Run Capacitor Fundamentals Class
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- เผยแพร่เมื่อ 27 เม.ย. 2021
- In this quick class we cover run capacitor, fundamentals, how the are rated, how they are tested and how they work.
Read all the tech tips, take the quizzes
and find our handy calculators at www.hvacrschool.com/
The next generation of techs will be much more ethical and efficient with access to good training like this!
Even current techs like me are trying to get better every day.
I have yet to find a good tech where I live. Makes me think about changing careers to help people
@@tekjunkie28 It is a real challenge to find a great technician in the residential field. There are a lot of factors. In coastal Texas for one example, residential techs HVAC can make great money during the hot months of the year, but struggle to get enough hours during the mild winter months. The higher skilled techs tend migrate to the commercial field where the hours are steady year round , the work is less laborious and pay/benefits are typically better.
Too bad it will just be overshadowed by companies who only wants tech who can sell rather than fix. Only reason who I stay in commercial
This is the Golden age of HVAC information and it allows for us geek out on everything.
62 years old. I have been in the HVAC Trade since my early Teens in my Dad's Marine AC Biz. I am now Manager of Technical training for Home Serve USA and found all your Videos to be a great resource. And accurate.
Are yall hiring?
As a long time boiler operator and now moving into my company’s HVAC / electrical group this information is gold! Never stop learning and challenging yourself to master new skills!!!
For being in the trade for 36 years... I must say you have a great channel and us old dogs still learn something every day.
If we want a trade to be ethical we must train and promote a question friendly atmosphere. Providing content like this allows those seeking the knowledge to get what they need. Thank you.
More of these types of videos please Bryan. Great stuff man.
A meter could check the capacitance by putting a AC test charge on the capacitor and measure the phase shift in the circuit. It could also measure the voltage rise rate and /or decay rate over a resistive circuit. When an ac capacitor is installed on an AC circuit, the voltage of the capacitor is dependent of the current "pumped" into the capacitor, since the voltage would change direction before the current could completely build up the charge it would always lag the source voltage. This lag is really represented by the line resistance. The more line resistance, the more the lag.
Great!!! One of the fundamentals of capacitors is understanding they (many types) are rapid discharge devices. Several decades ago in electronics school, it was cool to see the spark when leads were shorted together. Yes, safety first, but we did learn a few pranks/tricks.
Nice job instructing. I’ve been a radar design engineer for over 30 years and it amazes me how many engineers lack those fundamental concepts.
Wow, THIS was the Best CLASS yet…!!! ✅
That was a Good breakdown of the subject at hand 🤚 so far.
This dispels so many myths about discharging caps And how they work. Your helping not only customers to put more faith in the trade due to good workmanship but helping techs do their job safely and with professionalism. I’m sure you’ve saved the life of a young tech somewhere for sure. most companies don’t offer any training but rely on senior techs to do that for them. you give a great resource for those guys and gals lol. Great resource. I refer you to all new and old techs. And installers for that matter. 😏👍
There's a channel Ludic Science that has a video 'Making a High Voltage Capacitor' out of 3 disposable plates, a couple pieced of aluminum foil and baby oil. Very good if you need a visual of what makes a capacitor. They just roll something like that up in the can for run caps. Also, his 'Electrical Reactance Demonstration' video is the best for seeing how inductors/windings and capacitors act like resistors in AC series circuits.
Man, you guys got to be one of the BEST.... tech schools out there thanks for the lessons and keep them coming.
Very good instructing, made very plain and simple.
Awesome stuff. Much appreciated. Thanks for sharing this. It is VERY helpful.
I'm not sure why this video was I my feed today,but I'm absolutely ectatic after two years of not being able to figure out why my air compressor wasn't working properly.. I had replaced the start capacitor a year ago ,cause it kept blowing the breaker when I tried to turn it on. Well I was having a issue with the parts guys about getting a new run capacitor,and I don't have a credit card s online wasn't happening, well after watching this video I got my voltage meter went down stairs to the thing ,and low and behold someone had put the wires on the one terminal on the run capacitor,I switched it not knowing which one went where,but it fired up and kept going!wow! I'm very happy. This was a compressor that someone had given me cause it didn't work 👌🙂👌it's a 6hp 27 gallon🙂 ps I'm now a subscriber!
