6_Troubleshooting

Section 6

Troubleshooting

Figure 6.1 Unit Troubleshooting Sequence

TS Flowchart

Table 6–1 Troubleshooting Symptoms

Condition	Possible Cause	Remedy / Reference
6.1Unit will not Start or Unit Starts then Stops
No power to unit	External power source OFF	Turn on
	Start-Stop switch (ST) OFF or defective	Check
	Circuit breaker tripped or OFF	Check
	Autotransformer not connected	Section 5.2.2
Loss of control power	Circuit breaker OFF or defective	Check
	Control transformer defective	Replace
	Fuse (F3 / F4) blown	Check
	Start-Stop switch (ST) OFF or defective	Check
	AC Line Filter fails or is defective	Section 7.20.5
Component(s) not operating	Evaporator fan motor internal protector open	Section 7.10
	Condenser fan motor internal protector open	Section 7.5
	Compressor internal protector open	Section 7.2
	High Pressure Switch (HPS) open	Section 6.7
	Heat Termination Thermostat (HTT) open	Replace
	Current sensor malfunction	Replace
Compressor hums, but does not start	Line voltage is low	Check
	Single phasing	Check
	Motor windings shorted or grounded	Section 7.2
	Compressor seized	Section 7.2
6.2Unit Operates Long or Continuously in Cooling
Container	Hot load	Normal
Container	Box insulation defective or air leak	Repair
Refrigeration system	Refrigerant shortage	Section 7.1.7
	Evaporator coil covered with ice	Section 6.6
	Evaporator coil plugged with debris	Section 7.8
	Evaporator fan(s) rotating backwards	Section 7.10
	Air bypass around evaporator coil	Check
	Controller set too low	Reset
	Compressor service valves or liquid line shutoff valve partially closed	Open valves completely
	Condenser dirty	Section 7.4.1
	Compressor worn	Section 7.2
	Current limit (Cd32) set to wrong value	Cd32
	Economizer Solenoid Valve (ESV) malfunction	Section 7.13
	Digital Unloader Valve (DUV) stuck open	Replace
	Electronic Expansion Valve (EEV)	Replace
6.3Unit Runs but has Insufficient Cooling
Refrigeration system	Abnormal pressures	Section 6.7
	Abnormal temperatures	Section 6.15
	Abnormal currents	Section 6.16
	Controller malfunction	Section 6.9
	Evaporator fan or motor defective	Section 7.10
	Compressor service valves or liquid line shutoff valve partially closed	Open valves completely
	Frost on coil	Section 6.10
	Digital Unloader Valve (DUV) stuck open	Replace
	Electronic Expansion Valve (EEV)	Replace
6.4Unit will not Heat or has Insufficient Heating
No operation of any kind	Start-Stop switch (ST) OFF or defective	Check
	Circuit breaker OFF or defective	Check
	External power source OFF	Turn ON
No control power	Circuit breaker or fuse defective	Replace
	Control Transformer defective	Replace
	Evaporator fan internal motor protector open	Section 7.10
	Heat relay defective	Check
	Heater termination thermostat open	Section 7.8
Unit will not heat or has insufficient heat	Heater(s) defective	Section 7.9
	Heater contactor or coil defective	Replace
	Evaporator fan motor(s) defective or rotating backwards	Section 7.10
	Evaporator fan motor contactor defective	Replace
	Controller malfunction	Section 6.9
	Wiring defective	Replace
	Terminal connections loose	Tighten
	Line voltage is low	Section 3.10
6.5Unit will not Terminate Heating
Unit fails to stop heating	Controller improperly set	Reset
	Controller malfunction	Section 6.9
	Heater Termination Thermostat (HTT) remains closed along with the heat relay	Section 7.8
6.6Unit will not Defrost Properly
Will not initiate defrost automatically	Defrost timer malfunction (Cd27)	Cd27
	Terminal connections loose	Tighten
	Wiring defective	Replace
	Defrost Temperature Sensor (DTS) defective or Heat Termination Thermostat (HTT) open	Replace
	Heater contactor or coil defective	Replace
Will not initiate defrost manually	Manual defrost switch defective	Replace
	Keypad defective	Replace
	Defrost Temperature Sensor (DTS) open	Replace
Initiates but relay (DR) drops out	Line voltage is low	Section 3.10
Initiates but does not defrost	Heater contactor or coil defective	Replace
Initiates but does not defrost	Heater(s) burned out	Section 7.9
Frequent defrost	Load is wet	Normal
6.7Abnormal Pressures
High discharge pressure	Condenser coil dirty	Section 7.4.1
	Condenser fan rotating backwards	Section 7.5
	Condenser fan inoperative	Section 7.5
	Refrigerant overcharge or non-condensables	Section 7.1.7
	Discharge service valve partially closed	Open
	Electronic Expansion Valve (EEV) control malfunction	Replace
Low suction pressure	Software and/or controller configuration incorrect	Check
	Suction Pressure Transducer (SPT) or Evaporator Pressure Transducer (EPT) failed	Replace
	Suction service valve partially closed	Open
