HVAC Run Capacitors

[youngsplash85]

you have more balls than i do, i never touch the prongs on top, instructor use to scare the piss outta us about it holding charges lol

[DrZarkloff]

@youngsplash85 I always discharge any possible charge before I tough the terminals.

[WiseInfant]

You hiring DrZ?

[DrZarkloff]

@WiseInfant I don't have an air conditioning company. I'm a tech for the school board.

[Billyboy7908]

Is there any way to check a capacitor without a capacitance tester? I think the one in my a/c unit may be going bad.

[DrZarkloff]

@Billyboy7908 A capacitance tester is only one way to tell is the run cap is bad. It's best to just replace it if you feel that it could be bad.

[phuckq]

Your video are really great. Thanks so much for posting them!

[gatorbait1810]

Thanks for the help id like to keep my fingers! !!!

[gatorbait1810]

Hi just wondering if u could explain discharging of caps.what's the best way? I hear a screwdriver across the terminals but which ones? And does the screwdriver need to b insulated or can u use a regular one

[kj7ym]

I am looking for instructions to convert a dual capacitor to two independent capacitors. I have done it in the past. But lost my notes. Can you help?

[DrZarkloff]

@kj7ym I'm not really sure about your question. A dual capacitor is already used as two independent run capacitors. If you mean to use two independent run capacitors for the compressor and the fan motor then it is a bit different. The fan motor will use it's own run cap and the wiring can be different. It all depends on if you're using a 3 wire or 4 wire configuration.

[findvoltage]

hi, can you tell me about run/start capacitors, do they exist? thanks Doc.

[DrZarkloff]

@findvoltage I can very confidently say that run caps and start caps do exist.

[findvoltage]

@DrZarkloff hi again, i ment run-start capacitor, as a single unit. if it does exist can you give me an example how it works, i know that two metal foil sheets hold a charge and relese that charge, but a normal start cap would malfunction if i used it for a run CAP. so what is the difference between the two, thanks again DOc.

[DrZarkloff]

@findvoltage The internet can be a good place to find info on run caps and start caps. The run cap is used by the compressor or motor during the run time. The start cap just gives the compressor an extra boost of power only at start up.

[ylor123]

Dr. Z that mean the condensing unit with just the run capacitor will work just fine without the start capacitor. Why bother install a start capacitor?

[DrZarkloff]

@ylor123 A good start capacitor can save your compressor from those high in-line rush current amp draws.

[ylor123]

Hi, Dr. Z, I'm new to this field and your videos teach me a lot. Can you explain why some condensing units have both start and run capacitor, while some units have only run capacitor? Thanks. waiting for your respond.

[DrZarkloff]

@ylor123 Most condensing unit will come with just a run capacitor because of the expense. You can field install a start capacitor later.

[sakitlikod1]

Hi Doc, can you help me ?. I need a dual capacitor for my weatherking condensing unit # 10aja6001, the capacitor(aerovox # sh1238) doesnt have any info, but the fan motor is 5uF, but no info for the compressor,only a # of P55-23148-31,any help is greatly appreciate. note: I took it to the ac parts place, but they couldnt get anything in their meter & couldnt help me, any advice? I just need to replace it, thxxx

[headscratcher99]

Hi Doc,

I took your advice! I replaced the dual cap, and sure enough both the fan and the compressor are up and running. My friend has a capacitance checker. Both caps on the old unit were open. I read on the internet that my 5 year old Carrier model has a capacitor problem. This bears it out. Thanks for your help.

[DrZarkloff]

@headscratcher99 Thanks for watching.

[headscratcher99]

Hi Doc,

Hey! It's hotter than Hell here in Philadelphia! A perfect day for my whole-house Carrier outside unit to fail. :-) I suspect the dual starting capacitor. What do you think? The compressor will not turn on (I think I hear it trying to start, but it shuts down), and I need to manually spin the fan motor to get it to come up to speed. The capacitor is hot, but then again, everything here is hot! Thanks in advance, Headscratcher

[DrZarkloff]

@headscratcher99 You could try to replace the dual run cap. If that doesn't work for the compressor then you might want to check into getting a hard start cap.

[LONESTAR1045]

What kind of meter is that? I work for a HVAC company I started as a helper and they are now training me and I need to start getting some tools together.

