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 328)

 Posted: 1/22/2021  Latest

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  Latest

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

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  Latest

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

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  Latest

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

 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?
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InyoPools Product Specialist  Posted: 1/4/2021 

The correct capacitor replacement for the R63MWENA-4727 is the 50 MFD (RD-50-370)
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 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.
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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.
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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.
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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.
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 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!
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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?
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InyoPools Product Specialist  Posted: 9/10/2020 

I do not have a parts sheet for their motors. But, if you actually look at the capacitor, the casing should have the part number and the microfarad ratings needed to figure which one of these (Start Capacitors) you need
 Reply

 Posted: 9/8/2020 

I have a Pentair SF-N1 2A/ 340040 2hp pool motor. When it is turned on a loud hum and it trips the breaker. I took the motor apart and the shaft spins freely with no debris inside. Does this motor have a start cap? I removed the back and nothing was there but the electrical connections so it looks like it only has the run cap in the doghouse on top. I removed it and inspected it and it is a C65R 30uF 50/60hz 10000AFC. I checked it with my meter and it read around 29.3 so I thought that would be considered good. I had an old motor with a 50uF capacitor on it and tried it , I was able to get the motor to start and run but the loud hum was still there but once it started it ran fine. It sound like the run cap is bad but not sure if this motor has one. Any help is appreciated, thanks- Brad
 Reply

InyoPools Product Specialist  Posted: 9/9/2020 

That motor does not have a replaceable start capacitor. The correct run capacitor replacement is the 30 MFD (5VR0303) (2444)
 Reply

 Posted: 7/31/2020 

Any chance you guys could help me out on what start capactior i need this is what i see on the one im trying to replace SH DB SO 40U F1 5% 250VAC 50/60 Percent CBB60 ZHE JIANG WUFENG R E476412 40/70/21
 Reply

InyoPools Product Specialist  Posted: 8/24/2020 

Here you go: Essex Group Capacitor, Run 370v 40 Mfd (rd-40-370)
 Reply

 Posted: 7/25/2020 

I couldn't find a genteq replacement 27L1576 - 30uf(+/-6) 50/60hz 440 vac anywhere. I did find a genteq 97F9635 - 30uf(+/-6) 50/60hz 440 which appears to be the same exact specs from what I can tell. the only difference other than size (my failed capacitor is shorter and wider and the new one is taller and slimmer) is that the old on has a yellow dot spray painted and the new one has a white dot spray painted. Does the color dot on top mean anything? can I go ahead and replace it with the white dot one or is their some risk or danger if I don't use a replacement with a yellow dot instead.Any feedback is appreciated. Thanks
 Reply

InyoPools Product Specialist  Posted: 9/8/2020 

I have not aware of the spray-painted dots on the capacitor jackets having a specific meaning. But I did a quick google search and found this capacitor code guide: Molded Mica Capacitor Color Code.If this is for a pool pump motor, the capacitor replacement for the original you listed is the 30 MFD (5VR0303) (2444)
 Reply

 Posted: 7/25/2020 

I cant find a genteq 27L1576 replacement (30uf (+/-6) 50/60hz 440 vac. I found a replacement 97
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InyoPools Product Specialist  Posted: 8/24/2020 

This one will work: U.S. Seal Manufacturing RUN CAPACITOR, 30 MFD (5VR0303) (2444)
 Reply

 Posted: 7/19/2020 

I have a Marathon mod # 5KCP49SN9117X motor for a spa. I have the hump for the run capacitor, but do not see any type of end cap to get to a start capacitor. Does this motor have a start capacitor? Just looking to make sure.
 Reply

InyoPools Product Specialist  Posted: 9/1/2020 

From what I have found on it, that motor only has a start capacitor
 Reply

 Posted: 6/28/2020 

Hi, I have a Hayward Super 2 Pump model SP3010X15A with a bad start capacitor. Do you know which capacitor I should be purchasing? Do you know if this model also has a run capacitor? Much appreciated!
 Reply

InyoPools Product Specialist  Posted: 9/23/2020 

The correct run capacitor for the SP3010X15 Hayward Super II is the Start Capacitor 161-193 MFD - BC-161.
 Reply

 Posted: 6/25/2020 

Hi I need a capacitor for a century b687 motor. The capacitor is rusted out can’t see any info?
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InyoPools Product Specialist  Posted: 9/24/2020 

The B687 motor requires the 25 MFD run capacitor
 Reply

 Posted: 6/17/2020 

im looking for the start capacitor for asparco pump # 193743. Can tell me the part #?
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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