This was both informative and entertaining. No interest in becoming an HVAC tech, but I think I'm going to watch all your videos.
Very much appreciated. Learning made interesting.
Thanks for the video, it is great learning the wiring of compressor and fan capacitors. Way back in the 80s when I worked on cars, one of the practical jokes was to take a ignition capacitor and charge it with a spark plug wire and the lay it somewhere where you know someone would pick it up and of course it would shock them :-)
Yes, this also proved that the condenser (capacitor) was good. I was surprised that the capacitor only retained 9.6 volts after being hooked up to a 9 volt battery. In the old ignitions the condenser served two purposes. First it reduced arcing at the contact points & second when the points broke contact it discharged at about 250 volts to the coil (transformer) which in turn boosted the voltage up to 20,000 volts. At least that's what I was taught.
excellent .. thank you for making this kind of videos.
Well done. We're always learning. Thanks again.
What a capacitor does with an induction motor is create another line phase. A capacitor connected to AC makes the voltage lag. This is handy with single phase motors to give you phase angle to develop torque. You're sure not using the capacitor to store a charge while a motor is connected to line voltage. There's plenty of charge on the line all the time.
Thank you for your great video
Best instructions ever to learn on line
So far I'm up to 4:20 and I gotta say, my hairs are standing on end. I feel like I just struck gold here. WOW ! ! !
I was taught that in a sine wave, the amps lead the volts which means they do not happen at the same time, so they are essentially out of phase. A run capacitor works to put the amps and the volts in phase and this gives a running motor much more torque.
Depends on the load, for a purely resistive load the voltage and current waveforms are completely in phase. A motor is a highly inductive load though, which is the case you described.
A run capacitor let's you use a 3 phase delta motor on a single phase supply.
You are right that a capacitor will shift the phase.
Connect line across 1 winding and the correct value capacitor across another will shift the phase on that winding by 120 degrees.
The third winding will "see" the difference of the first 2,and that is the 3rd phase.
ELI The ICE man!
@@dougaltolan3017 Actually, no. The capacitor is sized to shift the start winding current
by 90 degrees from the run winding, simulating a 2 phase motor.
@@cleansebob1 Actually yes. A delta wired 3 phase motor can be run from a single phase with a run capacitor.
A motor with 2 windings will have a main and an auxiliary. The auxiliary winding is normally thinner guage wire and have fewer turns.
Capacitors are used to shift the phase of the auxiliary winding to match the geometry of the layout in the stator.
Auxiliary windings have optionally a run capacitor, a start capacitor, or both. If a, start capacitor is used, it is switched out either by a centrifugal switch or a timer.
The meter is actually acting as a very high impedance path, that's why it is slowly discharging. If it were low impedance the cap will discharge rather quickly.
🎯 🎯🎯
I thought impedance only related to AC current whereas the meter operates in DC and has a high resistance but is nevertheless consuming some current while taking a voltage reading?
@@fahey6797 impedance is whatever opposes the flow of current. Impedance is the combination of resistance and reactance. So impedance changes with frequency. But there's still impedance even with DC. It's just a different impedance. Clear as mud!
Great information. Thanks
I will make only one comment, a board being able to be marked with dry erase marker showing the circuit path is such an advantage teaching students this theory, or any theory is very helpful. I listened to you but wished I was there to clarify by drawing the circuit path to aid in your teaching. Great job in your explanation I must add but adding drawing’s really helps solidify their understanding in theory.
super class give us an other one we love it
The first thing that should have been talked about in this class is how to safely discharge the cap.
Safe for who? The capacitor or the tech?
Thanks for the video =)
I like Your class.
No professional HVAC experience here. Great instruction and your principles are solid (from this old electrical/ electronics guy). Especially at the end: RMS 120VAC = 170 V-Peak
And he said the meter is averaging the value to read. Which is not correct.
