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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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(81 to 120 of 450)

 Posted: 7/31/2021 

I have an Emerson EB653 Model K63CXESL-4796 what capacitor do I need? I've been trying all morning to get the rusted lower screw out to get a look at it with no luck yet.
 Reply

InyoPools Product Specialist  Posted: 8/3/2021 

The EB653 pool pump motor uses the 55 MFD  - 628317-314 run capacitor.
 Reply

 Posted: 7/27/2021 

I have a 1.5 HP PowerFlo Matrix pool pump that is approximately 2 years old. The Pump has been working fine until a few days ago. Impeller spins freely. The pump works than stops and “hums”. Plugged it into receptacle (separate from the timer) and it worked for a few minutes then stopped and began to hum again. Do you thinks it’s the capacitor? If so, which model number do I need?
 Reply

InyoPools Product Specialist  Posted: 7/30/2021 

It could be the capacitor, but you need to test it to be certain. See this guide for more information - How to Test a Pool Pump CapacitorWhat is the part, model, or catalog number on your motor's label? A picture of the motor label would be most helpful.
 Reply

 Posted: 7/21/2021 

I have an Hayward Super Pump 1 1/2 HP, inground pool, Volts 115/230 Motor SPX1620Z1M - Can you please advise which start capacitor I will need. Thank you
 Reply

InyoPools Product Specialist  Posted: 7/21/2021 

Please verify the listed Hp and the model number of the motor you listed. They bring up conflicting results.
 Reply

 Posted: 7/22/2021 

Thank you Matt, I did find the part I needed.
 Reply

InyoPools Product Specialist  Posted: 7/23/2021 

You're welcome!
 Reply

 Posted: 7/18/2021 

Hello, could you tell me what start capacitor I need for our Hayward 2 HP Super pump Sp2615x20A. It has an A.O. Smith motor, model # C48M2N111B3. Thank you!
 Reply

InyoPools Product Specialist  Posted: 7/20/2021 

The C48M2N111B3 uses one of the 604005-001 and one of the 100025-002 bearings 
 Reply

 Posted: 7/11/2021 

Hi, I am looking for a start capacitor for an A.O.Smith Century LASAR Spa Motor. CAT BN60 Serial BY08-29 Part 7-186022-03 Can you help me with this? Thanks
 Reply

InyoPools Product Specialist  Posted: 7/14/2021 

the correct replacement capacitor for the BN60 is the 56-75 MFD (SCN-157699-03)
 Reply

 Posted: 7/11/2021 

i have a haward super pump model c48jn131b1 series 33512fm that will humm and stop half min later will hum and stop and then finally start up. i have been trying to find the part number for this models start capacitor without any luck.
 Reply

InyoPools Product Specialist  Posted: 7/14/2021 

Hello - the part number c48jn131b1 is missing a digit. Please verify the number on your motor label.
 Reply

 Posted: 7/10/2021 

My pool pump was working fine this morning as usual, then shut off. Maintenance guy came in cleaned pool and replaced the top off the valve assembly (filter/recirc/backwash/etc valve). Turned it on to backwash, worked fine. Switch to Rinse... nothing. You can hear the relay inside the control box switching on, but nothing from the pump. No humming, nothing. The motor is only a year old. I've looked at both capacitors and connections, which still look new. The motor has power to it.
 Reply

InyoPools Product Specialist  Posted: 7/23/2021 

You may try testing the phase windings. How To Use a Multimeter to Test a Pool Pump Motor - Winding Resistance
 Reply

 Posted: 7/1/2021 

The run capacitor on my Hayward MAX-FLO Century Model K48AA35A04 (HP 1.0/.16; Volts 230; AMPS SF 6.2/2.2; HZ 60 SF1.25; KW .93/.12; RPM 3450/1725/ ROT CWLE; SP2707Z2M2) pool motor goes out approximately every 2 months. The current capacitor i have been using is a Model #12718 (35.0uF +6% 370VAC/B 50/60Hz). Am I using the correct capacitor? Can I upgrade to a capacitor that will last longer? I would greatly appreciate your recommendations.
 Reply

InyoPools Product Specialist  Posted: 7/1/2021 

Is this the capacitor that came with the motor?There really isn't an upgrade when it comes to motor capacitors. If you are consistently blowing motors, it sounds like there is a circuit issue. I suggest reviewing this guide and video on the topic - Why is my pool pump motor capacitor failing?
 Reply

 Posted: 6/26/2021 

Looking for run Capacitor for Century Centurion 2HP motor. CATB130, 230V. Part 7-159988-06 25uf was installed & failed so wondering if it is correct size. Seems it has been replaced. Thanks
 Reply

