5-2-1 Compressor Saver®

How It Works

The video below demonstrates how the 5-2-1 Compressor Saver® (aka Hard Start Kit) works conceptually. The video is a non-technical representation on how the 5-2-1 Compressor Saver® works and helps protect your air conditioner so you can save you money, prolong the life of the air conditioner and reduce air conditioning repairs.


The 5-2-1 Compressor Saver® protects these components by significantly reducing the amount of time it takes for your compressor to start – in some cases up to 50%. This means your air conditioner and compressor will bear – the stress, strain and heat each and every time it starts. Considering that your air conditioner may start up more than 6,000 times in a single cooling season, the positive impact that the 5-2-1 Compressor Saver® has on your air conditioner is significant.

5-2-1 Compressor Saver®


90% LESS


95% LESS



The compressor on your air conditioner consumes more power on start-up than another device in your home! The 5-2-1 Compressor Saver significantly reduces the time it takes for your air conditioner to start – SAVING YOUR MONEY AND PROTECTING YOUR EQUIPMENT.

Technical Info

The 5-2-1 Compressor Saver® (aka Hard Start Kit) is only to be installed by a licensed air conditioning technician or electrical technician. Each 5-2-1 Compressor Saver® package has a schematic to help technicians install the device properly. In addition to these instructions below, air conditioning companies and air conditioning technicians please consult our Technical Installation Video.


Only trained and qualified personnel should install this kit. Most states require the installer to be licensed. Please check with your local government agency


Only trained and qualified personnel should install this kit. Most states require the installer to be licensed. Please check with your local government agency


Only trained and qualified personnel should install this kit. Most states require the installer to be licensed. Please check with your local government agency


Failure to properly install this kit can and will cause permanent damage to the compressor and related components.



Is the 5-2-1 Compressor Saver® approved by equipment manufacturers?

Yes. The 5-2-1 Method has been in existence for over 70 years and is used by all major equipment manufacturers.

Is there a warranty?

Yes. 5-2-1 Inc. provides a three years warranty on parts. Labor is not covered.

What’s difference between the 5-2-1 Compressor Saver® and other 2-wire hard start devices?

There are two main differences. With the third wire the potential relay on the 5-2-1 can read true back-emf. This means the device can accurately determine when it should go out of circuit. Other products with two wires are either operating on a timer and are not equipped to read true back-emf, which means that they be in circuit too long or not long enough. Secondly, the third wire isolates the start capacitor so that in the event of a potential relay failure you will only damage the start capacitor on the 5-2-1. With two wire devices, in the event of failure you have the potential to damage the actual

Is this new technology?

The 5-2-1 Compressor Saver® uses electrical principles that have been in practice for the past 70 years in the industry. 5-2-1 has made advances on the underlying components over time and has prepackaged the components in an easy to install package

Why are there three models?

The 5-2-1 Compressor Saver® comes in three different packages – CSR U1, CSR U2 and CSR U3. The difference is in the size of start capacitor. Smaller capacitors are needed with the smaller units and naturally larger capacitors are needed with the larger units.

Is the 5-2-1 Compressor Saver® UL listed?



How many do I need to order?

You will need 1 5-2-1 Compressor Saver® for each air conditioning unit, specifically each condensing unit. The air conditioning technician will identify which model is appropriate for your air conditioner. Our partners keep all models in stock on their service trucks.

How long will it take to install?

The entire installation process can take anywhere from 10 to 30 minutes, including taking the before and after data measurements.

Do I have to use one of your partner air conditioning companies?

No. Please feel free to have your local air conditioning technician perform the installation, but make sure that he/she installs a 5-2-1 Compressor Saver® and not a different hard start device.

Why would I want to use one of your partner air conditioning companies?

All of the ac companies listed on our website have a significant amount of experience with our product and all of their technicians have been properly trained. Any air conditioning technician can purcahse the 5-2-1 Compressor Saver® at the local air conditioning distributor, but they might not have the same level of experience and training as one of the companies we would recommend.

What type of improvement can I expect?

The results will vary, but the average air conditioner starts up 30-50% faster with the 5-2-1 Compressor Saver®.

What is the warranty?

2 years if installed by a licensed air conditioning contractor. Warranties for products sold via an unauthorized source (i.e. 3rd party, online, etc) will not be honored.


"We have been installing the 5-2-1 for several years and continue to offer it to
all of our clients."

Jared, Technician, Service Engineering LLC

Colorado, CO

"We have been using the 5-2-1 for a number of years. I haven't found
another product that does a better job."

John, Technician, LoneStar Services

Burleson, TX

"I have been impressed by the 5-2-1 products. They work very well on
all applications and have gotten alot of happy customers."

Anthony, Technician, AK2 Mechanical LLC

Lake City, FL

5-2-1 Compressor Saver®


Browse resources for 5-2-1 products, product sheets, logos, and more.


The video below is intended for a technical audience, specifically licensed air conditioning technicians. The purpose of this video is to train a technician on how to properly install a 5-2-1 Compressor Saver®. The video will first walk through the installation via a schematic and then actually walk through an actual installation on a condensing unit.

The installation portion of the 5-2-1 Compressor Technical Video identifies several important installation tips including how to easily identify the run side of the contactor and run capacitor. In addition to demonstrating the “before and after” in-rush measurements, we also demonstrate an important test to verify that the start components are working properly.

521 Compressor Saver Technical Installation Video

5-2-1 Compressor Saver Logo

(69KB, JPG, 300dpi, 640×258)

Where to Buy

      Contact a Dealer

      Enter your information in the form, and a team member will reach out within 1-3 business days.