Carrier 40MFC Service Manual

Also see for 38MFC: Installation instructions Owner's manual

Contents

Carrier 40MFC Service Manual Manual pdf 19 page image

19DefrostDefrost on heat pump units is controlled by the microprocessor andis initiated if either of the following conditions occur:1 If for the outdoor temperature, T4>32_F (0_C):— The outdoor coil temperature (T3) has been lower than37F (3℃) for about 40 minutes and during that period,the coil temperature is lower than TCDI for more than 3minutes.— The outdoor coil temperature (T3) has been lower than37F (3℃) for about 80 minutes and during that period,the coil temperature is lower than (TCDI+2℃) for morethan 3 minutes.2 If for the outdoor temperature, T4＜32_F (0_C):— If the conditions described above are satisfied, then theprogram judges if the evaporator coil temperature (T2)has decreased more than 41F (5℃). When theevaporator coil temperature has decreased more than41F (5℃), the defrost mode starts.3 At any value of outdoor ambient temperature (T4):— If the machine runs with a condenser coil temperaturelower than 37F (3℃) for more than 120 minutes and theoutdoor coil temperature (T3) has been lower than(TCDI+4℃) for more than 3 minutes, the machine willenter into defrost mode.Where: TCDI = --7_C = 19.4_FDefrost cycle termination:If any one of the following conditions is satisfied, the defrost cyclewill end and the system will return to normal operation:1 The outdoor coil temperature (T3) reaches (TCDE1).— For 9K--12K: TCDE1 = (64_F) 18_C— For 17K--22K: TCDE1 = (59_F) 15_C2 The outdoor coil temperature (T3) is kept at about 46F(8℃) for at least 80 seconds.3 The defrost cycle reaches 10 minutes.The cycles of defrost algorithm are shown below:For 9K,12K models:Compressoronoffonononoffoffoff4-way valveOutdoor fanIndoor fanIndoor fan breeze(10s)xx 10s30s10sDefrost Cycle(no longer than 10 min.)xx=60s for 9k & 12k modelsA14478For 17K, 22K models:XX=60 for 17k model, XX=90 for 22k modelCompressoronoffonononoffoffoff4-way valveOutdoor fanIndoor fanIndoor fan breeze(10s)xxDefrost Cycle(no longer than 10 min.)30s10s10sA14479AUTO MODEIn the Auto mode, the temperature can be set to values between62~86F (17~30℃). In this mode, the machine will choose cool-ing, heating or fan--only mode according to ΔT.NOTE: ΔT =T1--Ts, where T1 represents the indoor roomtemperature and Ts represents the set temperature.ΔT=T1--Ts Running modeΔT＞1℃ Cooling--1<ΔT≤1℃ Fan--onlyΔT≤--1℃ HeatingIndoor fan will run at an automatic fan speed for each running mode.The louver will also operate depending in relevant mode taking place.If the machine switches mode between heating and cooling, thecompressor will stop for 15 minutes and then choose a mode ac-cording to ΔT.If a new set temperature is commanded, the system will choose arunning mode according to ΔT.FORCED OPERATION FUNCTIONWhen the machine is off, pressing the manual button will carry themachine to forced auto mode. Pressing the button once again,within 5 seconds, the machine will turn into forced cooling mode.In forced auto, forced cooling or any other operation mode,pressing the manual button will turn off the machine.When in this mode, all general protections and remote controlfunctions are available.Forced cooling mode:The compressor runs at F2 frequency and indoor fan runs asbreeze.After running for 30 minutes, the machine will turn to auto modewith a 75_F (24℃) set temperature.Forced auto mode:The action of forced auto mode is the same as normal auto modewith a 75_F (24_C) set temperature.