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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) 



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Steps

Things You'll Need

Start Capacitors

Run Capacitors

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)

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(241 to 280 of 450)

InyoPools Product Specialist  Posted: 5/30/2019 

The replacement start capacitor is the 64-77 MFD (BC-64).The BN50 (still available) does not have an owner's manual as such, just a basic troubleshooting guide that comes with all the manufacturer's motors.
 Reply

 Posted: 5/27/2019 

Need start capacitor rating for Jacuzzi Magnetek Centurion SE switchless motor 10-184950-22 (HP 1.5 1.5 SF). Capacitor is so corroded that can’t find any uf or voltage rating on it.
 Reply

InyoPools Product Specialist  Posted: 5/28/2019 

The replacement run capacitor for the B796 is the 628318-313
 Reply

 Posted: 5/27/2019 

Hi after reading your article I believe I should take a shot at replacing my run capacitor on an older Hayward Max-Flo pump. I can't read much of the writing on the pump or capacitor but believe the model # is sp2800-z-1. Any help with which replacement capacitor I should try would be greatly appreciated. Thanks!
 Reply

InyoPools Product Specialist  Posted: 5/30/2019 

Can you read the HP, or Amps on the label? The SP2800Z1 part/model number is not bringing up any results, no matter which format we try it in.
 Reply

 Posted: 5/25/2019 

We have a hard 35 uf capacitor can I upgrade to a 50 uf?
 Reply

InyoPools Product Specialist  Posted: 5/30/2019 

Oversizing a capacitor can cause a rise in energy consumption. I would just stick with the one that is prescribed for your motor.
 Reply

 Posted: 5/22/2019 

Which is the correct start capacitor for a Hayward 1.0 HP motor? Thank you!
 Reply

InyoPools Product Specialist  Posted: 5/22/2019 

Hello Paul - What is the catalog or part number on the motor label?
 Reply

 Posted: 5/22/2019 

I need a replacement run capacitor for a Haward Tristar 1.5hp pump. Replacing a Genteq 27L1358 370VAC 50/60Hz. Can't find this part anywhere. Not sure what other capacitor will work. Thanks!
 Reply

InyoPools Product Specialist  Posted: 5/22/2019 

Hello Jeremy - Can you read the MFD/UF rating on the capacitor?
 Reply

 Posted: 8/7/2019 

Genteq 27L1358 Capacitor - Need a Replacement? Can't find the exact one... other info on it shows: 30uf , +6 -6% , Protected P965, P10000AFC , 628318-308, 50/60Hz, 370VAC.. Hopefully I got you all the info you need to tell me what get to replace my blown capacitor. Thanks
 Reply

InyoPools Product Specialist  Posted: 8/8/2019 

Using the part number 27L1358 in our product search, it came back with this match: Run Capacitor - 30 MFD (5VR0303)
 Reply

 Posted: 5/21/2019 

Which capacitor for a Centurion B2853, 1 HP, 60 hz. 230-115 volt, amp SF6.6/13.2
 Reply

InyoPools Product Specialist  Posted: 5/22/2019 

The replacement run capacitor is the 30 MFD (5VR0303).
 Reply

 Posted: 5/21/2019 

I need to replace a capacitor for a Pentair 1HP 208-230/115V 1 phase motor. Part number for the motor is WFE-4/.011513. Can someone help out and let me know exactly what I need?
 Reply

InyoPools Product Specialist  Posted: 5/21/2019 

The replacement run capacitor for the standard WFE-4 motor is the 50 MFD (RD-50-370).
 Reply

 Posted: 5/20/2019 

I have a new Polaris booster pump motor. US Motors 1081 pool motor, catalog # ASB625, model K63CXEAZ-5229. Running in 220 VAC. Is the correct start capacitor 35 microfarad 370 VAC? After ~ 5 months, it merely hums when power is applied, and has to be "jump started".
 Reply

InyoPools Product Specialist  Posted: 5/21/2019 

The replacement capacitor for the B625 is the START CAPACITOR, 124-149 MFD (BC-124)
 Reply

 Posted: 5/21/2019 

I took off the back cover and found a 35 uf cap. Is that the start capacitor location? Is there a run capacitor? Is this why it only worked for less than 5 months?
 Reply

