Carrier 48HG014 Controls Operation And Troubleshooting

Contents

Carrier 48HG014 Controls Operation And Troubleshooting Manual pdf 29 page image

29The burners will ignite within 5 seconds. If the burners donot light, there is a 22-second delay before another 5-secondattempt. If the burners still do not light, this sequence is repeat-ed for 15 minutes. After the 15 minutes have elapsed, if theburners still have not ignited, heating is locked out. The controlwill reset when the request for heat is temporarily removed.When ignition occurs, the IGC board will continue to moni-tor the condition of the rollout switch, limit switches, HallEffect sensor, and the flame sensor. If the unit is controlledthrough a room thermostat set for fan auto, 45 seconds afterignition occurs the indoor-fan motor will be energized (and theoutdoor-air dampers will open to their minimum position). Iffor some reason the overtemperature limit opens prior to thestart of the indoor fan blower, on the next attempt, the45-second delay will be shortened to 5 seconds less than thetime from initiation of heat to when the limit tripped. Gas willnot be interrupted to the burners and heating will continue.Once modified, the fan on delay will not change back to45 seconds unless power is reset to the control.When additional heat is required and the MBB senses thatW2 is On, the MBB closes the HTR.2 relay and sends power tothe second stage of the main gas valve. If the thermostatremoves the call for W2, the unit will turn off HTR.2 (mini-mum on-time 2 minutes [MRT.H], minimum off-time 2 min-utes [MOT.H]). If W1 is satisfied, the main base board willopen HTR.1 (minimum on-time 2 minutes and minimumoff-time 2 minutes), interrupting the flow of gas to the mainburners. The IGC also has a minimum on-time of 1 minute.Therefore, in modes such as Service Test where the long mini-mum on-time and off-times are not enforced, the one minuteminimum on-time for the IGC will still be followed. If the unitis controlled through a room thermostat set for fan auto, theindoor-fan motor will continue to operate for an additional45 seconds then stop. If the overtemperature limit opens afterthe indoor motor is stopped within 10 minutes of W becominginactive, on the next cycle the time will be extended by 15 sec-onds. The maximum delay is 3 minutes. Once modified, thefan off delay will not change back to 45 seconds unless poweris reset to the control.An LED indicator is provided on the IGC to monitor opera-tion. The IGC is located by removing the heat section sidepanel. See Fig. 4. During normal operation, the LED is contin-uously on. See Table 26 for error codes.If the user has selected Adaptive (see Cooling section) forits thermostat mode, the algorithm will follow the configurabledelays for adding and removing stages. When adding addition-al heat stages, the delay is measured from when the last stagewas added (H.INC). When removing stages, the delay is mea-sured from when the last stage was removed (H.DEC). There-fore, if W1 and W2 turn on simultaneously, the second stagewill turn on after a H.INC delay.NOTE: If the mode is not Adaptive, then there are no delaysfor adding and removing stages.SPACE SENSOR CONTROL — During Space Sensor con-trol, the electronic control uses information from the space sen-sor to determine the number of heat stages. Once the number ofstages needed for heating is determined, this information ispassed to the IGC by turning on either HTR.1 or HTR.1 andHTR.2. See Thermostat Control section for description of IGCoperation.NOTE: The jumper wire in the installer’s packer must be con-nected between R and W1 when using a T55, T56, or T58device. See Fig. 1 and 2.During Space Sensor control, two methods are used to addstages of heat and two methods are used to subtract stages ofheat. The first method of adding and subtracting stages causesthe unit to operate around its configured steady state number ofstages. For example, if the correct number of stages is between0 and 1, this method will cause the first stage to cycle. If thecorrect number of stages is between 1 and 2, this method willcause the second stage to cycle.The second method of adding and subtracting stages causesthe unit to find the steady state number of stages. The firstmethod will not add or remove a stage of heating unless thecurrent Heat Demand (set point – SPT), corrected by the rate ofchange in the Heat Demand, is greater than Heat DemandPositive Level (HT.PD) or less than Heat Demand NegativeLevel (HT.ND). The correction term is the Heat Thermal Lag(H.LAG) multiplied by the change in the Heat Demand. There-fore, if the corrected current demand is in between –1.0 and1.0, the number of stages will not change no matter how longthere has been a positive error. Because the corrected heatdemand incorporates the rate of change in heat demand, it willhave a tendency to add or remove stages earlier when thetemperature in the space is moving very rapidly, therebyreducing overshoot.Because the first method of adding or removing a stage ofheat is used to operate around the steady number of stages, thismethod can not be used to add an additional stage until a stagehas been subtracted. Likewise, if this method has subtracted astage, it can not be used again to subtract another stage until astage has been added.The second method will add additional stages of heat when-ever Heat Demand is greater than HT.PD + 0.5 and the heat de-mand is increasing at rate greater than 0.3 F per min. Addition-al stages of heat will be removed whenever the Heat Demand isless than HT.ND – 0.5 and the heat demand is decreasing atrate less than 0.3 F per min.Table 26 — IGC LED IndicationsLEGENDNOTES:1. There is a 3-second pause between error code displays.2. If more than one error code exists, all applicable error codes willbe displayed in numerical sequence.3. Error codes on the IGC will be lost if power to the unit isinterrupted.Heating (50HG Units)NOTE: THE 50HG units have 2 stages of heat.For 50HG units, the heat type will automatically be set to 2for electric heat units if the electric heat was installed in the fac-tory (HT.TY). If electric heat is being installed in the field, theuser must change HT.TY from 0 to 2. If a 15 kW heater is in-stalled, N.HTR must be changed from 2 to 1.Heat will not operate if the outdoor temperature is greaterthan the heat lockout temperature (HT.LO).THERMOSTAT CONTROL — The first stage of electricheat (HTR.1) will follow the W1 input and the second stage(HTR.2) of heat will follow the W2 input. During auto fan, theindoor fan will follow the HTR.1 output. During continuousfan, the indoor fan will follow the G input.ERROR CODE LED INDICATIONNormal Operation OnHardware Failure OffFan On/Off Delay Modified 1 FlashLimit Switch Fault 2 FlashesFlame Sense Fault 3 FlashesFive Consecutive Limit Switch Faults 4 FlashesIgnition Lockout Fault 5 FlashesInducer Switch Fault 6 FlashesRollout Switch Fault 7 FlashesInternal Control Fault 8 FlashesSoftware Lockout 9 FlashesIGC — Integrated Gas Unit ControllerLED — Light-Emitting Diode