Jandy LG125 Installation And Operation Manual

Jandy LG125 Installation And Operation Manual Manual pdf 32 page image

Page 30Note: Pump must be running during thetroubleshooting procedure.These procedures require a voltmeter with aminimum 0-1000 mVDC range. Figure 24 shows thepilot generator and control circuits, and where to takemeasurements. Location numbers and letters in circleshave been added, and will be referenced in the follow-ing sections.As stated at the beginning of this manual, someof these procedures are hazardous. Only a qualifiedservice technician should service the heater.During the trouble shooting procedure, the filterpump must be on, the pilot on the heater must be lit,the ON/OFF switch on the heater must be in the ONposition and the control knob must be turned to themaximum setting so that there is a call for heat. Werecommend turning the gas valve control knob to the"PILOT" position to prevent the main burners fromfiring throughout the procedure. Before starting theprocedure, be sure that the pilot has been lit for at least2 minutes and that the pilot generator (thermopile) ispositioned correctly within the flame of the pilot.The pilot generator also operates the pilot coil ofthe gas valve, allowing gas to flow to the pilot whenthe gas valve knob is released from the pilot lightingposition (see Section 7.3 "Lighting and ShutdownProcedures"). If the pilot will not stay lit when the gasvalve knob is released, check the pilot generatoroutput as described in Section 10.4.2 and replace ifnecessary. If the pilot generator output is sufficient,then check the gas valve as outlined in Section 10.4.1.10.4.1 Gas ValveThe gas valve consists of two separate internaloperating valves. The main valve supplies gas to themain burners for heater operation. The pilot valvesupplies gas to the pilot when the pilot generatoractivates the pilot coil.If the pilot will not stay lit after following thelighting instructions in Section 7.3, check for thefollowing:• Pilot generator output• Correct type of gas supplied• Correct gas supply pressure• Air in the gas line• Pilot coil wire connections clean and tightIf the pilot will not stay lit after checking theitems listed above, the pilot coil may be causing thefault. Replace the gas valve.If the main burners will not light after followingthe lighting instructions in Section 7.3, check thevoltage reading between the PP terminal on the gasvalve (test point 1) and the TH terminal on the gasvalve (test point 17). If the meter shows less than220mVDC then there is a problem with the pilotgenerator, the sensors in the safety loop or the controlpanel. Follow the trouble shooting procedure asoutlined in sections 10.4.2 through 10.4.7.If the meter shows more than 220mVDC at testpoint 17, then check for the following:• Correct type of gas supplied• Correct gas supply pressure• Correct gas manifold pressure• Correct orifice size• Air in the gas lineIf the main burners will not stay lit after check-ing the items listed above, the gas valve may becausing the fault. Replace the gas valve.10.4.2 Pilot GeneratorThe pilot generator generates a 700-750mVDCsignal when heated by the pilot flame. When the pilotgenerator is connected to the heater's control compo-nents, there will be some voltage drop in the circuit sothat the measured voltage will be less than 750mVDC.But the measured voltage should never be below500mVDC when the ON/OFF switch is in the "OFF"position or 220mVDC when the ON/OFF switch is inthe "ON" position.With the pilot generator connected to the gasvalve and the ON/OFF switch in the OFF position,place the red lead of the voltmeter on the PP terminal(test point 1) of the gas valve. Place the black lead ofthe meter on the PP/TH terminal (test point 2) of thegas valve. The meter should show a minimum of500mVDC. If the meter show less than 500mV, checkfor partial shorts, loose or corroded connections orpartially broken wires between the pilot generator andthe gas valve.If the wires and connections are sound, check thepilot generator output. Disconnect the pilot generatorfrom the gas valve. The pilot will go out. Light thepilot while pressing down on the gas valve controlknob. Continue holding the knob for at least oneminute. Immediately measure the voltage between thetwo wires of the pilot generator. If the meter does notshow at least 700mV, replace the pilot generator.10.4.3 Fusible LinkCheck the voltage going to the safety circuit. Besure that the pilot generator is correctly wired to thegas valve, the pilot is light and the control knob on thegas valve is in the "PILOT" position. Leave the redvoltmeter lead in place at test point 1. Touch theblack lead of the meter to the terminal of the fusiblelink where the white wire from the gas valve isconnected (test point 3).