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Started By
Message
Replacing AC capacitor.
Posted on 6/13/24 at 4:43 pm
Posted on 6/13/24 at 4:43 pm
Does it take a bit for it to build up a charge? Our air wasn’t cooling so I replaced ours. Still wasn’t blowing cold after about 20 minutes so I turned it off and was planning on calling someone. Turned it back on a couple hours later just to check and it cooled just fine.
Did the capacitor take a bit to charge or do I still have some other issue?
Did the capacitor take a bit to charge or do I still have some other issue?
11
Posted on 6/13/24 at 4:53 pm to OysterPoBoy
I don’t think the capacitor has anything to do with the cooling
Posted on 6/13/24 at 4:55 pm to OysterPoBoy
Did your compressor kick on during these runs or did it not?
Posted on 6/13/24 at 4:56 pm to OysterPoBoy
Capacitor just stores energy for the initial start of the compressor. If the compressor starts and is running, you have some other problem.
Posted on 6/13/24 at 5:06 pm to OysterPoBoy
It’s alternating current. Takes 1/240th of a second to build its charge.
Posted on 6/13/24 at 5:10 pm to OysterPoBoy
Maybe the unit or thermostat needed to reset itself. Maybe some sort of compressor protection?
Posted on 6/13/24 at 5:18 pm to LEASTBAY
I don’t think the compressor was running before. That’s why I thought it could be the capacitor. I’ll just be happy it’s working for now.
Posted on 6/13/24 at 6:51 pm to Shexter
There are 2 types of capacitors on PSC(permanent split capacitor) type motors that are inside AC compressors. The run capacitor and start capacitor. You will always see the run capacitor on every single PSC type motor. The start capacitor is an as-needed component depending on if you need it to help start the compressor.
Now the purpose of these capacitors is not to store charge. The purpose is to provide a phase shift in the current flowing into the start winding. The start winding sits 90deg offset from the run winding. The 90deg offset of the start winding and the phase shift from the capacitor provides a starting torque on the rotor to get the motor spinning. Without the start capacitor there is no phase shift made for the start winding, meaning the magnetic field produced would be in-phase with the run winding, which produces no torque and the motor won't spin. This is why when it fails your compressor doesn't run. Sometimes you need extra starting torque to get the motor spinning, adding extra capacitance temporarily in parallel with the run capacitor can give the start winding extra push to get the motor spinning, however it needs to be removed after the motor starts spinning as it is only momentary rated.
and oh yeah:
Now the purpose of these capacitors is not to store charge. The purpose is to provide a phase shift in the current flowing into the start winding. The start winding sits 90deg offset from the run winding. The 90deg offset of the start winding and the phase shift from the capacitor provides a starting torque on the rotor to get the motor spinning. Without the start capacitor there is no phase shift made for the start winding, meaning the magnetic field produced would be in-phase with the run winding, which produces no torque and the motor won't spin. This is why when it fails your compressor doesn't run. Sometimes you need extra starting torque to get the motor spinning, adding extra capacitance temporarily in parallel with the run capacitor can give the start winding extra push to get the motor spinning, however it needs to be removed after the motor starts spinning as it is only momentary rated.
and oh yeah:
This post was edited on 6/13/24 at 6:55 pm
Posted on 6/13/24 at 9:23 pm to OysterPoBoy
quote:was the evaporator froze up? Is the evap and condenser coils clean.
Our air wasn’t cooling so I replaced ours. Still wasn’t blowing cold after about 20 minutes so I turned it off and was planning on calling someone. Turned it back on a couple hours later just to check and it cooled just fine
Posted on 6/13/24 at 9:50 pm to DVinBR
Man, that’s an impressive explanation….unfortunately, I have no idea what you said! 
Posted on 6/13/24 at 10:56 pm to OysterPoBoy
Is the contractor closing when the thermostat kicks on?
Posted on 6/13/24 at 11:43 pm to OysterPoBoy
Check the drip pan, if it’s full it won’t let the unit start up, but after a couple of hours it will evaporate some and start back up
Posted on 6/14/24 at 7:23 am to DVinBR
quote:
DVinBR
Was all that bs really necessary? It pretty much holds a charge, that's why you have to discharge it when replacing.
