What does the capacitor do in the PSC motor

This one shows how the run capacitor works to limit start winding current. With demonstrations. This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

[@griffmustard]

With an inductive load, such as a Motor, you will have current lagging the voltage. This will lead to a power factor of less than (1). If you have a low power factor, to correct it, you would add capacitance to the circuit. The goal is to try and reduce the phase angle between the voltage and the current. The ideal is to have the voltage and current (in terms of a sine wave) rising and falling at the same time.

[@alpena2835]

Griff Mustard well said! 👍🏼

[@thedavesofourlives1]

judging by his other videos, greyfurnaceman doesn't fully understand power factor: "I can't say i understand why it helps the efficiency of the motor" he says. Also there's a video where he judges the power draw by just the amp draw of a motor with no regard for PFC.

[@McCurtainCounty888]

If the curent rose and fell with voltage only the resistance of the windigs would limit current flow and the motor would burn up. There must be some Xl and Xc to add to the resistance resulting in impedance that limits current flow along with back emf. Without impedance there would be the same amp draw as locked rotor .An ac motor MUST have a phase shift to start.

[@hg2.]

Great follow-up to the "no-capacitor" video.

[@kennethchristensen7457]

Kenneth christensen You got this one wrong.The current travels through the start winding and then into the run capacitor.When the cycle changes the capacitor pushes the current back to the source at the same voltage cycle as it was on when it went into the capacitor. This creates a third leg we call split phase.There is no current going through the capacitor and no resistance.The larger the capacitor the greater the current draw on the start winding and the greater the torque.

[@grayfurnaceman]

You might check a video I have done that will be published 7-16-19. The capacitor is not a dead end. GFM

[@KennethTLong]

The capacitor reactance current leads the supply voltage by 90 degrees and the inductive reactance current of the motor lags the supply voltage by 90 degrees . The run cap is for efficiency by cancelling out the reactive power load which will provide a better power factor close to unity or 100% .

[@CeilingFanVideosOnYT]

Yeah, and when it's out of sync, the motor can buzz. Some ceiling fans use lower capacitor to start windings for medium and low, I have a Hampton Bay Rockport that's like that and it's silent on high but noisy on low and medium. I hooked remote receiver to it once, and as long as the chain was on high, it was silent on all 3 speeds with the remote!

[@alchemy1]

What is the main actual cause that auxilliary winding provide and therefore is needed not just for one reason that it gets the armature to get going but also determines which direction it should move? How does it do it? In other words how does the phase difference takes place in case that is the term that gets thrown out all the time like a hick up.

[@markallan9050]

That radiant heater on your wall is really neat! Did you fit it with an aftermarket intermittent pilot kit? And now can thermostatically control it with an external gas valve? Thats genius! Curious to see the rest of the setup. Great video explaining how permanent split capacitors work and the purpose of the capacitor as well. Great video as always!

[@grayfurnaceman]

Its quite simple. Its a propane heater converted to natural gas with a Honeywell S86 gas control system. There is no thermostat except for the limit switch in the upper left of the radiant heater to shut the unit off if it is blocked. Maybe I will do a video on it someday. GFM

[@markallan9050]

@@grayfurnaceman do you have a toggle switch to turn it off and on?

[@grayfurnaceman]

@@markallan9050 There is a switch. You can see it labeled "heat". There is also a proximity switch to shut down the gas supply when no one is in the location. GFM

[@markallan9050]

@@grayfurnaceman that is so cool! I love making things like that...and tinkering with cool gas projects. Would love to see a video of it and its sequence of operation

[@Karnol428]

So when the capacitor is charged up that charge helps get the motor spinning easier and right direction. But once it is the capacitors charge acts as a impedance to the current draw allowing less current to the motor?

[@grayfurnaceman]

That is true. GFM

[@sivucit]

Hi, i am your new subscriber.. quick question please. does capacitor have polarity when you connect the blower motor to the capacitor.

[@toneblair]

Ok, I think this was the video I was thinking of. So voltage is literally flowing through the capacitor, and being "impeded", and the limit on the voltage, causes the motor to run more efficiently? Is it lowering the voltage? If you have a higher micro farad capacitor, does that cause the "impedance" to increase, or decrease?

