SPX Cooling Technologies MHF705, MHF702 user manual Troubleshooting, Trouble Cause Remedy

Troubleshooting

Trouble	Cause	Remedy
		Check power at starter. Correct any bad connections between the
		control apparatus and the motor.
	Power not available at motor terminals	Check starter contacts and control circuit. Reset overloads, close
		contacts, reset tripped switches or replace failed control switches.
		If power is not on all leads at starter, make sure overload and short
		circuit devices are in proper condition
Motor will not start	Wrong connections	Check motor and control connections against wiring diagrams.
	Low voltage	Check nameplate voltage against power supply. Check voltage at
		motor terminals.
	Open circuit in motor winding	Check stator windings for open circuits.
	Motor or fan drive stuck	Disconnect motor from load and check motor and fan drive for cause
		of problem.
	Rotor defective	Look for broken bars or rings.
	Motor running single-phase	Check motor and attempt to start it. Motor will not start if single-
		phased. Check wiring, controls and motor.
	Motor leads connected incorrectly	Check motor connections against wiring diagram on motor.
	Bad bearings	Check lubrication. Replace bad bearings.
Unusual motor noise
	Electrical unbalance	Check voltages and currents of all three lines. Correct if required.
	Air gap not uniform	Check and correct bracket fits or bearing.
	Rotor unbalance	Rebalance
	Cooling fan hitting end belt guard	Reinstall or replace fan.
	Wrong voltage or unbalanced voltage	Check voltage and current of all three lines against nameplate values.
	Overload	Check fan blade pitch. See Fan User Manual. Check for drag in fan
		drivetrain as from damaged bearings.
	Wrong motor RPM	Check nameplate against power supply. Check RPM of motor and drive
		ratio.
	Bearing overgreased	Remove bearing reliefs. Run motor up to speed to purge excessive
		grease.
	Wrong lubricant in bearings	Change to proper lubricant. See motor manufacturer's instructions.
	One phase open	Stop motor and attempt to start it. Motor will not stat if single-phased.
		Check wiring, controls and motor.
Motor runs hot
	Poor ventilation	Clean motor and check ventilation openings. Allow ample ventilation
		around motor.
	Winding fault	Check with ohmmeter.
	Bent motor shaft	Straighten or replace shaft.
	Insufficient grease	Remove plugs and regrease bearings.
		Limit cumulative accelerations time to a total of 30 seconds/hour. Set
	Too frequent starting or speed changes	on/off or speed change set points farther apart. Consider installing a
		Marley VFD drive for fine temperature control.
	Deterioration of grease or foreign material in grease	Flush bearings and relubricate.
	Bearings damaged	Replace bearings.
	Voltage too low at motor terminals because of line	Check transformer and setting of taps. Use higher voltage on
		transformer terminals or reduce loads. Increase wire size or reduce
Motor does not come up to	drop
		inertia.
speed
	Broken rotor bars	Look for cracks near the rings. A new rotor may be required. Have
		motor service person check motor.
Wrong motor rotation	Wrong sequence of phases	Switch any two of the three motor leads.

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