What about Multi-Stage or Variable Capacity Compressors? - Part 1

The heat is on! For many of our customers and neighbors in the Beverly Hills, Culver City, Mar Vista, Miracle Mile, Hollywood, West Hollywood, Los Angeles, West Los Angeles, Santa Monica, Marina Del Rey, Pacific Palisades, Brentwood, Bel Air, Westwood, Downtown Los Angeles, Vernon, Huntington Park, Sherman Oaks, Encino area, it is time to seriously think about replacing their old and inefficient central cooling system with a new one. So, we’re going to talk about some technology that we’re seeing more and more of in the heating and cooling industry. That way, you’ll be in the best position to decide what type of air conditioning system is right for your needs. And also, if you have a Heat Pump system, then the same will apply for you in the winter time. The technology we are going to discuss is specifically about the key component of any central air unit, or heat pump: the compressor.

You’ve likely been spending some time researching AC units, and in doing I’m sure the following terms have popped up repeatedly: variable speed compressor, variable capacity compressor, multiple stage compressor, dual-stage compressor, two-stage compressor, single-stage compressor. What do those terms mean? What do they mean to you and your home? That’s what we’re going to consider now. Let’s start with the basics:

What is the compressor?

The compressor is located in the outdoor unit of a typical air conditioning system. Think of the compressor as the engine that drives your air conditioning system. It is the heart of the system, it is what gets things moving. What needs to be moved? Heat. In the summer, you want to move heat out of your house. And in the winter, you want to move heat into your house. That’s the job of the compressor.

More specifically, it is circulating refrigerant (some still call refrigerant “Freon” because of the common brand name of an outdated type of refrigerant.) But it does more than just circulate it; it is also compressing it. For comparison, think of a common air compressor. It pressurizes air it to use for pumping up your tires or in tools such as a nail gun or paint sprayer. In just the same way the compressor in your AC is compressing the refrigerant gas into a much higher pressure and pumping it through the system. At various stages of the cycle that compressed refrigerant changes states: first turning into a liquid, then a low-pressure gas, and back to a high-pressure gas. The circulation of the refrigerant, in its various states, is what moves heat from one place to another.

In the case of your car, the engine requires fuel to run, which traditionally has been gasoline or diesel fuel. In the case of your AC, the compressor has a motor that runs on electricity. The more efficient the motor, the less electricity is needed to operate the system. And that means less money out of your pocket to keep your family comfortable.

And that’s where we come to the different types of compressors. Let’s start with the basics:

Single-Stage Compressor

Put in other words, a single-stage compressor is a one-speed compressor. It is a motor that can turn on, and it can turn off. It’s as simple as that. This is the type of compressor that started it all in the field of cooling and refrigeration. Was your AC unit or heat pump installed before the year 2000? Or, did you move into a newly built house that already had an air conditioning system installed? If so, then chances are you have a single-stage compressor.

In terms of efficiency, this is the least efficient type of compressor. It is either off, or running at 100% capacity. When the temperature is not at extremes, then the AC will have to cycle on and off. A compressor draws the most power when it starts up. This means that during most of the season, when it is starting frequently, it is consuming start-up energy and decreasing efficiency.

We’ll be back soon with more details about multi-stage and variable capacity compressors.

Do you have other questions that are nagging you? Visit our Ask an Expert page, fill out the form, and the resident expert at GAMA Air will get back to you quickly with an answer.

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