[@grayfurnaceman]

It does limit the voltage in the start circuit. The higher MFD has multiple effects as it interacts with back EMF and the position of the motor windings. GFM

[@hg2.]

If I may add a non-engineer's comment to this interesting discussion of capacitors: they "produce heat" - got to have the "oil" in there to absorb it (it used to be high-performance PCBs, right GFM? ;) That heat comes from somewhere, specifically the "electricity" going into the capacitor. Volts x Amps? Lower voltage --> the difference coming out as heat?

[@grayfurnaceman]

Capacitors are semiconductors. They are neither load nor conductor. As in all semiconductors, there is some voltage drop across them. That voltage drop is converted to heat. Depending on the application, oil may be needed to transfer that heat from the interior of the component to the shell of the component. GFM

[@TeaWhyElleAr]

very good video and explanation. thank you

[@grayfurnaceman]

Welcome GFM

[@robertmunguia250]

I always saw that capacitor as a run cap. The black plastic type is a start actually 150-175 mfd on some models. Is it better to have a dual run cap in this case?

[@grayfurnaceman]

The dual cap will work about the same as a single cap. GFM

[@mikumiku925]

Excellent video!!! Thank you so much Sir~~ 😄

[@thomascoolberth2648]

Are you referring to the "Auxilliary Winding" in a PSC as the start Winding? According to Beckett Corp and the NORA Oil Technician's hand book , it has an "auxilliary" not a "start" winding.

[@grayfurnaceman]

It is the same thing. GFM

[@hg2.]

@@grayfurnaceman TG it's called a "start winding" - the name actually describes its function. Now I wish "start capacitors" weren't called "run capacitors".

[@kylefaubert7768]

does the other side of the capacitor draw the 2.3 amps? does it change the total amp draw of the circuit or does it stay the same?

[@grayfurnaceman]

The draw is the same on both sides. GFM

[@muniznick]

I found a weak cap on an old Lennox and the cond fan was running backwards, replaced and it worked fine.

[@grayfurnaceman]

It does happen. I don't know how but it does. GFM

[@danball4410]

Think of the two phases like pedals on a bicycle. Since the pedals are exactly opposite on the crank shaft will not be able to start at 0 & 180 degrees. With a bike you start by manually rotating one pedal forwards past 0 degrees, and then pushing that pedal first. The capacitor is like rotating the a pedal on the crank shaft - a phase delay so that they are no longer 180 degrees apart. Now you will always be able to push and rotate. You can shift it up to 45 degrees, or 1/8 turn and then pushing will always get rotation. However if you rotate it too much, past 90 degrees turn then you may not have momentum get a complete rotation since both pedals are on the same quadrant of the cycle. As you rotate to 180 you cannot move out of the bottom position. Continue shifting the adjusted pedal past 180 degrees on the shaft, now pushing only down, it will turn backwards. Adjust past 270 and it will always move backward until to shift past 360 and start the forward motion of the cycle again. That is what a capacitor does - shift one of the two phases so you can always get the rotation that you need.

[@hg2.]

@@danball4410 This needs a cartoon animation for visual aiding.

[@MrJRamal]

Can you do some videos of ecm variable speed motors?

[@grayfurnaceman]

I already did several. Check my channel. GFM

[@billmore6676]

When u call for heat the puge motor don't start but after bunner comes on hear click motor starts shut power off fault code 12 when I shut power on purg motor starts and shouts off so when heat comes on motor starts puge motor won't come on next

[@MsFishingdog]

great video. thanks

[@grayfurnaceman]

Welcome GFM

[@wrayman63]

When you removed the capacitor and ran ac directly to the run winding, you put the two wind in phase with each other and they were fighting each other. NOT because you put too much power to the winding. You really need to research this, rather than putting out false information.

[@CeilingFanVideosOnYT]

Yeah and in fact, capacitor to one winding can tell the motor which direction to spin. If you switch capacitor and full power between 2 windings, direction can change. That's how some ceiling fans change direction.