	Filter drier partially plugged	Section 7.7
	Refrigerant charge low	Section 7.1.7
	Evaporator air flow not existent or air flow restricted	Section 7.8
	Frost on evaporator coil excessive	Section 6.6
	Evaporator fan(s) rotating backwards	Section 7.10
	Electronic Expansion Valve (EEV) control malfunction	Replace
	Digital Unloader Valve (DUV) failed	Replace
Suction and discharge pressures tend to equalize when unit is operating	Compressor operating in reverse	Section 6.14
	Compressor cycling / stopped	Check
	Digital Unloader Valve (DUV) failed	Replace
6.8Abnormal Noise or Vibrations
Compressor	Compressor start up after an extended shutdown	Normal
	Brief chattering when manually shut down	Normal
	Compressor operating in reverse	Section 6.14
	Mounting bolts loose or resilient mounts worn	Tighten / Replace
	Upper mounting loose	Section 7.2
	Slugging loose	Section 7.2
Condenser or Evaporator Fan	Bent, loose or striking venturi	Check
	Motor bearings worn	Section 7.5 / Section 7.10
	Motor shaft bent	Section 7.5 / Section 7.10
6.9Microprocessor Malfunction
Will not control	Software and/or controller configuration incorrect	Check
	Sensor defective	Section 7.22
	Wiring defective	Check
	Refrigerant charge low	Section 7.1.7
6.10No Evaporator Air Flow or Restricted Air Flow
Evaporator coil blocked	Coil has frost build-up	Section 6.6
Evaporator coil blocked	Coil dirty	Section 7.8
No or partial evaporator air flow	Evaporator fan motor internal protector open	Section 7.10
	Evaporator fan motor(s) defective	Section 7.10
	Evaporator fan(s) loose or defective	Section 7.10
	Evaporator fan contactor defective	Replace
6.11Electronic Expansion Valve Malfunction
Low suction pressure	Software and/or controller configuration incorrect	Check
	Suction Pressure Transducer (SPT) or Evaporator Pressure Transducer (EPT) failed	Replace
	Suction Service Valve partially closed	Open
	Filter drier partially plugged	Section 7.7
	Refrigerant charge low	Section 7.1.7
	Evaporator air flow not existent or air flow restricted	Section 7.8
	Evaporator coil excessive frost build-up	Section 6.6
	Evaporator fan(s) rotating backwards	Section 7.10
	Electronic Expansion Valve (EEV) control malfunction	Section 7.12
	Digital Unloader Valve (DUV) failed	Replace
	Sensor loose or insufficiently clamped	Replace
High suction pressure with low superheat	Valve contains foreign material	Section 7.12
	Suction Pressure Transducer (SPT) or Evaporator Pressure Transducer (EPT) failed	Replace
	Electronic Expansion Valve (EEV) control malfunction	Section 7.12
	Powerhead improperly seated	Ensure powerhead is locked and in place
Liquid slugging in compressor	Suction Pressure Transducer (SPT) or Evaporator Pressure Transducer (EPT) failed	Replace
Liquid slugging in compressor	Electronic Expansion Valve (EEV) failed	Section 7.12
6.12Autotransformer Malfunction
Unit will not start	Circuit breaker (CB1 or CB2) tripped	Check
	Autotransformer defective	Section 7.19
	Power source not turned ON	Check
	460 VAC power plug not inserted into the receptacle	Section 5.2.1
6.13Water-Cooled Condenser or Water Pressure Switch
High discharge pressure	Coil dirty	Section 7.6
High discharge pressure	Non-condensables	Section 7.6
Condenser fan starts and stops	Water pressure switch malfunction	Check
Condenser fan starts and stops	Water supply interruption	Check
6.14Compressor Operating in Reverse NOTE: The compressor may start in reverse for up to 10 seconds to determine correct phase rotation if required for phase detection.
Allowing the scroll compressor to operate in reverse for more than two minutes will result in internal compressor damage. Turn the start- stop switch OFF immediately.
Electrical	Compressor incorrectly wired	Check
	Compressor contactor(s) incorrectly wired
	Current sensor incorrectly wired
6.15Abnormal Temperatures
High discharge temperature	Condenser coil dirty	Section 7.4.1
	Condenser fan rotating backwards	Section 7.5
	Condenser fan inoperative	Section 7.5
	Refrigerant overcharge or non-condensibles	Section 7.1.7
	Discharge service valve partially closed	Open
	Electronic Expansion Valve (EEV) control malfunction	Replace
	Suction Pressure Transducer (SPT) or Evaporator Pressure Transducer (EPT) failed	Replace
	Discharge temperature sensor drifting high	Replace
	Economizer Expansion Valve (EEV), Economizer coil, or Economizer Solenoid Valve failed	Replace
	Economizer Expansion Valve (EEV), Economizer coil, or Economizer Solenoid Valve plugged	Replace
	Sensor loose or insufficiently clamped	Replace
6.16Abnormal Currents
Unit reads abnormal currents	Current sensor wiring	Check