Residential A/C Capacitors

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I watched this video and the guy said that A/C condensing unit capacitors are a wear item and eventually they all fail. When the capacitor fails, your compressor and the condensing unit fan will not start. You don't want them failing on the weekend because the retail home centers will not have them. He recommends everybody should have a spare as a backup. I'm trying to figure out why my condensing unit has two capacitors plus a starter. Usually all you need is one capacitor and starter as illustrated on the starter itself (see 3rd picture). So I'm wondering if I should keep an extra genteq capacitor on hand, or an extra of all three.

Goodman Condensing Unit Model CKL30-1F
genteq 25L502 440 VAC capacitor
Mars2 12905 370 VAC capacitor
Supco SuperBoost SPP6 hard start kit

1. https://flic.kr/p/W8DxQQ
2. https://flic.kr/p/W8DxHf
3. https://flic.kr/p/Xpv8nV
 
In 53 years of having to use AC systems in the south (which means they run nearly year-round) I can count on three fingers the number of times a capacitor has failed. My point is although you are correct that a normal retail place will not have a capacitor, the odds of it actually failing are quite low.
 
Carriers are solid units IMO. Our experience with the old one here was amazing, the thing just wouldn't stop.

But around these parts lightning is a significant threat. Poor quality power and huge surges don't do anything to help. Caps do occasionally fail...
 
The local HVAC store sells caps, their markup included, for $10-20.
If it makes you sleep better, go ahead and buy one, but odds are you won't ever need it.
 
Get a test meter that can check the capacitor versus the rating marked on the side yearly (unplug the power and discharge the capacitor before removing!). If it is out of spec, replace it before it fails. Don't buy Chinese run capacitors. Pay the extra and get made in USA.
 
Originally Posted By: Merkava_4
I watched this video and the guy said that A/C condensing unit capacitors are a wear item and eventually they all fail. When the capacitor fails, your compressor and the condensing unit fan will not start. You don't want them failing on the weekend because the retail home centers will not have them. He recommends everybody should have a spare as a backup. I'm trying to figure out why my condensing unit has two capacitors plus a starter. Usually all you need is one capacitor and starter as illustrated on the starter itself (see 3rd picture). So I'm wondering if I should keep an extra genteq capacitor on hand, or an extra of all three.

Goodman Condensing Unit Model CKL30-1F
genteq 25L502 440 VAC capacitor
Mars2 12905 370 VAC capacitor
Supco SuperBoost SPP6 hard start kit

1. https://flic.kr/p/W8DxQQ
2. https://flic.kr/p/W8DxHf
3. https://flic.kr/p/Xpv8nV


I can't see how it's wired but it could be one of two things.

1) Two of the run caps are together to get the correct capacitance, either in series or parallel.
I've done this heaps of times when I don't have the right one with me.

2) The 5 mic run cap is for the condenser fan motor.

Back before DC variable speed inverter driven compressors became the most common, PSC (permanently split capacitor) style compressors ruled on single phase installations.
Run capacitors would be the most common replacement parts.
 
Run caps tend to dry out, lose their capacitance, & eventually open, causing high run amps. They don't need to be discharged (unlike a start capacitor), but you'll need a meter with a microfarad scale to test them. Or just replace it & check the running amperage of the compressor or fan motor & see if it drops. If you have a hard start kit, then there can also be a start relay, which should always be replaced with the start cap.
 
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Originally your unit had only one dual run capacitor but seems like they have replaced the fan motor which normally gets a new capacitor (which is the little one). Then someone replaced your dual cap with a single cap for your compressor and installed a hard start kit ( which is your black gismo ).

I've seen 30 year old units still running on their original capacitor meanwhile the capacitor on my 3 year old unit went bad about a month ago, ( replaced under warranty).
 
Originally Posted By: tdi-rick
2) The 5 mic run cap is for the condenser fan motor.


Is that the short oval capacitor?
 
Originally Posted By: Merkava_4
2015_PSD,

I've had it happen twice since 2004 when I first got the new condensing unit.
You have more going on there than just a bad/weak/poor quality capacitor. One thing that I have seen happen fairly frequently is sometimes the technicians do not have the correct sized capacitors when they come out and make the repair and put an undersized capacitor in place that will work but only for a shorter period of time.
 