Posted on 6/14/24 at 7:59 am to WigSplitta22
because holding charge isn't the purpose of capacitors in AC circuits, it is in DC circuits though
regardless of the purpose, the property of energy storage within the electric field remains, despite the alternating nature of current in an AC circuit, depending on when the AC circuit is turned off a residual charge can be left in the capacitor that can kill you if you don't discharge it before servicing, but the amount of charge entirely depends on when you turn the circuit off
regardless of the purpose, the property of energy storage within the electric field remains, despite the alternating nature of current in an AC circuit, depending on when the AC circuit is turned off a residual charge can be left in the capacitor that can kill you if you don't discharge it before servicing, but the amount of charge entirely depends on when you turn the circuit off
Posted on 6/14/24 at 8:06 am to OysterPoBoy
You probably had a frozen coil. It thawed and ran then. I would get an AC guy out there to check for leaks or such in the coil before it is an emergency on a Friday at 3.
Posted on 6/14/24 at 10:53 am to DVinBR
quote:
because holding charge isn't the purpose of capacitors in AC circuits, it is in DC circuits though
I did not know that.
Posted on 6/14/24 at 11:04 am to DVinBR
quote:
The purpose of capacitors in air conditioning units is to store and release electrical energy to start and maintain the motor, ensuring efficient cooling.
quote:
An AC capacitor, or any type of capacitor, is a battery-like device that holds an electrical charge. It releases that charge to give a motor, like an AC fan motor or blower motor, a little extra “juice” at the start – extra torque to get the motor going.
This post was edited on 6/14/24 at 11:17 am
Posted on 6/14/24 at 11:20 am to WigSplitta22
https://en.wikipedia.org/wiki/AC_motor
https://en.wikipedia.org/wiki/Motor_capacitor
quote:
Permanent-split capacitor motor
Another variation is the permanent-split capacitor (or PSC) motor.[26] Also known as a capacitor-run motor, this type of motor uses a non-polarized capacitor with a high voltage rating to generate an electrical phase shift between the run and start windings. PSC motors are the dominant type of split-phase motor in Europe and much of the world, but in North America, they are most frequently used in variable torque applications (like blowers, fans, and pumps) and other cases where variable speeds are desired.
A capacitor with a relatively low capacitance, and relatively high voltage rating, is connected in series with the start winding and remains in the circuit during the entire run cycle.[26]
https://en.wikipedia.org/wiki/Motor_capacitor
quote:
Run capacitors
Some single-phase AC electric motors require a "run capacitor" to energize the second-phase winding (auxiliary coil) to create a rotating magnetic field while the motor is running.[5]
[5]
This post was edited on 6/14/24 at 11:37 am
Posted on 6/14/24 at 11:25 am to WigSplitta22
Can’t everybody be right?
Cap is in series with auxiliary phase so that the main phase can do its job. It provides the aux phase with a 90 degree offset (4ms) to give the motor both added torque and a predictable direction.
Without an auxiliary phase, the motor would just shake back and forth. Even if it did find a direction and get somewhat synchronized, that direction would not be predictable and its continued operation would depend on momentum.
It certainly stores and releases energy, but its overall function is to add a slight delay.
Cap is in series with auxiliary phase so that the main phase can do its job. It provides the aux phase with a 90 degree offset (4ms) to give the motor both added torque and a predictable direction.
Without an auxiliary phase, the motor would just shake back and forth. Even if it did find a direction and get somewhat synchronized, that direction would not be predictable and its continued operation would depend on momentum.
It certainly stores and releases energy, but its overall function is to add a slight delay.
Posted on 6/14/24 at 12:11 pm to Dallaswho
everybody is sorta right....
it is the charge storage phenomenon in the capacitor that causes the voltage to lag the current...this lag is the phase shift necessary on the start winding to make it's generated magnetic field generate a torque relative to the main winding to start the rotor turning....once the rotor starts turning, it's magnetic field locks onto the rotating magnetic field generated by the main winding that powers the motor
Eli the Iceman....IYKYK
it is the charge storage phenomenon in the capacitor that causes the voltage to lag the current...this lag is the phase shift necessary on the start winding to make it's generated magnetic field generate a torque relative to the main winding to start the rotor turning....once the rotor starts turning, it's magnetic field locks onto the rotating magnetic field generated by the main winding that powers the motor
Eli the Iceman....IYKYK
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