My pump motor is running very hot and eventually reaches thermal shutdown. It also has trouble starting. I replaced the bearings and cleaned the contacts of the centrifugal switch. However this did not solve the problems. Should I change out the start capacitor? Could a bad start capacitor factor into the overheating?
Pump Overheating & Trouble Starting
- Thread starter az1324
- Start date
mgarf33
Well-known member
- Oct 27, 2013
- 207
How old is the pump?
Has the motor ever been replaced?
How long does it run before tripping OL?
Is the operating current exceeding RLA?
Is the input voltage correct?
Does the capacitor get hot?
There are a lot of things that can cause over heating, including a cap.
I believe the motor is 10 years old. It is not original to the pump, but wet end is also approx 10 years old. It can run (hot) for several hours before shutting down. I don't have a clamp meter to read the current. The voltage is correct. The whole housing gets hot, I haven't checked the capacitor separately. Even if the start capacitor is causing the poor starts, it is presumably disengaged once the motor has started so not sure that it could cause the overheating.
mgarf33
Well-known member
- Oct 27, 2013
- 207
The reason I ask if the cap is hot indicates there is excessive starting time, or it may have to re-energize if speed decreases.
If the electrolyte solution in the cap dries up, the mfd capacity may diminish causing the cap to underperform not providing the proper boost to the aux winding.
You are correct, once ~ 80 operating speed is achieved, the centrifugal switch removes the cap from the circuit and the aux winding is de-energized.
If the cap never de-energizes it will blow or trip OL.
If it starts, I don't think a start cap is going to cause the overheating, unless the speed slows for some reason, in which case it's a secondary issue.
When a motor operates it produces work and heat. The less work it performs, the more heat it produces.
So, if the motor is oversized it will produce more heat, because the rated impeller can only produce a given amount of work at a certain rpm.
If the motor is undersized, it will not be able to maintain rpm again causing less work, and will likely cause added stress on the aux winding as well.
Both cases can cause intermittent overheating, and it can weaken the OL.
A weak OL will trip more frequently.
There also needs to be good air flow to cool the windings. If possible use some compressed air to clear any debris which can insulate the heat on the windings.
If the voltage is 240, I would check each leg to ground.
If it's 120v check neutral to ground. Hopefully you have a GFCI to eliminate this issue.
If the electrolyte solution in the cap dries up, the mfd capacity may diminish causing the cap to underperform not providing the proper boost to the aux winding.
You are correct, once ~ 80 operating speed is achieved, the centrifugal switch removes the cap from the circuit and the aux winding is de-energized.
If the cap never de-energizes it will blow or trip OL.
If it starts, I don't think a start cap is going to cause the overheating, unless the speed slows for some reason, in which case it's a secondary issue.
When a motor operates it produces work and heat. The less work it performs, the more heat it produces.
So, if the motor is oversized it will produce more heat, because the rated impeller can only produce a given amount of work at a certain rpm.
If the motor is undersized, it will not be able to maintain rpm again causing less work, and will likely cause added stress on the aux winding as well.
Both cases can cause intermittent overheating, and it can weaken the OL.
A weak OL will trip more frequently.
There also needs to be good air flow to cool the windings. If possible use some compressed air to clear any debris which can insulate the heat on the windings.
If the voltage is 240, I would check each leg to ground.
If it's 120v check neutral to ground. Hopefully you have a GFCI to eliminate this issue.
- May 22, 2013
- 2,796
- Pool Size
- 12000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Do you know if your motor has one or two capacitors ?? Some have a start and a separate run capacitor. What are the Mod. / Ser. numbers off your motor ??
The motor has only a start capacitor ~300uF.
It is a 2HP 240V motor. It stutters when it starts. Once it has been running for an hour the case measures around 80deg C. I just noticed these issues recently and it has been installed for several years.
When I changed the bearings I made sure it was clear of debris.
I will have to take it apart again and get another look at the centrifugal switch and other parts.
Possibilities for excess heat generation are mechanical friction or electrical friction (windings deteriorating?)? Anything else to look for?
It is a 2HP 240V motor. It stutters when it starts. Once it has been running for an hour the case measures around 80deg C. I just noticed these issues recently and it has been installed for several years.
When I changed the bearings I made sure it was clear of debris.
I will have to take it apart again and get another look at the centrifugal switch and other parts.
Possibilities for excess heat generation are mechanical friction or electrical friction (windings deteriorating?)? Anything else to look for?
Capacitors are not very expensive. I replaced mine this spring for around $15 There's a video on utube for how to test a capacitor.
Capacitor gives correct value on a meter. The hottest part of the case is directly above the coils. Capacitor housing is not hot compared to that.
- May 22, 2013
- 2,796
- Pool Size
- 12000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Might be the insulation on the windings is starting to break down and it's causing a limited short that's building heat through it's resistance without actually being a more direct short that would trip the circuit breaker. 
You would need to try and separate the leads to the individual coils (if possible) and measure their resistance to see if one is noticeably higher or lower than the others.
When you did the bearings did you notice either one was bad ??
