Compressor saver kit for AC

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Submitted by kcal09 on September 11, 2017 - 10:32pm

I recently had my AC serviced here in San Diego. The tech suggested I get a compressor saver kit. He stated that it will save in energy cost and cut down on premature failure of my compressor. Is this really true and is it worth $220?

Submitted by RichardJamesEsquire on September 12, 2017 - 4:50am.

Short version: not needed, overprice, uniformed/misguided/dishonest, 1 more thing to break, cheap electrical parts like to melt and potentially start fire.

A hard start kit creates a lot of additional starting torque. It's a $15 part. There's a half dozen conditions why one would be needed (some listed at bottom). But if you've never had any problems starting you don't have any of them and it's not worth $15 let alone 200.

Additional torque will get the compressor from 0 to 3450 RPM's faster. So you will use less electricity...for less than 1 second at start-up. So yes you will use less electricity. But so little less you would never be able to measure it in any practical or reasonable way.

As far as premature failure (whatever "premature" means) additional starting torque is good, but not really beneficial if you don't have the reasons listed.

The hard start kit is a great tool to try to break free a seized motor and get it running again. So if your motor was to seize up (locked rotor) and that extra torque then broke it free on the next start, or after it cooled off (Some huge ifs). Well it didn't really prevent anything, it just sort of repaired it and you never knew. So that's sort of true...should the motor have that one specific type of failure but not so to bad that the additional torque could overcome it.

Now if a technician ever tells you a single phase compressor (or even a fan motor in some cases) is locked rotor, ask them if they have a hard start kit on their truck and ask them if they tried it. It might save you a lot of money.

Would I add one to any and every unit, no way.

Needed when:
Low voltage, like below 198V.
No 5 minute time delay built into thermostat or outdoor unit to allow pressures to equalize between cycles.
Metering devise that does not allow for equalization during off cycle.
Really long refrigerant pipes, like 150+'.

Submitted by Hobie on September 12, 2017 - 4:54am.

Upselling by the tech. These kits are a capacitor to boost the start load.

I would find a new tech.

ps. either by mistake or on purpose a more common problem that causes a compressor to fail is to mix refrigerants. Slow death and you won't know until the next guy opens up the system.

Submitted by ocrenter on September 12, 2017 - 5:56am.

I recently replaced my AC unit's fan blade, motor, and capacitor for total of $220.

I don't know much about this "compressor saver kit," but seems awfully pricey when compared to the total combined cost of fan blade/motor/capacitor.

Edit: found a nice explanation regarding utility of compressor saver kit on youtube:

if you still want to go for it, Amazon has it for just over $30:

Submitted by RichardJamesEsquire on September 12, 2017 - 11:57am.

The video. His conclusion is the same as mine. But he's claiming inrush current was reduced by a 3rd.

I don't know if inrush current is reduced at all but he only measured 1 (of 2) legs of power with a non RMS meter. There is no way that statement can be made.

Capacitors alter the sine wave so a RMS meter would be required.

Even if current was reduced, watts is actually volts x amps x power factor. Capacitors increase the power factor. So the watts, what you pay for, can be the same while current is lower.

and with the motor starting faster his cheap meter might not have read inrush current as accurately.


Submitted by FlyerInHi on September 12, 2017 - 1:07pm.

Richard, sounds like you know a lot about AC.
When would you say the outside AC unit needs to be replaced? Or can it always be repaired. I had to replace a 3 ton unit. The AC guy said about $1000 to replace compressor and refrigerant or replace the whole thing for $2500. I chose to replace because the unit looked rusty. I didn't have time to research.

Some AC units seem to work for 30 years just fine. Some other ones break much sooner.

Submitted by RichardJamesEsquire on September 12, 2017 - 3:40pm.

It can always be repaired. But you did good.

If the compressor grounded there was likely moisture and then acid in the system. Most guys aren't good at cleaning that up. Each new compressor would fail sooner as the problem gets worse. Throwing away more of the skanky piping better, which you did. That's the safer, easier, bet.

On the coast a new outdoor units condenser coil must be treated or copper. Just a mile or 2 inland untreated coils hold up fine.

Most new units, the fins on the coils are made very thin to look good in energy efficiency tests. But aluminum oxides and then stops corroding. Fins so thin, if not coated with something, they will be gone before they stop corroding. Another problem is dirt and pollen get caught in the complex shapes of the "high efficiency" coil fins and need to be cleaned often to keep them running if there's a lot of dirt and pollen around.

So yeah on the coast a 30 or 40 year old condenser coil with thick fins holds up indefinitely while a new untreated coil will be gone in 5 years. But a untreated coil should never have shipped to that location. And there is a lot of energy to be save with a new properly speced, installed, and balance system.

That being said if you did the outdoor unit why not do the indoor unit with something matching and high efficiency at the same time?

I should add, 15 years ago doing a compressor for 2k would have been giving it away. 1k? Glad I'm not anywhere near that business anymore. Kind of makes me think the compressor was still under warranty? Unit less than 5 years old? He probably got a free compressor out of deal, to sell to someone else, by warrantying yours.

Submitted by FlyerInHi on September 12, 2017 - 3:54pm.

The unit was about 15 years old.
The guy said $1000 to repair (no warranty how long it would last) and $2500 for whole new outside unit. He said no need to replace indoor coils. Sounded reasonable so I went with it. I don't know much about AC and I was time constrained.

Very interesting. I like to understand how things work.

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