Components ......................................................................................................................................................................... B-2

Component Overview ......................................................................................................................................................... B-2

Service Monitor Board (SMB) .............................................................................................................................................. B-3

Inverter Power Module (IPM) ............................................................................................................................................... B-3

PCB ....................................................................................................................................................................................... B-4

Power Filter Board (PFB) ...................................................................................................................................................... B-5

Operations............................................................................................................................................................................ B-6

Cooling Mode Sequence of Operation ............................................................................................................................... B-6

Heating Mode Sequence of Operation ............................................................................................................................... B-8

Defrost Cycle Sequence of Operation ............................................................................................................................. B-10

Electronic Expansion Valve (EEV) Control ........................................................................................................................ B-11

4-Way Valve Heating Control ............................................................................................................................................ B-11

Compressor Sump Heater ................................................................................................................................................ B-11

Defrost Control .................................................................................................................................................................. B-12

Base Pan Heater Control Logic ......................................................................................................................................... B-12

Troubleshooting the Base Pan Heater Error .................................................................................................................... B-12

Discharge Sensor Protection ............................................................................................................................................ B-12

High Current Protection .................................................................................................................................................... B-13

High Pressure Protection in Cooling ................................................................................................................................. B-13

High Pressure Protection In Heating ................................................................................................................................ B-13

Low Pressure Protection ................................................................................................................................................... B-14

Oil Return Cycle ................................................................................................................................................................. B-15

Testing ................................................................................................................................................................................ B-16

Outdoor Fan Motor ............................................................................................................................................................ B-16

Temperature Sensor .......................................................................................................................................................... B-16

4-Way Valve ....................................................................................................................................................................... B-17

Electronic Expansion Valve (EEV) ..................................................................................................................................... B-17

Variable Speed Compressor ............................................................................................................................................. B-18

Wiring Error Check ............................................................................................................................................................. B-18

Wiring Diagrams ................................................................................................................................................................. B-19

DIP Switch Settings ............................................................................................................................................................ B-22

Error Codes ......................................................................................................................................................................... B-24

OUTDOOR TECHNICAL OVERVIEW

Table of Contents

OUTDOOR TECHNICAL OVERVIEW

ASH220NCDWA

ASH324NCDWA

ASH436NCDWA

B-1

Table of Contents