How To Select the Right Capacitor For Your Pool Pump Motor

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This guide discusses the two kinds of capacitors that could be used on pool pump motors: start capacitors and run capacitors. It also addresses how to know a capacitor is failing and how to replace it.

Click Here to View All Motor Parts (Capacitors, Bearings, Switches & More) 


Things You'll Need

Step by Step

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Step 1

CAPACITOR TYPES -  A pool pump can have two types of capacitors: a Start capacitor and A Run Capacitor. The Start capacitor is switched into the the motor's winding circuits on start up to help the motor turn over and come up to speed. When the motor is close to running speed, the Start capaciotor is switched out of the winding circuits. The Run capacitor is incorporated in the motor circuit to help increase running efficiency. It remains in the circuit as long as the pump motor is running. The start capacitor will generatlly be rated at 50-400 MFD and 125 or 250 VAC. The run capacitor will generally be rated at 15-50 MFD and 370 VAC. The capacitor in the picture is a Start Capacitor rated at 124-149 MFD 125 VAC.

Step 2

MOTORS WITH CAPACITORS - Not all pool pump motors use capacitors.  There are four common types of residential pool pump motors: Split Phase, Capacitor Start, Permanent Split Capacitor and Capacitor Start/ Capacitor Run.
The Split Phase motor is used extensively in spa and jetted tubs, and above ground pools. This design has a start winding and a start switch, but no capacitors.

The Capacitor Start motor is used commonly is in ground pool pumps.The starting torque is higher (150-175% of full load) and starting current lower than the split phase equivalent. The operation is similar to a split phase in that there is a start switch to take the start winding and capacitor out of the circuit once the motor reaches 2/3 to 3/4 of full speed.

The Permanent Split Capacitor motor does not have a start switch and is often referred to as a “switchless” motor. It does use a Run Capacitor that remains in the circuit at all times. The PSC design has significantly less starting torque than the capacitor start design.
The Capacitor Start/ Capacitor Run motor design is used to increase efficiency in run mode. Both Start and Run Capacitors are used. In run mode, PSC and Cap. Start/Cap. Run motors are the same.

Step 3

START CAPACITOR LOCATION - START capacitors are usually hard or glassy looking plastic enclosed can that are typically, though not always, found under the non-drive end canopy of the motor.

Click Here to Find Your Start Capacitor 



Step 4

RUN CAPACITOR LOCATION - RUN capacitors are usually the METAL (aluminum or steel) enclosed can capacitors that are most of the time, but not always, found under the "hump" on top of the motor - also referred to as the capacitor housing or "doghouse". This picture shows the location of the run capacitor under a doghouse.

Click Here to Find Your Run Capacitor

Step 5

START CAPACITOR FAILURE - Usually the effect of a failed START capacitor is a "sluggish startup" or "humming with no startup. When a START capacitor is starting to go bad, you might see some leakage of electrolytic oil,  and when it fails the vent opens and expells the electrolytic oils. A failed start capacitor will have a physical hole in the vent after it has failed.

Step 6

RUN CAPACITOR FAILURE - The effect of a failed RUN capacitor is usually "hi amps" and sometimes "humming with no start" and often times motor won't run in the hi amp condition without tripping thermal protector.  When a RUN capacitor is starting or has gone bad, the end of the capacitor that has the terminals and sometimes the opposite end without terminals bows outward. 
The capacitance reading would be significantly lower than rated if its failed.  There isn't a "vent" typically on RUN capacitors -- they expand/bow outward with a fail safe internal structure so that the bowing out of the terminals breaks the contacts internally in the capacitor in a fail safe mode.

Step 7

REPLACING START CAPACITOR - See our guide on "How To Replace a Pool Pump Capacitor". When you replace a capacitor, never put in a lower rated capacitor. If you can't find your size capacitor, it is acceptable to use the one rated one step higher. If you pump motor is continually burning up capacitors, try using the next one up in size. Capacitors are susceptible topower variations or increases. If you can't control your system power, you may need a capacitor with a little higher rating. Use this link to purchase the Start Capacitor you need.

