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Q&A on Thermal Overload Switch on Electric motors

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Electric motor thermal overload switch FAQs:

Frequently asked questions about the thermal overload and reset button on electric motors.

This article series 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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Electric Motor Reset Button & Thermal Overload Questions & Answers

Photograph of the overload reset button on an electric motor

Questions & answers about the reset button or reset feature on electric motors, posted originally at ELECTRIC MOTOR OVERLOAD RESET - topic home page.

On 2017-05-27 by (mod) re: what to do if the fan motor won't run

Percey:

If a check shows voltage at the fan motor terminals then the motor is shot and needs replacement.

WATCH OUT: turn power off when accessing equipment and watch out for hazards of death by electrical shock.

On 2017-05-26 by percy

I have a heatpump. The fan motor will not come on. It is a Gentec X13 1/2 HP. It does not have a reset switch.

On 2017-04-13 by (mod) re: water pump won't stop running

Sure, Spenc.

By using the search box just above to search InspectApedia for PUMP WON'T STOP RUNNING we find WATER PUMP WONT STOP RUNNING at http://inspectapedia.com/plumbing/Pump_Runs_On.php that explains how to diagnose and fix the problem. It sounds as if your pump is having trouble reaching the cut-off pressure but we don't know if that's because of a low flow well, piping leaks, low voltage to the pump, a damaged pump impeller, etc.

On 2017-04-13 by spenc

cut-in an cut-out reach the proper lbs it takes about 20min to reach the cut-out pressure an by then the pump is extremely hot.....can anyone help me out please

On 2017-01-26 by (mod) re: Signs of an overheating electric motor on an HVAC system

I can't say what's wrong from the information in your question, Fatima. But it might be an overheating or failing motor.

On 2017-01-26 by Fatima

I have a Lennox cooling / heating electric system. It starts working pretty well, but the condenser stops working after 10 minutes working. Why?

I have a Lennox heat/heating system. It starts pretty well, but the condenser stops after 10 minutes working. Why?

On 2017-01-07 by (mod) re: turn off electrical power to a seized motor

Yes, Stephen, that would be the normal case.

I would add that if a motor is seized it would be safest to turn off its electrical power.

On 2017-01-07 by Stephen

We had an ice storm last night and the outdoor moter siezed up. Does the emergency heat bypass the heat pump and just run the fernace? (It's duel fuel tran)

On 2016-01-20 by (mod) re: well pump protector may shut down the pump if water is low

If your system has a well protection circuit or control or switch it may be shutting down the pump to prevent a burn-up of a pump running constantly but unable to find enough water to reach the cutoff pressure. Then when the pump is off the well slowly recovers so that by day time you can turn it on again and reach cutoff pressure again.

I'd look for
- leaky foot valve
- leak in well piping
- slow well recovery rate
- high current draw at the pump indicating a pump motor failure developing

On 2016-01-20 by Dan

My well shuts off at night. I have to hit the reset button every morning then it is OK for the rest of the day.

On 2016-01-19 by Anonymous re: intertherm blower motor won't start

I think you needed a service tech to confirm power & check relay and control board but first confirm the thermostat is calLing for heat.

On 2016-01-18 by KATHY R.

INTERTHERM BLOWER WON'T START, MOTOR TURNS FREELY,REPLACED CAPACITOR, STILL WON'T START.

On 2015-12-20 by ken walsh

Im contending with a efm motor problem unit modelpk750-4206-2 motor s#316p-393 first I had to restart with reset switch on the pump multiple times it started rite up it shut down again and then had to start with motor reset switch then shut down again motor reset switch was not triggered hit the pump reset switch and was getting a buzzing noise took a brick and banged on the motor wile it was buzzing and the unit started rite up is there a low spot in the motor brushes and if the motor is defective what would the retail price be new or used

On 2015-12-12 by (mod) re: reset button on a Trane electric furnace

Ann:

Trane sells heat pumps, gas furnaces, perhaps heat pumps with electric backup heat.

An electric furnace may trip a circuit breaker if the electric heaters are in trouble. Those'd be in the electrical panel.
There may also be local circuit breakers in the unit controlling the heating elements.

If a blower motor won't run there MIGHT be a re-set button on the motor itself.

On 2015-12-12 by ANN

FIND RESET BUTTON ON A 2000 ELECTRIC TRANE FURNACE

On 2015-08-14 by (mod) re: internal thermal overload in electric motor turns it off and back on

The motor may have an internal thermal overload switch that automatically re-sets when the motor cools.

I'm not a motor expert but I'd at least check for

- improper voltage
- improper wiring
- a binding bearing or moving part that is stressing the motor
- missing motor lubrication
- a motor winding that opens up (and stops the motor) when the motor gets hot

On 2015-08-13 by dave.irland@gmail.com

I repowered a direct drive organ blower from the 1920s with a Baldor airover .5 hp 1100 RPM (same specs as original) and made it a belt drive. The motor shuts off after about an hour, very hot to the touch. The motor does not have a thermal overload switch (Baldor CHC365A) but it will re-start when it cools off. Question 1: if it doesn't have an overload switch, what is happening? Question 2: (this is where it gets weird)

The motor is on a switched duplex outlet. I have a small fan plugged into the other receptacle to cool the motor. When the motor switches off, the small fan also stops (??). AFter five minutes the small fan will come on again, run for a few minutes and then shut off; the motor does not come on until the small fan has started and stopped a few times.

