Posted: 9/23/2014 6:50:36 PM EDT
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Just came home to a warm house...
Air handler running... blowing warm air out of the registers. I went out to check the condensing unit and the fan was running but the compressor was not. As I turned to go inside and shut the system down I heard the compressor try to start but it did not. I came in and shut the system off via the thermostat. The capacitor and contactor were both replaced a year ago due to both the fan motor and compressor not working. Any thoughts? |
| I'd check out your compressor contactor and see if it's still functional, and then check your compressor capacitor with a multimeter (you'd want to turn off the condensor breaker first, and then momentarily ground, and then remove the capacitor terminals). Worst case senario, your compressor is bad and over amping, tripping it's internal overload. |
I'll place this here for those interested in how an AC motor actually works.  |
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I'll place this here for those interested in how an AC motor actually works. http://m.youtube.com/watch?v=07uXnc1C5CA&desktop_uri=%2Fwatch%3Fv%3D07uXnc1C5CA  http://m.youtube.com/watch?v=07uXnc1C5CA&desktop_uri=%2Fwatch%3Fv%3D07uXnc1C5CA
Oh hell yeah. Going old school baby. Same one I got to watch in USAF AIT. 
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| If the contactor went bad the condenser fan wouldn't be coming on. I would start with the run capacitor too as it's the cheapest thing to try. If it isn't kicking the breaker, on start up, the compressor isn't locked up or it would trip the breaker pulling locked rotor amps. It's more than likely the capacitor, OR could be the overload is weak if it has been cycling on overload for awhile, or weakened last time when the contactor/capacitor had to be replaced.... or something as simple as a loose connection or burnt wire where it attaches to the pins on the compressor itself. A couple of easy cheap items to check into before calling out a "trained professional". Good luck! |
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Went and took it apart and checked it...
Compressor not hot. Turned it back on and the compressor would try to start several times but wouldn't. Contactor seems to be operating correctly from what little I know... thermostat sends the signal and boom contactor "contacts" and stays "contacted"... at the same time the fin starts ad stayy on but the compressor only tries to come on. I put a meter on the capacitor and was getting ~89.0 capacitance... something tells me that is not what it should be.... off to google. |
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Went and took it apart and checked it... Compressor not hot. Turned it back on and the compressor would try to start several times but wouldn't. Contactor seems to be operating correctly from what little I know... thermostat sends the signal and boom contactor "contacts" and stays "contacted"... at the same time the fin starts ad stayy on but the compressor only tries to come on. I put a meter on the capacitor and was getting ~89.0 capacitance... something tells me that is not what it should be.... off to google. You need to remove the wire from "herm" on the capacitor to check microfarads. Also need a meter that reads them. Put probes on c and herm on the cap and it will give you the value. My guess is the capacitor and you need a hard start kit. |
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Quoted:You need to remove the wire from "herm" on the capacitor to check microfarads. Also need a meter that reads them. Put probes on c and herm on the cap and it will give you the value. My guess is the capacitor and you need a hard start kit. Well damn... just went and retested the capacitor (the right way this time) and the values were within spec. Now what? |
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Huh? 
Do you have any idea how a single phase motor works? Quoted:
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I'd check the capacitor again. Sounds like the compressor needs a little more power to start. Huh?
Do you have any idea how a single phase motor works? Do you have any idea how a hard start kit works?
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Increases starting voltage to start up faster & use less current to improve compressor longevity. Doesn't have anything to do with what I was talking about. Single phase motors use their start capacitor to throw the voltage out of phase with the current, so it will spin. A common misconception is that it gives the motor a power boost at start up. |
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Increases starting voltage to start up faster & use less current to improve compressor longevity. Doesn't have anything to do with what I was talking about. Single phase motors use their capacitor to throw the voltage out of phase with the current, so it will spin. A common misconception is that it gives the motor a power boost at start up. Quoted:
Increases starting voltage to start up faster & use less current to improve compressor longevity. Doesn't have anything to do with what I was talking about. Single phase motors use their capacitor to throw the voltage out of phase with the current, so it will spin. A common misconception is that it gives the motor a power boost at start up. You obviously don't know the difference between a PSC and a CSCR, so you really need to stop commenting on stuff you know nothing about. Basically a hard start kit adds a start cap to the run cap (along with a potential relay to disconnect it), basically turning the Permanent Split-Capacitor motor into a Capacitor-Start Capacitor-Run motor, adding a torque boost to the motor at start up. So yes, it DOES give the motor a power boost on start up. You might want to do your homework before posting again. For my reference, I use my copy of Refrigeration and Air Conditioning Technology, the text book from my HVAC course. What about you? |
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You might want to do your homework before posting again. For my reference, I use my copy of Refrigeration and Air Conditioning Technology, the text book from my HVAC course. What about you? Explain to me where I was incorrect? And again, what does a hard start kit have to do with the OP's unit? |
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Quoted: You obviously don't know the difference between a PSC and a CSCR, so you really need to stop commenting on stuff you know nothing about. Basically a hard start kit adds a start cap to the run cap (along with a potential relay to disconnect it), basically turning the Permanent Split-Capacitor motor into a Capacitor-Start Capacitor-Run motor, adding a torque boost to the motor at start up. So yes, it DOES give the motor a power boost on start up. You might want to do your homework before posting again. For my reference, I use my copy of Refrigeration and Air Conditioning Technology, the text book from my HVAC course. What about you? Quoted: Quoted: Increases starting voltage to start up faster & use less current to improve compressor longevity. Doesn't have anything to do with what I was talking about. Single phase motors use their capacitor to throw the voltage out of phase with the current, so it will spin. A common misconception is that it gives the motor a power boost at start up. You obviously don't know the difference between a PSC and a CSCR, so you really need to stop commenting on stuff you know nothing about. Basically a hard start kit adds a start cap to the run cap (along with a potential relay to disconnect it), basically turning the Permanent Split-Capacitor motor into a Capacitor-Start Capacitor-Run motor, adding a torque boost to the motor at start up. So yes, it DOES give the motor a power boost on start up. You might want to do your homework before posting again. For my reference, I use my copy of Refrigeration and Air Conditioning Technology, the text book from my HVAC course. What about you?  Hard starts are great to keep one running a while longer. |
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I'd check out your compressor contactor and see if it's still functional |
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Huh?
