Carrier 48EN Installation, Operation And Maintenance Instructions

Contents

Carrier 48EN Installation, Operation And Maintenance Instructions Manual pdf 9 page image

Packaged rooftop unitswith integrated gas burner9CO2 CONTROLOFFSETCONTROLCALIBRATEDVENTURIGAS INLETTO THE BURNERPRESSURE COCKGAS INLETmodels 150/200CALIBRATEDVENTURICO2 CONTROLPRESSURE COCKGAS INLETOFFSETCONTROLGAS INLETTO THE BURNERmodels 032/0927. GAS BURNERFlueAirGasEVPEV2 EV1Condensationdrainfor mod.150/200 onlyOperating principleConnection / disconnection of the burnerWhen heating is required (A), the burner remote control starts the workingcycle of the modulation board which activates the flame control device.This device starts up the burner combustion air fan (A), thus starting anair current in the combustion chamber for a preset period of time.When this phase has been completed the ignition cycle begins: theelectromagnetic valve EV1 opens at the same time as the EVP valve (B),supplying the pilot burner. When the device detects the pilot flame it willopen the main gas valve EV2 (C) to supply the main burner.The pilot and main burner will work together for a short period of time.After this, the modulation board will close the electromagnetic valveEVP (D) and disconnect the pilot burner.The one electrode only guarantees the detection of the flame for thepilot and main burner.pilot burnerBurner groupEVPEV1EV2detectionelectrodestart-upelectrodenozzleControl deviceOn/off signalBurner fanEVP - pilot light flameEV1 - 1st electromagnetic valve gasEV2 - 2nd electromagnetic valve gasA B C D E FOperation of the air-gas premixThe air and the gas mix inside the vanes of the motor fan assembly.The air inlet is achieved via a calibrated Venturi pipe from which thegas is taken in.The air/gas pressure ratio is 1:1 and can be adjusted by turning theoffset screw in the gas valve. The burner is supplied with the offset setand the screw sealed.The burner can also be regulated by adjusting the screw located abovethe Venturi which establishes the maximum air flow rate value and, assuch, determines the carbon dioxide content in the condensates. Thisscrew is factory-set and must not be touched, although it is not sealedthus allowing a changeover to another type of gas (before doing so thismust be consulted).The modulation board installed in the burner regulates the fan speed (indirect current) in accordance with the requirements of thermal capacity.The gas flow rate changes at the same time as the variation in the motorspeed. The minimum and maximum values for the motor speed arestipulated on the plate and cannot be changed.The ignition cycle connects the burner to half capacity (approx. 70% ofits maximum thermal capacity). Two minutes after starting the burnerreduces its capacity to the minimum and as from this moment starts tohave modulating control (0-10Vdc) in accordance with the installationrequirements.