Air Cond. compressor motor starting capacitor

[Merc]

We came home from the cottage today to find the temperature inside the house in Pittsburgh was a steamy 84 degrees F. The air conditioning unit was installed on my furnace in 1995 so it’s not exactly state-of-art, but it works so I won’t replace it until it becomes too costly to repair. I checked the 220 volt air conditioning circuit breaker and it was tripped.

The problem this time and many prior times was the failure of the motor starting capacitor on the compressor. I have replaced it many times before so keeping an extra capacitor on hand is a necessity. The original capacitor lasted for about 8-10 years and the replacements fail every other year. I’ve tried several different brands but they all failed every other year. They all have one thing in common. You guessed it - all were made in China.

The capacitor that I just installed was made in the USA by Turbo 200. I won’t know for two years whether or not this one will last longer than two years, but you know Einstein’s theory of insanity is doing the same thing over again and expecting different results.

Any DIYrs out there with similar problems?

[togor]

Our unit is a Heil, from the 1980s, which, knock-on-wood, keeps going strong. The only issue was an AC contactor that was corroded by mouse piss. I plugged the access holes with copper scrubbies and no mice problems since. Two winters ago the furnace guy wired the AC control circuit wrong when he wired in a new furnace but I untangled that myself without trouble.

Regarding your starter cap, it's important to size it to the application. Higher uF ratings will also mean a higher current rating for the device, which is good. But too many uF can be bad also. This web page might be useful.

https://inspectapedia.com/electric/Motor_Capacitor_Selection.php

And...kudos for fixing it yourself!!!

[Merc]

It’s good to have knowledge of all things electrical.

My furnace guy says my AC unit could go on for many more years and saves me money every day by continuing to work.

Older gas furnaces, on the other hand, can be dangerous. The heat exchanger can develop cracks and allow carbon monoxide to circulate into the house. It happened to us 2 years ago. Our carbon monoxide detector sounded off and warned us.

[PaFrank]

I had the same problem last year and it turned out to be the fan motor that was seizing and drawing too much and burning out the capacitors. Replaced fan for $85 bucks and not i can hang meat in my house... AC was installed in 1971

[Merc]

Come to think of it, I also had to replace the main contactor, probably 10 or more years ago. It was the only other problem I’ve had with the unit. The old and new furnaces and AC unit were made by Bryant.

[Merc]

I had the same problem last year and it turned out to be the fan motor that was seizing and drawing too much and burning out the capacitors. Replaced fan for $85 bucks and not i can hang meat in my house... AC was installed in 1971

Yes, the multi range capacitor starts both fan and compressor.

[Sunray]

"...and it was tripped..." Probably due to the much higher temps in the house with said house being closed up while you were away. Might be the same issue with the capacitor.

[togor]

"...and it was tripped..." Probably due to the much higher temps in the house with said house being closed up while you were away. Might be the same issue with the capacitor.

Usually inrush is the killer.

[Merc]

Without extra electrical energy provided by the capacitor, the motor won’t spin on startup. It’s trying to start under a physical load of the refrigerant. I can hear the motor humming for a few seconds and then it kicks out on its own internal thermal overload switch. The thermal overload cools down after a few seconds and reconnects power and the motor hums again but won’t spin under the refrigerant load and the thermal OL kicks out again. This repeats a few times until the 220 volt circuit breaker finally sees enough heat to trip. Physically, without capacitor assisted starting, you’d need a motor many times the size of my AC compressor motor to be able to start under load.

The washing machines from years past had a start winding and a run winding that allowed it to start under a physical load. The start windings drew a lot more current and provided more torque than the run windings but were controlled by a centrifugal switch that would switch to the run windings after the motor started to spin.

[Clark Howard]

AC units of that age are so inefficient compared to modern units of the same capacity. Capacitors need some "help" from other components, (compressor, fan, etc.), in order to fail so regularly. The problem is finding an AC contractor who is willing to install a new unit without having you pay for his new boat, truck, or cottage on top of the installation cost.