Since it's shuddering on start up it could still be something with the cap, but that's more guessing then solid fact. Not sure in a 10+ yr motor you want to take a 10-20 buck shot at a new cap but you already have your time and bearings into it
I'd also start at the breaker box and follow and check all the connections from the main box to the motor just to make sure it's all tight.
You would need to try and separate the leads to the individual coils (if possible) and measure their resistance to see if one is noticeably higher or lower than the others.
When you did the bearings did you notice either one was bad ??
Since it's shuddering on start up it could still be something with the cap, but that's more guessing then solid fact. Not sure in a 10+ yr motor you want to take a 10-20 buck shot at a new cap but you already have your time and bearings into it
I'd also start at the breaker box and follow and check all the connections from the main box to the motor just to make sure it's all tight.
mgarf33
Well-known member
- Oct 27, 2013
- 207
In your signature, you show having a 1/2HP pump. My guess is, somewhere along the line it was replaced with a 2HP, and now it's more noticeable due to more frequent OL trips. As the OL is abused it may trip easier, and sooner or later not reset.
There are likely hot spots on the rotor reducing both start and run winding ability.
Just a guess, as I can't diagnose it without testing.
There are likely hot spots on the rotor reducing both start and run winding ability.
Just a guess, as I can't diagnose it without testing.
- May 22, 2013
- 2,796
- Pool Size
- 12000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
If you went from a 1/2 to a 2 hp motor there should be plenty of power available if it's the same pump and same pool so the motor shouldn't heat up and trip. If you went the other way I'd understand it causing a problem trying to spin a 2hp rated impeller !!
Why would you think putting in a 2hp motor would cause more trips from overloading
Why would you think putting in a 2hp motor would cause more trips from overloading
mgarf33
Well-known member
- Oct 27, 2013
- 207
Again, a motor produces work and heat as a result of energy consumed.
If a motor is spinning an impeller at full rated rpm a certain amount of work is achieved.
The remainder of the energy consumed results in heat generation.
So, if an impeller was sized for a 1/2HP, 2 pole electric motor designed with a slip factor of 4.1% yielding 3450rpm, then it will produce the same work at much less energy consumption than a 2HP pump with the same impeller.
This excess heat can break down copper windings, separate or burn spots on the rotor or stator.
Keep in mind the rotor and stator are compiled plates glued and pressed. This design reduces Eddy currents and hysteresis.
If a motor is spinning an impeller at full rated rpm a certain amount of work is achieved.
The remainder of the energy consumed results in heat generation.
So, if an impeller was sized for a 1/2HP, 2 pole electric motor designed with a slip factor of 4.1% yielding 3450rpm, then it will produce the same work at much less energy consumption than a 2HP pump with the same impeller.
This excess heat can break down copper windings, separate or burn spots on the rotor or stator.
Keep in mind the rotor and stator are compiled plates glued and pressed. This design reduces Eddy currents and hysteresis.
- May 22, 2013
- 2,796
- Pool Size
- 12000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
I'm sorry that doesn't make sense to me. You said "it will produce the same work at much less energy consumption". With a 2hp motor replacing a 1/2hp motor it easily achieves full RPM, the cooling fan is spinning and moving air really well, it easily does the work the 1/2hp motor did and because it's working so easy it's consuming less energy and it's also producing less heat.
Then you mention on the next line "This excess heat", what excess heat? The 2hp motor is barely being used so why is there excess heat from a motor that can easily do the job, has a cooling fan running at full speed and is using very little of the amperage it's rated to safely and comfortably work with ??
But the story is the OP has a 2hp motor that thermal overloads. He installed new bearings. It's a 10yr old motor that I assume has been working OK running the pump for those years and something recent went wrong.
My guess would be it's something like what you said with the coils or rotor - > "There are likely hot spots on the rotor reducing both start and run winding ability." Maybe insulation breaking down from age, hard to tell without seeing it.
The other thing since it will run is to make sure there is good suction in the skimmers and pressure at the returns to make sure something isn't partially plugged somewhere making the pump and motor work overtime trying to do their job.
There was no mismatch of motor/impeller. I have now swapped filter pump and water feature pump so I can work on it without filtering downtime.
mgarf33
Well-known member
- Oct 27, 2013
- 207
A common misconception.
Another common misconception is that increasing flow restriction will increase amperage on the motor.
This is also not true. As restriction increases, current draw decreases.
Don't believe me? Test it for yourself.
So I pulled the motor apart again and can't see any obvious problems. When spinning the shaft, it will stop and shudder like some sort of magnetic brake has been applied. Is this normal?
Voltage is fine and I'm running a different motor on the same supply right now with no issues.
Any comments on whether it should spin freely? My other motors do but they do not have start capacitor/centrifugal switch.
It should spin freely. Whatever that resistence is, must be causing your overheat. Seems like you already replaced the bearings so it can't be that. I have followed your thread because of my own starting and overheating problems. Found out that my seal plate was misaligned causing the impeller to drag on the plate, hence overheating and trouble starting. But I have both kinds of motors on my pad and they all spin freely when working properly.