Step 8

REPLACING RUN CAPACITOR - To replace a Run Capacitor, remove the Capacitor Cover (bump)  by removing the two screws. Then follow the precautions above to disconnect and replace the capacitor. As stated above, when you replace a capacitor, never put in a lower rated capacitor. If you can't find your size capacitor, it is acceptable to use the one rated one step higher. If you pump motor is continually burning up capacitors, try using the next one up in size. Capacitors are susceptible topower variations or increases. If you can't control your system power, you may need a capacitor with a little higher rating. Use this link to purchase the Run Capacitor you need

Click Here to View All Motor Parts (Capacitors, Bearings, Switches & More)

Comments

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(1 to 40 of 426)

 Posted: 12/30/2021 

I have a US Motors model K63CXDFN-5152 and believe the start capacitor has failed after just over a year. Can you help with the replacement part number for the start capacitor?
 Reply

InyoPools Product Specialist  Posted: 1/3/2022 

The recommended capacitor for your K63CXDFN-5152 motor is the 161-193 MFD - BC-161 - Start Capacitor
 Reply

 Posted: 12/19/2021 

I have a 1 HP in ground pool pump and need to find a 200-240 uf 250 vac start capacitor. Can’t find a replacement with those numbers. What’s a good replacement?
 Reply

InyoPools Product Specialist  Posted: 1/3/2022 

What is the part number of the capacitor? If that is unavailable, what is the motor's part, catalog, or model number?
 Reply

 Posted: 10/26/2021 

Hi, I'm need to find the correct replacement dual pool pump capacitor and the current model shows the following: 30+10.0 uf +-6% 30CAC/B 50/60Hz
 Reply

InyoPools Product Specialist  Posted: 10/27/2021 

What is the part, model, or catalog number on the motor label?
 Reply

Anonymous  Posted: 10/27/2021 

Appreciate the help, I haven't had to buy a capacitor before so hopefully this is the info you're looking for. This is a Century Pool & Spa Motor: Cat B2977 Serial 24715J2 Type CXCP Part 7-K56AB45A01-05 Total HP = 1.95 Thank you!!
 Reply

InyoPools Product Specialist  Posted: 10/27/2021 

The parts schematic for the B2977 dual speed motor lists the 25 MFD - 628318-307 (2443). But if you want the same type of capacitor you have now, it would be the 30 MFD (5VR0303) (2444). I am not sure if the previous owner changed the capacitor in a previous repair or not.
 Reply

Anonymous  Posted: 10/15/2021 

Hi, I have an XP@ pump with an emerson 3HP motor model 06130453-2 also has 1563 +1795 on the casing. I need a run capacitor but the numbers are smudged off any help would be greatly appreciated thank you.
 Reply

InyoPools Product Specialist  Posted: 10/15/2021 

That model number (06130453-2) is not bringing up much information. That is the number on the motor label or on the capacitor? What is the model number of the pump housing?
 Reply

 Posted: 9/30/2021 

: I have a swimming pool pump with a Magnatek Century 230/115 VAC, Amps: SF 7.9/15.8, 1HP, 3450RPM , part 7-187524-20 with the capacitor missing, may I have a copy of the diagram to know which capacitor is needed?
 Reply

InyoPools Product Specialist  Posted: 10/1/2021 

Can you verify that 7-187524-20 is the part number written on your label? That number doesn't come up anywhere in our database.
 Reply

 Posted: 10/1/2021 

It reads on the label: CAT B376, PART 7 -187524 -20 HP 1.0
 Reply

InyoPools Product Specialist  Posted: 10/1/2021 

Is this motor on a pool or spa pump?
 Reply

Anonymous  Posted: 10/1/2021 

pool filter Pump motor
 Reply

InyoPools Product Specialist  Posted: 10/1/2021 

What is the model number of the pump it is on? Because we only carry schematics for pool & spa 1081 type motors; they are the standard for the industry. Neither of that motor's model numbers cross-references to anything. And when I do a regular google search, nothing pool and spa pop ups.
 Reply

 Posted: 9/29/2021 

I have a 1 hp AO smith pump and I need a new capacitor, but can't figure out which one I need. Motor Model # is : C48L2N134C2 Serial Number is: 16112CH Current Capacitor number is 61b1d110161nnao, 161-192uf, 110vac
 Reply