Nice video. I tend to think of a capacitor as a mini, fast recharging, UPS. It smooths and boosts voltage when large motors kick on and run, helping them operate more effectively. Since they cycle so much, they do have a lifespan and are one of the more common components to fail. Just the nature of the design and their purpose.
More importantly the capacitor causes a phase shift.
remember: ELI the ICE man..
PFM LOL! I think “the math” is probably based on this equation. Amps x 2652 / Volts=MFD. For example you can check a capacitor on a running system without disconnecting by measuring the amps on the start wire multiplied by the constant 2,652, and then dividing that number by the voltage across the capacitor terminals. This trick comes in handy in situations when shutting the system down is not an option or when using a meter that doesn’t measure MFD.
good source of info .
Some good info about capacitors per se, not much at all about their function as run caps in AC motors - or how to diagnose bad ones - symptoms of failing / failed parts.
Great video..
Thanks for demonstrstion
Great video! Packard Capacitor Training video on TH-cam is helpful too.
The capacitor meter Measures the curtentxtime to get qoulombs at its test voltage. Then calculates capacitance.
You are mixing start and run capacitors, even though at one point you stated they aren't the same thing.
A run capacitor allows a 3 phase delta motor to run from single phase supply. The capacitor is connected across one winding, the line across another. The combined inductance of the winding a d the capacitor phase shift the voltage on that winding by 120 degrees ie a second phase. The 3rd winding is subject to line minus run capacitor winding, which is equal to the equivalent of the 3rd phase.
A start capacitor is used in an induction motor that has 1 main winding and an auxiliary. Without the start capacitor it is 50 - 50 which way it will run at each start. The addition of another (smaller) winding and a capacitor means that the motor will always run the same way.
You confuse even more. 3 phase motors do not need capacitors to run. Back to basics please.
Where can I get the alligator clip meter leads that you guys were using in the video? I don’t care for the ones that came with my Fieldpiece meter so I bought some Amprobe alligator clips which look similar to the ones in the video but much larger. And by much larger I mean way too large. I like the ones in the video, they look like just the right size for me
New to the field. I was told replace cap. If system works after then is was cap. If that doesn’t fix then it’s motor. Providing there is actuallypower. Labor wise, does it make sense to go through all this?
The caps generally have bleed / discharge resistors fitted just as a side note
rumor has it they're still putting out the fire from that off-camera test
Did you do the capacitor test ?? with AC voltage . What were the results
ThankYou
High impedance for voltage; low impedance for current. @12:10 ish or so.
Great video but maybe i missed it, question... I realize it's been 2 years since you did it But... say you had a capacitor that was out of the tolerance by far yet the compressor does start up... is it possible that that out of tolerance capacitor would cause the compressor motor to work harder, leading up to thermal overload protection activating on the compressor after it's been running for a while during the day?
I can't get to coils to check / clean unless I take it apart even more quite extensively than I have so far and so I guess I'm going to try replacing blower motor capacitor . Coils sitting on top of furnace and I would have to cut freon and drain lines . Yes it might be very dirty but don't wnat to go further and capacitor is only $12 . That might work ?
I have a coleman RV ac on the compresser start capacitor with a resistor in the one wire it is bad as well,, my question is do I need the resistor OR can I do away with it ??
Lots of thanks sir
Your videos are really good and helped
I've heard that standard reasoning, of back EMF from the motor causing higher voltage drop across the upstream capacitor, but I think it's not accurate. It's a confusing topic because there are two kinds of back EMF, the kind of reverse voltage that comes from the motor acting as a generator, and the kind that comes from inductive properties of the coils inside the motor. I think the higher drop across the upstream capacitor comes from the inductive properties, not the generator effects. You can easily model the higher drop across the upstream capacitor with an A/C series LC circuit. At resonant frequency you get huge drops across the cap, since electrons are shifted back and forth between capacitor and inductor like a juggler tossing a ball. That's why it is so important to have the correct run cap in line. The circuit needs to be tuned to resonant frequency. On the other hand, the generator effects of the motor cause a reverse voltage (in phase) which can never exceed incoming voltage. A reverse voltage charging the downstream side of the capacitor would tend to increase voltage on the downstream plate, effectively reducing the drop across the capacitor plates. Unless the generator effects are out of phase, you shouldn't see big voltage drops across the capacitor coming from pure generator effects.
