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NORA Oilheat Technicians Manual

Chapter 10 Motors Heating system motor troubleshooting chart (courtesy of R.W. Beckett Corp.) Trouble Cause What To Do Motor fails Blown fuses Replace with time-delay fuses. Check for to start grounded winding. Low voltage Check for inadequate wiring or extension cords. Check for low system voltage. Call electric company. Improper line Check connections against diagram supplied with motor. connections Overload (thermal Check and reset overload relay in starter. Check heater protector) tripped rating against motor nameplate current rating. Check motor load. If motor has manual reset thermal protector, check if tripped. If three-phase, one Indicated by humming sound. Check lines for open phase. phase may be open Check voltage with motor disconnected, one fuse blown Defective motor Repair or replace or starter Motor stalls Overloaded motor Reduce load or increase motor size. Low motor voltage See that nameplate voltage is maintained. Motor does not Not applied properly Consult motor service firm for proper type. Use larger motor. Voltage is too low at Use higher voltage tap on transformer terminals, increase motor terminal due to wire size. Check for poor connections. Voltage unbalance. line drop Starting load too high Check load motor is carrying at start. Motor takes too Excess loading; tight Reduce load; increase motor size. Adjust belts. long to accelerate belts. High inertia load Inadequate wiring Increase wire size. Check for poor connections. Applied voltage too low Reconnect to a higher tap. Increase wire size. Check for poor connections. Defective motor Repair or replace. Inadequate starting Replace with larger motor. torque Motor vibrates or Motor is misaligned Realign Three-phase motor Check for open circuit, blown fuses or unbalanced running single phase voltages. High or unbalanced Check wiring connections, transformer. voltages Worn, damaged, dirty Replace; check loading and alignment. or overloaded bearings Loose sheave or Tighten set screw(s); replace. coupling come up to speed is excessively noisy Is the motor off on overload? If manual reset, push the button. If auto, reset and wait for or assist the motor to cool until it resets. Is the capacitor (if needed) OK? The simplest way to test the capacitor is to replace it with one of the same rating. Is the load on the motor excessive? If the motor starts after the load is removed, this could be the problem. Are the bearings on the motor seized or dry? If so, free up and lubricate. 10-16 Motors


NORA Oilheat Technicians Manual
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