[DrZarkloff]

@LONESTAR1045 I used a Fieldpiece HS33 in this video.

[thorsmum]

Hi Again Doc,

I replaced the cap with a new one. It measures 15.12uF. Installed, but blower is still making humming sound and seems down on power. Is my blower motor bad? Can I test it somehow? Thanks again.

[DrZarkloff]

@thorsmum Yes, it is very possible that you have a bad motor.

[DrZarkloff]

@thorsmum What is the run cap rated at? If it's not rated at 15 mfd then you might want to replace the run cap.

[thorsmum]

Hi Dr. my central heating fan seems to be down on power and is making a humming noise. I pulled it apart and found nothing binding it up. I checked the run capacitor with my multimeter on capacitance. The cap says 15uF on it, but measured only 11.13uF. Is the run cap responsible for the loss in power. Should I replace it? Thanks mate.

[DrZarkloff]

@thorsmum You really should replace the run cap. It's bad.

[kb0nly]

That works if you can actually find a meter which tests capacitance, haven't seen any available locally, and the ones online are around $100, so this video is rediculous. Anyone can do it if they spend the money on a meter, but who can afford that?

[catdaddy750]

thanks. for the info.

[catdaddy750]

ok, i have a question my air conditioning capacitor burn a wire twice from ''C'' and ''H'' side. i fixed by my self but the wire getting short and i want to know why is burn it wire?

[DrZarkloff]

@catdaddy750 The wire could have burnt at the connection because the terminal connection was loose.

[thereelmaster]

i have a question, if you hook up a run cap to a motor's ground lead. and the hot to the ground, will the motor run back word's? i need to know becuase im working on a reel to reel tape recorder that run's a clockwise motor,and i got a motor that originaly ran counterclockwise. please reply.

[DrZarkloff]

@thereelmaster If you short the line voltage to ground, it will trip the breaker or fuse. I'm not sure about what you'd have to do to get the motor inside of a reel to reel tape recorder to run backwards. Maybe you can figure out what happens when you put it in rewind.

[Railroadertwo]

Say, that Fieldpiece HS33 meter looks awesome, do you have some of the other heads for it, I was looking at the them for perhaps doing some testing of my HVAC system.I am a DIY type of person.

[DrZarkloff]

@Railroadertwo I've since then purchased the HS36. I have a non contact temperature thermometer.

[Railroadertwo]

1.206mfd is what I meant, I thought it should test out in the vicinity of 5mfd. Thank You Very much for your timely reply, I appreciate you sharing your experience.

[Railroadertwo]

My single fan run Cap is a 5MFD /370Vac and tests out at 1.206, is this cap good?

[DrZarkloff]

@Railroadertwo If you mean 1.206 mfd, it's bad.

[BGreenHVAC]

Cool! I feel stupid though, I knew this but failed to perform this test one time that I should have. Thanks for the reminder. I had a customer who was told by another tech that the compressor needed replaced. I took a look and seen the cap was bulging a little on one side more than the other. I should have performed this test first. My hunch was right the dual purpose cam was bad.

[DrZarkloff]

@BGreenHVAC Sometimes, it's the obvious stuff that gets overlooked.

[pylgrym]

SAFETY FIRST, gang! As my old instructor, Dave Sizemore of Chattanooga State would say:" This ain't a FAITH TRIP!"

[Serostern]

Add a bleed resistor to the terminals.

It will save your life some day.

[radnitzku]

I wouldn't touch the terminals of an unshorted C.

[chidouan1]

HEY DR Z ,LOVE YOUR VIDS! COULD YOU DO ONE ON BAD OFM AND HOW TO TROUBLESHOOT THEM ,THANKS!

[jwablueeyes]

hi im jeff,im a teck ,i seen a odd thing.it was six 5mfd in the place of 30 mfd,is there a problem with me leaveing them that way,i never herad of something like this in school,i finish school last year jeff.ahner@yahoo.com, thank you

[DrZarkloff]

@jwablueeyes I know that it seems odd but you can run your run caps in parallel to add up the rating you need. I don't recommend making this a common practice. It's good in a pinch.

