Nu-Way MGN 2800N Installation & Maintenance Manual

Nu-Way MGN 2800N Installation & Maintenance Manual Manual pdf 16 page image

MGN 2800N HP 15MODULATING OPERATIONNu-way MGN modulating burners are similar in construction and operation to the two stage, high/lowversions, 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 adjustablefuel throughput.The control output of the RWF40 is a potential free, 3-position switch, which is used to control the airdamper motor.When the boiler control calls for heat, the modulating servomotor will travel to the ‘high flame’ positionand interlock the control circuit. An air pre-purge will take place at this position for a pre-determinedperiod, at the end of which the burner sequence controller will stop until the modulating servo hastravelled to the ‘low flame’ position and interlocked the control circuit again. The sequence controlwill now recommence its operational cycle and the burner will light and remain at low flame until thehigh flame release signal is given by the sequence control. The modulating servo will now move tohigh flame and remain at this position until the desired boiler temperature/pressure is attained. Fromthis stage the modulating unit will commence to move towards the low flame position, but, dependingon the temperature/pressure, will stop in any intermediate position between low and high flame.Burner Control PanelThe control panel is fitted to the rear left hand side of the burner fan casing. The panel is of the fullyenclosed type containing the fan motor starter, relays, burner sequence control, RWF40 modulatingcontroller. Access to the panel is gained by loosening the two crosshead screws on the right handedge of the panel door. The door may then be swung open to the left and removed from its hingepins if required.Manual OperationCheck that the RWF 40 controller is configured correctly refer to page 20). Press and hold ‘EXIT’ keyuntil 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 ‘manualoperation’ indicator extinguishes to return to automatic mode.Temperature DetectorThe immersion temperature detector type QAE22 is used on all Hot Water boiler applications. Thedetector has a plastic casing to IP42 with a snap-on cover and an immersion stem. The connectionterminals 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 aflat 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 DetectorThe pressure sensor type QBE 2002 is used in all steam boiler applications. The sensor has acasing to IP65 and a 1.5 metre long, 3-core connecting cable. The mounting instructions suppliedwith the sensor are to be strictly adhered to.Gas ControlsThe gas train is of the same type and design as fitted to 2-stage high/low models.