Homes in the United States are supplied with what we call split phase power which is basically single phase power with two hot legs which is perfectly adequate for all home appliances except your HVAC system. True three phase power is more efficient so the motors in the outdoor (condenser) section of your air conditioner technically need 3 phase because this is how they are designed. Three phase power requires three legs of power and since your home only has two, we need to create that third leg. This is where the capacitor comes in. You can think of a capacitor as kind of like a battery although a battery and a capacitor are different in so many ways. A capacitor stores excess energy created by the motor it's supporting, and then discharges that energy back into the motor during the lag of energy that naturally exists in the split phase supply. I tried my best to keep that as simple as possible, but basically know that the motors (compressor and condenser fan motor) can't run without a good and properly rated capacitor.
Now that we know the purpose of a capacitor, lets talk about the different quality capacitors. This section is going to based on my experience and some preferences, but I will only state facts I know to be true. Lets start with factory capacitors or the ones that come originally with your ac unit. From my experience, most factory capacitors won't last more than 7 years of operation. I have seen Trane and Goodman factory capacitors last longer while others sometimes won't make it 2 years, but on average 7 years is in the ballpark. After the factory capacitor fails you will likely call a service company out who will either install the brand that they keep on their vehicles or they may give you an option. There are basic or standard aftermarket capacitors that are typically comparable to factory capacitors in terms of how long they will operate in the field. I have found that most aftermarket basic capacitors are good for between 3 and 6 years before you will need another capacitor. A company called American Radionics produced a line of capacitors years ago called the Turbo series (and no I'm not sponsored by AmRad, I've just used their products for many years) that last much longer. Based on my experience in the field a Turbo lasts somewhere between 12 and 18 years. Obviously these are higher quality capacitors with a bigger ticket price.
Standard quality capacitors typically get installed between $80 and $340. This is a wide range because of company cost as well as the brand of the capacitor which I discuss in detail here https://www.simplyrighthvac.org/post/breaking-down-labor-and-material-costs-a-guide-for-homeowners feel free to read that article is you would like a deeper understanding of cost breakdown. Turbo capacitors can range anywhere between $200 and $500 (figures are based on my local market averages, prices may vary from market to market). I think it's important to note here the price of a service visit as it needs to be part of the equation. If your contractor charges a service fee of $100 and you expect your ac unit to last 15 years, you will likely replace the factory capacitor once and have two standard quality capacitors installed for a total of 3 service calls. That's $300 dollars in service calls plus the $150 (mean average) you will spend for each standard capacitor, for a total of $600. If you take that same math and apply it to one Turbo, you would likely expect to spend at most $500 for the life of your ac, plus you likely alleviate one more service call meaning that was one less time you were without air conditioning. Bare in mind that ac units typically breakdown when it's really hot out. There's a bigger impact behind the scenes that you won't know about until it's too late.
We discussed early how the capacitor supports the compressor and fan motor, so what happens when a capacitor fails? When a capacitor fails to produce the energy it's designed to, the motor it supports won't start. Electricity is applied to the windings but the motor lacks the energy needed to produce the starting torque so the resistance in the motor increases until the motor either trips on internal thermal overload (over heating) or in some cases the windings burn up all together. If the windings burn up, your getting a new motor which can be very costly, oh by the way you also need a new capacitor at this point so tack that on. Even if the motor doesn't burn up, it was sitting there overheating which weakens the insulation of the windings ultimately reducing the life of that motor. It's imperative to be proactive with capacitor maintenance to ensure not only that your ac stays running, but that you get a good functioning life from your ac system without spending a bunch of money.
In all my years of doing HVAC I've heard many clients who loved and swore by a brand and likewise I've heard people say they would never have another __________ because it was a piece of junk. I'm here to tell you now that very rarely is any equipment a true dud. The manufacturer's spend millions to ensure that their systems are designed to last at least an average expected life. The biggest factors of equipment life are the quality of the install first and foremost, and the upkeep/maintenance thereafter. Typically it's the small things that make the biggest impact on the equipment's life and performance such as having clean coils, good capacitors, properly sized and torqued electrical connections, and properly running motors for air flow. A bottom of the line builder grade unit has the ability to last 20 years just like a vary expensive inverter driven unit can have a multitude of issues and headaches if not installed and maintained properly.
Kenneth Casebier
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