InspectAPedia®   -   Search InspectApedia

Starting capacitors in place on an air conditioning compressor (C) InspectAPedia.comElectric Motor Start / Run Capacitor Location
Find Proper Location of Electric Motor Start-Boost or 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.

Motor capacitor location:

How to find & recognize the electric start, run, or hard starting capacitor on an air conditioner or heat pump system.

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.

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

Where to Find the Starter Capacitor in or on Electrical Equipment

Starting capacitors in place on an air conditioning compressor (C) InspectAPedia.comHere we list the locations where a start or run or start/run capacitor will be found on various electric motors used in residential and light-commercial installations.

Capacitors are used in many but not all electric motors including air conditioners, heat pumps, furnace or air conditioner blower fan motors, refrigeration equipment compressors, and well pumps.

AO Smith 1.5 hp electric motor (C) InspectApedia.com

Also see MOTOR CAPACITOR TYPES for help in determining which capacitor is which on your HVAC or other electrical equipment.

Start & Run & Dual Capacitor Specification References

Examples & Sources of Start / Run Motor Capacitors

 




ADVERTISEMENT





Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-04-30 by Inspectapedia Com Moderator - start/run capacitors for HVAC blower unit fans

@Ryan Self,

It's common for HVAC blower unit fan motors to use a start/run capacitor. Those will be located in the blower cabinet, often right on the blower motor itself.

Yes those indoor blower unit fan motors and their capacitors are completely separate and distinct from the start/run caps that may be found in the outdoor condenser / compressor unit.

In your outdoor compressor/condenser unit there may be Start/Run capacitors for both the compressor motor itself and separately on/for the fan motor.

In your indoor air handler there will be a Start/Run capacitor for the air handler's blower fan.

Note that you may see two (one, the larger will be the starting cap) capacitors, one for starting and one for running the fan -
OR
you may see just one physical capacitor with 3 rather than 2 terminals - combining start and run in one device.


Shown here, a 5 uf RUN capacitor for a blower motor


Below is a dual Start & Run capacitor from Huarew, rated at 45uf (start) and 5 uf (run).

Note the 3 (rather than 2) terminals; they'll be labelled S, R, and C for "Common"

On 2022-04-30 by Ryan Self

so I have an important question. I live in hot Phoenix Arizona. I have a 2 story house with 2 Ac units. they are both heat pumps split units. they are Lennox the one downstairs is a 5 ton and the one upstairs is either a 3 or 3.5 ton unit.

my question is I know there is a run capacitor in both outdoor units because I've replaced them both several times. I would like to know if there is a run capacitor for the indoor fan motor and if so would it be located in the attic with the air handler? both units are down now. 1st the upstairs unit fan started blowing slow and then it would intermittently come on but not run long and start humming before it stopped and I had to shut down the unit.

just today on the downstairs unit it started getting hot inside but I could hear the condensing unit running outside. so I went upstairs where the return duct is at to listen if the fan was running and it is not. I turned the unit off and waited several hours as it rose to nearly 100 degrees in here and I turned it back on and nothing. I think I heard humming from the attic but I am not sure.

I am sure that the outdoor unit is working though. so now here I am with 2 units down and both have the same symptoms which is the outdoor units work but the indoor fans do not.

I had an ac guy out here last time and he visually looked at my outdoor units and said oh those must be 10 years old you are going to need 2 new ac systems and I started to hyperventilate because I am disabled and cannot afford something like that even if it was $1k it would be undoable but $12k would be impossible.

the fact that he didn't want to even look at the air handler in the attic and just jump to new units made me not trust him so I passed and went through the entire summer with just 1 unit. but now the other one is down too and I'm melting already. is there a run cap for the blowers and if so where is it please?

I saw little capacitors next to the bigger round ones inside the cabinet on the outdoor units and they look like the ones in your video but again they are outside so I assumed they are run & start capacitors for the condensing unit only...

On 2022-02-18 by Inspectapedia Com Moderator - what does this motor sound mean for my Trane?

@Jan,

That sounds like a compressor having trouble starting, possibly against high head pressure, or there can be other causes like a bad start capacitor or low voltage.

To reduce the chances for more costly damage, it'd be best to turn the system off right away, then call for repair.

On 2022-02-17 by Jan

We have a Trane dual heating and air conditioning unit. It was running but it wasn’t a steady hum, it almost sounded like a car that the motor was turning over very slowly it would Sound like rur rur rur rur

The whole time it was running. I was thinking it was the run capacitor, but the technician said it was the motor itself and charged us over $700 to replace it. I was very suspicious but the air conditioner is on the roof and you need a 30 foot extension ladder to get there and I wasn’t about to go up there myself.

What are your thoughts on a motor making that type of sound. It started fine but just was not a constant hum while running

On 2021-07-24 by inspectapedia.com.moderator

@k,

I don't know that unit specifically. So if I were faced with that capacitor location question I would follow the wires. Or grab the manual.

More examples are in the page above.

On 2021-07-24 by k

Where is run/start cap on 5T Carrier Infinity packaged unit?

On 2020-10-31 by danjoefriedman (mod)

Raheem

Please see the guidelines at CAPACITOR SIZE DETERMINATION for ELECTRIC MOTORS

On 2020-10-31 by Raheem

Good morning. I have bench grinder of size 150*16*12.7mm with a model number: .CN3215S. My question is what is the capacitor size for this motor. If i can get it asap i will be glad. Thanks you in anticipation.

On 2020-06-29 by danjoefriedman (mod)

I would start right at the motor. If there is no capacitor in or mounted on the motor then I would follow the motor wiring back from there through the various control and relays. Normally the capacitor if there's an extra Lon would be mounted quite close by. Follow the wires.

On 2020-06-29 by Todd

I have a question, how do I find a start/ capacitor on a 2014 Bryant model fan blower motor.

On 2020-06-04 by danjoefriedman (mod) - do I need a start or run capacitor and how do I tell?

Fred

There are several approaches to finding the right capacitor for your pump. The best would be to take a look at the manual for your specific pump in which the manufacturer will name in the wiring diagram the specific capacitor that they installed originally.

In general, we can tell if a capacitor is a single start or run capacitor by the number of terminals on the capacitor. If it has three terminals it's a combined start and run capacitor. If it has two terminals it is either a start capacitor for a run capacitor. Once we have decided those questions we look at the value on the existing capacitor and we can tell by the capacitor size or rating whether it is most likely to be a start which will have a bigger capacitor for a run which will have a much smaller capacitance rating in microfarads.

However it doesn't make sense to me to look at the existing capacitor on your pump if you are telling me that you already know it is the wrong one.

Instead we look at the data tag on your pump to get the pump voltage and horsepower and from that you can use the simple cables above as an alternative approach to finding the correct capacitor. But remember that the best approach is to look at the manufacturer's actual specification.

Even if you don't have the manual and wiring diagram for your pump we can usually find it if we know the pump brand and model.

On 2020-06-04 by Fred florendo

sir what capacitor is located inside the black box atop my Myers jet pump QD52S .5 HP 230 Volts....Is it starting or running capacitor...

please advise the correct uf if this is starting or running... the former owner of said pump failed to replace the original capacitor thank you

Question: can I build a submersible well pump

(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 CAUSES of HARD STARTING ELECTRIC MOTORS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

Suggested citation for this web page

LOCATE the STARTING CAPACITOR at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or see this

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

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification
when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Comment Form is loading comments...

Citations & References

In addition to any citations in the article above, a full list is available on request.



ADVERTISEMENT