Motor Start Capacitor Selection FAQs
How to specify motor start/run capacitors

POST a QUESTION or COMMENT about installing a hard-start capacitor to get an air conditioner motor, fan motor, or other electric motor running.

Electric motor start-run capacitor selection guide Questions & Answers:

This article series explains how to choose & buy an electric motor start capacitor, hard start capacitor, or run capacitor that is properly rated for and matches the requirements of the electric motor such as an AC compressor motor or fan motor where the capacitor is to be installed.

This electric motor capacitor article series explains the selection, installation, testing, & use of electric motor starter start and run capacitors used on various electric motors found in or at buildings such as air conditioner compressors, fan motors, some well pumps and some heating equipment.

These electric motors use a capacitor to start and run the motor efficiently. We explain the choice & wiring procedures for a hard start capacitor designed to get a hard-starting air conditioner compressor motor, fan motor, refrigerator, or freezer compressor or other electric motor (such as a well pump) going.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

FAQs About How to Find, Choose, a Motor Starting Capacitor

Recently-asked questions & answers about how to select the proper start or run motor capacitor posted originally at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS - be sure to review that article.

[Click to enlarge any image]

On 2023-03-15 by InspectApedia Publisher - there is no plus or minus terminal and no polarity on a capacitor

@Jason,

See

MOTOR CAPACITOR WIRING GUIDE

You will see that there is no plus or minus terminal and no polarity

On 2023-03-15 by Jason

I've got a 250uF /125v start capacitor on an ice machine that doesn't have a +/- % on it, does it have to test as 250uF? Motor is over amping and the cap tests at 266uF

On 2023-01-15 by InspectApedia Publisher

@ Jordan,

I think the MFD requirement may not change. That's the "amount of energy stored to get the motor moving".

But to be sure why not give one of the capacitor suppliers a call with this question - I don't want to steer you into a ditch by being embarrassed to say I don't know - but I don't know. I'll research the question further too, but let me know what you're told as that will help other readers.

On 2023-01-14 by Jordan

@InspectApedia Publisher, Hey there - thanks for the fast help! I've attached a picture of the capacitor I have on the motor, for others to see as well.

When looking for a motor start capacitor that would work, I would obviously want the same size (1 & 13/16 dia x 3 & 3/8" length), but how exactly do I know what MFD rating I need? If it's 460-552 MFD for 110/115V, what is the equivalent in 230v?

On 2023-01-14 by InspectApedia Publisher - what a typical SAFE-T-MIKE (or MOTOR MIKE) capacitor looks like

@Jordan,

For other readers, here is what a typical SAFE-T-MIKE (or MOTOR MIKE) capacitor looks like - notice that this one, #H-124 is rated at 124-149 MFD and just 124VAC

Here's a closer look at the capacitor data for this device.

On 2023-01-14 by InspectApedia Publisher - Most capacitors include the allowed voltage range in the device labeling

@Jordan,

Most capacitors also include the allowed voltage range in the device labeling. If yours doesn't, I'd swap it for one that is rated for 230V or higher.

Grainger sells a "Universal Motor Start Capacitor" (manufactured by Global) rated at 23-302 Mfd and 330VAC - you can use a cap like that on a lower-voltage motor as well. I have to say the price is a bit stunning - I'd suggest you stop by your local electrical supplier.

On 2023-01-14 by Jordan

The motor for my Delta 34-450 Unisaw is a model 83-611. It is 115/230v, 1.5HP. I am switching it from the current wiring of 115v to 230v. I noticed that a large capacitor on the side of the motor is a "SAFE-T-MIKE" Motor Starting Capacity, model 4488-500. It shows that it is 110/115 VAC.

Do I need to also switch this to a 230v capacitor in order to run this motor at 230v, or is this irrelevant for 230v operation? It's also worth noting the capacitor is 460-552 MFD.

On 2022-07-06 by InspectApedia-911 (mod) - how to select the right capacitor

@Jerry,

At

CHOOSE a START / RUN CAPACITOR, HOW TO

https://inspectapedia.com/electric/Motor_Capacitor_Selection.php

You will see that you don't have to match the old capacitor exactly but the article will give you the percentage by which you can exceed the original capacitors value. Please take a look.

On 2022-07-05 by Jerry

My condenser fan motor label read 7.5 370v. What size DUAL Capacitor can I use? I’m installing a new motor on HVAC and needing different sized capacitor. Old was 35 5 370/440. Can I use a 40 7.5 440 v capacitor? Thank you.

On 2022-03-16 by Inspectapedia Com Moderator - choosing a replacement capacitor as well as 'ballpark' sizes based on motor type or motor horsepower

@Harold Swanson,

Take a look at this page where you'll find 4 methods for choosing a replacement capacitor as well as 'ballpark' sizes based on motor type or motor horsepower.

MOTOR CAPACITOR SELECTION - the home page for this topic

Please let us know if you have additional questions.

On 2022-03-16 by Harold Swanson

my 5hp compressor has 2 start and 1 run capacitors, I need to replace the start capacitors but can't find them. they say 216-259, 370-440

On 2021-12-30 by Inspectapedia Com Moderator - Can you use a 250 vac 189-227uf in place of a 189-227uf 110 vac ?

@Charles,

Yes, the voltage rating on a capacitor is its maximum not its minimum rating

On 2021-12-30 by Charles

Can you use a 250 vac 189-227uf in place of a 189-227uf 110 vac for a irrigation pump

On 2021-07-12 by (mod) - capacitor substitution rule of thumb: upper limit 20% µF over-size

@Margot D,

From the article CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS we have this note:

As a general rule of thumb, electric motor start capacitors can be replaced with a micro-farad or µF or mfd rating equal to or up to 20% higher µF than the original capacitor serving the motor. On the replacement capacitor the voltage rating must be equal to or greater than the original.

That's about a 10 uf difference from the high-end of your stock motor cap, so you could try a capacitor that puts out up to 62 uf 250VAC

For example this capacitor (shown below) sold by grainger.com is described as

DAYTON 2MEL2 Round Motor Start Capacitor,53-64 Microfarad Rating, 330VAC Voltage

Also check out the explanation of capacitor voltage also discussed in the article I just cited above. You should agree that the 330V is simply an upper limit.

On 2021-07-12 by Margot D - Alternate size start capacitor for roof top AC fan motor?

Alternate size start capacitor for roof top AC fan motor?