[@ammaralyasiri4191]

How to Identify the Terminals of fan window air condetioner (6 or 5)wires

[@grayfurnaceman]

ammar alyasiri The only way to know is by using the wiring diagram. It should be located around where the power wires enter. GFM

[@billmore6676]

So is cap bad the motor on mine only runs after fire up only

[@grayfurnaceman]

If the motor starts and runs with no excessive amp draw, the cap is ok. GFM

[@geojor]

helpful, thank you ...

[@billmore6676]

No I turn off funace get fault code 12 motor starts when I start it but after that when call for heat the motor only comes on after bunner lights bad bord maybe

[@grayfurnaceman]

So, if there is a call for heat, the burners come on then after about 30 seconds, the fan motor comes on. If this is the sequence, it is normal. Let me know. GFM

[@albertoluna2339]

what if you put an oversize cap on a motor?

[@grayfurnaceman]

I have one on that. Check my channel for the playlist on motors. GFM

[@wrayman63]

A capacitor is not a resistor, perhaps google phase shift for an understanding of what a capacitor does in a psc motor.

[@grayfurnaceman]

It is not a resistor, but it does introduce impedance as it charges. The overall effect is to reduce electrical flow to the start winding. GFM

[@wrayman63]

The Start winding? I thought this was about PSC (Permanent Split Capacitor), so I am not sure what you mean by Start winding. The start winding and the auxiliary winding on a PSC motor are completely two different things. This is not the reason the capacitor is in the circuit. The capacitor is in the circuit to create a phase shift of the second winding. As I said in an earlier post, the reason the motor is overdrawing when you introduce an AC field into the Second winding, is because they are in the same phase. This IS the reason the Capacitor is introduced into the circuit, to create another field that is OUT of PHASE with the primary winding. It HAS nothing to do with being a resistor. Any capacitor, winding, inductor, resistor will effect the reactance/impedance of a circuit, that doesn't mean and is hardly ever why they are used, especially in motor circuits. And to clarify, IF you are TALKING about the "Impedance" factor of a Capacitor, it is expressed always in REACTANCE, or Capacitive Reactance, not impedance. Did you know you can take a 3 Phase motor and use it as a PSC? So what does resistance or impedance have to do with that? I am not going to beat this horse anymore, I suggest you look at the Wikipedia article here and see if impedance is mentioned??? en.wikipedia.org/wiki/AC_motor#Permanent-split_capacitor_motor

[@grayfurnaceman]

I think that's best. We are simply getting into semantics and talking around each other. GFM

[@robertcherry4971]

wrayman63 The dynamic resistance of a capacitor Xc, or capacitance reactance,can be used as a type of resistor.

[@armandomartinez4152]

🤯🤯🤯

[@alchemy1]