[automan1223]

what if you had the same 5/60 uf 370 vac but your available replacement was 5/60 uf 440 vac ? would the extra voltage rating be ok ?

[DrZarkloff]

@automan1223 Yes.

[cincocapacitor]

good video.it is very useful for us to learn more about the hvac capacitor.

[MrTERRYD55]

what is the problem using the step up on the voltage ...for instance the old cap unit is a 50 / 5 x 370 and used 45/5 x 440 what is the harm if any....the fan side on the old unit was bad...

[DrZarkloff]

@MrTERRYD55 The problem is that the compressor side on the old run cap is 50. You could use a 50/5 X 440. A 45 wouldn't give you enough capacitance, causing the compressor to not start at times and making it overheating while it would be running.

[cincocapacitor]

@MrTERRYD55

hi,terry.

you could try the capacitor 55/7.5uf or 55/5uf capacitor.

[MattixIcexBaby]

Wat model of meter is this? I have seen a few techs using it before but never looked at it closely, I need a new meter, this must be a good choice.

[DrZarkloff]

@MattixIcexBaby I made this video with my older Fieldpiece HS33. Now I have the HS36.

[YummyMercury]

MFD is the old terminology for uFD so dont confuse it with mFD!

[mexman000]

no you cant

[artgoat]

Capacitors usually fail open or short, rarely change value (split-phase caps are plus/minus twenty percent anyway, so a 5MFD could be anywhere from 4 to 6). You can test with a normal DVM by charging the cap with a 9V battery. Just short the battery lugs to the cap terminals for a few seconds, take it off, wait a minute or so, then test with the meter set to DC voltage.  It should start out very close to 9V and slowly drop as the cap drains through the meter. Zero volts means a bad cap.

[estrelladelnorte1308]

Can you test it with a multimeter that doent have a mfd test choice ? is ther another way to do it and how??

[DrZarkloff]

@estrelladelnorte1308 You really need a multi meter with a mfd setting to do it right. There is a way to using the volts setting while the system is running. I don't find it to be very reliable.

[kolocho7777]

ur the man!

[disconnected007]

i got this submersible pump a single phase IM 220V. Now it wont run unless u give it a initial turn. i found out the capacitor (8MFD 500V with 3 terminal) bulge up. My question is... is it a run or a start capacitor? and why is there 3 terminal? got a hard time looking for it in the market... can i replace with something the same?

[DrZarkloff]

@disconnected007 It could be a run cap. Some run caps have a terminal that is connected to an overload relay.

[Guacatechs]

Can you replace a bad capacitor with with a replacement of the same MFD but higher voltage?

[DrZarkloff]

@Guacatechs Yes.

[GregA64]

I have a campbell hausfeld compressor where the Run Capacitor ruptured and leaked out it's fluid. Is this just normal failure or is something else going on? I have had problems recently that the Compressor wouldn't run beyond 40 PSI without tripping the breaker. Was this all just the normal progression of the Run Capacitor going bad?

[DrZarkloff]

@GregA64 Those are two separate problems. It is possible that your compressor windings are ohming to ground.

[bsnegi24]

i have a capacitor which is totally dead and name plate is wiped away. how find the the capacitors mfd pl reply me.

[DrZarkloff]

@bsnegi24 Look at the motor. The run cap info should be on the data sticker.

[MrLastyme]

i replaced a bad fan motor on a carrier unit and used the same dual cap that was there but it didnt work.. i had to actually buy a seperate run cap for just the fan i dont know why it didnt work with the dual cap???

[DrZarkloff]

@MrLastyme Was the old run cap rated the same as the new run cap? Also, was the old dual cap good?

[madamerotten]

Can walk capacitors be tested the same way?

[DrZarkloff]

@madamerotten lol. Walk capacitors.

[krisachar]

Thanks for that informative video ! Now we have learnt how to test our Cap's..

Love,

kris.

[hntnman34]

I thought you had to dis-charge a cap before testing it. Or is that just if your meter does not read MFD?

[DrZarkloff]

@hntnman34 It's always a good idea to discharge the run caps for safety reasons.

[zer0dahero]

thanx... this is exactly the information i needed and in a hurry. Youtube is the best.

[ab9957]

DrZ, what happens to an indoor fan motor when its run cap is removed from the circuit?

