Carrier 48FK Controls Operation And Troubleshooting

Carrier 48FK Controls Operation And Troubleshooting Manual pdf 34 page image

Table 18 — Sensor Resistance ValuesTEMP(F)RESISTANCE(Ohms)TEMP(F)RESISTANCE(Ohms)TEMP(F)RESISTANCE(Ohms)−60 362,640 45 11,396 150 1,020−55 297,140 50 9,950 155 929−50 245,245 55 8,709 160 844−45 202,841 60 7,642 165 768−40 168,250 65 6,749 170 699−35 139,960 70 5,944 175 640−30 116,820 75 5,249 180 585−25 98,420 80 4,644 185 535−20 82,665 85 4,134 190 490−15 69,685 90 3,671 195 449−10 58,915 95 3,265 200 414−5 50,284 100 2,913 205 3800 42,765 105 2,600 210 3505 36,475 110 2,336 215 32310 31,216 115 2,092 220 29915 26,786 120 1,879 225 27620 23,164 125 1,689 230 25525 19,978 130 1,527 235 23630 17,276 135 1,377 240 21935 14,980 140 1,24440 13,085 145 1,1263. Quick Test Steps 2.4.-3.3. — Output Relay CheckThese quick test steps allow microprocessor to checkoutput signals from relay boards in unit control system. In ad-dition, operation of all the condenser fans, compres-sors, and economizer (if equipped) are checked at each step.Normal display for Steps 2.4. through 2.8. is 1. In Steps2.9. through 3.2., each compressor and unloader is startedand allowed to run for approximately 10 seconds. At start-up, a 0 will appear on the display followed by a 1 (Steps2.9. and 3.2.) in a few seconds. Steps 3.0. and 3.1. willalways be 0 since there are unloaders, and Step 3.3. willalways be zero since it is not used.At end of the 10-second time period, a 0 will return to thedisplay board indicating that test step has been success-fully completed (Steps 2.9. and 3.2.). The 1 indicates thatwas tested.Fan and compressor operating sequence for quick testSteps 2.4. through 3.3. are shown in Table 17.If the quick test steps do not operate as described above,a defect exists in one or more of the following: relay beingtested, electronic control, or unit wiring. Determine problemand correct.OPERATING INFORMATIONDigital Display — The VAV control system uses a 2-digitLED display located on the display board to display opera-tional information and diagnostic codes.CODES 0 THROUGH 8, CAPACITY STEPS — These codesindicate the number of cooling stages active at the time thedisplay button is pressed. The highest code indicated on thedisplay will be 6 for the 034,038 and 048-088 units, 4 for the044 units, and 8 for the 104 units.Capacity steps are directly related to pin terminal connec-tor J6 output. At step zero, the unit has no mechanical cool-ing on, and the economizer may or may not be operating(depending on the outdoor air conditions). Once a coolingload is detected (T1 thermistor reads above the supply-airset point), the economizer will begin modulating to meet theload if the outdoor enthalpy is good. As long as the outdoor-air enthalpy is acceptable, no mechanical cooling will takeplace until the economizer dampers are fully open. The restof the steps and the operational sequence vary due to thenumber of compressors and unloaders. Refer to OperatingSequence section on page 35 for the unit stages of operation.CODES 20 THROUGH 30 AND 88, OPERATIONAL STA-TUS — These codes indicate special operational modes, suchas initialization, morning warm-up, temperature reset, de-mand limit, or an internal failure of the board. Codes 23-25and 27-29 are not used on these units.Initialization — When the control is turned on, the display20shows a for approximately 2 minutes to indicate that thecontrol is in the initialization mode. During this time, theeconomizer dampers open and close to determine the resis-tance range of the economizer position potentiometer (P2)for full economizer operation. The processor loads the nec-essary constants for proper unit operation and checks the ther-mistors and other potentiometers for their values and valid-ity. After the initialization period, the display screen goesblank until the display button is pressed. If the display but-ton is pressed during the 2-minute initialization period, thecontrol goes into the Quick Test mode.Temperature Reset — If the unit is equipped with the ac-cessory temperature reset package, and DIP switch 2 is inthe ON position, the unit will reset the supply-air tempera-ture to a calculated value when necessary. When this con-21dition is in effect, a will appear in the display.Demand Limit — If the unit is equipped with the accessorydemand limit control module or the field-supplied, single-step demand limit potentiometer, and DIP switch 5 is in theON position, the unit will limit the capacity stages to a pre-22determined value. When this condition is in effect, a willappear in the display.Morning Warm-Up —If the morning warm-up heat routineis enabled using DIP switch 4, and conditions of the occu-pied space warrant, the unit will begin the morning warm-up26routine. When this condition is in effect, a will appearin the display.Internal Failure — If the unit detects an internal fault (suchas a time measurement failure), or detects an incorrect volt-30age on an input channel, a will be displayed, and theunit will shut down.Quick Test — If the display button is pressed during theinitialization period of the processor, the unit will run its self-88diagnostic routine. When this is in effect, an will appearin the display screen.CODES 51 THROUGH 87, DIAGNOSTIC INFORMA-TION — These codes indicate diagnostic information whenthere is a unit problem such as a faulty thermistor, potenti-ometer, or compressor fault. Refer to Diagnostic Codes sec-tion on page 45 for more details. Codes 53, 54, 57, 58, 61,62, 65-69, 73, 74, and 77-80 are not used on these units.Under normal operation, only the stage number is dis-played when the display button is pressed. If a status or over-load code is displayed, the display will rotate every 2 sec-onds and will display up to 3 codes. Overload informationtakes priority over all other codes. The codes are stored inthe microprocessor as long as the board remains energized.34