Carrier 38VMA Series, Service Manual, Page: 33 / 112

Indoor unit Operation Cooling oil return operation
Status Fan Electronic Expansion Valve
Thermal ON OFF 480P
OFF OFF 480P
Thermal OFF OFF 480P
Defrost starting condition: Defrost operation is started when the outdoor heat exchanger temperature becomes lower than
threshold temperature. Defrost operation is conducted once in a maximum of 2 hours.
Table 27 - Restart Standby
Component Cooling Operation Heating Operation
Compressor OFF OFF
Outdoor unit fan (FAN A) OFF

OFF

Outdoor unit fan (FAN B) OFF OFF
Four way valve (ST1) OFF

Holds
Electronic expansion valve (EXV A) 350P Initial pulse step
Electronic expansion valve (EXV B) 350P Initial pulse step
Electronic expansion valve (EXV C) 0P 0P
Solenoid valve (SV4) OFF OFF
Solenoid valve (SV7) OFF OFF
Ending conditions 12 minutes 12 minutes
3. Overload Control
To maintain the required set point, the air flow of all indoor units are set to low speed if the connected capacity of the indoor
units is more than 120%. However, the air flow of the indoor units will return to normal once the connected capacity of
indoor unit is less than 105%.
4. Stopping Operation
Table 28 - When System is in Stop Mode
Component Operation
Compressor OFF
Outdoor unit fan (FAN A) OFF

Outdoor unit fan (FAN B) OFF
Four way valve (ST1) OFF

Electronic expansion valve (EXV A) 350P
Electronic expansion valve (EXV B) 350P
Electronic expansion valve (EXV C) 0P
Solenoid valve (SV4) OFF
Solenoid valve (SV7) OFF
Ending conditions Indoor unit thermostat is turned ON
Stop operation of follower units while header unit is still in operation in a modular system.
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