Hi, I currently have a 43-52 microfarad 250 VAC start capacitor that I need to replace (AC starts and gets cold but fan does not turn on). This type of capacitor is sold out everywhere (or long lead times). What other size capacitor can I look for to start a 1/5 HP, 1650 RPM, 3 speed, 115 Volt, 2.5 Amp fan motor(Century ORV4540)?

Thanks! Margot

On 2021-07-07 by (mod) - How does the start capacitor get turned off when the motor has reached its rated speed?

@How start capacitor working,

Thanks for your helpful question that I'd re-phrase as

How does the start capacitor get turned off when the motor has reached its rated speed?

Answer:
On many motors a centrifugal switch built into the motor and held closed by springs keeps the start capacitor in the motor power circuit until the motor has reached its rated speed.

At that point the rotating speed of the motor is sufficient to open the centrifugal switch against its spring pressure, thus taking the starting capacitor out of the circuit, leaving the run capacitor in use.

To give you an idea what the centrifugal switch looks-like, below we show a Speedaire (brand) Centrifugal Switch Set Mfr #: PN22N031G as listed for sale at Zoro.com, Zoro #: G8641053

More about centrifugal switches is at

ELECTRIC MOTOR CENTRIFUGAL SWITCH or PTC PRD

where we'll include your question as that will be of help to other readers.

On 2021-07-07 by How start capacitor working

How difer start capacitor off state after motor in rated speed

On 2021-06-30 by Anonymous

@inspectapedia.com.moderator, Thanks for the quick reply. I'll try my luck with RUUD Service first.
;)

On 2021-06-30 by inspectapedia.com.moderator (mod) - Start/Run Capacitor for a RUUD Condenser unit

@Thomas,

To select a start/run capacitor for an old AC unit when the values of the original capacitor are not legible,

A service tech might use the capacitor selection rough guidelines like those at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS , or

consult the service manual for the compressor/condenser unit that may give the exact OEM specification, or

she might give Ruud service a call - for which one needs just what you have on that service tag: the Ruud A/C model no. UND-030JBZ
and they may want its serial number

On 2021-06-30 by Thomas

Hi experts!

I'm looking for a dual capacitor replacement for an old RUUD AC compressor model UAND-030-JBZ, the serial number start with 7259.
The capacitor's housing is in plastic and the specs (etched) disappeared over time, so I have no idea which capacitor I should order.
:(

I'm attaching an image of the compressor's specs if it helps.

Thanks for your help!

On 2021-06-26 by inspectapedia.com.moderator (mod) - What size capacitor is required to run a 115VAC, .74amp motor

@Ted Hunt,

Please check the motor capacitor size general guidelines and tables in the article CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

A 0.74 Amp electric motor, 120V, single phase, with a typical power factor of 0.9 is microscopic: its horsepower calculates (using a typical online amps to horsepower calculator) to about 0.096 hp - or about a 1/10 HP motor.

On 2021-06-26 by Ted Hunt

What size capacitor is required to run a 115VAC, .74amp motor

On 2021-05-27 - by (mod) - 30 uf is common size starting capacitor for small motors

@Tim,

Your photo was a bit blurry so I can't see whether it has two terminals or three.

I mention this because if there were three terminals than the capacitor would be a dual function start and run cap.

I can tell you that depending on the size of your motor, the 30 microfarad rating that shows in your photo might be used in a starting cap - for example on an air conditioner motor or on a pump.

Run capacitors for such motors generally would use a smaller number as you'll see in the capacitor selection tables at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

On 2021-05-26 by Tim

I have a 1.5 hp jacuzzi hot tub pump. The motor hums but wont start. I check the shaft and that spins freely. I'm guessing capacitor. It only has one and its located on top of the meter. Is that a start capacitor or run.

On 2021-04-23 - by (mod) - convert a three phase (380V) compressor motor into single phase (240V).

@nkatu30, I don't have an authoritative answer

but it seems to me that as the motor's basic mass and windings haven't changed you'd need the same sized cap; typically in motor capacitor specifications the voltage range given is a safe upper limit and it's ok to use, for example, an XXufd starter cap or run cap rated for 380V on a 240V application.

Shown is a Round Motor Run Capacitor,30 Microfarad Rating, 370-440VAC Voltage from Titan

On 2021-04-23 by nkatu30

I want to convert a three phase (380V) compressor motor into single phase (240V).
What is the right capacitor size to use?

On 2021-04-15 - by (mod) -

@Tom,
We do not sell anything. No products, no services. And no motor start capacitors.

But you can find your capacitor very easily at your local electrical supplier, at some building suppliers and at a stunning number of online vendors, starting perhaps with grainger.com or amazon. An example is below.

InspectAPedia.com provides building and environmental diagnostic and repair information.

In order to absolutely assure our readers that we write and report without bias we do not sell any products nor do we have any business or financial relationships that could create such conflicts of interest.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information for the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website.

A brief summary about InspectAPedia.com can be read at ABOUT InspectApedia.com - https://inspectapedia.com/Admin/About_InspectApedia.php

On 2021-04-15 by Tom

I have a Belsaw 1/2hp 3450 rpm that is old and need a capacitor 210-260 mfd

On 2021-04-14 - by (mod) - you don't have to replace a capacitor with the same brand, just match the rating; the shape? Depends on where it fits.

@Devan,

Sure, glad to help.

You may have made the very common mistake of thinking that to replace a motor capacitor you have to buy the exact brand and shape as the original. You don't.

Key is the capacitor rating - yours is 35uf or 35 microfarads - probably this is a motor run capacitor.

All of the data for your motor capacitor is written out as: 35uf +-5% (tolerance), 240V, 50/60 Hz. You'll read in the article CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS that a suitable match that's 35uf will be ok even if it's voltage rating is higher (as that's simply a safe upper limit);

The shape of the capacitor isn't critical, though it'd be nice if it would fit where the original did; if it won't it can be mounted and wired from outside the space used by the original capacitor.

The cap you want is available from any electrical supplier, motor repair shop, or HVAC supplier, and also from many online vendors, even big Amazon.

Below is an example, a QH QX6535 35uf Capacitor Motor Run Round 35 uF MFD 370V HVAC as shown at Amazon.

Please also take a look at the electric motor capacitor selection advice CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS on this page.