InyoPools Product Specialist  Posted: 7/1/2021 

The correct capacitor replacement for the B130 pool pump motor is Part #: 628318-307
 Reply

 Posted: 6/17/2021 

Hi, we started our pump and it hums and then clicks and never starts,. We are now looking into the capacitor. It looks like it might only have one capacitor, but the rating is 25uf 370VAC which sounds like it would be a run capacitor. Is this normal for a single capacitor motor? If so what size motor do I need?
 Reply

InyoPools Product Specialist  Posted: 6/17/2021 

The humming is a symptom of a bad start capacitor; if the motor were shutting down erratically, flipping the breaker of overheating, that would be a sign of a bad run capacitor. Have you checked the line voltage reaching the motor?
 Reply

 Posted: 6/14/2021 

Could you tell me which capacitors to use for a Sta Rite Max-E-Pro pump (single speed, 1HP - P6RA6E-205L)? Thanks!
 Reply

InyoPools Product Specialist  Posted: 6/17/2021 

What is the part, model, or catalog number on your motor's label? A picture of the motor label would be most helpful.
 Reply

 Posted: 5/22/2021 

Hi there, I am looking for the correct start capacitor for my pool pump. The pump itself says 1081 Pool Motor. Model K63CXERN-4780. The capacitor has the following on it: C107558550061 CBB65A-1 35 uF +/- 6 % 370 VAC 50/60 Hz 40/70/21 10,000 protected AFC Can you please let me know which one i need and i will place order on your website right away? Thank you so much! Chris
 Reply

InyoPools Product Specialist  Posted: 6/4/2021 

The correct capacitor for your K63CXERN-4780 motor is the 35 MFD (RD-35-370).
 Reply

 Posted: 5/11/2021 

Hi I am trying to find out which start capacitor is installed in my pump motor its a Magnetek Century Centurion 1hp 230/115v Part# 10-186085-20. Ser# BS11-09 Also looking for a manual and wiring specs. Thank you
 Reply

InyoPools Product Specialist  Posted: 5/13/2021 

The correct replacement capacitor is the 55 MFD 370 VAC - 628318-314. I don't have wiring instructions for this motor the B638 motor capacitor but I would take a picture of the wire connections before you disconnect the old one when installing the new.
 Reply

 Posted: 5/3/2021 

I need a capacitor for a Hayward SP3215X20 2 HP Pool Pump, Would you please tell me which one is for this pump. Thank you.
 Reply

InyoPools Product Specialist  Posted: 5/13/2021 

What is the part, model, or catalog number on your motor's label? A picture of the motor label would be most helpful.The info provided is for the pump-end but does not directly identify the motor. If this is a replacement motor there is a wide host of options the previous installer could have used. So, we need to nail down the motor model to get the right capacitor.
 Reply

 Posted: 4/30/2021 

Hello any help would greatly appreciated. Looking for a run and start capacitor for a emerson t55mwcce-1208
 Reply

InyoPools Product Specialist  Posted: 5/13/2021 

I don't have a reliable source for schematics for that model of that pool pump motor. I've mentioned this in the comments below and I think it is said in the article above, remove the capacitor and check the ratings. Once you have that you can refer to our Run Capacitors and Start Capacitors charts for a match.
 Reply

 Posted: 3/31/2021 

Can you help with which replacement to order for hayword super pump 700 series.
 Reply

InyoPools Product Specialist  Posted: 4/1/2021 

Yes, we can help but we need the usual information. What is the part, model, or catalog number on your motor's label? A picture of the motor label would be most helpful.
 Reply

 Posted: 3/28/2021 

Can you please tell me a replacement capacitor for the Pentair Whisperflo PN 011772. The original capacitor that was installed is a C65R 30MFD+-6%?
 Reply

InyoPools Product Specialist  Posted: 3/29/2021 

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

 Posted: 3/6/2021 

Hi. Can you tell me the correct capacitor for an A.O. Smith Century Centurion SP1615-Z-1-BNSC?
 Reply

InyoPools Product Specialist  Posted: 3/8/2021 

The correct capacitor for your USN1202 or SN1152 is the Run Capacitor, 35 MFD (RD-35-370) - 628318-309
 Reply

 Posted: 3/4/2021 

Polaris PB4-60 boost pump hums when turned on. It has a 61B1D160124NNAO (124-149uF, 165VAC) capacitor. Can you recommend a replacement?
 Reply

InyoPools Product Specialist  Posted: 3/8/2021 

I searched the part number "61B1D160124NNAO" and I found this one: Start Capacitor, 124-149 MFD (BC-124)
 Reply