Great video!!! I looked in a condenser unit and it had a dual cap with a 60 MFD herm. Looking on repair clinic the model showed it should use a 30 MFD. The 60 MFD was out of spec but must have been in this unit for years. Should I replace with the 30 MFD? I did not look on the compressor unit itself but need to do that too to see if the MFD is noted on the compressor. Trane model TTD760B100A2. Thanks!!
It is very important to use the correct value capacitor. It is matched to the motor windings and line frequency.
A run capacitor let's a 3 phase motor run from a single phase supply by phase shifting the voltage on one of the windings. The wrong value capacitor will create the wrong phase shift.
The result is a motor that will not be able to reach rated power and will get a bit hotter.
If the motor is sufficiently over spec and there are no cooling issues then yeah you can get away with it for years. But it will run better and more economically if the right cap is fitted.
@@dougaltolan3017 - after doing some further digging I realized that the 60 was replacing the original two 30 µF capacitor‘s. So two 30s equals 60 so all is good
The run capacitor creates a 90 degree phase shift in current when properly sized for the load with ac going through it. This causes a rotating magnetic field around the rotor.
So it does what to the speed and torque of said motor. Its the core answer to why you have one in use on many items.
That would be a start capacitor, a run capacitor corrects power factor. Once a single phase motor is running the start capacitor is removed and the run capacitor is not.
AC rotates. A sine wave is just a circle stretched out. As the circle spins and time is mapped on the Y axis you get a sine wave. That curvy up and down is really round and round. Just looking at the waveform that way isn't so useful to us. So on a scope we express it differently. Visualizing all of this was the brilliance of Nikola Tesla. He saw it all in his mind before any of it existed.
RPM-run/power to the marked side, never seen one. Understand the marked side terminal is the plate closest to the housing and would short to the can and kick the breaker.
Am Rad, built in Palm Coast Florida. I only use them.
Love it.
Thanks for a great video. I just subscribed so I can watch more of them. I know nothing about HVAC, and don't plan to watch 2 videos and then run out and electrocute myself! I would just like to know a little more about how it works and be able to understand what the tech is telling me when they come to maintain or repair it. Thanks again for sharing 😊
Thx HVAC S for an informative and interesting video brought back memories of '70s Mt Sac College and Mr Motter's Aviation electronics class driving home Xl and Xc calculations to match capacitance to reactance to improve delivered power factor in a motor. Now days a Micro Aire soft starter does it all for me on my RV ACs allowing me to run 2 ACs from 30amp 120vac shore power. Sub'd
Some confusing moments in this video, wanted to clarify..
Start winding need a start capacitor which is usually disconnected by a centrifugal switch. The start capacitor is usually of large value and short time rated.
Run winding requires a run capacitor which is always connected to the power in series and continuous rated..
The higher voltage that you measure across the capacitor is because of the LC circuit impedance. You will also measure higher voltage across the run winding for the same reason. Not because of the motor back EMF
It is because of this the capacitor must be purchased with the voltage as per the defective unit and not based on supply voltage.
Start and run winding should not be confused.
All capacitors in market will have a higher capacitance value than the nameplate. If the measured value is less than nameplate value by more than 10%, needs a replacement soon.
The run capacitor provides a phase shifted current on the run winding with respect to the main winding, creates a rotating magnetic field which turns the rotor.
Regards.
Thank goodness for this reply.
Your the Only person in the top 100 comments that understands what this idiot was grying to teach.
Which alligator leads are you using, i cant find them on amazon?
Don't know why the algrorhythm gave me this video but this channel was a instant subscription for me. Thanks for the content.
It's very simple explanation easy to understand thanks alot
Volt meters are high impedance devices, like in the mega ohms. Current meters are low impedance.
Hey I wanna see that last experiment. 😂
I stupidly didn't pay attention to the color of wire coming out of the starter capacitor on my washing machine before I disconnected it so now I don't know how to tell which side gets power and which side connects to the motor. Now there is a diagram on the side of the capacitor, but I can't seem to find anybody mentioning how this pertains to which side is power in and which side is power out. Is the side showing the coil power out?
