber. If necessary, a water separator
must be provided.
EMERGENCY INSTRUCTIONS
This product has been designed and constructed to meet all of the essential requirements of the GAS
APPLIANCE DIRECTIVE 90/396/EEC, and under normal circumstances should not give occasion to
any hazardous conditions. If such a condition should occur during commissioning or subsequent use
of this product, be it a fault of the burner, the appliance or of any instrument, machine or service in
the proximity of the burner, then the GAS and ELECTRICITY supply to the burner should be
IMMEDIATELY ISOLATED
until such time that the fault has been investigated and rectified.
BURNER OPERATING SEQUENCE
The operating sequence begins with an air pre-purge on full air, followed by start rate gas flame
which, when proved, allows the burner to operate on the High/Low/Off or Modulating principle. The
sequence is determined by the demand of the appliance control instruments.
Initial Burner Setting
Remove the cover from the air damper motor on the end of the air inlet casing. Check the cam
positions and adjust if necessary (refer to settings on pages 13 & 14.
Air/Gas Ratio Controller
Remove the small plate on top of the regulator and keep it in a safe place, Set the air/gas ratio at 0.8
on the visual scale by adjusting the screw (1) anticlockwise to increase, or clockwise to decrease.
Set the air/gas ratio on the visual scale, adjusting screw 92) to half a division on the ‘+’ side of ‘0’.
turn the adjusting screw clockwise to decrease, or anticlockwise to increase.
Start Rate Gas Governor
Remove the metal cap from the top and turn the adjusting screw until it is approximately halfway
between the maximum and minimum setting, clockwise to increase, and anticlockwise to decrease.
Never adjust to its maximum limit.
