In this video we test a dual run capacitor that SEEMS to show a higher microfarad test measurement than the rating, but we discover something interesting.
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So one of my favorite topics that i always talk about is run capacitors because they're so often misunderstood inside these things we just have basically these wraps of plastic, with a metallic coating on either side and then inside you've got an oil and then you have connections. Now, obviously, this is a turbo, so this one has a lot more wires and connections inside it than a normal capacitor. So your common or c terminal connects to one side on this. It's the bottom, and that goes up to this ribbon that connects up to the center and then the other side of the foil throughout is connected to your other two capacitors generally with a dual cap.
This one just has a lot a lot more of them, because it's a turbo, so the question comes up a lot. People will say: can a capacitor fail with higher capacitance than what the rating is. So this is a 35 by five meaning that in between herm, which is for your compressor, start winding and common, it should be 35 and in between fan and common. It should be five and that's for your fan motor start winding, but could it have a higher rating than what it came from the manufacturer meaning? Could it fail with a higher measurement and i always contend that it can't, but one of the technicians in the class brought this in and said this.
One indeed shows that it has a higher microfarad rating, and so we started testing it and it was kind of befuddling a little bit um. But let's, let's just show what we've got here so first off on our multimeter. Here we've got a just a very simple field: piece meter, we're going to put it on the ohm and microfarad scale, so it auto ranges depending on what you have it connected to. So it does that automatically, and so you can see right now.
We've got nothing. I'm using alligator clips here, but we're just going to connect them and make sure that it's measuring in the home scale. So it is so that's good. We have connect through our leads.
I'm going to connect one side to herm, i'm going to connect the other side to c now, one little trick here whenever you're working on a run capacitor. If you can't see what it says on it, the one with three terminals is usually herm. The one with four is c and the one with one or two is usually the fan. Now, that's not always the case, but that is pretty common, so you can see here we're measuring 93..
So that seems to tell us that we're measuring high that's what the tech thought now in his to his credit. He went ahead and replaced the capacitor anyway, because obviously he was measuring outside of range, but it seemed to prove that i was wrong. We got it in here to the bench, though, pay close attention. What it says here does that say: microfarad is that the symbol for micro, let's check by measuring on a different capacitor, so we're going to measure on our turbo here, that's in good working order, 24.55 and you're going to notice it's a different symbol.
That's the micro symbol. This capacitor is not reading in the microfarad scale it's reading in the nanofarad scale, so it's not actually measuring high it's measuring low, but because of the auto ranging feature that could throw you off, and this can happen in a lot of different areas. This can happen with voltage some cases they're going to auto range in between dc and ac, and that can create confusion, but here you can clearly see it's measuring in nanofarads, not in microfarads. I thought that was a pretty interesting thing. Luckily, you know correct conclusion was come to capacitor is replaced because it is failed, but like they always do when they fail, they fail with a lower microfarad measurement, not a higher microfarad measurement, and if you are measuring higher than the rating significantly it's some issue with Either the way it's being measured or the auto, ranging on your meter, or maybe even the meter itself, thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to The channel and click the notifications bell to be notified when new videos come out. Hvac school is far more than a youtube channel. You can find out more by going to hvacrschool.com, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more. You can also subscribe to the podcast on any podcast app of your choosing.
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I was wrong. !! Thanks for saving my Friday
Enjoyed this video too! Are you in Ottawa ?
Capacitance can only increase if the two conducting plates get more surface area, they get closer together (without touching), or the dielectric between them gets stronger. None of that is likely to occur in the field.
Great, I've never seen such thing before! Usually it would be 2-3 mFD or 0…. Thank you for the video!
Bryan, I test under load and have seen plenty measure out of range higher than rated.
Please tell me how can A×2652÷V be off?
Or does this not apply to load calculations because of (capacitive reactance?) Or something else.
This is why we use fluke
Not a fan of auto mode selection on meters. Resistors can be capacitive and capacitors can become resistive. Autorange is okay if you pay attention to the units being displayed. Manual mode if in doubt. Service area Barrhaven??