I need some assistance concerning a capacitor. I am replacing a capacitor that reads 370/440. My replacement capacitor reads 370 VAC. Can I use it. The other question: if only 240 volts are going in why is it use for a max of 440 volts. Finally, a capacitor test is in mfd. so why is voltage a concern or a measurement for a capacitor. Thanks for your support.
check into what an "R C time constance" is
Awesome! I’m a hvac technician now.
where can i find those alligator clips off that meter?
Very helpful class 👍
Hello
I have a120volt 1hp motor single phase do I need a capacitor to transfer power from house current to generator so the motor doesn't stop using a 4000 watt electric generator
Thanks bill
I've got a new 25mfd AmRad cap, it has a black and a white terminal, no other markings, which would be common? Or does it matter?
Ok. Cool video
Can I use a 10+5% in place of 7.5+5% for my indoor blower motor. Just for a day.
*QUESTiON* CAN WE USE A RUN CAPACiTOR iN THE PLACE OF A START CAPACiTOR?
ARE THEY iNTERCHANGEABLE?
good teacher ,admitting he don't know everything but that is how he was taught and just passing along his knowledge.
Still need these with soft start?
There's a wide range of capacitors.Those are starting capacitors filled with electrolyte.Some are ceramic or use other materials.In a circuit a capacitor will block DC but not AC.It will phase shift the AC signal.RMS (root mean square) voltage is 0.707 of peak AC voltage.Some things aren't explained in the video,but otherwise good presentation.
Great video! Question: Should you always discharge the cap before you perform the capacitance measurement? Thanks!!
Does it matter at all if you replace a 30 uf with say a 50 uf?
Pretty good learning experiment I done worked on heating and air conditioning for over 20 some year I've had my experience with some capacitors the worst I ever had was start capacitor I've had them blow the electric box completely up they're dangerous you ought to teach them about them things . They act like a half a stick of dynamite when they go off got to teach them how to wire them up.
You are correct. In fact, these big capacitors should be labeled as dangerous. They explode, and also the current can kill you. Far too many inexperienced guys screw around with these things, without understanding the risk.
In the case a capacitor has common, herm and fan, but fan is not connected on a fully functional condenser unit, what information about the fan can be assumed? Does the fan simply not require a capacitor? 1:38
What were the details of the dangerous test that they wanted to do? I couldn't hear what the bad idea was.
Are you not able to connect 120v to the capacitor using a switch, then turn the switch off, and then measure the voltage?
If it was 120VDC, yes. The surge current would be close to infinite, but if it survived the surge, you would read 120V across the terminals. At 120 VAC the cap would constantly be drawing current as it continuously charged/ discharged. When the switch was opened you would read the voltage that was present at the INSTANT the switch was opened (0 to +/- 170 volts). If you've ever switched on a light and it instantly blew out (very brightly), the instantaneous voltage was approaching the peak of 170V. This doesn't happen often, but it does happen.
@@rickvia8435 when they said they might do the test off camera, do you think they did? Is there a way to do the test with safety precautions that mitigate the danger to reasonable levels?
@@realSamAndrew Not with AC, Man. A human cannot open (or close) a switch fast enough during an AC cycle to be able to determine where in the AC cycle the amplitude (voltage) is.
@@rickvia8435 I understand the wave moves too fast to be useful in a test, but I wish to understand why it is dangerous. For example, you can connect a light bulb to 120vac and measure the voltage across it as it is powered. Why can't you do the same with a capacitor? Even though you might have to connect other things to complete the setup.
@@realSamAndrew The basic purpose of a capacitor is to block a direct current, while passing an alternating current. In the case of a direct current across the terminals of a capacitor, current will flow until the capacitor has charged to its capacity, then no more current will flow. If an alternating current is connected across the same capacitor, the capacitor will tend to conduct the current in relation to its capacity vs the frequency of the AC. If the voltage of the AC across the plates of the cap are reasonable, a voltage WILL develop across the capacitor that can be measured (by an AC volt meter). The voltage that is read will be determined by the value of the capacitance vs the frequency of the AC (this is the impedance at a given capacity and line frequency). If the AC voltage exceeds the rated voltage of the capacitor, it will act like a short (or near short) and the capacitor will be destroyed.
