Carrier 38VMA Series, Service Manual, Page: 31 / 112

IV. Special Control
1. Startup Control
Table 20 -
Startup Control in Cooling Operation
Component Operation Remarks
Compressor Capacity control Compressor operational frequency increases by 1 step / 1 sec
Outdoor unit fan (FAN A) High pressure control
Initial step for 90 seconds
1-step increase with Pc > 392 psi
1-step decrease with Pc < 305 psi
Outdoor unit fan (FAN B) High pressure control
Initial step for 90 seconds
1-step increase with Pc > 392 psi
1-step decrease with Pc < 305 psi
Four way valve (ST1) OFF
Electronic expansion valve (EXV A) 350P
Electronic expansion valve (EXV B) 350P
Electronic expansion valve (EXV C) PI control
Solenoid valve (SV4) 1000 seconds ON After, Normal control
Solenoid valve (SV7) Normal control
Ending conditions 1000 seconds
Table 21 -
Startup Control in Heating Operation
Component Operation Remarks
Compressor Capacity control Compressor operating frequency increases by 1 step / 1 second
Outdoor unit fan (FAN A) T4 and capacity control
Outdoor unit fan (FAN B) T4 and capacity control
Four way valve (ST1) ON
Electronic expansion valve (EXV A) Heating EXV control
Electronic expansion valve (EXV B) Heating EXV control
Electronic expansion valve (EXV C) 0P
Solenoid valve (SV4)
200 seconds OFF
，
800 seconds ON
After, Normal control
Solenoid valve (SV7) Normal control
Ending conditions 1000 seconds
2. Oil Return Operation
Table 22 -
Oil Return Operation in Cooling mode
Outdoor Unit Component Pre Oil Return Operation Oil Return Operation Post Oil Return Operation
Compressor 22 Hz + 20 Hz 68 Hz + 66 Hz Normal control
Outdoor unit fan (FAN A) Normal control Normal control Normal control
Outdoor unit fan (FAN B) Normal control Normal control Normal control
Four way valve (ST1) OFF OFF OFF
Electronic expansion valve (EXV A) 350P 480P 350P
Electronic expansion valve (EXV B) 350P 480P 350P
Electronic expansion valve (EXV C) Normal control Min 80P, PI control Normal control
Solenoid valve (SV4) Normal control Normal control Normal control
Solenoid valve (SV7) Normal control Normal control Normal control
Ending conditions 75 seconds
120 seconds
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