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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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InyoPools Product Specialist  Posted: 9/2/2020 

The BN37 Pump Motor (p/n: 193743) uses the 64-77 MFD (BC-64) start capacitor
 Reply

 Posted: 6/13/2020 

I have an intex sand pump model number sf20110. The capacitor is 35uf +5%c 250vac50/60hz -40/70/21 now this one has 2 wires coming out of the top. Do you carry any of these.
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

The correct run capacitor replacement is the 35 MFD - RD-35-370
 Reply

 Posted: 6/11/2020 

Hello I have a pentair pump for pool, you know what capacitor It's the right one.
 Reply

InyoPools Product Specialist  Posted: 10/20/2020 

The capacitor is matched to the model of your motor. 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: 6/8/2020 

Hello, I have an Advantage Manufacturing Motor, 2HP, 230v, 3450 RPM, 10.5amps. The Run Cap is bowed out and looking bad, plus the motor wont start. I want to replace the Cap, but there is no visible markings on it. I have googled it, but cant seem to find the proper size. Hoping you can help!! Cheers
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

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: 6/4/2020 

Please confirm Run Capacitor and Start Capacitor (if one exists) for Century 1081 Pool Pump Motor SP3220Z1M, Part 7-F56AA14A04-02, FR Y56Y, HP 2.50 . Thanks!
 Reply

InyoPools Product Specialist  Posted: 10/23/2020 

The 7-F56AA14A04-02 motor requires just the run capacitor part number, 30 MFD (5VR0303) (2444)
 Reply

 Posted: 5/25/2020 

I have a Sta-rite Supermax 3/4 HP pump with a busted capacitor on the hump of the pump - I can’t read the writing on the capacitor, it’s so faded. The Pump model no. / part no. PHK2RA6D - 10 I L Motor # 196248. Do you have the capacitor I will need? Thanks!
 Reply

InyoPools Product Specialist  Posted: 10/23/2020 

Your motor part number 196248 (B852) used the 25 MFD run capacitor.
 Reply

 Posted: 5/20/2020 

I have a hayward maxflo 1.5HP pump that is two years old and it is not starting up and is humming and causing my breaker to blow. If it is the start capacitor what model do I need?
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

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: 5/15/2020 

I bought a pool motor a couple of years ago from you and now I am only getting a humming sound when I try to turn it on. I've deducted that I probably have a bad capacitor. It is located in the rear of the motor and is rated at 30uf 370/VAC 50/60Hz. I tried to replace it with my old capacitor but noticed that it was labeled as a starter capacitor and much smaller. The motor I bought a couple years ago always ran extremely hot. My question is: Is there a chance that the capacitor form the factory was the wrong one. Did they install a run capacitor instead of a starter capacitor and that's why it runs so hot? I also noticed that when I opened the back of the motor I had a lot of a white powder substance all over the inside. It wasn't rust but looked like it was some sort of white calcium build up???
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

I doubt the manufacturer installed the wrong type of capacitor. There is a chance the motor may have been defective, but it would not have lasted 2 years if it was. Also, motors run hot; a byproduct of the motor spinning is heat. A pump motor's temp usually hovers around 150 degrees Fahrenheit, and can reach 215 degrees before degradation of the motor components begins. A hot motor usually not an issue until it begins to trip your breaker.
 Reply

 Posted: 5/6/2020 

I need to find out what size start compacitor for a U.S. Motors pump Model # K63CXERJ-4776 to use.. All the numbers on the compacitor are missing.
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

The K63CXERJ-4776 uses the 161-193 MFD (BC-161) 110-125VAC  start capacitor
 Reply

 Posted: 5/3/2020 

Hello, I have a problem with my Hayward Turbo II pool pump. After only one season using it, I turn it on this year and hear a "hum" but won't start. Based on the comments i've seen looks like it may be the capacitor. I opened the box on top and found what looks like it could be a capacitor black, round and two wires coming out of top. Manufactured by Rihuan withs specs - 60 uf 250VAC - 25/70/21. Is this something I can order from you ? Tks for helping. Tom
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

According to the ratings on your old capacitor, the replacement is the 50 MFD (RD-50-370)
 Reply

 Posted: 5/2/2020 

Hi I have a waterway pn: 3421621-10 model #: sd-40-2n22cg. Can you tell me the start cap i need?
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

The 3421621 Waterway pump uses the 56-75 MFD (SCN-157699-03) start capacitor and the 50 MFD (RD-50-370) run capacitor.
 Reply

 Posted: 3/19/2020 

I have an energy saver spa equipment spa and pump and the capacitor says not 370 or 440, but 450vac and has a 40 uf rating. I didn't see anything like that on yalls site. The pump model number is WUA400-1 and the cap model is CBB60. Any idea on the correct replacement part? Thanks
 Reply

