How To Fix a Hot Pump Motor


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This guide discusses the common problems related to a motor that runs very hot. If not corrected, a continually overheated motor will fail. Note that it is normal for a motor to run somewhat hot to the touch but if it's too hot to touch or is dis-coloring the paint, you have a problem that has to be corrected.

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Step by Step


Step 1

Pump in an unventilated enclosure - An operating pump needs air circulating around it to cool. It cannot be enclosed in a closed unventilated container or shed.

Step 2

Motors bottom vents are clogged - A motor has to have air circulation under it, If the vents at the bottom of the motor are clogged with debris or dirt, clear the vents.

Step 3

Low voltage to pump - Check the voltage coming into your pump. Low voltage will overheat your pump. The voltage must be within 10% of the motor's data plate rating. If it is not, then a qualified electrician and/or the power company must be involved to correct the low power supply.

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Step 4

Pump overloaded - Impeller is too large for motor. If your recently replaced a motor with a smaller motor and did not reduce the size of the impeller, you may be overloading your motor. The smaller motor is trying to move the same amount of water that the larger motor moved because it is driving the same size impeller. This is a common problem when your replace a Full Rated motor with a Uprated motor They both are labeled as the same HP, but the uprated motor is actually 25-50% smaller than the old Full Rated motor.

Step 5

Impeller worn and rubbing on diffuser - If your impeller is old and the threads are loose or if it is broken by hard debris, it may be rubbing against the diffuser inside the pump. Pull the motor out and check the impeller. Replace the impeller and possibly the diffuser if required. See our guide on "How To Replace A Pool Pump Impeller" for more information.

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Step 6

Note: a partially clogged circulation system or dirty filter will not cause the motor to run hot unless there is little or no water to cool the motor. When the water flow is reduced due to a clog, the pump is moving less water which converts to less work and less energy expended.


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InyoPools Product Specialist  Posted: 5/29/2017 

Derail - Changing to 230V will not keep your motor any cooler. If you have a long run between you pump and the breaker box, try increasing the gauge of the wire to the pump. Also, make sure the vents at the base of the motor are not clogged. If possible raise the motor up off of the slab to provide better ventilation. One customer noticed a marked difference when he raised the motor. Other than that, motors do run hot, especially in a hot climate.

 Posted: 5/26/2017 

My pump motor is very hot. Can't keep my hand on it long. It's set at the 230v setting. Should I set it back to 115 ?

InyoPools Product Specialist  Posted: 6/22/2016 

rbba - Air comes into the motor vents to help cool the motor. Any suction leaks you may have would occur before the pumps impeller. After the impeller, including the shaft seal, you would only see discharge leaks and these would show as squirts of water. And only the newer VS motor are sealed from the environments which might be considered a closed system.

 Posted: 6/22/2016 

I have an air leak - smoke test show air entering motor at the vents behind the motor mount plate. (Diagram shows shaft seal enters here from pump). Is this a cause of air intake? I read that the motor should be a closed system, so I am confused with this test. Thank you.

InyoPools Product Specialist  Posted: 5/31/2016 

storm/ power outage - It sounds like your pump might have been hit by lightning. You might have to consider replacing the pump's motor.

Anonymous  Posted: 5/29/2016 

Had a storm and power outage. Now b128 pump is hot and won't turn on. Switch moves to on position but motor won't start

InyoPools Product Specialist  Posted: 3/22/2013 

Mathieu - Using the smaller impeller with the larger motor will not overload and heat up your motor. In fact the smaller impeller will under load the motor. One more thing to check is the size of the supply wire. Make sure it is heavy enough to carry the additional amperage of the larger motor. An undersized wire will overheat your motor.

 Posted: 3/19/2013 

Hi, I have a Hayward Northstar who had a 1 Hp motor I had to change, I had two 1.5Hp motor in hands so I switch the 1Hp for one of the 1.5Hp.

I wired it on the 115V position, changed the ceramic seal, but lets the old 1Hp impeller and diffuser (didn't have the 1.5hp version in hands). I started the pump and it prime well, didn't make any special noise and the flow seems good, but after 20 to 30 min of running it shut down and the motor was very hot, so I guess the thermal protection shut the pump off (it restart by itself after a few minutes, before shutting off again).

As I'm able too turn the shaft easily by hand I guess the problem wasn't the impeller or the shaft who were blocked. Then I assume my newly install motor was defective, so I install the second one I had in hand, wired it on the 115V, changed the seal again and the same problem arise.

I call the local electrician, who came to verify my wiring and everything is fine, the Voltage is at 115V and the Amperage is good too.

Can a 1Hp impeller and diffuser with a 1.5Hp motor can conduct to the overheating problem? Or did I get two defective motors in a row (I paid 260$ each so I guess those two are refurbished)?

I used to speak French so I hope my English isn't too bad.