On 2021-04-13 by Devan

I have been looking all over for a replacement to this capacitor 35/5 240V, but to no avail. It is for a Leeson 1/2 hp greenhouse exhaust fan motor. Do know where I can find one? Thanks.

On 2021-04-02 - by (mod) - typical motor start capacitor ratings in uF and voltage for motors of various horsepower or size.

@Anonymous,

Not likely, anon; take a look through the motor start capacitor selection advice in the article CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS and you'll see typical motor start capacitor ratings in uF and voltage for motors of various horsepower or size.

On 2021-04-02 by Anonymous

Can i use 10 MFD capacitor as start capacitor

On 2021-03-17 - by (mod) -

@Sal Licata, I suspect that the "5904708 MFD" is either a misprint or a mixup of part number and MFD value. A 1.8 HP motor would typically use a starting capacitor somewhat smaller than 105-126 µF / 220VAC (Don't fret the voltage; these capacitor values and their sources are found in tables at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS)

The breaker trip could be due to a non-starting motor due to a bad cap as you've diagnosed, but be alert for a motor with failing bearings or a shorted winding too. The fact that your motor starts to rotate and then trips the breaker argues for a motor failure, perhaps a winding that shorts when the motor gets to speed or simply a bad bearing, giving the motor-rotation resistance that soon causes an over-current.

On 2021-03-17 by Sal Licata

I have a 2 capacitor 1.8 hp 120 volt motor on an old ridgid air compressor . I'm confused about the values on a black plastic round cap that has 5904708 mfd 125 vac 60 hz and has 2 terminals .I did not see any thing like this on your web site .What do I have to do to replace this. I ohmed it and it comes up ( 0 ) I think that say's it's open circuit . The problem I have is the the motor runs 5 seconds and cuts off and pops a breaker . Can you help me.

Regards
Sal licata
sallicata66@yahoo.com

On 2021-03-11 by Mr Casey

need start and run caps for this pic motor it runs an air compressor the one is readable the other blew out and is not readable
the one has the number but can not find
need to order both if replacable is possible
Thanks

On 2021-03-11 - by (mod) -

@keithhfletcher@gmail.com, Sorry you can add an image (.jpg .gif .img .jpeg etc) but not a PDF

On 2021-03-11 by keithhfletcher@gmail.com

Hi I got this price pump motor that's a three-phase on my research says I can convert it to single phase but I need to know what size capacitor. And do I need a stat capacitor and a run capacitor? See the PDF

On 2021-03-01 - by (mod) -

@Paul,

thanks for the helpful feedback-follow-up;

Sometimes all we need is a new start/run capacitor;

but be warned that sometimes the failed cap is a telltale that the real issue is a failing motor - such as due to a bad bearing. Keep me posted.

On 2021-03-01 by Paul

Hi, Dan. Sorry for the delay in responding. Got slammed with work; I finally was able to get the washer up and be able to get at the motor, transmission, capacitor, etc. Checked the transmission, turns smoothly and effortlessly. Motor is fine. Replaced the capacitor as we talked about earlier-was able to zip tie the new, cylindrical one to the original mounting bracket of the old box shaped one and started washing a full load. I watched it through the first cycle, and when the spin cycle started, it kinda of stumbled before the motor kicked. It continued to drain and spin afterwards until the 'unbalanced' notification stopped it.

I had to re-level the clothes twice, then reset the controls to spin only; this time, the motor kicked in almost immediately and finished the cycle without a hitch. I also monitored the control panel/circuit board temp. as it would very noticeably get quite warm a few minutes after starting the washer (with the original capacitor)

. With the new one installed, there was a only the slightest sensation/feeling of warmth, but nothing compared to the original. Let's hope this turns out to be a successful fix for the problem. Thanks for your insight and help with this! I'll keep you notified if anything else happens.

On 2021-02-15 by Paul

Thanks, I will as soon as I can get full access to the 'innards'... ;)

On 2021-02-15 by (mod) - Strong electrical odor of something overheating coming from the area of the capacitor. /p>

Be sure we've not missed a bearing somewhere else such as in the tub assembly.

Also you may be able to check the motor remotely by checking its current draw.

On 2021-02-15 by Paul

Thanks for the quick response, Dan! The symptom that leads me to the capacitor is a failure for the washer to spin/drain in the last part of the cycle...turning off the power and shutting off the breaker, then waiting 30-45 minutes to allows it to cool off enough to re-engage and drain and spin effectively. I recently replaced the drain motor (broken impeller) and drive motor, but problem still exists.

Strong electrical odor of something overheating coming from the area of the capacitor. The location of the washer prohibits quick access to the motor/mechanical interior of machine to check/feel what is overheating. I'll replace the capacitor and report back in the near future as to whether or not this works. Thanks again!

On 2021-02-15 by (mod) - Can I use a replacement capacitor for a GE washing machine even though the original is no longer produced?

Paul:

Normally it is absolutely reasonable to replace a motor start or run capacitor with another one of the same specifications in voltage and capacitance - as we describe

at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

Sometimes there is a physical "fit" problem that an original cap fit into a special and odd space where its replacement, that may be different in size or shape, is not so comfy.

But nonsense: capacitors are connected by wires. If a cap doesn't fit in its old cubby, as long as it can be safely secured and protected from damage and thence connected to the motor it serves, it ought to be fine.

It may be that whomever spoke with you doesn't want to crawl out on the limb of common sense, having perhaps Liticaphobia.

Watch out: Keep in mind that if a motor capacitor burnt up because of an underlying problem with a motor that's dead or dying or unsafe wiring, replacing the capacitor won't address the motor and fire-safety concerns.

You might ask that person

1. What's the technical or safety objection to replacing the GE OEM washing machine capacitor with a replacement unit of equivalent value in volts and farads

and depending on that answer,

2. Ask that person to review the costs of spending other people's money for the person's peace of mind.

Or give out a copy of

inspectapedia.com/home_inspection/Other_Peoples_Money.php OTHER PEOPLE's MONEY

On 2021-02-15 by Paul

Can I use a replacement capacitor for a GE washing machine even though the original is no longer produced? I will post pics of the original (w/specs) along with a possible replacement. GE says the capacitor is model specific, but the replacement is from GE and is exactly the same specs and is used in later units with the same motor. Thanks!