I can only surmise that the circuit in the church has some sort of automatic overload switch?? It does not trip a breaker.
thanks

On 2015-07-06 by (mod) re: signs of a seizing AC compressor

Sounds like a seizing compressor motor drawing high current. Leave it OFF while waiting for a repair, lest you have a fire or cause further equipment damage.

On 2015-07-06 by Sal

Condenser sounds like it wants to start and does not. You can see the power drain on the lights as it tries to start up. Any thoughts on what might be causing this?

On 2015-04-08 by (mod) re: how to get help with a mobile home where nothing is to code

Robin

You might give a call to your local building department (or hire a private home inspector) for help in setting repair priorities.

On 2015-04-04 23:12:37.732760 by robin Monterastelli

great site ... also does you company help in CA? my Mobile home is 1964 NOT ONE THING is TO CODE...
I NEED HELP

On 2015-03-11 00:13:34.591000 by (mod) re: table saw motor quit running

Sure Bruce; and easy to test = if you're able to disassemble and rebuild a motor, probably you're up to testing the switch for continuity.

An alternative is more subtle: an open winding in the motor.

See ELECTRIC MOTOR WON'T START in More Reading above.

On 2015-03-10 by Bruce s

my table saw motor quit. I took it apart and cleaned everything brushes look good , fan is clear, no spin drag or interruption bearings seem to be in tact . could it be the reset switch? it is located on outside of saw cabinet

On 2015-03-03 by (mod) re: furnace motor always runs

Sorry Nick I don't understand the situation from just your e-text but I can hear that it'd be appropriate to call-back the service person who did the motor replacement to check on wiring and control connections.

On 2015-02-28 by Nick

Hi, my motor in the furnace was changed and now it always runs, also my thermo pump does not go on. Can you help.

Question: where to obtain safe internal operating temperature for an A-insulated 1952 elecgric Singer Sewing Machine Motor?

Im am rewiring a 1953 Singer Featherweight 222K with original 220 volts motor. I plan installing some small thermostatic circuit breakers to protect the motor, the foot switch and machine arm (with the wiring for the Singerlight lamp) from owerheating.

I will use silicone-insulated cables standing uo to 200 C heat, so the first component to be damaged from exess heat is the motor windings, insulated by dipping in with shellac insulating varnish, which was the standard industry procedure in 1953.

If one chooses breakers with a too low trip value they will stop the machine at normal operating temperatures, if one chooses breakers with too high trip value, the insulation could burn.

Now, what would be a suitable trigger temperature for those circuit brakers, or in other words,
what is your informed oppinion on the maximum recomendable and safe internal operation temperature for a A-insulated electrical motor from 1952 in original condition? - Gunnar Pettersson, Finland 3/10/2014

Reply:

G.P. Thank you for an interesting question; with regrets, I do not have an answer immediately at hand. I'm a bit nervous about citing a specific "safe temperature" for a 1952 electric motor as I suspect that there was a range of acceptable temperatures based on motor design and application.

I can suggest some references that might help narrow the question to help a bit, for which Farrell's article might be most helpful.

Reader followp-up:

... this question seems to be difficult to find an answer to on the web. I am very far from beeing an electricien (or how one puts in English) but I understand here are two things in play: the normal calculations and safety margins for a modern motor with modern materials, and then the older designs, using older materials and thereupon the ageing factor of those old time materials. Kind of industrial archeology. In my basement I have a thick book, I think it is Swedish, but it may be in Finnish, named "Electricity". I have it after my uncle whom I never saw, as he was killed as a young officer in the war, I think it was 1941. He was a quite promising electrical engineer, and he wrote nice and clear formulas in his workbooks, where I write as we say crow's feet. He must have had a good mathematical sensem where I am almost illiterate.

Among his books was one with the title "Introduction to higher analysis" (in Finnish) by Ernest Lindelöf:
http://en.wikipedia.org/wiki/Ernst_Leonard_Lindel%C3%B6f

Some professor in mathematics heard that my sister, professor H. had this book and begged for the favor to keep it for some time. It was well before the internet era.

So, still we do not now, what the temperature limit inside a Singer external, pre-1960 motor for home sewing machines model NN should be. We do, however know, what solder one should use in the rewiring: "“63-37” means it’s 63% tin and 37% lead. This specific percentage is what Singer 221 guru Graham Forsdyke’s motor specialist uses, and he used to work in the Singer factory in Kilbowie, so I’m sure he knows his stuff."

I am sure the information on "aged shellac safe" internal motor temperature can be found in the books you name, maybe as a tabel, or formula in them. Or maybe I find it in "Elektricity". I read the book in my childhood and remeber it beeing full of illustrations of vintage applications. But as it was a brave new world and the technology of tomorrow for the writer, they probably were not observant of the problematics concerning ageing of insulation materials.

If your electric motor won't start, vibrates or is noisy, see our diagnostic guide to problems with electric motors at ELECTRIC MOTOR DIAGNOSTIC GUIDE.

Air conditioning & Heat Pump Compressors & Other Motors

See

Heating system reset switches: If you are looking for the main oil burner reset button on heating equipment you'll want to see:

Controls on well pumps and water supply equipment that may require reset or repair are discussed at

And see CAPACITORS for HARD STARTING MOTORS for advice on adding or replacing a start/run capacitor for an electric motor that has trouble starting.

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.

When the resistance between each lead wire are those listed in the specifications for your equipment the fan motor should be normal. Zero resistance or infinite resistance are indicators of a problem.

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