Nice job and video
A capacitor is not going to grow more foil and more oil and fail high. So Bryan, tell the truth, was it Kaleb that couldn’t read his meter? 🤪
I would think having more capacitance than designed would be bad because it would cause the phase shift of voltage relative to amperage to be located differently than designed.
This whole problem comes down to the meter manufacturer trying to add value where none is to be had. Auto ranging is one thing but auto function changes are just over the top. If you don't know whether you need to be on ohms or capacitance scales then maybe you need to revisit your electrical skills. This stupid feature sounds like a good idea until you think it through for about 7.359 seconds.
What about the capacitor reading just increasing with no stop? I had a 45/5 and the 45 went to like 200 before I removed my leads and just replaced it. Sounds like an OL to me, but I’m curious on what you think.
If you compare it to an engine, if you advance your capacitance to far, you now make the motor work against the capacitor. Essentially yes you can fail if its higher than what the label says, granted more often it will be below or lower mfd readings. Its just better for the longevity to stay within the limits of manufacturing specifications.
The best way to test capacitor is using ESR
Most multimeters measure capacitance by measuring how long the capacitor takes to charge when power is applied from the meter. If the capacitor is electrically leaky, it will take longer to charge and your meter will read a value higher than the true capacitance. If you ever come across a capacitor that reads significantly higher than it's rating, it's probably leaky and should be replaced.
I had a condenser fan cap fail at about 75uf once, strait out of the box. I don’t use auto range, this actually happened, with a fluke meter and it overheated the new fan motor. What made it so great is that it was for the Diversitech maintenance guy and it was a Diversitech capacitor. Fan motor overheated, after changing it, while we were talking. Found the cap failed with crazy high reading. Put another cap on and it’s still running 8 years later.
I know we use a capacitance range on a meter because it's practical. The most accurate way to measure is an ESR meter or an LCR meter and check if it's within the tolerance listed on the component's datasheet. Context: I repair Electronics.
Actually you are wrong (no offense). Look on the label at the microfarad rating. Notice how next to it says "+ – 5 %" what this means is that this. Capacitor has a range of 10% (5% less than the microfarad rating, 5% MORE than the microfarad rating). We tend to not pay attention too much to a higher rating because in general the motor it's controling will still start with a higher rating. But if we are doing everything by the book then Technically the capacitor should be changed.
Why did Fieldpiece even include nF as an option? How many techs have ever had a need to measure in that range?
I came across a cap reading 234mfd on the fan side 50 instead of 70 just yesterday. Not the first one I've seen it kept the fan and Compressor from even starting up.
This happened to me last week 10 muf run cap was reading 15 muf never seen something like that before, but this video really explained what happened to me lol
The Fieldpiece SC680 about got me, fan was reading 5.3nF and not 5uF. Great meter but better check the scale.
Press select and change to the desired measurement
Now try this, stick a cap that's rated higher than called for in your hvac at your workplace and see how long it takes for the blower motor to fail. Are you in Orleans ?
Auto scale , auto correct, auto park, auto drive, ………… where does it end. It’s not always to our advantage. It makes us lazy and sloppy. This would never have happened with a Simpson 260 meter!! For those not old enough to know what is is, Google it. 😂 Are you in Nepean ?
You should’ve selected the micro farad rating… I’m curious what it would have said.
He can't just let somebody win… Brian is always holier-than-thou, bro when you gonna admit you ain't always got the answer? Lol I'm not mad just saying
I dont like the field piece combining the mfd and ohm measurement. It should be 2 different clicks. This has confused me one time for about seconds. Great video. If you're checking a cap use the manual range button
Where was all this information when I was going to school(s)?
Your making it to easy for them 😅🤣🥃🥃🍺🍺🍺🏌🍇
Stay safe.
Retired keyboard super tech.
Wear your safety glasses.
I was like . I gotta see this 😁.
Sure enough , Wrong scale / range
It pays to take the time to learn your meter and to read it correctly. Service area Kanata??