On 2021-02-04 by (mod) - burnt connections on the start capacitor

A reasonable guess is that the motor that is trying to start is failing, perhaps with a bad bearing or burnt winding and it is drawing High current

On 2021-02-04 by SFCJerry

I find burnt connections on the start capacitor. Looks as though the start terminal was over heated. I cant figure out why.

On 2019-10-08 - by (mod) - 3 phase compressor that I would like to run on single phase current

Mogamat

It looks as if your motor runs at 220 or 380 Volts 3 phase and at 220V runs at 16.5A while at 380V it runs at 9.6A.
The CAV on the data plate of this Italian motor from Tavernelle indicates that it's a 5.5 hp motor.

Typically the run capacitor on a 5 hp. motor is around 30 µF - 40 µF 370VAC

Typically the start capacitor for a 5 hp motor is around 600uF

To take a stab at answering "how to convert a 3 phase motor to run on single phase power" I found a variety of answers ranging from "it's easy" to "it's a really bad idea, even dangerous".

Kemet (cited in the guidebooks given in the article CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS ) notes: By connecting a capacitor to the two phases it is possible to make a three-phase motor work as a single-phase motor.

Watch out: you cannot simply hook up a 3 phase motor arbitrarily to single phase current; you need to review the wiring recommendations from motor companies or engineers.

Options include:

A phase shift capacitor;

Motor re-winding

Using a VFD or variable frequency drive

Use a converter to convert your single phase power to DC (Direct Current) and then use an inverter to power the motor. From what I read this is your best bet. As one EE notes "You can run a three phase motor from single phase by converting the single phase AC-DC(rectification) and then DC-AC(3 phase inverter)."

However pretty much everyone says this is an inefficient way to run a motor - i.e. your electric bill will be higher than necessary.

On Quora a Bombay writer recommended:

Use capacitor of say 36 / 72 / 108 mfd 440 V rating.

Depending upon motor rating. Connect one end of this capacitor to open unconnected terminal of motor.

The other terminal of capacitors can be connected to one of the two live phases, and the motor will start running.

If you change over the capacitor terminal to other phase , its direction of rotation will get reversed.

This system is routinely used in India particularly in rural areas for running of pumps.

This arrangement is certainly not the optimum for the motor, and the phase difference between the windings will differ from 120 degrees needed.

However, this does makes the motor start and save the day for farmers when 3 phase supply is not available. - www.quora.com/How-do-I-run-a-3-phase-motor-in-a-single-phase-line-using-a-capacitor

See: www.gohz.com/3-phase-motor-running-on-single-phase-power-supply

See this article by Chuck Yung: www.plantengineering.com/articles/how-to-properly-operate-a-three-phase-motor-using-single-phase-power/ on running a 3-phase motor on single phase power.

Note that operating the motor on single phase may be expensive.

On 2019-10-08 by Mogamat

Good day. I have 3 phase compressor that I would like to run on single phase current. What size capacitor would I need and will it need a run cap as well?

On 2021-03-05 - by (mod) -

@Guisepi,

Most likely "ABC" is the brand; you can use any brand, if you properly-match the capacitor specifications for voltage and capacitance.

See details at

CHOOSE a START / RUN CAPACITOR, HOW TO - topic home

On 2021-03-04 by Guisepi

I need to replace a capacitor that says "ABC" on it. I've found a lot for sale that say "ABS." Is there a difference?

On 2020-06-27 - by (mod) -

Steve

Capacitor voltage rating can be higher than your motor but it should not be lower. Otherwise it's likely the capacitor will burn up or fail quickly.
We don't sell any product or service, in order to protect the trust of our reader
if you need d a hard start kit are plenty online.

On 2020-06-27 by Steve

I have a lathe with a dayton motor (5k482-B) everything is set up on 220v the capacitor however is rated at 110v is that normal? If so I would like to buy a "hard start capacitor" any guidance or recommendations appreciated!......Steve

On 2020-05-13 - by (mod) -

Thanks for asking Dan, that's a helpful question.

The range in uF listed on a capacitor is the range over which the capacitor can be used successfully.

For example, a 270-324uF capacitor can be used in any application **within that range**

Put another way, if a cap had a minimum capacity of 100uF and maximum capacitance of 200 uF you could **not** use it for a motor that required a 300 uF Cap, but you **could** use it safely on a motor that required a 150 uF cap

On 2020-05-13 by Dan

Why do some capacitors specify their value in uF as a range? For example: 270-324uF. Surely the capacitor can only have one value.

On 2020-04-05 - by (mod) -

Sonny

Capacitor "size range" means the voltages at which the capacitor can be used and the capacitor's power usually in uf or microfarads.

For example if you Look for and record all of the markings on the capacitor.

Typically on the capacitor's markings or label you'll see a rating in microfarads like the 25uF and you'll also see a voltage range rating such as the 370VAC (maximum voltage) rating also in the red circle of our photo.

Details are at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

On 2020-04-05 - by (mod) -

Sonny

There are some electric motors that don't use a start-run capacitor, but if yours does use capacitors then you cannot run it without them. Even if you gave the motor a spin to get it running without a working "starting" capacitor, if it's "run" capacitor isn't present the motor will not work properly, may not run at all, and is going to be damaged.

On 2020-04-05 - by (mod) - Can you run a bench grinder without its capacitor?

On 2020-04-05 by Sonny

Can you run a bench grinder without its capacitor?

What do you mean by size range?

On 2019-07-15 - by (mod) - Can I add start capacitor to RV conditioner for generator for smoother startup

You can try it as long as you stay in proper size range for the capacitor. See

CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

On 2019-07-15 by Mike

Can I add start capacitor to RV conditioner for generator for smoother startup 15000 but rv ac, 4000 watt generator

On 2018-12-30 - by (mod) - what capacity run capacitor I need for 1.5 hp sukuna compressor motor for borewell?

Sure Sekar

See the capacitor selection guide at

CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORSp

On 2018-12-30 by sekar

can you please tell me what capacity run capacitor I need for 1.5 hp sukuna compressor motor for borewell?

On 2017-12-13 3 - by (mod) - How do I figure out what size start and run capacitors I need.?

Just start choosing the proper capacitor you'll look at the voltage and current that the motor uses. Then take a look at

CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

On 2017-12-13 by Bruce Cunha

I am fixing up a air compressor that has a 5 hp 60 cycle 220 volt single stage motor. The capacitors were removed some years back but the owner did not keep them or replace them. Tried a set of 220 capacitors and the motor started but blew out the capacitor. Question.

