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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and find our handy calculators at https://www.hvacrschool.com/
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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.
Read all the tech tips, take the quizzes
and find our handy calculators at https://www.hvacrschool.com/
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It pays to take the time to learn your meter and to read it correctly.
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.
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