[Merc]

I don’t doubt that the age of my AC unit is a contributing factor in the high rate of capacitor failure. I’ve often wondered if the replacement capacitors were equal to the original equipment.

It takes me about 10 minutes to replace a capacitor and they cost about $60/each. I keep at least one on hand so down time is minimal. My AC guy recommended the Turbo 200 capacitor because he was also having a longevity problem with the capacitors that were made in China. I’ll know in 2 years if these are any better.

[Former Cav]

I have a Trane unit that I spent about 11 grand on, new everything. It has been the worst AC unit I have ever owned in my lifetime. The AC ALWAYS fails every June, compressor, (they give you the compressor "free" under warranty and charge you 1300 bucks for an install.) Mean while you are in a hotel for a week as I live in Phoenix.

[Allen]

I have a Trane unit that I spent about 11 grand on, new everything. It has been the worst AC unit I have ever owned in my lifetime. The AC ALWAYS fails every June, compressor, (they give you the compressor "free" under warranty and charge you 1300 bucks for an install.) Mean while you are in a hotel for a week as I live in Phoenix.

Sorry to hear that. I thought Trane was the best by leaps and bounds. I currently have a York 4 ton that barely keeps my house livable. Prior to that I had a 4 ton Janitrol that suffered an inside coil that wasn't installed correctly and didn't cool. I have a 3200' home with vents closed off to the rooms we seldom use bringing down the footage to about 1200' and a 4 ton unit can not cool the house enough to ever shut off during the heat of the day.

The only good news is I spent about half on the York (outside unit and inside closet or air handler) as what the Trane would have cost. So far just a capacitor or blower motor here and there.

[Merc]

Consumer Reports doesn’t rate central AC performance but they do rate reliability based on a consumer survey. They are rated on a scale of 1-10. The following are the recommended brands:

Trane 8
American STD 7
Armstrong 7
Bryant 7
Carrier 7
Ducane 7
Lennox 7

My unit is a 1995 Bryant and it has always cooled my house. I can’t really say that its tendency to blow capacitors is the fault of the unit since they aren’t original equipment.

The only maintenance I do is clean the electrostatic air cleaner in the furnace at the beginning of the heating season and flush the coils of the condenser with a garden hose every summer. Dirt that plugs the condenser coils will have a negative effect on its ability to cool the air. I also remove the leaves and twigs that collect inside of the condenser. Other that keeping it clean, I don’t think there’s much more that an owner can do. Some people put a cover on their condenser in the winter, but I don’t. Be sure to open the breakers that supply power to the compressor and furnace before working on the condenser.

The newer electronic digital thermostats work so much better than the old mercury wetted relay type. I replaced my old thermostat almost two years ago when the new Bryant furnace was installed.

Speaking of furnaces, gas furnaces are pretty much the gold standard for performance in my part of the country, but I wonder what the average life span is for the heat exchanger. Mine lasted for 22 years before developing holes and allowing carbon monoxide to enter the house. Is this about average? My CO detector worked well and warned us of the danger (I now have two detectors - one in the furnace room and one in the hall near the bedrooms). The question might be, do you wait for the CO detector to tell you that you have a problem, or do you just replace the heat exchanger every twenty years figuring its about to fail. Or, do you spend a few more bucks and just install a new, often more efficient furnace?

[Merc]

I have a Trane unit that I spent about 11 grand on, new everything. It has been the worst AC unit I have ever owned in my lifetime. The AC ALWAYS fails every June, compressor, (they give you the compressor "free" under warranty and charge you 1300 bucks for an install.) Mean while you are in a hotel for a week as I live in Phoenix.

My late sister lived in Cave Creek and I understand how brutal the heat of the day can be in the summer.. She had two Trane heat pumps and failures were common. She replaced one that was less than ten years old and the replacement failed after only two years. I think I’d be tempted to go with a different mfr. rather than continuing to throw money into the Trane unit even though it’s rated so highly by the CR consumer survey.