How do I determine run capacitor wires from start capacitor wires. (I have 4 black wires with female spade terminals coming out of the motor)

How do I figure out what size start and run capacitors I need.?

Motor capacitor box has spaces for 4 capacitors. so I assume there was a jumper between each two.

I cant find the run capacitor information on the motor plate. I think it is a Baldor.

On 2017-05-22 - by (mod) - when I turn on my air conditioner, it shuts on and off every 5 seconds

C

That's certainly a malfunction; I can't guess from your note if it's a bad control relay, loose wire, or a safety device that's shutting off the unit.

If you don't see an obvious problem like a loose wire at the thermostat connections it's time to call tech support.

Let me know what you're told - as we may be able to comment further and as that will help other readers too.

On 2017-05-22 by C Shah

This summer season I noticed when I turn on my air conditioner, it shuts on and off every 5 seconds and so not cooling fully. What is to be done? Thanks

On 2019-08-25 by (mod) - Reading the specifications on a Facon motor capacitor

Your photo (shown above) of your old capacitor is a 16 uF 42-50Hz 280V capacitor made in Italy - you'll see that data imprinted on the capacitor cover.

If you can't find an exact match to that capacitor at your local electrical supplier, details on how to get a sufficiently-close match to the original capacitor are found

at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

On 2019-08-25 by mick

i have had a capacitor blow on my home made compressor which my Dad made many years ago so has great sentimental value i use it but have had this capacitor blow and would like to repalce it.

it has an italian motor on it and the make of cap is FACON but i am having problems tracking down a repacement

can i just replace the one thats blown or would it be wide to repalce both sorry to show my ignorance but i have no clue to whatthe middle one is i am assuming it could a starter cap? thank you in advance mick c

On 2019-08-25 by Anonymous

could anyone please help me in selecting the correct capacitor to replace the blown one in pic or would it be best to replace the lot

On 2019-08-06 by (mod) -

OUr best data on capacitor selection is in CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS ; please take a look.

On 2019-08-05 by Anonymous

What are the capacitors for a Motor 7.5 HP 4P 213/5T 1Ph 208-230 V 60 Hz IC01 - ODP ... - WEG? The run cap is 60uF. I'm missing the start caps. WEG has not responded after a week.
Thank you!

On 2019-05-31 by (mod) -

While the tolerance varies, it wouldn't surprise me for a capacitor to test a bit off from the kabel rating.

Look for a plus / minus specification on your capacitor to tell us what the manufacturer's expected variation was.

Perhaps you can attach photos of the labeling on the capacitor. One per comment.

On 2019-05-30 by Craig

Is it common for a newly purchased capacitor to test below the listed rating right out of the box? Bought a 55 mfd recently and tested at 52.92 out of the box.

On 2019-05-17 by (mod) -

Rick

In the article CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS there are tables of motor size with suggested capacitor values as well as a table of typical capacitor values for some common motor types.

Or

Looking at the data tag on your Century brand AC Compressor motor we see that it's a 230VAC motor that is rated for a maximum of 15Amps.

Watts = Amps x Volts

Watts (of your motor) = 15 x 230 = 3450 Watts

Any online converter of Watts to mechanical horsepower will give us 3450 = 4.6 hp.

OR we can just read the motor data tag where it says the motor is a 3. HP unit. (Which is more conservative in a sense).

AND stop by your electrical supplier for that data to ask the service tech to recommend a different value than what we have below:

THEN we can use either the watts or the HP to choose a "typical" capacitor value from tables given at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS
That would suggest a starting value for a run capacitor of 20-25 µF 370VAC

And a starting value (to try) for a start capacitor of 500-580 µF or a bit larger

IF Century were still in business (apparently now Century / Regal Beloit ) you could simply have contacted Century Electric Inc., in St. Louis, give them the part No. of your AC Motor: 8-158630-02 Type CS HP 3.0 SPL, 60 Hz, RPM 3450 Volts 340, Amps 15.0 and ASK them what start / run capacitor(s) they use with that motor.

Century Regal Beloit Website: www.regalbeloit.com/Brands/Century - evidently the company does NOT want to be called (not so consumer friendly, right?) but their website includes a contact page that might work for you.

IMAGE LOST by older version of Comments code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2019-05-16 by Rick

Can anyone tell me what capacitor I would need for this air compressor motor? Previous owner took the old one off so I dont have it to get a replacement.
IMAGE LOST by older version of Comments code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2019-04-26 by (mod) -

Nicole

CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS explains how to choose the right replacement capacitor - please take a look and let me know if that information is unclear.

You'll also see that there is a bit of latitude, so you don't have to get exactly 45uF.

You'll read there that

as a general rule of thumb, electric motor start capacitors can be replaced with a micro-farad or µF or mfd rating equal to or up to 20% higher µF than the original capacitor serving the motor. On the replacement capacitor the voltage rating must be equal to or greater than the original.

So don't buy a cap that is rated LOWER than 45uF but you can go up to (1.20 x 45 = 54 uF)

Or contact Bryant directly to ask for an OEM replacement and to confirm the cap they recommend.

Bryant A/C customer support: 1-800-428-4326 for assistance in locating a dealer in your area.
Or submit a non-emergency question to Bryant at https://www.bryant.com/bryant/en/us/contact-us/

On 2019-04-25 by nicole wallace

Hello, I have a Bryant AC unit model # 698BNX036000ABAA and I saw the compressor capacitor is bulging and I want to replace it. The current capacitor is 45 uF, 370VAC, 50/60 Hz but I cannot find out online if this is the correct specs for the capacitor or if someone installed the wrong capacitor for this unit and that is why it has gone bad.

On 2019-01-18 by (mod) -

Org

The cost to try a new capacitor is trivial so sure go ahead and try it. However if the underlying problem is a failing pump motor, a new starting capacitor will give but short term relief. So be sure you can exchange the pump within warranty period if needed.

Before replacing the cap, you might want to test it to see if the problem lies there.

See https://inspectapedia.com/electric/Motor_Capacitor_Tests.php

Watch out: if you are not trained in safe electrical wiring and work you could be shocked or killed.

On 2019-01-18 by (mod) - The cost to try a new capacitor is trivial

Org

The cost to try a new capacitor is trivial so sure go ahead and try it. However if the underlying problem is a failing pump motor, a new starting capacitor will give but short term relief. So be sure you can exchange the pump within warranty period if needed.