InyoPools Product Specialist  Posted: 5/22/2019 

The 35 MFD - 370 VAC are run capacitor ratings. With the B625, all the replacement part manuals state it only has a start capacitor. Whether or not that is the reason your pump failed, I cannot say for sure.
 Reply

 Posted: 5/13/2019 

Need a replacement capacitor for Hayward super 2 pump, model C48L2N134B3, 1.5 hp, 115/230v
 Reply

InyoPools Product Specialist  Posted: 5/14/2019 

The replacement capacitor: U.S. Seal Manufacturing START CAPACITOR, 161-193 MFD (BC-161)
 Reply

 Posted: 5/13/2019 

need a replacement capacitor for a centurion pump M/N B130, Part 0-159988-06, 2 HP; 230 v, 10.5 Amp
 Reply

InyoPools Product Specialist  Posted: 5/13/2019 

The replacement run capacitor is the 628318-307
 Reply

 Posted: 5/11/2019 

Need a replacement capacitor for a 2.0 HP Century Centurion motor model USN1202. What do you recommend?
 Reply

InyoPools Product Specialist  Posted: 5/13/2019 

Hello Jim - the replacement capacitor for the USN1202 is 628318-309.
 Reply

 Posted: 5/8/2019 

Need a start capacitor replacement for an NGM 61B1D160124NNAO. It is a 124-149uF but 165 VAC. I recently bought another replacement that worked once but the next time I tried to start the motor it just hums and won’t turn over. That one was 124-149 uF but just 110VAC. That voltage difference might have been the issue. What start capacity should I get considering I might need to go up a level. Thanks
 Reply

InyoPools Product Specialist  Posted: 5/9/2019 

The standard replacement motor start capacitor is this 124-149 MFD (BC-124); which is rated for up to 125 volts. If your motor is blowing through capacitors, it is probably not the capacitor's fault. Your lines may have abnormally high voltage spikes, or your motor windings are going bad causing the capacitor to fail.
 Reply

 Posted: 5/4/2019 

Can anyone assist please?? I have a 1 1/2 HP Hayward Pump. Model #C48L2N134B1 Serial # OF06 115/230 Volts Which motor start capacitor should I purchase to replace?
 Reply

InyoPools Product Specialist  Posted: 5/6/2019 

The replacement start capacitor for the UST1152 is the BC-161
 Reply

 Posted: 5/1/2019 

Hi I have a SP 2610X15A Dual Speed pump, does this model have a run capacitor? I only see a start capacitor.. My pump is only able to run on low speed, as soon as i put the pump on high speed it shuts off in less than 2 minutes. I've had an electrician check the electrical box ( no issues ) , the impeller is the correct model. Could a bad shaft seal cause the pump to shut off that quickly on high speed? The pump has never shut off while on low speed
 Reply

InyoPools Product Specialist  Posted: 5/2/2019 

To verify the correct parts, we will need to identify the motor using the Part, Catalog (CAT), or Model (MOD) number. At least one of those numbers will be listed on motor label.Regarding the shaft seal, are you seeing any water underneath the pump?
 Reply

Anonymous  Posted: 5/4/2019 

Thanks for your reply. The motor is AO Smith C48L2N125 . And yes there is a small amount of water underneath. The shaft seal is definitely bad, i just want to know if that could cause the motor to shut off on high speed - if not i imagine the motor needs to be replaced
 Reply

InyoPools Product Specialist  Posted: 5/6/2019 

The bad shaft seal likely played a part in the motor failing. The issue could be a bad capacitor or a phase windings; there's a way to test for both: How to Test a Pool Pump Capacitor & How To Use a Multimeter to Test a Pool Pump Motor - Winding Resistance
 Reply

 Posted: 4/28/2019 

I have a three year old stay right three-quarter horsepower Supermax. It buzzes when power is on and will not run. I pulled the doghouse and the capacitor is all rust and cannot read specs. Can you help out?
 Reply

InyoPools Product Specialist  Posted: 4/29/2019 

Are the specs on the motor rusted off or is it just the capacitor?
 Reply

 Posted: 4/29/2019 

Capacitor is rusted
 Reply

InyoPools Product Specialist  Posted: 4/29/2019 

If the capacitor is illegible we can find the find part using the motor label. What is the part, catalog, or model number on the motor label?
 Reply

 Posted: 4/30/2019 

I found capacitor from Inyopools. Thanks for your response
 Reply