In 1973 a very bulky expensive meter was needed to test capacitors.
You could test for opens or shorts with your ohm meter but you couldn't test the MFD's .
Yes, but then if a cap was bad, it would drain itself real quick and not hold a charge, as it's internally shorted. Charging it with a DC voltage like they did, then testing the voltage of the cap will reveal a short or not, as the voltage will drop and not hold unless it's a good cap. A ohms test is not sufficient for testing caps, as the test itself will drain the cap which leads to continuity.
Really wish I work here man so much knowledge
I wish fieldpiece meters would display OL. I don't have one. I've been using a UEI. But that's a little petty thing I don't like lol
They do, just a different field piece model that he is using. Mine shows 0L
Lol in electrical class in college I was the guy in the back who would take the little capacitors from our little electrical circuit builder kit and get everyone to pas thier 9v batteries to me connect them in series and then Hook the cap to the battery bank as the instructor was talking and suddenly hear a sizzle a bit of smoke and bang the cap pops and launches pieces of itself and obviously everyone is now looking at me as I laugh my ass off
Capacitors store charge electrostatically while Batteries store charge chemically in the form of ions in solution.
The meter has high impedance when measuring voltage...not low impedance. This makes the discharge go slowly
True
He can keep his propaganda health advise to himself.
Always good info.
You need to a video within the next week before my final exam lol!!! A video on how the electrical is hooked up on a wooden simulator board thing in our classroom showing the wiring from the the thermostat to the transformer, contactor, heat relay, indoor fan relay, compressor, electric heat, indoor fan and outdoor fan!! I bet you $100 bucks you can't make this electrical video with a week!! Really lol 🤷♂️
There is no capacitors on this board simulator thing...
Lol I I can follow the schematic its just.. well idk what it is!! For some reason I am just having the hardest time time with this!! I believe I am just making it more complicated than what it really is!! Its like where to plug in the wires on a contactor and where to plug in the wires on the relays??
@@Trust_Jesus you have to think about what loads connect to what switch. where is the line voltage going on a contactor. what tstat wire connects to each switch. contactor Y relay G sequencer W. where is the common going from the step down transformer ( to the 24 volt coils) and you have your R power wire going to the tstat block
@@anom2789 yea.. I'm just making it harder than what it really is!! I got the colored tstat wires down to which switch it goes to and I know where the 24 volt transformer wires go but its like i start getting everything messed up with all the common wires and the load side!! Smh... I just need to take one step at time and slow down!! I think I really am just making it harder than what it is lol
@@anom2789 it just looks like a big jumble of wires when my teacher does it lol... I need to just slow down and connect one wire at a time!! I've been struggling with this for 2 weeks and the final is next week 😫!! I'm in class for 5 hours tomorrow so all focus is gonna be on that lol!!
Very nice presentation.... Very clear explanation
Can these also be checked with a capacitor tester, The sane kind used in electronics?
Yes so long as the tester is designed to read the scale the cap runs at. Most all testers will, as these caps are at low capacitance. In electronic circuits, capacitance can get higher in scale, which might require a tester design for high capacitance. Generally, just about any tester will read these caps. If you want a tester to read higher scales, like for electronic circuits, it might require a different tester, depending on the scale design of the tester. Farads, micro farads, pico farads and nano farads all are on different scales. It would take a real good tester to test all those scales, be an expensive unit which most people won't even need.
question: If a cap is fed AC120V and unplugged , then measured would the maximum voltage read be < 60V? since is the difference between the Hot and Neutral. will only be charged up by half of current as it alternates?
or would that only be true on a 240V line?
you can safely do that last a.c. experiment using a low voltage on the secondary of a transformer!
In a microwave oven a capacitor and a diode is a voltage doubler circuit. The 2000 volts becomes 4000 volts...technically you are right the capacitor itself doesn't boost voltage. But in a circuit with a diode it can double it.
mF usually means milifarad, no microfarad, uF