Watch out: if you are not trained in safe electrical wiring and work you could be shocked or killed.

On 2019-01-18 by organizome49

I have a 1hp water well jet pump (115vac, 11 amp) with a startup capacitor that is beginning to fail. Its 10 months old with a one year warranty,

I'm sure it the capacitor because the motor struggles to startup after cut-out and will struggle to restart. So far it will eventually restart and runs well when it does restart but the condition is getting worse.

I was told by the supplier I can return and exchange the whole unit, a major undertaking. I was thinking that I could replace the capacitor and that would resolve the problem. I've included an image of the capacitor markings and would like your input on finding a replacement. The unit was made in China for Tractor Supply Company. Anything else you could tell me would be appreciated. Thanks.

IMAGE LOST by older version of Comments code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2018-07-05 by (mod) Is it permissible to replace the 12uF cap with a 15uF, 440V?

You can safely go about 12% over original rating, Peter so I'd guess 15uF is ok.

But I suspect the problem is a different one: the wrong pump for the application, or pump clogging, or something causing bearings to overheat.

What are the brand and model of your septic pump? We can take a look at its specifications, duty cycle, and perhaps even check with the manufacturer. After all there are plenty of motors that work hard for many hours daily for many years.

To get the right capacitor for your motor you can almost always find a suitable product from an electrical supplier, matched to the motor specifications - as we describe

at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

Capacitor Voltage Rating Selection Limits

The voltage rating of a capacitor indicates the highest nominal voltage at which it is designed to operate.

Use of a capacitor at voltages below its rating will do no harm.

Run capacitors must not be subject to voltages exceeding 10 percent of the nominal rating, and start capacitors must not be subjected to voltages exceeding 30 percent of the nominal rating.

The voltage to which a capacitor is subjected is not line voltage, but is a much higher potential (often called back electromotive force or back EMF) which is generated in the start winding.

On a typical 230 volt motor, the generated voltage may be as high as 400 volts and is determined by the start winding characteristics, the compressor speed, and the applied voltage.

PARALLEL AND SERIES CAPACITORS Capacitors, either start or run, can be connected in series or parallel to provide the desired characteristics if the voltage and MFD are properly selected.

When two capacitors having the same MFD rating are connected in series, the resulting total capacitance will be one half the rated capacitance of a single capacitor. - Copeland Electrical Handbook

Explanation of how to calculate the value of capacitors wired in series or parallel

When two capacitors are connected in series to achieve a desired total capacitance you can calculate the total capacitance by adding the reciprocals of the rated capacitance of each and then inverting or taking the reciprocal of the result.

1/µF total = (1/µF-capacitor #1) + (1/µF-capacitor# 2)

You'll need to use simple algebra to complete this calculation by finding a common denominator for the two fractions on the right of the equation. Let's wire a 7µF and a 10µF capacitor in parallel (or in series):

1/µF total = (1/7) + (1/10)

To find a common denominator multiply the numerator and denominator of each fraction by the other fraction's denominator:

1/7 can be re-written as 10/70 (multiply both numerator and denominator by 10)

1/10 can be re-written as 7/70 (multiply both numerator and denominator by 7)

Remember that if you multiply both the numerator and the denominator of any fraction by the same number, the overall value of the fraction is un-changed. 1/7 = 10/70 in value since we can simply 10/70 by dividing back by 10 to get 1/7.

1/µF total = 10/70 + 7/70

1/1/µF total total = 17/70

Now invert that fraction

70 / 17 = 4.11 µF total

On 2018-06-18 by (mod) - specifications for replacement capacitor for a 1.5 hp AO Smith electric motor

Sharon

We asked for help from CSH Electric Motor Supply Corp at http://www.cshincorporated.com/
Whose online chat tech contacted a company rep who specified:

Start cap part # 15769655 ratings 189-227 mfd @ 125 Vac

Run Cap part # 17586315 ratings 15 mfd @ 370vac

You can substitute equivalent parts, for example a 15DVR, 15MFD-370V Motor Run Capacitor available from www.cshincorporated.com/15dvr-15mfd-370v-motor-run-capacitor-round/

Product description:

15DVR, 15MFD-370V Motor Run Capacitor (Round) as of 6-28-06, Now being replaced with dual voltage 370V-440V, dimension Dia. 1.65 in x 3.15 in. height.

Cross Reference: 6100-6022

On 2018-06-18 by Sharon Lehman

What Capacitor would I need for this motor?

On 2018-06-16 by Dan Jacobson

What does the "VC 12/13" of
Metallized Polypropylene Capacitor
YUHCHANG 30uF 250VAC MPP VC 12/13
mean?

On 2018-06-04 by (mod) - Greg says electrical suppliers can't help select the right capacitor

Greg

thank you for your comments they're perfectly reasonable. The article I cite below does give some methods for determining the appropriate capacitor size based on what the capacitor is being asked to support.

I will however review the CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS article to see what useful material we could add. If you have specific suggestions to add to your complaint I'd be grateful to have them.

On 2018-06-04 by Greg

The 'take your cap to an electrical supplier and he'll match it for you' is a cop out. The purpose of this sort of article should be to expand the reader's knowledge, not pass the buck to some unknown 3rd party.

If we can't figure it out here, who's to say some 'electrical supply house' will know how to figure it out? Most of all, the average electrical supply house counter jockey probably has no experience or education in this sort of issue - he probably was washing cars last week and will be painting houses next week.

If nothing else, this discussion should put a person in a position to question or assess what the supply house is telling him.

On 2018-05-12 by jeremy

What is the perfect running capacitor to use?

This is the specs of motor
: 220 volts
:1 hp
:1720 rpm
:single phase

On 2018-04-15 by (mod) - typical run capacitor sizes for various sized electric motors

Ruel

In the article CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS you'll find a couple of tables giving typical motor start/run capacitor sizes matched to motor current draw in Amps.

Typical run capacitor sizes that will be in the “ballpark are

1/8hp motor: 4 to 5 µF

1/2 hp motor: 10 µF

1-2 hp motor: 10-15µF

3 hp motor: 20µF

5 hp motor: 40µF or more likley 30 µF

On 2018-04-15 by ruel quiambao

how to know the size of run and start capacitors of this kind of motors
60hz
1740 rpm
5 hp
220v
26amp
single phase

On 2018-03-14 by Anonymous

what is the suitable size starting capacitor for a 3HP single phase motor

On 2018-01-22 by CWHONKAHI

I have a hand me down 125 vac, 1/2 hp bench grinder. It had a Jerry rigged replaced 100mF start capacitor that wasn’t a replacement of original.

