Carrier WeatherMaster 48HC04 Series Installation Instructions Manual

Also see for WeatherMaster 48HC Series: Installation instructions

23LOW AMBIENT CONTROL (FACTORY OPTION)If the unit comes with Electro-Mechanical (EM) control, thenno adjustment is necessary.If the unit comes with PremierLink™ or RTU Open control op-tion, then refer to its installation control manual for details onadjusting “Cooling Lock-Out” setting and configure for thespecific job requirements.INTEGRATED GAS CONTROLLERThis unit contains an Integrated Gas Controller (IGC) board.The IGC control board uses a flue gas pressure switch thatsenses pressure drop in the heat exchanger due to the combus-tion inducer. See Fig. 43.Fig. 43 — Flue Gas Pressure Switch and PressureSense Tube (Typical Location)When the thermostat calls for heating, power is sent to W onthe Integrated Gas Controller (IGC) board. An LED (lightemitting diode) on the IGC board turns on and remains onduring normal operation. A check is made to ensure that therollout switch and limit switch are closed, and that the pressureswitch is open. If the check was successful, the induced draftmotor is energized. When the pressure in the heat exchanger islow enough to close the pressure switch, the ignition activationperiod begins. Once ignition occurs, the IGC board will contin-ue to monitor the condition of the rollout switch, the limitswitches, the pressure switch, and the flame sensor. Assumingthe unit is controlled through a room thermostat set for “fan au-to,” 45 seconds after ignition occurs, the indoor fan motor willenergize, and the outdoor air dampers will open to their mini-mum position. If the “over temperature limit” opens prior tothe start of the indoor fan blower, the IGC will shut down theburners, and the control will shorten the 45 second delay to5 seconds less than the time to tip the limit. For example, if thelimit trips at 37 seconds, the control will change the “fan on de-lay” from 45 seconds to 32 seconds. Once the “fan on delay”has been modified, it will not change back to 45 seconds unlesspower is reset to the control. On units with 2 stages of heat, W2closes and initiates power to the second stage of the main gasvalve when additional heat is required.When the thermostat is satisfied, W1 and W2 open and the gasvalve closes, interrupting the flow of gas to the main burners. Ifthe call for W1 lasted less than 1 minute, the heating cycle willnot terminate until 1 minute after W1 became active. If the unitis controlled through a room thermostat set for fan auto, the in-door fan motor will continue to operate for an additional45 seconds, then stop. An LED indicator is provided on theIGC to monitor operation.See Fig. 44 for IGC board component layout. Fig. 45 is a typi-cal IGC control wiring diagram. See Table 5 for IGC Boardfault indications.NOTE: If more than one error mode exists, they will be displayed on theLED in sequence. Limit switch is ignored in all modes except heatingmode.COMFORTLINK (FACTORY OPTION)For details on operating 48HC units equipped with the factoryinstalled ComfortLink option, refer to “Controls, Start-Up, Op-eration and Troubleshooting for 48/50HC 04-28 Single Pack-age Rooftop Unit with ComfortLink Controls.” See Fig. 46-50for wiring details.FLUE GASPRESSURESWITCHFLUE GASPRESSURESENSE TUBETable 5 — IGC Board FaultsLED INDICATION ERROR MODEON Normal operationOFF No power or hardware failure1 Flash Fan on delay modified2 Flashes Limit switch fault3 Flashes Flame sense fault4 Flashes Consecutive limit switch faults5 Flashes Ignition lockout fault6 Flashes Pressure switch fault7 Flashes Rollout switch fault8 Flashes Internal control fault