How to check the starting capacitor

Let's look at how to check the starting capacitor of a circulation pump. Any starting capacitors are examined using this principle.

An asynchronous motor is used to rotate the pump turbine. To start the armature, it is necessary to create a phase shift at the initial stage of starting. This action is achieved using a capacitor placed on the auxiliary winding.

Operating principle

The capacitor consists of two metal plates placed in parallel, relative to each other, and connected to each other by a dielectric spacer. The larger the area of ​​the plates, the greater its capacity, which is measured in microfarads, picofarads, etc. When a positive voltage is applied to the contacts of the capacitor, this energy accumulates between the plates, and when a negative voltage appears, it is released into the circuit. Since alternating voltage consists of constantly changing negative and positive charges, thanks to the capacitor, equalization of oscillations towards positive voltage is achieved.This contributes to the creation, at the initial stage of operation of the asynchronous motor, of a magnetic field, which rotates the armature.

Symptoms of a problem

If the capacitor breaks down or loses capacity by more than ± 15% of its nominal value, in the first case the circulation pump will not start, in the second case the engine will rotate jerkily.

Capacitor check

There are several ways to test capacitors. A safe method is to test using a special device for testing capacitors or an ohmmeter, and a dangerous method is to draw conclusions about its performance by discharging a charged capacitor. Also, a broken capacitor has external characteristic signs of a malfunction: leakage of electrolyte, swollen housing. It is not difficult to measure the capacitance of a capacitor with a special device. To do this, you just need to turn it on and, setting the lever to a value greater than the value being tested, touch the contacts with the probes. Then compare the obtained value with the information indicated on the case.

How to check the starting capacitor

If the deviations are small (± 15%), the part is serviceable; if the values ​​are missing or below the acceptable range, then the starting capacitor should be replaced. We will not consider this dangerous method, since it violates safety precautions when working with capacitors.

Let us dwell on the indirect method of determining the condition of a storage device using an ohmmeter.

Testing the performance of a capacitor with an ohmmeter.

To check the functionality of the starting capacitor:

1. Disconnect its contacts from the engine.

2. For the convenience of taking readings in some circulation pumps, the outer cover and terminals should be disconnected.

How to check the starting capacitor

3.Before checking, discharge the capacitor; to do this, short-circuit its contacts, for example, with a flat-head screwdriver.

4. Switch multimeter to the resistance test position at 2000 kilo-ohms.

5. Inspect the terminals for mechanical damage and oxidation. A poor connection will negatively affect the measurement accuracy.

6. Connect the probe to the capacitor terminals and monitor the numbers. If the values ​​begin to change like this: 1...10...102...159...1, then the capacitor is working. The numbers may be different, the main thing is that changes occur from 1 to 1. If the device values ​​​​do not change (the number 1 lights up on the display) or zero is displayed, then the part is faulty. To recheck, the capacitor should be discharged and step No. 5 should be repeated again.

How to check the starting capacitor

The provided method will not allow you to fully measure the capacitance of the capacitor, but it will reveal its condition without a special device.

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Comments (11)
  1. Alexander Solodovnikov
    #1 Alexander Solodovnikov Guests March 3, 2017 06:26
    2
    Interesting article
  2. Vasya
    #2 Vasya Guests December 5, 2017 20:17
    8
    It is not difficult to measure the capacitance of a capacitor with a special device. To do this, you just need to turn it on and, setting the lever to a value greater than the value being tested, touch the contacts with the probes.

    what device? set the lever?? what what what? write more correctly and intelligibly
    1. Guest Sergey
      #3 Guest Sergey Guests 3 May 2018 20:53
      3
      Previously, this device was called a tester. Now, like in the photo in the article - multimeter (measures several quantities, usually direct and alternating voltage, current, resistance, checking the health of transistors of different polarities, and measuring K gain; more expensive models can measure capacitance and inductance).
      To make a measurement, the measurement type switch (in the text - “lever”) is set in accordance with the measured value, to the MAXIMUM limit. If the reading is too small, the measurement limit is reduced.
  3. Roman Serov
    #4 Roman Serov Guests 25 September 2018 19:12
    2
    Nowadays there are enough inexpensive testers that can measure the capacitance of a capacitor. At the moment, I just determined that the starting condenser, instead of 7 microfarads, has a capacity of 21 nanofarads. And that makes me happy. Because the windings are intact and at least I can still fix the pump. Otherwise it’s an expensive and rare model (due to the type of float).
  4. Denis
    #5 Denis Guests 7 December 2018 18:43
    3
    and if a 0.1 MF condenser, when measured with a multimeter at 2000 kOhm, gives a flat figure of 497 and does not move, then is it working or not?
  5. Guest Vladimir
    #6 Guest Vladimir Guests February 15, 2019 00:54
    2
    In this way, you can only make sure that the capacitor is leaking. Measuring the capacitance, without measuring its internal resistance (ESR), will not give an affirmative answer that the capacitor is good. To make sure that the capacitor (from 1 μF) does not increase ESR, after measuring the capacitance, turn on it is connected to a 220 volt network in series with a 40 W incandescent lamp. If the lamp lights up, the capacitor is good.
    1. Oleg
      #7 Oleg Guests March 17, 2021 07:10
      1
      ECR for electrolytes in my opinion
      1. Yuri_
        #8 Yuri_ Visitors 17 March 2021 16:33
        1
        All capacitors have ESR. But usually in non-electrolytes its value is so small that it can be neglected, and over time it hardly changes.
  6. Guest Alexander
    #9 Guest Alexander Guests 21 February 2019 21:12
    0
    “Since alternating voltage consists of constantly changing negative and positive charges, thanks to the capacitor, equalization of oscillations towards positive voltage is achieved. This contributes to the creation, at the initial stage of operation of the asynchronous motor, of a magnetic field, which rotates the armature.” - this is what he came up with or subtracted Where? What nonsense!
  7. Jackson
    #10 Jackson Guests 13 August 2019 15:50
    2
    When checking a capacitor using multimeter you need to calculate the duration of a full charge. For a 30 mF capacitor, this time should be at least 50 seconds. Otherwise, the conder is in a landfill.
  8. Mauser
    #11 Mauser Guests 18 May 2021 12:35
    2
    Also, a broken capacitor has external characteristic signs of a malfunction: leakage of electrolyte, swollen housing.

    The starting capacitor is not polarized and there is no electrolyte, therefore, it is unlikely to swell.