I replaced it with a new 100mF but it went out after a few starts. Looking at your charts I see the motors are rated in kw not hp.

Doing the math I come up with .367 kw.

So I am assuming that I need a start capacitor in the 320 - 400mF range? Thanks for the great site.

On 2017-12-08 by (mod) -

're posting

tibcon said:
Interesting blog ...very useful information provided to users ... ...thanks for sharing us...keep it posting

Note, Tibcon is a supplier of motor capacitors

On 2017-12-07 by mark p

I need to replace an old 270-324 mfd 110-125 vac from an baldor single phase 1/2 hp motor. Will any brand with the same mfd and vac work? Some brands seem to be about a half inch or so shorter, but same dia.
Got to get my log splitter goin again.

On 2017-10-26 by Anonymous

I have an induction motor, with 60 Hz 220 volts, 25 amps, 3600rpm 1 phase 2 pole, class A .
What size starting capacitor, do I need ?
Raul. Woodworking shop

On 2017-10-10 by (mod) -

Mark,

Some motors do not use capacitors for start/run - it depends on the motor type and application.

Typically a motor uses a start and run capacitor combined in one physical device or sometimes as two separate devices.

The specific capacitor size or rating you need depends on the motor: see the examples and data

in CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS .

Do let me know if I can clarify further.

Thanks

Daniel

On 2017-10-09 by MARK

Could you roughly tell what caps I will need

On 2017-10-08 by (mod) - Emerson lr 63596 model t63bxbyf133 240v 15.0amp 3450rpm capacitors

Mark, abut the capacitors you need, you can indeed find those from online vendors, but not from InspectApedia.

We do not sell anything.

InspectAPedia provides building and environmental diagnostic and repair information.

In order to absolutely assure our readers that we write and report without bias we do not sell any products nor do we have any business or financial relationships that could create such conflicts of interest.

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information for the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. We very much welcome critique, questions, or content suggestions for our web articles. Website content contributors, even if it's just a small correction, are cited, quoted, and linked-to from the appropriate additional web pages and articles - which benefits us both. Working together and exchanging information makes us better informed than any individual can be working alone.

On 2017-10-06 by MARK

I need booth caps for a ......Emerson lr 63596 model t63bxbyf133 240v 15.0amp 3450rpm both where missing when I took over this project.The motor is on an air compressor.....Any help would be appreciated

On 2017-10-05 by Binod Mool

My stand fan original capacitor is 1.2 uf +_5% and motor is 3 watt 400v.ac not working n it has been replaced by 1.5uf+_ 5% n motor <4watt 450 v.ac. bl the fan blade does not spin n but it swings. could you please suggest me whether the replace parts are compatible to the previous parts.
waiting for ur kind information,
yours' sincerely,
binod mool
kathmandu nepal>

On 2017-09-04 by Muhammad Hanif

Total Load 50 kw
we are working on Injection Molding Machine.
we have two machine

[1] A/C Electric motor power Three ph 18.5 KW

[2] A/C Electric Motor Power three ph 18.5 kw

we are interested save of electric bill.
have you method increase the electric power?

[note]
we obtained 7 kw electric load from government department.
and increase 18.5 kw load for each machine.
please send us complete information with price for our study.
Please advise us .

Thanks
Muhammad Hanif
Street No: 8
House No: 36
Salamat Pura
Lahore
Pakistan
Mobile: 03224916443
e-mail: mianhanif76@yhoo.com

On 2017-08-17 by harshan

I am installing 1hp water cooled submersible Borewell pumb,which starting ,run capacitor required the panelbox

On 2017-07-31 by don

I am installing a new fan motor in my central air rheem unit. The new motor reads 3/370 5/370. My capacitor reads- 45+5 plus or minus 6%. Are these parts compatible?

On 2017-06-30 by israel

If the starting 300uf what would be the size of the run capacitor

On 2017-06-30 by (mod): how to choose a run capacitor if you know the start capacitor µF

Israel

There is no direct translation between an arbitrarily-specified 300 µF motor start capacitor and the required run capacitor for the same motor - of unspecified voltage in your question.

Electric motor "run" capacitors are typically in the 2 µF 70 or 80 µF range of capacitance and their voltage rating will be 370 Vac or 440 Vac. But that's a general remark not an exact specification.

If the run capacitor is too big or too small in µF rating, the result can be motor vibration, exceeding the motor's rated run temperature, motor vibration and noise, motor wear and thus reduced motor life, and more expensive motor operation.

Typical run capacitor sizes that will be in the “ballpark are

1/8hp motor: 4 to 5 µF

1/2 hp motor: 10 µF

1-2 hp motor: 10-15µF

3 hp motor: 20µF

5 hp motor: 40µF or more likley 30 µF

(Similarly, you will find tables matching motor size in kW and capacitor value in µF for starting capacitors. But read on before slapping a capacitor you found in a toolbox or in a table of data.

When choosing the run capacitor for your specific motor, the µF you choose should match the run Capacitor rating on the motor's data tag. It's almost certainly going to be below 70 µF . But to repeat a key point: you need the manufacturer’s run capacitor rating to get the right capacitor.

There are rule-of-thumb equations for guessing at the run cap µF if you don't have the manufacturer's data tag, but those rely on measuring the motor when running under load - and can be in error depending on the existing motor and capacitor when the measurements are made.

So I cannot recommend that approach for choosing a new or replacement capacitor, even if the motor is running. An accurate measurement to choose the run cap size would require use of an oscilloscope and examination of the motor power phase to compare start vs run windings - not something a field technician is likely to do.

Another approach suggested by Lemau is to install a run capacitor of 30-50 uF/kW, measure the motor’s performance, and choose a subsequent capacitor rating accordingly. Lemau offers a formula to calculate the capacitor size that is a function of current, Hz frequency, applied voltage, a power factor, and a dissipated power in watts.

Best bet: read the data tag, or if it's illegible, let's find the motor's manufacturer and model and then look up the specifications.

When you have the motor's run-capacitor specification, typically the run capacitor you install can be +/- 6% (or by some writes +/- 5-10%) of that rating (according to what I've found by researching this question).

