How to Find & Reset the Thermal Overload Switch on Electric motors
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How to find and reset the thermal overload switch found on many electric motors
Electric Motor Troubleshooting Guide - Diagnostic Table
How to reset the motor switch on a furnace or air conditioner blower fan unit
How to reset the motor switch on water pumps and well pumps
Electric motor troubleshooting guide for electric motors that won't start
Electric motor troubleshooting guide for electric motors that overheat
Questions & answers on electric motor problems, motor overheating, thermal overload protection devices
This article describes how to find and reset the thermal overload button on an electric motor and we give suggestions for repairing hard-starting or non-starting electric motors such as on air conditioning condenser fans and blower fans.
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The page top photo was taken of of an oil burner electric motor not an air conditioning blower fan motor or pump motor, but you'll see that all of these electric motors look a lot alike. Sometimes the reset button on an electric motor is hard to find, and sometimes there is no reset button!. But this
photo shows the red reset button most clearly. We provide a diagnostic guide to problems with electric motors at ELECTRIC MOTOR DIAGNOSTIC GUIDE.
How to Find and Reset a Heating System or Air Conditioning Electric Motor
Electric motor overload reset buttons - how to find and reset motor overload switches
An electric motor used in lots of equipment may include overload reset button on the motor body. If the motor is overloaded or if it overheats, this button will pop "out" indicating that an internal electric safety device has tripped,shutting the motor off.
Once the motor has cooled sufficiently it can be re-started, usually by pushing the popped-out reset switch back down.
If the motor turns off again on re-set you should not keep running it as it may be damaged and the system may be unsafe.
Tips for Finding the Motor Reset Button
Find the electric motor that operates the device that has been shut down. For example on a warm air heating system or central air conditioning system look in the air handler/blower compartment.
On the blower motor itself, look for a red or yellow
button which is normally flat with the motor surface but which will pop up to show that the motor has been shut off by its internal overload protection
circuit.
If the installer
rotated the motor so that the button is facing away from you and impossible to see, feel around on the bottom and back side of the motor for
the button's presence. Especially if the motor's internal protection has tripped, it should be easy to feel the button since it'll be sticking
up about 1/2".
When and How to Reset the Electric Motor on a Heating Blower, Air Conditioner Blower, or Water Pump
When the air conditioner fan or blower motor has cooled sufficiently this button can usually be simply pressed back down to "reset" the switch. If the motor overload
switch won't reset (stay depressed) either the motor is still too hot (wait) or there is another failure that needs diagnosis.
Sometimes the reset button is present but hard to find, depending on the position in which the motor was bolted in place.
What the Reset Button Looks Like When it has Not Tripped
You can see that in this picture the button is flush with the motor surface. Sometimes these
buttons are hard to find but they are usually present on heating and air conditioning system electric motors for fans and blowers.
Electric Motor Troubleshooting Guide
Some of the electric motor troubleshooting suggestions in this list can be found at the Betta-Flo Jet Pump Installation Manual from the National Pump Co.
Things to Check if an Electric Motor Will Not Start
Using a well pump motor as an example, most of these troubleshooting tips pertain to other electric motor applications in buildings too such as in an air conditioning air handler blower compartment
Motor Trouble Cause
Diagnostic Procedure
Repair Procedure
Electrical Power is Off
Check that all service switches for the equipment are in the "on" position.
Check for voltage at the pump motor or pump controls. If no voltage is found, check for voltage at the electric panel.
If power is on to the building, check fuse or circuit breaker serving the electric motor that won't run.
Check for local reset button on the motor (popped out = off )
Check for other power reset or power off buttons such as an access door compartment safety switch that turns off power to the equipment (found on A/C blower compartment doors)
Turn on "off" switches.
Replace bad fuse. Reset circuit breaker; if necessary replace bad circuit breaker.
Let hot electric motor cool down, then push in its reset button.
Be sure all safety interlock switches such as on compartment doors are depressed and that the doors are securely shut. Replace a bad safety switch.
Check with VOM at the pressure control switch or at the motor wiring
Be sure the proper size of wire is used for the ampacity and length of circuit; Test for low voltage to the building.
Loose, improper, or broken motor wire
Check wiring against the motor installation manual diagram, check all connections for tightness, shorts, burns, damage
Rewire or repair or replace wiring
Bad motor control switch
Check the control switch contacts for burning or wear.
If the motor control is a well pump pressure control switch,check the pressure control switch settings - cut-in and cut-out; inspect for burned, pitted switch contacts or for dirt or wear.
For water pumps, adjust or replace the pressure control switch.
Clogged or leaky tubing connecting a water pump pressure control switch to the water system results in failure to properly sense and respond to water pressure.
Debris clogging can also occur in the bottom of the pressure control switch where it mounts or connects to the tubing.
Check and clear tubing blockage (blow air through tubing). Or install new tubing.
Be sure tubing is proper diameter and type to seal properly with other fittings.
Tighten tubing fittings to be sure there are no water or air leaks. Soap solution may help find air leaks in tubing fittings.
Clear or replace clogged pressure control switch if the bottom sensor opening is clogged and cannot be cleared.
Bad mechanical parts being turned by the motor - e.g. blower assembly or well water pump impeller
Turn off electric power to motor, see if you can move the impeller or blower assembly or motor shaft - if it won't turn it is jammed or damaged
Remove obstruction in mechanical components, inspect for and replace damaged parts or a frozen electric motor itself
Bad electric motor starting capacitor
Use a VOM in ohms setting to check resistance across the capacitor. If the meter does not move (no current flows) the capacitor is "open". If there is zero resistance the capacitor is shorted.
Use a VOM to check the voltage level at the pressure control switch
If voltage is too low, check voltage at the electrical panel and check that the proper size wiring was used for the ampacity and length of run and that there are no partial shorts or damaged wires or connectors
Incorrect motor wiring
Check the actual electrical wiring against the motor wiring diagram or the installation manual for the equipment
Reconnect wiring properly
Motor is too hot due to surroundings - inadequate ventilation
Check the air temperature where the motor is located. If the air temperature is over 100 degF, the pump may be too hot and its thermal overload switch tripping because of the environment, not a pump problem.
Install adequate ventilation, or if needed, shading, or relocate the motor/equipment to a cool location
Motor subjected to repeated overloading, overheating
A motor subjected to overloading due to very long duty on-cycles may run hot and trip the thermal overload protection device. Eventually the thermal overload switch may itself fail and the motor will no longer restart nor can you reset the thermal overload switch.
Check the recommended duty cycle and loading on your motor; check also for abnormally low voltage levels in the electrical supply. If necessary, replace the motor with a heavier-duty unit.
Motor for a water pump operates too long at low water pressure
If the well recovery rate is too poor and the pump is operating at low water pressure, possibly because a tailpiece is installed to prevent air injection and pump burnup, the pump may be overheating.
Install a valve on the water discharge line and reduce water flow to increase water pressure inside the pump itself. See WATER PRESSURE PROBLEM DIAGNOSIS TABLE
General advice: Electrical Tests to Check HVAC Blower Fan Motor or Outdoor Compressor Fan Motor Winding on Heating or Cooling Equipment or on Other Electrical Motors
see USING DMMs VOMs SAFELY. Example: testing a blower fan motor winding: referring to the electrical diagram for your equipment, unplug electrical connectors at the fan motor. Measure the resistance between each lead wire with a multimeter or VOM. The multimeter should be set in the X1 range. For accuracy, don't measure when the fan motor is hot, allow it to cool off.
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Typical Deep Well Two Line Jet Pump Installation, Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend)
Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
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