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Helping my dad get ahead of a capacitor going out by just making sure he has one on hand. (Current ones are 10+ years old).

Anyway I’m going to attach an image of what was inside. Ignore the start capacitor, that was easy for me to understand because I saw a relay on it. However I see what looks like 2 run capacitors. I was under the impression the ones with 3 leads are usually dual run and help the fan and compressor. Well one of them is the one I’m used to seeing, but then I see one with only a couple leads just zip tied in the center. Could this be a single run (if that’s a thing) capacitor and it was just never removed from the loop?

Main question being why is this here and can I remove it?

multiple capacitors

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    What does the schematic show? There should be a copy of it inside the panel. It could be a dual start and two runs. It was designed that way so I wouldn't be removing it.
    – JACK
    Commented Jun 15, 2023 at 16:00
  • might be a cap for the fan, totalling a startcap for the compressor and a run cap each for the compressor and fan. Double check where the wires go. Commented Jun 15, 2023 at 16:15
  • it could be used just to improve the power factor.
    – dandavis
    Commented Jun 15, 2023 at 18:25

3 Answers 3

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Let me tell you what I see on that picture.

The big capacitor is dual function. You know that. It is a start capacitor with 60 uF and a run capacitor with 7.5 uF.

The centrifugal switch on the motor switches from Start to Run capacitor. That would be for one motor.

The second smaller capacitor is marked 10MFD, but it appears to be in series with the main capacitor. One would do that if 70 uF was needed but not available.

I am not sure where and what is the 3d capacitor and what motor does it serve.

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  • Compressor and fan?
    – keshlam
    Commented Jul 27, 2023 at 20:19
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Technically, there are four capacitors. A start cap, a dual function cap, and a 10MFD cap. We are concerned here with the 7.5 MFD side of the dual cap and the 10 MFD oval cap.

There are two possibilities. They could be wired in series or parallel. If in parallel, which it appears to be, you simply total the caps. Therefore, the 7.5 + 10 makes the effective capacitance 17.5 MFD. This would be unusually high for a fan motor, which are usually in the range of 5 to 12.5.

Secondly, they could be run in series. This would be the inverse divided by the sum of the inverse of each cap, or 1÷( 1÷C + 1÷C ). So 1 ÷ ( 1 ÷ 10 + 1 ÷ 7.5) = 4.35. Perhaps someone needed a 5, and was trying to get there by using two caps in series. However, they don’t look wired in series. That fan motor would probably be running hot.

Look on the fan’s data plate and get the mfg rating for the cap, and replace the caps with the correct one.

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I can't quite see the markings on the lower capacitor, but is the capicitor you've circled connected in parallel to one side of that one? If so, it may be that whoever replaced the last set didn't have the right mfd value cap, so they just put two in parallel to get to the required value.

In one of my units there is a 30mfd connected to a 15 mfd to get the required 45 mfd.

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