"Help! My AC isn't working!....

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MAC702 said:
And this is where, yes, I would replace both "sides" as soon as possible because when one blows, the other usually isn't too far behind. Often, we don't carry OEM dual caps. We just replace them with dedicated caps for each component.
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Does it work out better long run?
 
mbrooke said:
Try R-717, excellent phase change heat absorption capacity. ...
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I don't "miss" Refrigerant-717 because it's still around. It doesn't deplete ozone or contribute to global warming, and hasn't been regulated or legislated away.

But whatever its excellent thermodynamic properties, you really need to be cautious with it.
You think heroin and ketamine are addictive and problematic? Or phosgene and chloroform? Huff R-717 just once and you'll be in a world of hurt with a substance-abuse problem.
 
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drcampbell said:
You think heroin and ketamine are addictive and problematic? Or phosgene ...?
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I don't think phosgene is addictive. I'm pretty sure one huff can kill you dead.

Aside: I used to work in a specialty gas lab where we made calibration mixes for industrial gas chromatographs. One we made occasionally was a 5PPM mixture of vinyl chloride (a serious carcinogen) in nitrogen, as 5PPM is the established threshold for safety. We had to be very careful with that stuff.

I met a guy once who worked for a plant where they made vinyl chloride, and he told me that he and his buddies would sneak off and get high huffing it undiluted. I wonder if they are still alive.
 
drcampbell said:
I don't "miss" Refrigerant-717 because it's still around. It doesn't deplete ozone or contribute to global warming, and hasn't been regulated or legislated away.

But whatever its excellent thermodynamic properties, you really need to be cautious with it.
You think heroin and ketamine are addictive and problematic? Or phosgene and chloroform? Huff R-717 just once and you'll be in a world of hurt with a substance-abuse problem.
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That stuff stinks. :sick: Don't think I'd want it in me.
 
kwired said:
... Need 20 µfd, don't have one but have several 10s, I can get you by ...
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MAC702 said:
Indeed, if there is room in the compartment to secure them, they can be a permanent solution. ...
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Somebody with more motor-theory expertise than me ...
Say a compressor motor needs a 20-µF run capacitor and you install two 10s. What if one of the two fails? Assuming that it keeps turning, would there be any accumulating harm to the motor, or would it be better if it didn't run at all and opened the circuit breaker?

p.s: Don't mention this to the bean counters. If they learn that capacitances in parallel add, they might insist on carrying only 1-µF capacitors, to reduce the number of different part numbers in inventory.
 
drcampbell said:
Somebody with more motor-theory expertise than me ...
Say a compressor motor needs a 20-µF run capacitor and you install two 10s. What if one of the two fails? Assuming that it keeps turning, would there be any accumulating harm to the motor, or would it be better if it didn't run at all and opened the circuit breaker?

p.s: Don't mention this to the bean counters. If they learn that capacitances in parallel add, they might insist on carrying only 1-µF capacitors, to reduce the number of different part numbers in inventory.
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Yep, wrong cap sizing can lead to motor damage. Exact specifics vary.

The 2 vs 1 is still the same issue with just 1 when its actual capacitance degrades over time. This is why HVAC outfits always tell you "better get that yearly $100 27point check-up". :eek:
 
drcampbell said:
Somebody with more motor-theory expertise than me ...
Say a compressor motor needs a 20-µF run capacitor and you install two 10s. What if one of the two fails? Assuming that it keeps turning, would there be any accumulating harm to the motor, or would it be better if it didn't run at all and opened the circuit breaker?...
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I'm not a good motor theorist, but I've got a lot of experience in working with these PSC motors. That's a very good question. While a fail-to-0 condition is more common, we do get a lot of fail-to-low capacitor issues also. In most cases, the motor doesn't work, and the issue is then noticed and fixed in short order. In short, I don't think it would make much of a practical difference. I've had to do plenty of call-backs for motor replacements after a fail-to-0 cap repair got the motor working again for a few days only. I always warn customers that this is a possibility with a cap replacement.
 
drcampbell said:
Somebody with more motor-theory expertise than me ...
Say a compressor motor needs a 20-µF run capacitor and you install two 10s. What if one of the two fails? Assuming that it keeps turning, would there be any accumulating harm to the motor, or would it be better if it didn't run at all and opened the circuit breaker?

p.s: Don't mention this to the bean counters. If they learn that capacitances in parallel add, they might insist on carrying only 1-µF capacitors, to reduce the number of different part numbers in inventory.
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AC compressors typically only have one capacitor, but I see a lot of other motors, especially when you get over 5 Hp that have multiple capacitors connected in parallel to effectively make a larger capacitor. See this with both start and run capacitors at times.

Most the time when I run into one that has failed, motor simply can't develop enough torque to drive the load and trips motor overload (if properly utilized). Failed start capacitors on larger motors often will trip circuit breaker before tripping motor overload if starting from a standstill and need high starting torque to get it going.
 
drcampbell said:
I don't "miss" Refrigerant-717 because it's still around. It doesn't deplete ozone or contribute to global warming, and hasn't been regulated or legislated away.

But whatever its excellent thermodynamic properties, you really need to be cautious with it.
You think heroin and ketamine are addictive and problematic? Or phosgene and chloroform? Huff R-717 just once and you'll be in a world of hurt with a substance-abuse problem.
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I already have a severe R-718 addiction. And my family is worried, since every murderer in history has been a user. So please be kind.

-Jon
 
winnie said:
I already have a severe Refrigerant-718 addiction. And my family is worried ...
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As well they should be. That stuff is a potent reactive chemical compound, and it's almost everywhere.

Outside of the refrigeration & air-conditioning biz, Refrigerant-718 is known as DHMO, and the list of its hazards is staggering:
poisonbottle.gif

  • Death due to accidental inhalation of DHMO, even in small quantities.
  • Prolonged exposure to solid DHMO causes severe tissue damage.
  • Excessive ingestion produces a number of unpleasant though not typically life-threatening side-effects.
  • DHMO is a major component of acid rain.
  • Gaseous DHMO can cause severe burns.
  • Contributes to soil erosion.
  • Leads to corrosion and oxidation of many metals.
  • Contamination of electrical systems often causes short-circuits.
  • Exposure decreases effectiveness of automobile brakes.
  • Found in biopsies of pre-cancerous tumors and lesions.
  • Given to vicious dogs involved in recent deadly attacks.
  • Often associated with killer cyclones in the U.S. Midwest and elsewhere, and in hurricanes including deadly storms in Florida, New Orleans and other areas of the southeastern U.S.
  • Thermal variations in DHMO are a suspected contributor to the El Nino weather effect.

More information at http://dhmo.org/
(warning: the emotional impact of learning about DHMO can be significant -- browse with caution)
 
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