[DrZarkloff]

The motor won't run.

[simon1tan]

Thanks for the videos, I'm learning lots.

[DrZarkloff]

Thanks for watching.

[rogperdiaz]

Mfd=2650xI/E

Take the amps on start winding this value times 2650 and total divided by voltage on capacitor (common to herm or fan depend what you want) thats gonna give you capacitance

[kosukissa]

Hi, What is difference between capacitor like beginning this vid, o.40 sec, oval single, and round one, plastic covered capacitors available as run capacitors as well. Will it work if I put of course same uf, is it only difference what it looks like?

[linoleumcarving]

i was using a capacitor on a test bench at HVAC class and it sort of pooped and sprayed goo on me. what was that stuff.?

It smelled too.

[DrZarkloff]

You might want to look on the capacitor and make sure that it says NO PCBs. If it does then you were sprayed with an electrolyte that we all hope won't later be found to cause cancer in California. By the way, PCBs have already been found to cause cancer in California and most other states.

[simon1tan]

probably electrolyte

[Rueuhy]

I was cleaning out my van today and came across a 25uf run cap. It looked like it was fairly new so I checked it and it read 12uf. I was curious if anyone might know why the value on capacitors drop by half like this one did. I've seen 2uf - 5uf drops in value but not in half like the one I found today. It wasn't the only capacitor I checked so I know my meter was okay. Any ideas?

[TehMG]

Capacitors do have a shelf life and will deteriorate if stored for very long periods of time. Typically this is around 5 years.

Often the capacitors just need 'reforming' which is done by applying voltage and discharging to the capacitor a number of times. Sometimes however the deterioration can be permanent.

[TehMG]

The following blurb is copied from a manufacturer's run capacitor datasheet:

"Capacitors may be stored for periods up to 2 years without detriment, but after long periods

it is a safeguard to test them before putting them into service. In service, the oxide film,

which is the dielectric of the capacitor, is maintained in good condition because any

imperfections permit a current to pass and the resulting electrolysis forms a new oxide layer.

[TehMG]

Deterioration of the film takes place if the capacitor is stored for long periods and it is

preferable for the reforming of the film to be brought about before the capacitor is subject

to its full duty. If a motor start capacitor is already connected to the motor, the reforming

can be achieved by freeing the motor from its load and switching on several times."

[DrZarkloff]

It's junk. It's not a good idea to use it any more.

[edhubbard45]

I just replaced my indoor Blower motor and capacitor I have 2 purple wires that go from the motor to the capacitor. Are there polarities for these and if so what are the polarity indicators, I do not see anything marked with + or - ?

[DrZarkloff]

There are no polarities on a single run cap. Although, dual run caps have do have a common terminal.

[wargasmn]

duals don't really have a common its more of a common connection point isn't it

[shragakrigel]

Hi DrZarkloff

How do I know the correct size of the capacitor, is it by table ? calculation ?

Thanks

Shraga

[DrZarkloff]

The label on the motor should tell you which capacitor to use.

[Gordon302]

I'm surprised that you actually touched both of those open terminals like that with stored voltage in them. From what I understand, these H.V.A.C. capacitors can charge up from ions in the air. So, most electronics stores that sell them, short out both terminals with a piece of wire to prevent that. Also, a general safety warning should be posted, since you never know what of of audience on Youtube will be watching.

[DrZarkloff]

I have explained how to short the capacitor before handling them. The ones that I'm touching aren't even connected to a machine.

[juancmendez38]

DrZarkloff , most of my experience is from apartments , so i do not get to see much of what is out there. for the first time i saw a solenoid valve on the high side of evaporator ,this valve is wire to the low volt going to the condensing unit, my question is what is the purpose of this valve ?

[biga100able]

DrZarkloff Ive learned more about hvac watching your videos and im a student so i have to say thanks u are truly a blessing to guys really wanting to learn this trade

[DrZarkloff]

Thanks for watching.

[juancmendez38]

thank you for this wonderful tips, is making me a more efficient maintenance person.

[DrZarkloff]

Thanks for watching.

[TheGatordogman]

That sounds good. Only one thing, Iam not sure how to do that. Can you help?

[DrZarkloff]

I probably should just make a video showing this.