That's for capacitance. The voltage rating needs to be equal to or greater than the motor's voltage rating. Unlike the µF rating, a higher voltage rating won't cause the same troubles. A lower capacitor voltage means a shorter capacitor life. Industry standards for motor capacitor life and testing, including the Highly Life-Testing methods include the

EIA-456-A Standard, Electronics Industries Alliance (USA Standard for motor run caps and other special capacitors)
IEC-60252-1 Standard for run capacitors, International Electrotechnical Commission (Europe and Asia Pacific Region)
Techumseh H-115 Standard for Run Capacitors

Question:

(Feb 21, 2014) Anonymous said:

is it possible to rebuild a submersible well pump

Reply:

Yes ... maybe; it depends on the condition of the pump casing, parts, an in my opinion, an accurate diagnosis of the trouble; at some point rebuilding is not cost effective. Indeed there are specialists (H Shreck in Poughkeepsie used to be one of them) who rebuild electric motors of all kinds.
There are also many water pumps whose design makes it quite reasonable to replace pump impellers.

So to answer your question, I dunno - it depends on what's broken.

Question: fan will start but won't keep running.

(June 1, 2014) Anonymous said:

The fan on my Conquest 80 will not stay on (interior fan). It starts and then stops after a few seconds. It was installed in 2005. Help.

Reply:

Anon,

The start capacitor is for getting a motor started, not keeping it running.

Often motors have two windings, a start winding and a run winding. Your motor's run winding may be damaged.

Or your fan motor may require a dual capacitor (start and run) or a separate run capacitor to keep it spinning.

Or your system may have a faulty control.

Question: will a hard start capacitor reduce current drawn and stop tripping a breaker

(June 7, 2014) Joel said:

I have a commercial hood & exhaust fan (120v) running in a food truck that is used for catering. We occasionally need to run off a generator (3000w) and we've found that the fan cause the generator overload to trip.

The fan has been tested and observed to draw 8 amps running at full speed. Given this, would it be possible to add a hard start kit, such as SUPCO SPP4E? Will need to confirm the motor size, just wondering if this would help.

The total draw of all items is less than 20 amps and the generator is capable of supplying 25 amps constant.

Thanks for the advice.

Reply:

Joel I think the problem lies elsewhere and needs some further diagnostics. I suspect that your total current draw is exceeding the ability of the generator - you may be running more than the fan, such as lighting, a cooler, toasters, other electrical appliances. If it were just the fan, drawing 8A, it has no business tripping the breaker.

Put another way if the problem is the fan and there are NO other appliances running, then there is a failing fan motor drawing high current, or an electrical short circuit or other unsafe condition to find and fix.

A start capacitor or a run capacitor won't change the current drawn by the motor.

...

Continue reading at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see CHOOSE a START RUN CAPACITOR FAQs-2 - more-recent questions and answers about how to select a replacement motor capacitor.

Or see these

Suggested citation for this web page

CHOOSE a START RUN CAPACITOR FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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Motor Start Capacitor Selection FAQs
How to specify motor start/run capacitors

FAQs About How to Find, Choose, a Motor Starting Capacitor

On 2023-03-15 by InspectApedia Publisher - there is no plus or minus terminal and no polarity on a capacitor

On 2023-01-14 by InspectApedia Publisher - Most capacitors include the allowed voltage range in the device labeling

On 2022-03-16 by Inspectapedia Com Moderator - choosing a replacement capacitor as well as 'ballpark' sizes based on motor type or motor horsepower

On 2021-12-30 by Inspectapedia Com Moderator - Can you use a 250 vac 189-227uf in place of a 189-227uf 110 vac ?

On 2021-07-12 by (mod) - capacitor substitution rule of thumb: upper limit 20% µF over-size

On 2021-07-07 by (mod) - How does the start capacitor get turned off when the motor has reached its rated speed?

On 2021-04-14 - by (mod) - you don't have to replace a capacitor with the same brand, just match the rating; the shape? Depends on where it fits.

Capacitor Voltage Rating Selection Limits

Explanation of how to calculate the value of capacitors wired in series or parallel

Question:

Reply:

Question: fan will start but won't keep running.

Reply:

Question: will a hard start capacitor reduce current drawn and stop tripping a breaker

Reply:

Recommended Articles

Suggested citation for this web page

INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

Ask a Question or Search InspectApedia

Citations & References

InspectAPedia®

FREE Encyclopedia of Building & Environmental Construction, Diagnosis, Maintenance & Repair The accuracy & trustworthiness of every article or Q&A is researched by human experts. See WHO ARE WE?

Question? Just ask us!

Motor Start Capacitor Selection FAQs How to specify motor start/run capacitors

FAQs About How to Find, Choose, a Motor Starting Capacitor

On 2023-03-15 by InspectApedia Publisher - there is no plus or minus terminal and no polarity on a capacitor

On 2023-01-14 by InspectApedia Publisher - Most capacitors include the allowed voltage range in the device labeling

On 2022-03-16 by Inspectapedia Com Moderator - choosing a replacement capacitor as well as 'ballpark' sizes based on motor type or motor horsepower

On 2021-12-30 by Inspectapedia Com Moderator - Can you use a 250 vac 189-227uf in place of a 189-227uf 110 vac ?

On 2021-07-12 by (mod) - capacitor substitution rule of thumb: upper limit 20% µF over-size

On 2021-07-07 by (mod) - How does the start capacitor get turned off when the motor has reached its rated speed?

On 2021-04-14 - by (mod) - you don't have to replace a capacitor with the same brand, just match the rating; the shape? Depends on where it fits.

Capacitor Voltage Rating Selection Limits

Explanation of how to calculate the value of capacitors wired in series or parallel

Question:

Reply:

Question: fan will start but won't keep running.

Reply:

Question: will a hard start capacitor reduce current drawn and stop tripping a breaker

Reply:

Recommended Articles

Suggested citation for this web page

INDEX to RELATED ARTICLES: ARTICLE INDEX to ELECTRICAL INSPECTION & TESTING

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Citations & References

InspectAPedia^®

FREE Encyclopedia of Building & Environmental Construction, Diagnosis, Maintenance & Repair
The accuracy & trustworthiness of every article or Q&A is researched by human experts. See WHO ARE WE?

Motor Start Capacitor Selection FAQs
How to specify motor start/run capacitors