Single phase motors have zero starting torque. To overcome this problem a start winding is added and start capacitors are used to produce some phase shift. The more capacitance present the closer to a 90 degree phase shift and the greater the starting torque (the inductance of the start winding itself cancels some of the phase shift form the start capacitor). At startup an induction motor pulls current limited by the resistance of the windings (very low) and the inductance at 60 Hz of the windings and iron present in the motor. The faster the motor can be brought up to operating speed the faster this excess current (and its heating effects) can be reduced the better for long term reliability. The typical hard start kit adds some additional start capacitance and a 'timer' to pull it out of the circuit. Just about anything that can reduce the starting current demand will improve long term reliability. many units come with hard start kits already installed, and just about all the rest recommend them if the run to the unit is long or prolonged starting is present. A larger start capacitance is never a problem. Capacitors are expensive, and the engineering around the selection of the cap value is to minimize the capacitance needed to save money.

In the spring I had maintenance done on my 6 year old Infinity system. I alternate the AC and furnace maintenance each year. During the diagnostic testing the tech found one of the capacitors to be marginal. I think it was the start capacitor, but it could have been the run capacitor. I have a 10 year parts and labor warranty so the replacement was done for free. It was a little disappointing. The previous Carrier equipment was 25 years old when I replaced it. I never replaced any capacitors. Many capacitors are made in Mexico and are not good quality. The original capacitor was rated for 370V, the tech put in one rated at 440V. In theory it should last longer, but if the dielectric material is low quality it will also fail. If the capacitor showed signs of swelling, then it is time to replace it. Not sure if a bad start capacitor would cause damage to the compressor, but eventually the compressor will not start. The price seems high if you are are supposed to be getting a discount. I would be curious to know what is the non-discounted price.

Extremely unlikely because as the guy said... eventually the unit starts and runs fine. Voltage drop = no run. "If voltage drop occurred while unit was running... it would not stay running." No where does OP say anything about unit cutting out while after starting and running. You have to know what you are talking about to come to such conclusions. LOL. Does a car keep running if there is no gas? Can a car be hard to start, but then run fine once started? Yeah ok, common sense. While a car is a poor comparison more people understand the operation of a car than anything else I could use as an example. voltage drops tend to stay, not magically disappear and reappear. But thanks for playing.... In over 22 years of diagnosing only 1 voltage drop problem... if you have a voltage drop you will know it quite easily. (More complex problems in regards to start up? Uh no. Guess again and again and again.) More common to drop a leg from the pole... while also rare that's happened about half dozen times in 22 years of running service. Central AC Unit won't start with only 120v available, that confuses people because some things inside the house will still operate normally as long as it doesn't require the full 240v to operate. In Vegas, they give you odds... in a forum board that's also what I give. Magic 8 ball --- out.

OEMs don't have an economic interest that's served by extending the useful life of their equipment beyond the warranty period, especially if doing so adds to the upfront cost as would be the case with hard starts. Distributors that sell the equipment are there to also sell me the garbage that causes damage to a compressor over time. It's a vicious circle to say the least. I know better now (2023) than say 25 years ago... from the perspective of doing HVAC for 29 years. Just because someone or some entity within the HVAC realm is attempting to sell you something doesn't mean you should buy it. Nor that I should sell it. To gain trust --- home owners trust me with my recommendations for real reasons. My market in Katy, Texas has knuckle heads running around for free advice. I don't do free advice except here on this board to more or less explain the hidden cost of just doing something because someone is selling it. If the advice is free it's not worth anything to begin with. My advice is worth what you pay for it in person. If you don't think so you're fine by me to go that route. I know I can lead a horse to water, I can't make him drink it. I can print truth(s) here all day long I can't make you believe it. The best case is to buy the OEM spec hard start kit for a particular unit that currently doesn't have any start up issues and doesn't need the hard start to start --- the manufacturer specifies when one is required for certain applications (like long line set application). As I have stated before required hard starts are different electrically from one compressor to another, size of the compressor etc. Put the wrong one on your AC unit and you're doing damage in small bits at a time every time the unit starts. Extending the life of a unit by adding a part is just regurgitated rhetoric used to sell you something in most cases. It took me a good long stretch of my career to separate the facts from fiction in this regard. When the hard start fails and it will along with the run capacitor -- these two could be responsible for the demise of your compressor in the future. It may not be evident / hard to prove in many cases what caused the compressor failure. But I thought you said it won't hurt anything? Yes provided you put the right one on your system, maintain it properly, replace the hard start again when it is determined thru a maintenance visit that it's needed. What I know for sure is that many people have trouble remembering to replace their filter, get maintenance done... not just done but done properly. If you're worried about what is reasonable in terms of cost to do this right... leave it alone if you don't have the money to do it right AND make sure it is done right. The manufacturer made your unit the way it is to function the way it's supposed to under most installation applications. If you needed a hard start for your particular installation it should have been provided at the time you had your system installed. If you got $250 burning a hole in your pocket? Find something more constructive to spend it on. If you wanted to cut your electric bill you should have bought a more efficient unit like a Bosch 2.0 Inverter. That can cut your electric bill by up to 50%. Like cool stories? Here's a recent one [video below]-- the first AC not cooling call of the summer? In February? (hot climate problems) This unit has no hard start kit -- it doesn't need one yet. I service the Katy, Texas area.