How To Select the Right Capacitor For Your Pool Pump Motor

WRITTEN BY:  Inyo Pools

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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.

Things You'll Need

Step by Step


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.

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.

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


(1 to 40 of 140)

Matthew  Posted: 09/20/2018 10:23 AM  Latest

Hello Ken - everything I have found on the Balboa Ultimax 1016026, says that it is a run capacitor only type.

Ken  Posted: 09/20/2018 0:42 AM  Latest

My pump is also doing the humming noise without starting. Upon inspection, I was only able to locate the run capacitor. After the end cover of the motor was taken off, it appears there is only the coil pack but no additional capacitor. Could you help confirming if the Balboa Part 1016026 Model PUUMC2252582FR indeed has just the one capacitor? Thank you!

InyoPools  Posted: 09/13/2018 10:03 AM  Inyo Product Specialist

Hello Paul - Your motor only has one capacitor. The replacement run capacitor for your 0-193986-24, also known as model B2854, is part number 5270-08.

Paul D  Posted: 09/13/2018 9:36 AM 

Hi, My pump is humming so I would like to try the capacitor(s) before I replace the motor. The motor can spin by hand. Unfortunately, the East Coast weather is not cooperating with taking the electrical parts of the motor apart to identify the capacitor(s). Would you be able to tell me what capacitor or capacitors it uses so I can have them in hand for when the sun peaks out? Its a Century Centurion attached to a Jandy pump. Part number 0-193986-24. Your website cross-references it to a b2854. It doesn't have the HP on the Century label but a separate Jandy label says 1.50 x 1.10 = 1.65. The Century label says type=CX frame=Y56Y HP= SF= PH=1 HZ=60 RPM=3450 Volts=230/115 Amps= SF 8.0/16.0 Time=CONT Encl=DP Form=KJM Code=J InsulClass=B AMB=50c

InyoPools  Posted: 09/11/2018 15:27 PM  Inyo Product Specialist

Hello Dan - We were able to identify the capacitors for your 7-187563-02, also known as a B2235 motor. It takes a total of three capacitors. The start capacitor is part number 610807-002. The run capacitors are 628318-309 and 628316-315. The run capacitors are in the same case on the motor.

Matthew  Posted: 09/05/2018 12:44 PM 

Hello Corin - The C48L2N134B1, also known as the UST1152, only uses a start capacitor. The correct replacement capacitor is the 5270-14.

InyoPools  Posted: 09/04/2018 15:38 PM  Inyo Product Specialist

Hello lleff - The correct start capacitor for model C48K2N143B1 (UST1102) is part number 5270-14.

Dan  Posted: 09/03/2018 14:45 PM 

Hi, I have this pump. Can you tell me what capacitor it requires? I've read it requires a split capacitor but I am not sure what that means and I want to ensure I put the right one on. A. O. Smith 4 HP, 12 AMP, 230 V, Dual Speed Part Number 7-187563-02, Type CXPM Frame R56Y Thanks Dan

Corin  Posted: 09/02/2018 8:02 AM 

If the motor hums and after a while starts, does that require to replace the start capacitor or the running capacitor or both? What start and running capacitors are required for a C48L2N134B1 pump?

lleff  Posted: 08/31/2018 11:21 AM 

Hi. What is the correct start capacitor for a Hayward Super Pump - Model c48k2n143B1? 1hp. 115/230 volts. 15 amps?

InyoPools  Posted: 08/28/2018 17:44 PM  Inyo Product Specialist

Hello txnplano - The correct run capacitor for the Pentair LA01N booster pump motor is part number 5270-08.

txnplano  Posted: 08/28/2018 15:17 PM 

What is the correct capacitor for a Pentair LA01N booster pump?

InyoPools  Posted: 08/27/2018 10:24 AM  Inyo Product Specialist

Hello Jason - It is acceptable to replace a capacitor with a higher voltage as long as the MFD rating is the same as the original.

