Motor cap keeps blowing

[Blue Star Services LLC]

Can anyone give me any advice? I have a 2 HP pool pump motor. The 1st pump blew the starting cap and the run cap. The customer assumed he had a bad pump motor and installed a new one. The new one is now blowing the run cap as soon as it is energized but the start cap is still good. This is a 240 V motor and electrically everything checks out for proper voltage and grounding. Any advice would be appreciated.

 

[Peter Furrow]

Is the motor running excessively hot? You should be able to keep you hand on it for 3 seconds without burning yourself.
If filter is dirty it will run hot.
Capacitor should have the correct microfarad and voltage rating. A higher voltage rating on the capacitor is ok. Dont go below the applied voltage of 240v.
And Make sure it has water
Thats all I got


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[ptonsparky]

Check to see if the motor and pump turns.
Motor not wired correctly.

 

[Blue Star Services LLC]

Thank you for your reply. The pump turns freely. The pump is wired correctly. This is new to me but the pump has a selector switch from 120 V to 230 V. I am use to the old jumpers to select voltage. The problem is the old pump motor blew the capacitors of which has been running for 3 years and the new pump motor is doing the same thing. Everything electrical is testing out fine. I was going to contact an electrical motor shop but this seems more electrical than a motor problem.
Thanks

 

[ActionDave]

Something is not adding up.

Run caps don't blow they just quit working and they usually don't quit working until the start cap has blown and the run cap is now doing double duty by trying to start the motor. Start caps do blow but they don't blow as soon as they are energized they blow when they are left in the circuit too long so it takes a 1 Mississippi, 2 Mississip.... and then you get various degrees of chaos and shrapnel.

Every time there is a problem when a motor is involved the first thing that gets blamed is the motor and it is usually the last thing that is the problem.

 

[Blue Star Services LLC]

Peter,
Thank you for the reply. The cap is only rated to 165 V. and the microfarad is correct. The replacement part was the replacement part that they gave me for the start cap. Please keep in mind that this is a voltage selectable motor which can do 120 V or 230 V. There is no tabs to install jumpers: It is just a switch to select voltage. The bigger question is that the original motor had the same problem as the new replacement.
Thanks for any info.

 

[Blue Star Services LLC]

Action Dave. I appreciate your response. I understand exactly what you are saying. The start cap is testing out fine. But we are talking about 2 different motors doing the same thing. Any thoughts would be appreciated.

 

[ActionDave]

Action Dave. I appreciate your response. I understand exactly what you are saying. The start cap is testing out fine. But we are talking about 2 different motors doing the same thing. Any thoughts would be appreciated.

Brand name of the original motor and the replacement would be some help at this point.

 

[Blue Star Services LLC]

The original motor was a Haward 2 HP the replacement is a Century 2.2 HP. Never came across a 2.2 HP before but it is what it is. I am totally stumped with this one. I might just take both motors and have them bench tested at an electrical motor shop to see if i'm not losing my mind. The customer is worried as they just left for a 10 day vacation and worried about coming home to a green pool! Thanks again for your input and advise.

 

[LarryFine]

I might just take both motors and have them bench tested at an electrical motor shop to see if i'm not losing my mind.

I would definitely do that before buying any more motors or parts.

I would also check the power source voltages, both L-L and L-G.

And double-check that you're setting the voltage selector correctly.

 

[Blue Star Services LLC]

Larry,
Thanks for the info. Checked everything and all is correct. Proper L-L and L-G. Voltage selector is set to the proper voltage. Just as you said. I will take to a shop and have them bench tested before spending any more money on this.
Thanks for the reply

 

[Peter Furrow]

Peter,
Thank you for the reply. The cap is only rated to 165 V. and the microfarad is correct. The replacement part was the replacement part that they gave me for the start cap.”

You initially said that your motor was set for 240 V. This is what concerns me. The capacitor you have is only rated 165 V.
That is under the 240 V rating.
In other words if the line voltage to the motor is 240 V then you should be 1.5 times the line rated voltage when selecting a capacitor.
A run capacitor for 240 V line voltage should be 370 V to 440 V


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[ActionDave]

The original motor was a Haward 2 HP the replacement is a Century 2.2 HP. Never came across a 2.2 HP before but it is what it is. I am totally stumped with this one. I might just take both motors and have them bench tested at an electrical motor shop to see if i'm not losing my mind. The customer is worried as they just left for a 10 day vacation and worried about coming home to a green pool! Thanks again for your input and advise.

It's a Century 2 HP pump motor and it is cap start/cap run not permanent split? What is the frame number?

 

[Blue Star Services LLC]

Peter,
Thanks for that info. I will look into it. The capacitors where just replaced with the same part number that they came with: identical to the factory ones that where installed. I have one more run capacitor at the same 165 V rating. I will try this at 115 V and see if it works. All be it the capacitor would still be short 7.5 V. If this works, I will look for the larger capacitor to run it at 240 V.
Will this make a difference on the start cap?
Thanks again for your time and info.
I'll let everyone know how I make out.

 

[zbang]

What is the frame number?

Better still, a photo of the ratings plate.

 

[ActionDave]

Better still, a photo of the ratings plate.

It would be the best but a lot of people have trouble posting photos here so I refrain from asking.

But yea, @ Blue Star, if you could post a pic of the motor nameplate and the caps you could get a lot better answers from the members.

 

[kwired]

dual volt motor simply puts windings in series for use at the high voltage and in parallel for the low voltage. Aux winding often is connected in parallel at low volts but to the "midpoint" at high volts so it will still see approximately same voltage either way, that is how same capacitor will work on either input voltage configuration.

Is your motor getting to normal operating speed? If so is there excessive load? This presuming you only changed the motor but are driving same load.

Did you measure voltage and current when running to make sure they are within range they should be?

Is pump/motor sized properly to begin with? If voltage is within tolerance but current is high, might be undersized for the job. Could even be something as simple as you have a 3450 RPM motor but driving a pump designed to operate at 1750 RPM, that extra speed would demand a lot of extra load out of the motor

 

[paulengr]

Pretty obvious. A starting capacitor is only rated to energize for a few seconds. The most common problem with an old one is they dry out and fail after about 5-10 years. That’s new so moving on. The second problem is there needs to be a switch to disconnect it once the motor starts running, usually either a centrifugal switch in the motor itself, a timer, or a potential relay. Whichever one you have, it has probably failed and that’s your problem.

Run capacitors generally last much longer and are designed for continuous operation. They usually fail over time from power issues (surges).

At roughly $20 each for each of the two capacitors and $50 for the potential relay often its cheaper just to replace all three than to try to diagnose it but there are several simple ways to verify everythjng. Single phase motors though are cheap and irritating to work on.

 

[ActionDave]

Pretty obvious. .....

Pretty obvious that everything you just said was covered either by the OP or by the discussion that followed.

Got anything new to ad?

 

[paulengr]

Pretty obvious that everything you just said was covered either by the OP or by the discussion that followed.

Got anything new to ad?

Again was the switch (centrifugal switch or potential relay) checked? If it stays in circuit the motor runs slow until the starting capacitor blows up.