HVAC hard start kit: worth the $350?

[Roger Feeley]

Our hvac guy is recommending a hard start kit for our 10 year old compressor. I looked around for an explanation but I didn’t find anything that explains what it really does.

I suppose I’m more knowledgeable than the average homeowner but I have very little knowledge about electronics.

as near as I can tell, the kit replaces the startup capacitor with a bigger one. Then there is something that takes the cap out of the circuit. It appears to be beneficial for older motors and compressors that may have marginal bearings and other mechanical parts that resist starting. Am I close?

I saw that these kits are recommended for compressors that don’t start. Ours works so I’m guessing that this is more of a prophylactic measure.

[Tom M King]

You have to find the right one for your compressor, but with a little study you may be able to save a few bucks for a simple job.

https://www.amazon.com/dp/B07X463KD1...v_ov_lig_dp_it


https://www.amazon.com/Supplying-Dem...ps%2C95&sr=8-4

[Bill Howatt]

I believe your analysis of the operation is correct, it parallels the start capacitor with a bigger one to give it a kick for a short period of time as determined by the relay box that comes with it. Since it is in the start circuit, and only for a second or so when starting, it will absolutely nothing for power-saving or the run power of the compressor induction motor.
The correct value of the start capacitor for an induction motor is determined "by the manufacturer" so this is not the recommended value but it only is briefly in the circuit. Motor starting capacitors do fail outright and may also provide a sluggish start by changing their value so I could see this helping in such a circumstance.
If your bearings or similar mechanical parts are bad then this could help but the reality is that the unit is on the way out. You could compare it to using a booster battery to start your care, it gets it going but the reality is that the car's battery needs replacing.
My 25+ year-old AC is still working fine without such a trick but that isn't an indication all will be and TBH, if it fails I'd be likely to get a new one anyway because they have improved the efficiency in that 25 years.

[Bill George]

From a guy who did HVAC for 30 years or so, if your unit is working fine its not needed. They are usually put on new units that may be a little hard to start or ones that run on low voltage at times. Otherwise save your money.

[Rod Sheridan]

If your unit has the compressor starting properly, you don’t need a larger starting capacitor…….Regards, Rod

[Roger Feeley]

Thanks to all. The explanations I read online promised lower utility bills which made no sense to me. You folks always make sense.

[Bruce Wrenn]

Thanks to all. The explanations I read online promised lower utility bills which made no sense to me. You folks always make sense.

A Soft Start Kit ( not a hard start kit) could possibly lower energy costs, but it would take a while to see a pay back on investment. It lowers inrush during start ups, but at close to $500 ( not installed,) it's hard to justify. On condensing units, both the fan, and compressor start at the same time. By installing a simple "Delay on Make" relay, one could have the condensing fan start up to a minute later. Condensing fan isn't needed till compressed hot gasses reach coils.

[Roger Feeley]

Thats good to know. We have a 26kw backup generator. I don’t think startup load will cause us to exceed the limit but if we get close, dividing up the start load might be a good thing.

[Bill George]

A Soft Start Kit ( not a hard start kit) could possibly lower energy costs, but it would take a while to see a pay back on investment. It lowers inrush during start ups, but at close to $500 ( not installed,) it's hard to justify. On condensing units, both the fan, and compressor start at the same time. By installing a simple "Delay on Make" relay, one could have the condensing fan start up to a minute later. Condensing fan isn't needed till compressed hot gasses reach coils.

Since he does not have a commercial account with a demand meter there is no savings. The 1 second of startup current will be billed at the normal cents per KwH and is nothing. Adding that time delay is just one more component to fail. I did this stuff for over 30 years and was a master electrician also.