Capacitor Test under Load 3D

[@AARONJL92]

These videos are great for reviewing with my technicians. Thank you!!

[@manschool4992]

Channels like yours have done so much to legitimize the HVAC trade. Gone are the beer can cold old-timers just winging it. I realize now, most of what I was taught was wrong but enough to get by. Thank you

[@kyleinthought]

Thanks from an engineer who appreciates all that tradesmen know and do.

[@j.carver8511]

This was perfect. I don't have a multimeter with capacitor setting, so I was able to figure out if my capacitor was good or bad under load following this video. Thank you!

[@greg5830]

Another quick and good video. Very well laid out and informative, thank you!

[@hvacresidentialbasics7684]

I teach all the new guys this and they are blown away 🎉

[@Jul1972]

Nice and very useful thanks for sharing.

[@sermore77]

Thanks great videos💪🏼👨🏻‍🔧

[@spelunkerd]

I get the practicality of a specific number that is easy to remember, and I love the way you can prove functional capacitance indirectly. For those interested, recall that Z=1/(2*Pi*f*C), and that Z=V/I. So, rearrange and you get C =I/(2*pi*f*V). Then note that you want the answer in microfarads, not farads, so multiply by 10^6. You get C= 10^6/(376.99)* (I/V), when in the 60Hz environment of North America. The constant simplifies to 2652. What I find interesting is that you don't need the phase shift angle of current to voltage to calculate this value, and you don't seem to need RMS values. Presumably the waveform is close enough to a sine wave, and the capacitance is so close to a pure -90 deg phase shift, that those details wash out.

[@realSamAndrew]

You made a typo. It's 376.99.

[@spelunkerd]

@@realSamAndrew yes, exactly, I corrected it, thank you.

[@ColossusEternum]

Yes, there's also another equation besides the reactance/impedance equation you provided, it works with both AC or DC, and it actually describes the reason that a pure capacitive reactance produces a negative 90 degree phase shift. Ic = C(dV/dT) So this states the the current flowing through a capacitor, is equal to its capacitance multiplied by the rate of change in voltage across the capacitor. You can test capacitors exactly like he did in the video, only use this equation(which is the one above rearranged) Start winding current ÷ dV/dT where dV/dT would simply be the derivative of this function: VcSin(2pi*F*T) Where Vc is voltage across capacitor, F is 60Hz, and T is usually just made to be 0(since the derivative of a sin function is greatest at 0, and 0 at the peaks, the derivative of a sin wave, is a cosine wave. Which is why capacitors shift voltage backwards by 90° relative to current

[@billl3936]

Thanks! I wondered where the constant came from. I ran the numbers in the calculator and got 2652.582 for the constant. Unnecessary accuracy for my Greenlee amp meter from Home Depot.

[@josephNguyen-rx7nd]

Thank you so much for your video teaching

[@mrshyst]

Thanks!

[@donkeygat93]

I use this test in the hvac school app like there’s no tomorrow ❤

[@kennethlobo4420]

U need more than a Thumbs up.Great video.truly great knowledge being imparted by U.

[@Ali_Haji_SouthAfrica]

This Vid made me Subscribe to your channel 🙏 Well explained

[@kingosaku8454]

Can a fieldpiece’s MFD setting be used to measure while running?

[@YTsux24-7]

I did not know the plus or minus percentage was an out of the box spec. We often recommend replacing the blower motors that have been running with extremely low capicitors as they often fail within a month or so of changing a run cap. Have you experienced this and is there a percentage where you'd recommend replacing the motor in this situation? TY in advance Bryan.

[@realSamAndrew]

I hear this all the time and I am amazed most techs don't know this. But it sells more repairs.

[@victork3397]

I haven’t heard of that. You sure the cap you replaced was the correct size? I always look at the motor nameplate if visible. If not visible, I call manufacturer and see what the value of replacement blower cap is. I had one call where a compressor was short cycling. Turned out the previous guy put in a 80/10 cap, when it needed a 55/10 cap. This caused the windings to overheat and the motor to go off on thermal overload. I imagine a similar thing would happen if you replaced a blower cap with one that was too big. Windings would overheat, and probably melt/ short out. And I don’t believe blower motors have a resettable thermal overload. Also those older motors tend to leak oil from the bushings, I always check for that and touch the bottom of the motor when visual inspection not possible. If it’s leaking oil, I’m recommending that they replace motor and cap and clean the blower wheel to remove oily residue.

[@YTsux24-7]

@victork3397 Yes, always confirm OEM spec'd parts before replacing. The motor windings burn out from low capacity. I've also cleaned extremely filthy blower wheels and had the motor die shortly afterward. I haven't seen this with compressors or outdoor fan motors.

[@XX-qf5zj]

What does “out of the box specs” mean? If it is out of that range it is NG. No manufacturer publishes otherwise. If you have a 10mfd +/- 10% cap and it is at 8.5mfd I list it in the recommendations for replacement. Don’t come at me with this “I don’t know why no one knows this” $hit. If the manufacturer is not clear than that’s their fault. I go by what is written. After all, that is what people sue you over.

[@realSamAndrew]

@XX-qf5zj what is written is what the manufacturer represents at production time. It does not imply that if it falls out of *manufacturing* range over time then it is out of *serviceable* range. That's ridiculous.

[@Kelly_Almond]

Thank you so much for the class ❤

[@TechTed1]

good video thanks

[@HumansAre3vil]

i there any game or website that help you like this.

[@TaylorLeteff]

I have the exact meter that he keeps showing. It always read like .2-.4 amps when not around a wire or anything. and I don’t know why. Is this because it’s a true rms?? Or is it broken?

[@thewoodlandforge9217]

Had the same thing happen with my old fluke meter, I was on tech support working on a commercial unit. I told him that the amps may be a little off due to this, and he said to replace the meter.

[@joehead1294]

Might be related to the earth's magnetic field. Does the meter have a zero feature? You could also subtract the error value from the test value. This test might be a little iffy if not using high accuracy meters or low mfd values. Stray magnetic fields may produce inaccurate results.

[@Toptech92186]

where the 2652 come from

[@shank2137]

Thank you for this!!

[@mikebrown4433]

Excellent can you do contactor as well. Nice golden nuggets you dropped in this video. Small but mighty

[@dalebabbitt6185]

Good stuff!!! Thank you!!

[@MolecularHeckler]

why the magic number of 2652?

[@m.a.6603]

I was shown this method by a senior guy when I was a new tech & didn't know any better. After almost getting shocked (more than once) I retired this method as I personally think it's super sketchy. I prefer to just shut the unit off &. Test the old fashioned way. The 60 seconds it saves you isn't worth getting electrocuted over in my opinion.

[@johnconnor7501]

I didn’t know the % printed on capacitor was just acceptable error for new ones.