Electrical System Service Procedures

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Front Cover

page 94 Input Voltage Measurements and fault isolation checks

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page 97 diagram for typical packaged heating/cooling unit

page 98 Fault Isolation tree diagram for typical heating/cooling unit

page 99 Procedure overview | instrument or device required

page 100 Input voltage and current measurement procedures (steps 1-3)

page 101 Single-phase and 3-phase input voltage measurement diagrams

page 102 Fuse and circuit breaker measurement procedures (steps 4-9)

page 103 Fuse and circuit breaker measurement procedures diagrams

page 104 Thermostat checks and measurement procedure (steps 10-15)

page 105 Thermostat checks diagrams

page 106 Control tranformer measurement procedure (steps 16 and 17)

page 107 Control transformer voltage measurements diagram

page 108 Component fault isolation checks and resistive/inductive load and switching device measurements

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page 111 Procedure overview | instrument or device required

page 112 Resistive and inductive load measurement procedures (steps 1-4)

page 113 Resistive load and inductive load resistance measurements diagrams

page 114 Switch/switched contacts resistance measurement procedure (steps 5 and 6) | diagram of same

page 115 Compressor checks and electricl measurements

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page 121 Procedure overview

page 122 Instrument or device required | Start relay checks and measurement (steps 1-3)

page 123 Start relay checks and measurements diagram

page 124 Start/run capacitor measurement procedure (steps 4-8)

page 125 Start/run capacitor measurements diagrams

page 126 Compressor motor open or shorted winding measurement procedure (steps9-11)

page 127 Compressor motor open or shorted winding measurements diagrams

page 128 Compressor motor grounded winding measurement procedure (step 12) | diagram of same

page 129 Single-phase compressor motor winding-to-winding resistance measurement procedure (step 13) | diagram of same

page 130 3-phase compressor motor winding-to-winding resistance measurement procedure (step 14)

page 131 3-phase compressor motor winding-to-winding resistance measurements diagram

page 132 Identifying unmarked single-phase PSC and CSR motor terminals measurement procedure (steps 15-18)

page 133 Identifying unmarked single-phase PSC and CSR motor terminals diagrams

page 134 3-phase compressor cureent impalance measurement procedure (steps 19 and 20)

page 135 3-phase compressor cureent impalance measurements diagram

page 136 Restarting a "stuck" PSC compressor procedure (steps 21-24)

page 137 Restarting a "stuck" PSC compressor diagram

page 138 Restarting a "stuck" 3-phase compressor procedure (steps 25-28)

page 139 Restarting a "stuck" 3-phase compressor diagrams

page 140 PTC start thermistor measurement procedure (steps 29-32)

page 141 PTC start thermistor measurement diagrams

page 142 Motor checks and electrical measurements (excluding compressor motors)

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page 145 Procedure overview

page 146 Instrument or device required | Run capacitor measurement procedure (steps 1-5)

page 147 Run capacitor measurements diagrams

page 148 Motor open, shorted, or grounded circuit measurement procedure (steps 6-9)

page 149 Motor open, shorted, or grounded winding measurements diagrams

page 150 Furnace thermocouple and flame rectification sensor measurement

page 151 Procedure overview

page 152 Instrument or device required | Thermocouple voltage measurement procedure (steps 1-3)

page 153 Thermocouple voltage measurements diagrams

page 154 Flame rectification circuit flame-proving signal measuremnt procedure (steps 4-6)

page 155 Flame rectification circuit flame-proving signal measuremnt diagram

page 156 Fault Isolation methods used with non-repairable electronic controls

page 157 Procedure overview | Instrument or device required

page 158 Fault isolation of non-repairable electronic controls (steps 1-3)

page 159 Fault isolation of non-repairable electronic controls (step 4) | diagram of same



Index of small diagrams not listed above

Equipment functional circuits - pg 94

Example of the Hopscotch method of troubleshooting - pg 108

Example of Hopscotch troubleshooting in circuit with open contactor contacts - pg 108

Example of Hopscotch troubleshooting in circuit with faulty load device - pg 109

Resistive loads, inductive loads, and contactor/relay switched contacts - pg 109

Schematic and wiring diagram contactor/relay switched contact symbols - pg 110

Capacitor discharging tool - pg 111

Hermetic and semi-hermetic compressors - pg 115

Seized compressor - pg 115

Capacitance-boosting PSC compressor motor - pg 116

Low capacity check - pg 116

Hermetic compressor leaks - pg 117

Internal line break overload - pg 117

Permanent split capacitor (PSC) motor schematic - pg 118

Capacitor start-capacitor run motor schematic - pg 118

3-phase motor - pg 118

Typical run and start capacitors - pg 119

CSR motro with voltage-actuated start relay - pg 120

PSC compressor motor with PTC start thermistor - pg 120

Typical HVAC motors - pg 142

Internal overload - pg 142

Multi-speed motor circuit - pg 143

Electronically-commutated motor (ECM) - pg 143

3-phase motor - pg 144

Typical run capacitor - pg 145

Thermocouple standing pilot - pg 150

Thermocouple testing - pg 150

Testing flame-proving signal - pg 151

Typical microprocessor furnace control system - pg 156

Schematic of microprocessor-controlled furnace - pg 156