InyoPools Product Specialist  Posted: 9/29/2021 

The correct capacitor for your C48L2N134C2 motor is part number 5270-14.
 Reply

 Posted: 10/1/2021 

Thanks SO much!
 Reply

InyoPools Product Specialist  Posted: 10/1/2021 

You're welcome! Have a great weekend.
 Reply

 Posted: 9/29/2021 

I have a Hayward Tristar high performance 2 speed pump csc 328p3510h37n37a5a0 capacitor 35 + 10 f + 6% 370 VAC/B . Can you please to help me find a right one ? Thanks in advance
 Reply

InyoPools Product Specialist  Posted: 9/29/2021 

What is the part, model, or catalog number on your motor's label? That 328p3510h37n37a5a0 looks like the serial number of the capacitor; we are unable to use those to find a match.
 Reply

 Posted: 8/31/2021 

Hi, I have an AO Smith SP1515Z1BC, 1.5 HP pool pump motor. Worked fine till the other day, now it hums when started. My first thought was the capacitor. But after some inspection I don't see one. Does this motor have one?
 Reply

InyoPools Product Specialist  Posted: 9/1/2021 

That specific motor does not have a capacitor; it is a split-phase motor. So the problem could be an internal switch or the windings. If the windings are bad, you will do your best to explore the whole motor. Unfortunately, I do not list a switch for that particular motor number. The whole replacement motor would be the ould be the Hayward Motor 1.5 HP w/ Switch - SPX1515Z1E
 Reply

 Posted: 8/30/2021 

Ho, What is the replacement capacitor for pentair 2 HP super flow 340040. It says 30 uf +_6 370v vac 50/60 hz
 Reply

InyoPools Product Specialist  Posted: 9/1/2021 

The correct replacement pump motor capacitor is the 30 MFD (5VR0303) (2444).
 Reply

 Posted: 8/27/2021 

I am trying to find the correct replacement start capacitor for a Hayward Century Lasar Pool/Spa pump. It says on the pump it's a: FR U48Y Part 7-193824-01 HP: 2-25 SPL Type: CSM RPM: 3450/1725
 Reply

InyoPools Product Specialist  Posted: 9/1/2021 

The most common capacitor replacement for that 7-193824-01 pump motor is the 25MFD 370V - 628318-307. Before purchasing, I would check the ratings of your current capacitor to make sure the replacement matches.
 Reply

 Posted: 8/27/2021 

I'm trying to find the capacitor rating for a hayward pump. It is an A.O. smith B228SE motor. I believe it is a PSC capacitor. The one that I took out is completely rusted. I can't see any numbers. It's from a 25 yr old hayward maxflo pump..
 Reply

InyoPools Product Specialist  Posted: 8/27/2021 

The replacement cap for the B228SE is the 25 MFD - 628318-307
 Reply

 Posted: 8/27/2021 

Thank you sir. You provide very much needed information.
 Reply

InyoPools Product Specialist  Posted: 9/1/2021 

You're welcome. Thanks for reading!
 Reply

 Posted: 8/23/2021 

I have an Emerson EB796 motor on a Hayward Super 2 pump. The motor only hums. The shaft turns freely. The capacitor does not show any visible bulges. Can you advise what capacitor I could buy to replace the existing? Thanks very much.
 Reply

InyoPools Product Specialist  Posted: 8/23/2021 

The B796 shows two different styles, one that uses a run and another that uses a start capacitor. What color is your capacitor? Also, if you have it out, do you see any ratings on it?
 Reply

 Posted: 8/23/2021 

Forgot to clarify that current capacitor is silver.
 Reply

InyoPools Product Specialist  Posted: 8/24/2021 

Thank you. Pump capacitors are easy to identify because the Start is usually black or brown and the Run has a silver/metal finish.
 Reply

 Posted: 8/23/2021 

Thanks Matt. It is a Shenge CBB65A 370 VAC. B 50 uf S2 It is rear-mounted to the motor and has two terminals.
 Reply

InyoPools Product Specialist  Posted: 8/23/2021 

The correct capacitor is the 50 MFD (RD-50-370).
 Reply

 Posted: 8/21/2021 

Hello, I have a Pentair pump. My capacitor is CSC 50UF +/- 6% 370VAC 50/60HZ 325P506H37N36N4X I am having hard time to find it on the web. Do you guys have it or even compatible model will be fine? If yes, can you please attached the link Thanks,
 Reply

InyoPools Product Specialist  Posted: 8/23/2021 

Yes, we do; it can be found here - 50 MFD (RD-50-370)
 Reply