Don't mind if I barge in. I have left my uneducated comments in two other of your videos for your head shaking moments. As I mentioned in your other video, it is not correct to say that a capacitor limit current flow, like a resistor. That is why, you can't explain why it does what it does in terms of making the motor run effeciently, smoothly or whatever. That teaching of motor running smoothly etc is how it is taught, put out there. It has no meaning. And the students ( folks) hearing it, memorize it and go just keep moving. Here in quotation: "A run capacitor is wired into the main coil circuit and is never disconnected from the circuit. The run capacitor holds a charge to help mitigate power issues while the motor is running. They help to smooth out the flow of power and improve the performance and efficiency of the motor". IT HAS NO MEANING, NOT TO SOMEONE WHO PAYS ATTENTION. I call that garbage, prententious, clown teaching. No wonder if flunked school. Here is my version: A capacitor does not remotely resemble, nor act like a resistor whatsover. Keeping the role of the capacitor within this subject is this it looks like this: The capacitor gets charged when the current moves through it ONE WAY and it discharges when the current CHANGES DIRECTION. And this is the big point to pay attention and stop to see what this means. Before I explain that, I will throw another one. You realize that it makes a difference if you place the capacitor in the black or the neutral wire. That reason goes with the my first point. The capacitor is to discharge in the different coil ( so called auxilliary winding) having a shift in phase and that discharge moment is to be in the same direction as the direction of armature. And it is to charge when the current is moving in the opposite direction. You should know exactly why. It is equivalent of pushing the child that is on the swing set in the same direction as the swing and not the opposite way. THAT IS EXACTLY WHAT A CAPACITOR IS FOR AND THAT IS EXACTLY WHAT IT DOES. A capacitor does not provide phase difference. The auxilliary winding with is position and it's inductive reactance does. Hence not only its position but is resistance, inductance, reactance all combined as impedence if you want to go that far. The capacitor has different impedence. Nonetheless lets not get to carried away here. So this detail should fill in all the rest be it a motor with run capacitor only, run and start capacitor or just start capacitor. Each type is designed so you don't screw things up. Notice that in blower motors which only have run capacitor you are not given the option to put the capacitor in one or the other ( neutral or hot) leg. It is set in stone for that reason. Typically it is in the common wire, whichever is considered common, usually white is called common. But these lingo cause more confusion than it solves. "netural, common, return, ground" mumbo jumbo. The real teaching is not exposed as that is not very economical. It doesn't make for repeat customers. Yes, students are customers. Armature will follow where is the phase shift magnetic flux takes place by means of reluctance. Notice that the armature have aluminmum short circuits. Aluminium is mildly attracted towards magnetic flux while copper is repulsed. Paramegnetism in one and diamgnetism with the later. There is a reason why alumiminum is used in the winding of the armature and not copper. So once the heavy mass of armature gets going in one direction, the last thing you want is to supply current to the auxilliary at the wrong time. No, when the direction of current changes, there is no effect on the main run winding as they are smack at 90 degrees, the armature can not tell the difference however you do not send current to the auxilliary when current changes direction. That is exactly what the capacitor does. The Auxilliary winding is dead, no current flows one way and then when current flows the other way, the direction that the armature is moving, after all that is the direction that it was pushed in the first place... that is correct so, the capacitor discharges in that same direction. Read that one more time. The capacitor discharges in the same directiion that it got the armature to move in the first place. READ THAT THREE TIMES IF YOU NEED TO. All of this clearity is reflected on the " how you change the direction of motor rotation". Something to think about. Don't you see? If you want the motor to run the other way, just move the capacitor to the other side of auxillary winding. READ THAT ONE MORE TIME TOO. Say instead of between black wire and the auxilliary winding, move it to the other side and place it between the auxilliary winding and the white wire. Or if it was between the white and the winding, move it between black and the winding. Are you getting it? This discharging clearly has two aspect. And it is a no brainer. One it sends current in the right direction, meaning at the right time and secondly it does it with one burst Examine the chart of charge vs discharge of a capacitor. It takes longer to charge than discharge and this is a good thing. Besides other reason the first instant of charging a capacitor it acts like a closed circuit, Not because it is, but because of existing electrons getting repelled on the positive plate. Just ask Maxwell. Do not buy for one New York second that there is an actual current flow through the dialelectric. There isn't. Period. NOW THAT YOU KNOW EXACTLY WHAT IS GOING ON. IT IS FINISHED. YOU DO NOT NEED TO SEND ME ANY TUITION.

[@6lu5ky86]

I wonder what a flux capacitor will do....lol.

[@grayfurnaceman]

It will hold 21 gigawatts of power. GFM

[@EnergyFabricator]

My guess is that it would alter the space-time continuum... Great Scott!!

[@rocker8692]

Great Scott Marty

[@hg2.]

Very funny.

[@billmore6676]

Next time no purge motor

[@coldfinger459sub0]

Can you run the same test with the blower on the motor in the furnace housing with ductwork attached and showed a difference with restrictive ductwork that often happens when somebody underbid the job and when the static pressure is correct with the correct ductwork. And show the difference and amp draw with and without a capacitor on a PSC motor under load is much greater.

[@grayfurnaceman]

I have done some on on blocking the outlet of the fan, but nothing on an installed system. I will put it on the list. I do have a video on operation of the motor with and without a capacitor. Check my channel for the playlist on motors. Hope it helps. GFM

[@hg2.]

Don't forget a Thank You to GFM for making all these great videos in the first place.

[@coldfinger459sub0]

grayfurnaceman thanks I’ve been watching your videos for years, I enjoy them.