Jason  Posted: 08/26/2018 14:44 PM 

Hi, is it OK to swap in a 370 volt run capacitor for a 440? i think the 440 is too much, as this size runs hot and burns out, as i've had to replace every year or so. thanks for any advice.

Matthew  Posted: 08/20/2018 13:22 PM 

Hello Tom - the correct start capacitor replacement for the C48L2N133, ST1102 1 HP motor is the 610807-002

Matthew  Posted: 08/20/2018 12:11 PM 

Hello Anita - The important ratings needed when matching a start capacitor is the microfarad (UF or MFD) rating part number shown as 680171-002. Sometimes the 'U' in the UF is lowercase, backward with a squiggly tail. The correct replacement is our part number, 5270-14.

Anita  Posted: 08/19/2018 18:29 PM 

I have a Hayward 1.5 hp pool pump with an AO Smith motor #C48L2N134B3. I think it is a super pump #SP1610Z1MBK it is a three prong motor start capacitor. The following information is listed on the start capacitor: JKD Motor start capacitor CD60B1AJ161192 AU-T2, 110vac, 161-192UF, 680171-002, 50/60Hz, E212600. All this is foreign to me, could you please let me know the part number of the correct start capacitor for me.

tom  Posted: 08/16/2018 19:44 PM 

what capacitor for a Hayward self priming super pump model C48L2N133 serial 1E97 115/230 volts

InyoPools  Posted: 08/16/2018 14:17 PM  Inyo Product Specialist

Hello Katie - The start capacitor for the C48K2N143B1 motor is part number 5270-14.

InyoPools  Posted: 08/16/2018 14:01 PM  Inyo Product Specialist

Hello Gregory - It sounds like you may have a bad capacitor. Check out our article titled "How to Test a Pool Pump Motor Capacitor".

Katie  Posted: 08/15/2018 22:40 PM 

I have a Hayward Super Pump SP1607Z1M that whines when turned on and than it does not start. I can move the impeller by hand so I think it is the capacitor. I need to know what one to order. The info on the pump is as follows: Self Priming, Model # C48K2N143B1 Ser # 07212FM, HP 1, KW .75, Volts 115/230, RPM 3450, Amps 15.0/7.5, HZ 60, SF 1,1, FR 56J, PH 1, Thermally Protected Auto, AMB 50 C, ENCL ODP,Type UAC, Duty CONT, Code J, Insul Class B. I hope this info is helpful.

Gregory Pratt  Posted: 08/15/2018 22:05 PM 

I have a hayward pump that this week decided not to start automatically with the timer. I found that trying the power switch several times eventually got the pump to start. each time I tried I could see that the pump attempted to go, but didn't make it. It takes on average about 7 power cycles before it kicks on. I am guessing this is the start capacitor?

InyoPools  Posted: 08/15/2018 15:02 PM  Inyo Product Specialist

The 1HP single speed Power Flo Matrix motor does not have a capacitor.

Matthew  Posted: 08/08/2018 16:44 PM 

Hello IDK - that seems more like a circuit issue than a capacitor problem. Low voltage can cause motors to overheat and shut down. We cover how to troubleshoot low voltage and other common causes of overheating in this guide: How To Troubleshoot a Pool Pump Motor - Motor Overheated

Matthew  Posted: 08/08/2018 12:27 PM 

Hello Chris - The Hayward Super Pump SP2615X20 2HP uses a UST1252 motor. That motor uses two capacitors, the run is the 628318-308 and the start is 610807-001.

Matthew  Posted: 08/08/2018 11:46 AM 

Hello Jon - The Pentair WF-30 uses a motor similar to the B840; which uses a 30 MFD Run Capacitor. If you were at the pump, you could remove the capacitor from the motor to read the ratings on its jacket.