This is good advice,

There are two types of capacitors commonly used. 1 is a combination cap with three terminals. It is a single large can that has both the compressor cap and the fan cal. Its usually marked something like 30uF and 5uf (Values vary depending on the unit). The three terminals are marked Com, HERM and Fan. Herm is the compressor since it is hermatically sealed.

You can also buy separate caps for the fan and herm and wire them together.

The "kickstarter" cap is typically optional and only needed in special situations. Did an AC tech add that during a service call? These are commonly a profit item for them.
smirk.gif


The capacitors of old has PCBs (chemincal not electronics) in them that was banned in the late 90s. These caps lasted forever. The newer caps are eco friendly and have a higher failure rate over time at temperature.

I had the same thing happen to my 2003 Carrier. Around 2008 the unit stopped and the fan on top would not turn and the HERM would humm loudly. I killed the power at the breaker and took a look (I and an EE by the way). The AC cap had its top domed out like a beer can left in the sun and when I looked it up on the internet they showed it built up internal pressure and broke a fuse when the top swelled so it wouldn't explode.

https://www.youtube.com/watch?v=mB89knyysFE


Of course this was a Sunday on a weekend with a Monday holiday (Labor day). and it was in the high 90s. I limped by with a window unit in a single "cool room" until Tuesday.

I replaced it with a Dayton from Granger (only place I could get one that day) for ~$50 and was back in business for about a year and a half. Then it popped.
frown.gif
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I also bought a el-cheapo backup from ebay for $30 as a backup. So it went into service while I ordered a Genteq cap and the final backup.
The Genteq cap was swapped in when it arrived, and was in service until 2016 when the evaporator developed a hole and I upgraded to a higher efficiency unit. 16 seer vs 12. It showed a noticeable decrease in energy usage but not dramatically so. I think the previous unit was not "hurt" by sitting there humming for a few hours before I found the capacitor problem.


There is also one in your furnace fan. Its is also about 5uF. Mine had degraded down to 3uF and the fan was struggling to start. It has a loud hum on startup. AC tech said the cap was bad and they cost $150/each to replace + service fee. I bought a Genteq for $20 off amazon and figured out the two prongs myself.


*****

Note these are high (lethal) voltage capacitors and connected to high voltage service lines. If you don't know the safety aspects of dealing with a few hundred voltages and charge storing components like capacitors, you should have a qualified tech do it for you. Saving a few dollars is not worth your risking injury or death

******
 
Originally Posted By: danez_yoda
Note these are high (lethal) voltage capacitors and connected to high voltage service lines. If you don't know the safety aspects of dealing with a few hundred voltages and charge storing components like capacitors, you should have a qualified tech do it for you. Saving a few dollars is not worth your risking injury or death.


That's where the magic of YouTube comes in. I learned that I can discharge the capacitors by laying a screwdriver blade across the terminals. I could've sworn that I heard a fizzing noise when I did that, but it was probably just my imagination.
 
Originally Posted By: Merkava_4
2015_PSD,

I've had it happen twice since 2004 when I first got the new condensing unit.


I also have had two failures since my new unit was installed in 2013.
 
From my experience owning a Goodman, stock a spare capacitor.

I've had 2 go out in eight years.

The repair man said its a problem during heat waves.
 
Electrolytic capacitors are like anything else, build them right and they last a long time. Cheap out on the materials and they will fail prematurely.
I am a retired electronics tech and have seem this proven many times over the decades.

Get a proven quality name brand (e.g. Panasonic in TV/stereo parts) electrolytic and forget about it - get a cheap off-brand from parts unknown and it'll blow up or loose capacitance from dryout.

I don't know who makes quality caps in HVAC equipment but I'm sure they are out there. Get one of those.
 
It's one thing they always warrantee everytime they come out. The thing that gets me is they always zip tie the new on. There was another time the guy disconnected like 10 different wires, then I could tell he was confused putting them back because it didn't work at first, then about a month later the ac went out again and the guy who came out, said a couple wires were backwards. Personally, I would just let the thing run until it quits, these technicians mess up more than they fix, wrong sized capacitors, wires crossed, etc.
 
I always have a spare cap and a contactor on hand. If I use one I order a matching part from Amazon or ebay. I had to install a contactor last year, ants.
A cap is less than $10 and a contactor about $12.

I found the local supply house sold the same stuff but at twice the price. Most all made in China.
 
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