 Posted: 4/24/2020 

Did you find a capacitor for your spa? We are having the same issue you were/having with finding the right capacitor. Thank you!
 Reply

InyoPools Product Specialist  Posted: 3/20/2020 

What is the part(P/N,) catalog (CAT,) or model (MOD) number of the motor label? Look on the main motor sticker that lists horsepower, amps, volts, frame.
 Reply

 Posted: 3/17/2020 

Hi; I have a Magnetek (Century?) motor: PN 8-177624-20 which was on a 20 gal air compressor. Someone removed both capacitors. Label info: HP: SPL, 3450 rpm, 115/230v, 15/7.5 amp, single phase,Type: CP, Ser: BK9-032. Can you tell from this info what the start and run capacitors should be? Thanks much for your help!
 Reply

InyoPools Product Specialist  Posted: 3/18/2020 

This is not a pool pump motor; we do not have a cross-reference for that style. You may want to contact the manufacturer of the compressor or an online dealer for compressors.
 Reply

 Posted: 3/18/2020 

OK; thanks for your reply.
 Reply

 Posted: 1/27/2020 

I have this type of Motor. Catalog #:ASB128Model #:K063DGC5164023J. It seems like the run capacitor is not working, would you happen to know what will be the replacement one for it, thank you so much.
 Reply

InyoPools Product Specialist  Posted: 2/10/2020 

The replacement for the B128 - 1 HP EE Motor is the, RUN CAPACITOR, 25 MFD - 628318-307
 Reply

 Posted: 1/27/2020 

I have a 2 speed HAYWARD SUPER II 1.5hp, and it has the outer hump with what I believe is the RUN capacitor, and I'm wondering does it also have a START capacitor? Because It doesn't want to start it just HUMS pretty loud then the thermal trips and it goes off. I checked the impeller it spins fine. So I was going to replace the run capacitor, or does it have a start cap. too?
 Reply

InyoPools Product Specialist  Posted: 2/10/2020 

The original Hayward Super II 2-speed motors have run and start capacitors. The start capacitor will be located in the back of the motor. Remove the back cover and you should be able to see the start capacitor as well as the capacitor ratings.
 Reply

 Posted: 1/24/2020 

What type of capacitor do i need for a Hayward Maxflo pump with HST150 motor in it?
 Reply

InyoPools Product Specialist  Posted: 2/10/2020 

The model number HST150 comes back with a few conflicting results, but I believe your motor is the UST1152 - 1.5 HP Round Flange 56J Up Rate. Click that link to verify your Horsepower (HP), Service Factor (SF), and Frame (FR) match the ones listed. Then I can confirm the correct capacitor.
 Reply

 Posted: 12/5/2019 

Hello can you tell me what capacitor is used on Pentair 340039 motor?
 Reply

InyoPools Product Specialist  Posted: 12/9/2019 

The 340039  is the model number for the Pentair Super-Flo. To find the right capacitor I would need the part. catalog, or model from the motor label.
 Reply

 Posted: 11/11/2019 

Hi. I have (in Surrey, UK), a vintage Sta-Rite 5p2RE (0.75 kw) pump with a AO Smith motor. Looks like the capacitor’s packed up after a season of humming and taking progressively longer to start. Capacitor carries the markings Aerovox M, 161-193 UF 110VAC, 60 Cycles, 610807. Nothing comes up in google. have I reached a dead end or will any capacitor of similar size (so it fits in the pump) and rating (161-193 UF 110VAC, 60 Cycles) suffice?
 Reply

InyoPools Product Specialist  Posted: 11/11/2019 

I searched "161-193 UF" in Google, and a very long list of compatible capacitors came back as a result. You should be able to find that locally, pretty quickly. We offer those capacitors, but it wouldn't be worth it to ship it to you.
 Reply

 Posted: 11/7/2019 

Hello, I have a Balboa 1/4HP Circulation pump for my Hot Tub (Part Number 1030056) I'm not sure if its the Run or Start Capacitor is damaged, but it is popped open with the hardened substance exposed, do you have happen to have a part number for this Capacitor (I believe its a 6,3 uF +/-5% 50/60hz)
 Reply

InyoPools Product Specialist  Posted: 11/7/2019 

We do not carry the 6.3 MFD start capacitor, but it should be available in a local hardware store or an online electrical component dealer.
 Reply

 Posted: 11/6/2019 

Hello. I have been looking everywhere for my spa run capacitor and cannot seem to get any answers. The one that’s on it is 30uf 330vac and it has three prongs on it. It’s in a balboa motor puums302582r or 1016176. PLEASE HELP!
 Reply