[TheGatordogman]

need to replace a 50uf/7.5uf cap.but i dont have one of that size. can i use a 20uf and 30uf and put them together.

[DrZarkloff]

Yes, as long as the voltage rating is the same or greater.

[onthecuttingedge2005]

clean them up and paint them, it is hard watching this video knowing they're just rusting away. sniff's!

[DrZarkloff]

lol

[QuaziGNRLNose]

what do run capacitors do exactly?

[DrZarkloff]

They sort of fakes out the motor into thinking that it has three phases.

[mslimskey]

You really just made me feel like a moron. I've been using the exact same meter you have for 4 years doing HVAC service. I always just Ohmed out the capacitors, to tell if they were shorted or open. NEVER even realized I could check capacitance with it....

[DrZarkloff]

I'm glad to have been a service. lol

[DrZarkloff]

Those are bleed resistors. They short the terminals when the power is off so that it can be touched without getting shocked.

[rolando7120]

great.. We really need people like you! I've watched all your videos thanx a lot!

[DrZarkloff]

Thanks for watching.

[THEtechknight]

theres another property of electrolytic capacitors that need attention: and thats the ESR. your capacitance can still be good, even though the ESR or equivalent series resistence is bad. meaning, its too high. so thats the same as having a capacitor with a big resistor in series with it, making the cap useless for starting/running an electric motor. RARE case, but needs looked at occasionally.

[alex681219]

Hi, I find some old filter-caps in a fleamarket.

One nichicon with 6 terminals a:200MFD 300WV b:10MFD C:20MFD D:20 and E:120MFD...I´m Newby in the electrical stuf and buy for the big size for experimentation, can i charge it with 12V? power suply...what means WV? the mega farads means more electricity storage capacity? tkz for share

[rastababy144]

God bless drzarkloff and youtube.

[DrZarkloff]

Thank you very much.

[kielwestongreta]

Yeah, hurts too! Learn that about 10 years ago! Always discharge

[DrZarkloff]

Yeowch!

[Cambria2007]

you forgot to tell people you can you these as a stun gun too!

[DrZarkloff]

lol

[burlesque78]

You're the best teacher online i ever saw .I learn a lot from you.

Thank you very much....

[DrZarkloff]

Thanks for watching.

[kjstrawder]

Your right about the blackhvac techs because I am one, so if your black dont join the union in the south to be a hvac tech

[garyomglol]

Hey Dr. Z, Love your videos. I have a question: I turn my ac on from the thermostat and my condenser doesn't kick "on". If I push "in" on the contactor it energizes and starts working. Once this happens, my ac works fine. When the desired temp is reached, the system goes off as it should with fan delay staying on a minute or so. When room temp goes back up, it would take the system 5-10 before the compressor would come on again. Should I replace the contactor or capacitor or both? Thanx

[DrZarkloff]

It sounds like the system is running normally. A time delay is probably holding the compressor out for the five minutes. The time delay is a safety device that prevent the compressor from short cycling.

[garyomglol]

I leave it off overnight.... then in the morning I go and turn on the ac and wait and wait for even half and hour, the compressor never kicks in... unless I physically go push on the contactor. Then it would work for the day. Could it be a "sticking" contactor...as once it warms up it would work for the day? Thanks for your reply Doctor Z.

[DrZarkloff]

The coil on the contactor could be bad. I recommend replacing the contactor.

[garyomglol]

I replaced the contactor. It worked for a day perfectly.... and now its still the same. When I turn on the thermostat, the wire to the contactor shows 24v, but the contactor failed to engage. Should I also replace the time delay relay too? (its located in the side panel of the condenser with 3 wires going into it?) Or is it located elsewhere? You response is greatly appreciated...thanks Doc.

[DrZarkloff]

There is a possibility that the time delay is going bad. I'd say that it would be the next logical step.

[ZmajSnoshaj]

Dr Zarkloff *Flash Gordon pun?? LOL* :))

I won an "Annie" model A-4 Capacitor Analyzer *can't get over the humor of this unit's name*.. hoping to use it to test the electrolytics on my 1964 Hammond L-103 organ.... but alas... I've learned *the hard and fun way* that it's used for testing these run/start capacitors... have you heard of these vintage testers? Are they desirable? What do you know about them?

