Carrier 42NQV025H Service Manual

Contents

– 39 –Item Operation flow and applicable data, etc. Description7. Defrost control(Only in heatingoperation)(This function removes frost adhered to the outdoorheat exchanger.)The temperature sensor of the outdoor heat ex-changer (Te sensor) judges the frosting status of theoutdoor heat exchanger and the defrost operation isperformed with 4-way valve reverse defrost system.The necessity of defrost operation isdetected by the outdoor heat exchangertemperature. The conditions to detect thenecessity of defrost operation differ in A,B, or C zone each. (Table 1)• Defrost operation in A to C zones1) Stop operation of the compressor for20 seconds.2) Invert (ON) 4-way valve 10 secondsafter stop of the compressor.3) The outdoor fan stops at the same timewhen the compressor stops.4) When temperature of the indoor heatexchanger becomes 38°C or lower,stop the indoor fan.• Returning conditions from defrostoperation to heating operation1) Temperature of outdoor heat exchangerrises to +8°C or higher.2) Temperature of outdoor heat exchangeris kept at +5°C or higher for 80 seconds.3) Defrost operation continues for15 minutes.1) Stop operation of the compressor forapprox. 50 seconds.2) Invert (OFF) 4-way valve approx. 40seconds after stop of the compressor.3) The outdoor fan starts rotating at thesame time when the compressor starts.Table 1* The minimum value of Te sensor 10 to 15 minutesafter start of operation is stored in memory as Te0.–5˚C0’ 10’ 15’ 27’40” 34’–7˚C–20˚COperation time(Minute)Start of heating operation*Outdoor heat exchanger temperatureC zoneA zoneB zoneA zoneB zoneC zoneWhen Te0 - TE ≥ 2.5 continued for 2 minutes in A zone,defrost operation starts.When the operation continued for 2 minutes in B zone,defrost operation starts.When Te0 - TE ≥ 3 continued for 2 minutes in C zone,defrost operation starts.FILE NO. SVM-07013