Matthew  Posted: 08/07/2018 12:08 PM 

Hello Al - we have a guide that shows the equipment needed and how to use it for testing each of the most commonly replaced parts on a pool pump motor. Give it a read: Using the Proper Test Equipment to Troubleshoot Pool Motors

Jon  Posted: 07/21/2018 9:37 AM 

Great article and thanks so much! I am out of town right now so unable to access the pump, but it seems we are possibly having issues with the start/run capacitor on our PENTAIR WF-30/011775. It is a 2.50 HP motor, 208-230V, 60Hz 1PH kW. 3450 RPM S.F. 1.04. MaxAmps SF 11.5-11.0. Any idea which capacitor would be compatible with this pump? I will be home in a few days to open the pump up and I'll be able to provide further info. Thanks so much!

tim  Posted: 07/20/2018 20:12 PM 

Hi, I have a 1hp Power Flo Matrix- I took off back cover and didn't see anything that looked like a capacitor. Does that model have one? What would it be? thx- Tim

Inyopools  Posted: 07/18/2018 15:38 PM  Inyo Product Specialist

Hello Brenda - If your 3/4HP Super II pump has a single speed motor with a 1.0 service factor, the replacement capacitor is part number 5270-11.

Brenda  Posted: 07/18/2018 14:23 PM 

Can you tell me what start capacitor is needed for a 3/4 HP SUPER 2 PUMP? Thanks so much!

Chris  Posted: 07/14/2018 23:05 PM 

I have a Hayward SP2615X20 2 HP - what capacitor do I need? The label on the motor housing is unreadable.

Inyopools  Posted: 07/13/2018 10:56 AM  Inyo Product Specialist

Hello Teresa - As long as the MFD (UF) and voltage rating match your current capacitor, the replacement will work.

Teresa Lyon  Posted: 07/12/2018 18:00 PM 

Replacing a CBB65A-1 370 VAC capacitor; every one I have found says =/- 5% but mine says =/- 6%, Is this going to be a problem and if so can you give me a suitable replacement (or upgrade). Motor in question is US Motors model K63CXEAP-5221, 1.5 HP, 3450 RPM, 60 HZ

I don't know  Posted: 06/29/2018 21:30 PM 

I have a Century HST150 pump. It turns on, runs a few minutes then overheats and shuts down. Is this a capacitor issue?

Inyopools  Posted: 06/15/2018 17:10 PM  Inyo Product Specialist

Hello Paul - You have a Century B128 motor. The correct run capacitor is part number 5270-08.

Paul  Posted: 06/13/2018 12:17 PM 

Hi there, could you please help me figure out which start capacitor I need? The information on the motor says Century Centurion Type CX, SF=1.40, Frame=m563, part=0-164303-23, hp=1.4, CAT=B12

Al  Posted: 06/01/2018 10:46 AM 

I have an A.O. Smith (Hayward) 1.0 HP Power-Flo LX motor, p/n SP1510Z1XBC that hums when power is applied. When I hand spin the shaft the motor kicks in and runs normally, but there is no start capacitor on this model. I'm guessing the motor has a starter coil, so my question is "which part or component is the most likely cause of the problem? The coil itself? Can that be tested (continuity check)? Could it be the start switch? The switch on my motor is not a V shaped switch as shown in your repair guide, so I have nothing to follow when it comes to removing and checking that switch. Or could it be the governor assembly? Any advice would be appreciated, and any diagrams or schematics that match my motor would be very helpful. Thanks!!!

Inyopools  Posted: 05/30/2018 14:23 PM  Inyo Product Specialist

Hello Dave - A bad capacitor could cause the motor to smoke. Check out our article titled "How to Test a Pool Pump Capacitor". Other reasons for smoke could include bad windings, low or high voltage, bad ventilation, damaged cooling fan, and high ambient temperatures.

Dave  Posted: 05/30/2018 14:05 PM 

I have white smoke coming out of the motor housing and a burning plastic smell when it is turned on. Would a bad capacitor cause this?