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 346)

 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
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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.
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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.
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 Posted: 4/30/2021 

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

 Posted: 2/15/2021 

I have a Power Right PUM22901091 that needs a start capacitor. Can you tell me which one is needed?
 Reply

InyoPools Product Specialist  Posted: 2/16/2021 

I am unable to identify the type of capacitor for that pump using the model number. Have you tried looking at the current capacitor's barrel for its ratings?
 Reply

 Posted: 1/22/2021 

I have a 2 speed Century motor, sts1102rv1, model k48a74a01, need to know what size start capacitor (mf ).
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InyoPools Product Specialist  Posted: 1/22/2021 

The part you need is the AO Smith Replacement capacitor, 25MFD 370V - 628318-307
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 Posted: 1/23/2021 

Matt - thanks, but that is a run capacitor, I need the mfd for the start capacitor.
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InyoPools Product Specialist  Posted: 1/25/2021 

Sorry about that. This is the one you are looking for 64-77 MFD (BC-64)
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 Posted: 1/25/2021 

Matt, Thanks, that is a big help. The one that was in the pump was dead, and I couldn't read the numbers on it. Mark
 Reply

 Posted: 1/19/2021 

Hello, what would be the correct capacitor for Sta-Rite DS3HF-01? Thanks!
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InyoPools Product Specialist  Posted: 1/21/2021 

 The DS3HF-01 is the pump housing model number for a sprinkler pump; the capacitor is matched to the motor. I would either need the model number of the motor or the specs listed on the old capacitor's barrel to find a replacement.
 Reply

 Posted: 12/27/2020 

I am looking for a replacement capacitor for Emerson R63MWENA-4727. The capacitor is labeled: M24P3750MT2 50UF 370V 50/60HZ 70C C22.2No190 MRP 181036. I have not been able to find either the exact part or a cross reference replacement part. Can you help me?
 Reply

InyoPools Product Specialist  Posted: 1/4/2021 

The correct capacitor replacement for the R63MWENA-4727 is the 50 MFD (RD-50-370)
 Reply

 Posted: 11/17/2020 

I have a failed start/run capacitor that NOBODY ever heard of. It sas cbb61, it's rectangular with 3 terminals and rated at 30UF, 250VAC, used with a motor xz10245S12 in a bestway coleman pool pump system 58392e. BESTWAY nor COLEMAN has a clue nor provides any actualy parts lists. I can't seem to find it in any of the capacitor companies. ANY help would be appreciated, the system is only 2 years old and too good to just through awa. Thankst I will NEVER recommend these two companies again for that reason.
 Reply

InyoPools Product Specialist  Posted: 11/18/2020 

I did a few searches for the CB661 30 uf capacitors and found tons of two-wire versions but no three-wire. When I search for CB661 30 uf three-wire, only capacitors with a 30 uF rating or lower show up. Can you check the capacitor again to verify the details listed?
 Reply

 Posted: 11/27/2020 

The pump has NO MFG name, just this number xz19245S12, the capacitor is flat rectangular, 3 terminals 2 black wire in/out AC to motor, and 1 orange direct to motor. The number on it is CBB61, 30uf, 250Vac, ROUclear. Apparently does not exist anywhere but in my bestway flo9wclear 58392e system. If you know of anyone who has EVER heard of one of these, PLEASE let me know. Thanks very much. P.S. Bestway nor COLEMAN does not support their pump systems. I would have thought this motor was a Hayward, but apparently not. NO MFG lists this capacitor..
 Reply

InyoPools Product Specialist  Posted: 12/3/2020 

I could not find any solid info on a replacement. It seems like this is a specially made part just for their whole goods. You should contact an electronic parts dealer specializing in all things capacitors, resistors, and the like. There are quite a few of them online.
 Reply

 Posted: 11/3/2020 

Need a capacitor for Northstar pump, century centurion motor 3/4 HP SP1607Z1BNSC (not BNS). The current capacitor is 35uF 370 volt JARD model 12718, but I think someone may have installed the wrong capacitor.
 Reply

InyoPools Product Specialist  Posted: 11/4/2020 

The correct run capacitor replacement for the SP1607Z1BNSC is the 35 MFD (RD-35-370).
 Reply

 Posted: 10/17/2020 

Hello, I just replaced my motor’s capacitor but the gasket that the “doghouse” cover sits on fell apart when the old capacitor blew its top. Is there anywhere I can purchase a replacement gasket? Motor is a Hayward 1.5 HP, but label is faded and can’t get much else off of it.
 Reply

InyoPools Product Specialist  Posted: 10/19/2020 

It is basically just a rubber foam material. Hardware stores may sell sheets of the stuff that you can then cut to form.
 Reply

 Posted: 9/26/2020 

I'm in need for a run capacitor for a super pump 700. I have no idea which capacitor to purchase.
 Reply

InyoPools Product Specialist  Posted: 10/6/2020 

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: 9/18/2020 

Motor hums, told the capacitor is out, Emerson agd15fl1 is what we have, knowing it’s an older motor I haven’t been able to find anything about what size capacitor is needed or even if this motor has a start capacitor. Your help would be greatly appreciated!
 Reply

InyoPools Product Specialist  Posted: 9/24/2020 

Because the brand Nidec makes a relatively small portion of the industry's motors, there is not much information on that motor. The best route is to open the motor to find the ratings of the capacitor written on its barrel.
 Reply

Anonymous  Posted: 9/10/2020 

Needing start capacitor for Doheney 1.5 hp in ground pump. Model # cs4m257i1l. Can someone please assist me?
 Reply