[DrZarkloff]

It's partly a Flash Gordon pun. My real last name is Starkloff. I've never heard of that model of capacitor analyzer.

[imsaeed]

DrZarkloff,

thank for your all videos,are very informatic .tell me what purpose of using the run capacitor for a motor or fan?what it does?

[DrZarkloff]

The run capacitor gives the motor continuous starting power even while it's running. Three phase motors don't need run capacitors because the third phase gives the motor more running power.

[The8thGame]

DO you think people should always discharge the capacitor before touching it ? You better let them know before they become one handed .

[ale24541]

LOL!!! May be you should hold the camera with your hands and take the proves with your feet to test the capacitors!!!

Good explanation!!!

[DrZarkloff]

Believe it or not, I've tried to use my feet to hold the camera. It doesn't work very well.

[Tonednguyen]

Dr Zarkloff,

What is the purpose of a run capacitor hooking up on motor ? Does it try to correct the phase shift caused by the motor? Thanks.

[ale24541]

The purpose is:

1 - Creates an impedance that limits the current trough the starting coil to a safe value. The starting coil has less impedance than the working coil (coils are in the motor stator)

2 - Shifts the power phase 90º, so the coils can create a rotative magnetic field causing the rotor to turn

If you want to correct the power factor you need to connect a capacitor in paralell to the whole motor.

In any case, the capacitance must be calculated

[ZX2ManDave]

What would happen if you would stick one of those to your tongue like you can with a 9volt battery?

[DrZarkloff]

If the run capacitor was charged at the time, your tongue would never be the same.

[ZX2ManDave]

Hehe thats what i thought. It could be the Ultimate Beavis and Butthead moment.

Just a silly thought. Kids, dont try that at home.

[rlewis1946]

Ooops, Just read my answer courtesy of

PutSome5tankOnIt. Sorry.

But this made me wonder if you have some tips and tricks on using VOM's for a video. Hope so.

Thanks again.

RL

Atlanta, GA USA

[rlewis1946]

Dr. Z - Really enjoy your videos!

Two questions:

Why discharge Run Caps in common to herm, then common to fan sequence?

What brand and model VOM do you use/recommend?

Keep up the good work!!

Roy

Atlanta, GA USA

[Oateys]

Hi Doc I wish to make the same request as the other Gentleman did. PLEASE PLEASE make a video actually showing us how to discharge a dual run cap!! I wonder how big of a spark to expect, on a dual run cap do you short out all 3 terminals at once?

[DrZarkloff]

Thanks. It just so happens that I plan to film a run cap 2 video today. It's a good idea to discharge common to herm then common to fan.

[mortakye]

While checking out my brother's A/C, I noticed that the blower inside the air-handler was cycling on & off. It runs for a minute-then shuts off for 15 secs. Run capacitor check?

[DrZarkloff]

I think you might just have it.

[quickfreeze45]

i love the stick field piece meter!

[DrZarkloff]

It's my favorite.

[dmz209]

excellent! thanx

[DrZarkloff]

Thank you

[mechanicwarrior20]

What type of meter you got there Fluke?

I need to grab one of those to test capacitance on capacitors... :)

[DrZarkloff]

I have a Field Piece.

[PutSome5tankOnIt]

That's a Fieldpiece HS33. I own TWO of them. Gotta have a spare, just in case one of them fails. I also own a LT17A.

I call my stick meter the Veg-O-Matic. It slices, it dices... it does almost everything a field technician needs, to diagnose most HVAC problems.

It's a volt meter (AC and DC), a thermometer, amp meter, capacitance meter and ohm meter.

I have accessories that measure RH%, dry bulb and wet buld temp, pipe temp, air flow (ft/min) and many other parameters.

[mechanicwarrior20]

thanks looks like one hell of a meter

[dinoasm]

How come you did not show how to discharge them like I posted in your other video? Is it because I am Black?

[DrZarkloff]

Say what? I would hope that you'd discharge any run capacitor before removing the wires from it. If you'd check out my HVAC air conditioning safety video you'll see how I discharge the run cap.

[shocknyall]

Way to educate Doc. Keep up the good work

[DrZarkloff]

Thanks