Carrier 58MCA Installation, Start-up, And Operating Instructions Manual

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Carrier 58MCA Installation, Start-up, And Operating Instructions Manual Manual pdf 42 page image

Disconnect 115-v electrical power before changing speed tap.Failure to follow this warning could result in personal injury.4. To change blower motor speed selections for heating mode,remove blower motor lead from control center HEAT termi-nal. (See Fig. 25.) Select desired blower motor speed leadfrom 1 of the other terminals and relocate it to HEAT terminal.See Table 12 for lead color identification. Reconnect originallead on SPARE terminal.Follow this same procedure for proper selection of COOLspeed selection.BLOWER OFF DELAY (HEAT MODE)The main blower off time delay period is factory-set at 135 sec andcan be adjusted. See figure 25.SET THERMOSTAT HEAT ANTICIPATORThermostat heat anticipator must be set to match amp draw ofcomponents in R-W circuit. Accurate amp draw measurements canbe obtained at thermostat subbase terminals R and W.Fig. 46 illustrates an easy method of obtaining these measure-ments. Amp reading should be taken after blower motor hasstarted. See thermostat manufacturer’s instructions for adjustingheat anticipator and for varying heating cycle length.CHECK SAFETY CONTROLSStep 1—Check Primary Limit ControlThis control shuts off combustion control system and energizesair-circulating blower motor if furnace overheats. Recommendedmethod of checking this limit control is to gradually block offreturn air after furnace has been operating for a period of at least5 minutes. As soon as limit control has shut off burners, return-airopening should be unblocked to permit normal air circulation. Byusing this method to check limit control, it can be established thatlimit is functioning properly and operates if there is a restrictedreturn-air supply or motor failure. If limit control does not functionduring this test, cause must be determined and corrected.Step 2—Check Pressure SwitchThis control proves operation of draft inducer. Check switchoperation as follows:1. Turn off 115-v power to furnace.2. Remove main furnace door and disconnect inducer motor leadwires from wire harness.3. Turn on 115-v power to furnace.4. Set thermostat to call for heat and wait 1 minute. Whenpressure switch is functioning properly, hot surface ignitorshould NOT glow, and control center diagnostic light flashesa Status Code 31. If hot surface ignitor glows when inducermotor is disconnected, shut furnace down immediately. De-termine reason pressure switch did not function properly andcorrect condition.5. Turn off 115-v power to furnace.6. Reconnect inducer motor leads, reinstall main furnace door,and turn on 115-v power supply.Table 11—Gas Rate (Cu Ft/Hr)SECONDSFOR 1REVOLUTIONSIZE OF TEST DIAL SECONDSFOR 1REVOLUTIONSIZE OF TEST DIAL1cu ft2cu ft5cu ft1cu ft2cu ft5cu ft101112131436032730027725772065560055551418001636150013851286505152535472716968671441411381361333603553463403331516171819240225212200189480450424400379120011251059100094755565758596564636261131129126124122327321316310305202122232418017116415715036034332731330090085781878375060626466686058565453120116112109106300290281273265252627282914413813312912428827726725724872069266764362170727476785150484746103100979592257250243237231303132333412011611310910624023222521821260058156354552980828486884544434241908886848222522021420920535363738391031009795922062001951891855145004864744629092949698403938383780787675742001961921881844041424344908886848218017617216716445043942941940910010210410610836353534337271696867180178173170167454647484980787675731601571531501474003913833753671101121161203332313065646260164161155150Table 12—Speed SelectorCOLOR SPEEDFACTORY-SHIPPEDCONNECTIONBlack High CoolYellow (WhenPresent) Medium High SpareBlue Medium Low HeatRed Low SpareWhite Common L2Fig. 46—Amp Draw Check with AmmeterA80201R Y W G10 TURNSTHERMOSTAT SUBBASETERMINALS WITHTHERMOSTAT REMOVEDHOOK-AROUNDVOLT/AMMETEREXAMPLE: 5.0 AMPS ON AMMETER10 TURNS AROUND JAWS = 0.5 AMPS FOR THERMOSTAT SETTINGFROM UNIT 24-VOLTTERMINAL BLOCK42

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