MGN 2800N HP 15
MODULATING
OPERATION
Nu-way MGN modulating burners are similar in construction and operation to the two stage, high/low
versions, utilising identical fan blower, combustion head and gas train components.
The standard method of operation is based on the Landis & Staefa RWF40 Universal Controller,
which provides temperature or pressure control of modulating burners, with continuously adjustable
fuel throughput.
The control output of the RWF40 is a potential free, 3-position switch, which is used to control the air
damper motor.
When the boiler control calls for heat, the modulating servomotor will travel to the ‘high flame’ position
and interlock the control circuit. An air pre-purge will take place at this position for a pre-determined
period, at the end of which the burner sequence controller will stop until the modulating servo has
travelled to the ‘low flame’ position and interlocked the control circuit again. The sequence control
will now recommence its operational cycle and the burner will light and remain at low flame until the
high flame release signal is given by the sequence control. The modulating servo will now move to
high flame and remain at this position until the desired boiler temperature/pressure is attained. From
this stage the modulating unit will commence to move towards the low flame position, but, depending
on the temperature/pressure, will stop in any intermediate position between low and high flame.
Burner Control Panel
The control panel is fitted to the rear left hand side of the burner fan casing. The panel is of the fully
enclosed type containing the fan motor starter, relays, burner sequence control, RWF40 modulating
controller. Access to the panel is gained by loosening the two crosshead screws on the right hand
edge of the panel door. The door may then be swung open to the left and removed from its hinge
pins if required.
Manual Operation
Check that the RWF 40 controller is configured correctly refer to page 20). Press and hold ‘EXIT’ key
until the ‘manual operation’ indicator illuminates. The modulating motor can now be inched using the
‘increase and reduce’ buttons on the controller face. Press and hold the ‘EXIT’ key until the ‘manual
operation’ indicator extinguishes to return to automatic mode.
Temperature Detector
The immersion temperature detector type QAE22 is used on all Hot Water boiler applications. The
detector has a plastic casing to IP42 with a snap-on cover and an immersion stem. The connection
terminals can be accessed by removing the cover.
Cable entry is made via a cable entry gland, page 10. In all applications an immersion pocket with a
flat seal is supplied.
The detector should be installed in an elbow such that the pocket points against the direction of flow.
With all detector versions, the immersion length must be a minimum of 60mm.
Pressure Detector
The pressure sensor type QBE 2002 is used in all steam boiler applications. The sensor has a
casing to IP65 and a 1.5 metre long, 3-core connecting cable. The mounting instructions supplied
with the sensor are to be strictly adhered to.
Gas Controls
The gas train is of the same type and design as fitted to 2-stage high/low models.