Do you have any idea how a single phase motor works? Quoted:
Quoted:
I'd check the capacitor again. Sounds like the compressor needs a little more power to start. Huh?
Do you have any idea how a single phase motor works? Greg, please educate me. Do you not like the terms "Power" or "Capacitor" or the idea that a single phase compressor motor requires a start capacitor? |
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Explain to me where I was incorrect? Quoted:
Explain to me where I was incorrect? Quoted:
Single phase motors use their capacitor to throw the voltage out of phase with the current, so it will spin. A common misconception is that it gives the motor a power boost at start up. Right there. Hard start kits specifically add torque on start up to motors that have a hard time starting. It's kind of why they have the name "hard start kit." And again, what does a hard start kit have to do with the OP's unit? We were discussing adding a hard start kit to the OP's compressor because it seems to be having trouble starting. Glad I could help set you straight. Feel free to call on me anytime. 
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We were discussing adding a hard start kit to the OP's compressor because it seems to be having trouble starting. Glad I could help set you straight. Feel free to call on me anytime. Quoted:
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And again, what does a hard start kit have to do with the OP's unit? We were discussing adding a hard start kit to the OP's compressor because it seems to be having trouble starting. Glad I could help set you straight. Feel free to call on me anytime. 
You sound like the guy trying to sell someone a bottle of Marvel Mystery oil to a customer with a rod knocking engine, rather than doing some checks to determine that the guy has a spun bearing. How about diagnosing the problem first genius? A hard start kit is needed for instances where line voltage is too low etc. OP's compressor was working fine last week, and now it won't come on, and you can diagnose that he needs a hard start kit over the internet without taking any voltage checks first etc? |
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Huh?
Do you have any idea how a single phase motor works? Quoted:
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I'd check the capacitor again. Sounds like the compressor needs a little more power to start. Huh?
Do you have any idea how a single phase motor works? I guess not. But luckily your here to edumacate me. Come on now, give me your best Norm Peterson. |
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Greg, please educate me. Do you not like the terms "Power" or "Capacitor" or the idea that a single phase compressor motor requires a start capacitor? http://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/VI_phase.png/1024px-VI_phase.png Leading or lagging. |
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Just came home to a warm house... Air handler running... blowing warm air out of the registers. I went out to check the condensing unit and the fan was running but the compressor was not. As I turned to go inside and shut the system down I heard the compressor try to start but it did not. I came in and shut the system off via the thermostat. The capacitor and contactor were both replaced a year ago due to both the fan motor and compressor not working. Any thoughts? I had a similar situation happen to me and my breaker needed to be replaced. It would *occasionally* work, but most of the time it didn't. Check the breaker and see if it feels warm. If the breaker is broken internally, it won't trip, but it won't provide enough power either. Mine happened to be almost completely melted underneath so I knew right away that's what the problem was. Yours may be hot or warm to the touch. |
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I'd check the capacitor again. Sounds like the compressor needs a little more power to start. Huh?
Do you have any idea how a single phase motor works? Do you have any idea how a hard start kit works? http://www.youtube.com/watch?v=Sd1577g0A0I
Did the tech discharge the cap with his finger at 2:58? He jumped, I heard a 'snap', then he stuttered. |
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Quoted: Did the tech discharge the cap with his finger at 2:58? He jumped, I heard a 'snap', then he stuttered. Quoted: Quoted: Quoted: Quoted: I'd check the capacitor again. Sounds like the compressor needs a little more power to start. Huh? Do you have any idea how a single phase motor works? Do you have any idea how a hard start kit works? http://www.youtube.com/watch?v=Sd1577g0A0IDid the tech discharge the cap with his finger at 2:58? He jumped, I heard a 'snap', then he stuttered.  |