Why is the AC Hissing?

Air conditioners produce liquid water by design and by the simple nature of physics. Sometimes this harmlessly leaks out around the air conditioner, such as with window units, and sometimes it leaks when a drain gets blocked. There is however, a second leak an air conditioner can develop: refrigerant leaks.   The Cooling Compound Air conditioners work by exploiting physics around state-changes. When liquid turns into a gas, it can absorb heat.The effectiveness of the state change varies from compound to compound. For air conditioning, we tend to use things like R134a (freon), R12 (phased out/illegal in much of the world now), and even propane. These are all chemicals which have particular properties ideal for cooling. For example, they won’t turn solid at 0 degrees C like water, so they won’t clog up the air conditioner’s tubing and fittings. These chemicals though have some downsides we can’t really escape. Propane is outright flammable and probably capable of turning your air conditioner into a flaming set piece in the next post-apocalypse movie. R12 destroys the ozone. And R134a is toxic. It causes a wide range of symptoms from headaches to hallucinations and death in the worst case exposures.   The Hissing Leak When the air conditioner is running or has recently been run, the refrigerant will be highly pressurized. In order for us to make it work, we compress it. We’re cramming a lot of material into a small space, which […]

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Variable Speed Compressors

Multi-speed compressors are a step in the right direction, but what about outright variable speed ones? Think about it, a two or three speed compressor has to pick the best speed for a given environment and it can only run at those two speeds. When it’s incredibly hot, full speed ahead. When it’s cooler, low speed. In between however, it becomes a game of the lesser evils.   Fixed-Speed Flaws This fixed-speed issue can be a bigger problem in the right scenarios. There’s only really a handful of conditions where the compressor can hit peak efficiency. You can crawl around the parking lot or go at highway blazing speeds, but you have no support for those middle roads between town. The same is true of the two speed compressor. The system can be forced to oscillate between stages or even be trapped in a single stage if the conditions are right. When it’s hot out, you’ll never get to use that second, lower speed. When it’s in between, the low speed might not be able to keep up and it’ll have to cycle between speeds, never really saving anything or improving comfort. It’ll almost always be this battle of the lesser evils: power hungry high speed and be too cool or have to work on wider margins of error, or fighting a losing battle with the low speed constantly running and only delaying the inevitable need for the high speed […]

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Multi-Stage Compressors

We often think of compressors as single-state devices. They’re on and they’re off. This holds true for most window units, portable indoor units, and even a number of central cooling systems. This simplifies things and lets us save power. Compressor on, hit target temperature, shut down. It’s better than running the compressor 24/7 and achieves the desired result.   Full Throttle The problem with this is that we have to constantly cycle. Imagine if your car had 1 speed. Instead of a gas pedal, you just had a button. Push the button, your engine revs itself through the roof, you do a burn out from your driveway, let off the button to avoid the kid running into the street, and you come to a dead stop in seconds. That’s how a single-stage compressor works and it’s a little wasteful. With this back and forth, on and off approach, you can never actually hit a precise temperature. You just hit a temperature range. When the thermostat is set to say 70 degrees, the air conditioner kicks on and runs until the room is approximately 65 degrees. Later, when the room has warmed to 75 degrees, it turns back on again. If we were to run the compressor at 71 degrees, it would be too soon, we’d be constantly starting and stopping. The air conditioner only spits out one temperature of air: really cold. If you run at 71 degrees, by the […]

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Why Are Compressors Measured in Tons?

When we look at compressors, there are a lot of numbers going around, but one of the bigger ones is the Tons. We sell compressors in all manner of weight-ratings, from less than a ton to hundreds of tons. The thing is though, this doesn’t mean we need a crane and a massive truck to load the compressor before it ships out. Compressor tonage is not actually a measure of weight. In fact, it is the result of some weird and convoluted math and history.   Old Fashioned AC Before we had the modern air conditioner, there were just a handful of ways to actually cool a room or a building. You could open a window, sit in front of a fan, use an evaporative cooler, or get a block of ice. That’s right, once upon a time we didn’t just have “ice boxes”, we had ice-conditioning too. The precursor to modern refrigeration was massive chunks of ice, usually cut from frozen lakes in the north and hastily delivered anywhere cooling was needed. You would go down to your local ice house and buy however much your fridge or cooling system needed. For building-scale cooling, there would be a block of ice essentially placed in a special cabinet in the air ducts and fans would blow air over it. The ice would remove heat from the air and melt. The air would be cooled and circulated around the room or […]

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What About the Other Compressors?

Just how many ways are there to squeeze down a gas? If you look at the entirety of the industrial world, there’s probably a few hundred different devices. If you look at HVAC, luckily the list is a lot shorter. The air conditioning world relies primarily on five compressor designs.   Reciprocating This compressor works pretty much exactly the same as a car engine does, but without the gasoline and combustion. Inside a car you have your cylinders and pistons. When the piston moves up it compresses, when it goes down it sucks. The same principal is used in a reciprocating compressor. At the base of the compressor there will generally be an electric motor, which turns a shaft. The shaft has a bend in it to allow for offset motion. At the bend there’s a connecting rod, which links the shaft to the piston. When the shaft spins, the piston moves up and down. On the downstroke, fresh refrigerant is pulled in. On the up stroke the refrigerant is compressed and injected into the refrigerant loop. This particular design is popular in residential scale compressors. There are more parts involved, so there’s a greater chance of hardware failure, but the well understood nature of the piston and cylinder as well as massive manufacturing tolerances make them cheap to manufacture. Consider, steam engines were around in the 1800s, and this is the same principle as their driving pistons. The complexity […]

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How Does a Scroll Compressor Work?

Once upon a time, I thought there was really just one kind of compressor. How many ways can their possibly be to make something smaller? Turns out, quite a few. Each type of compressor has its own quirks. Some designs are more efficient. Some require less maintenance. There’s just this endless list of trade offs in designs to get a […]

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Can Cold Weather Damage my AC?

Winter is slowly coming. Here on the East Coast, we’re starting to see a gradual cool down as Summer turns to Fall. We’re probably near our last week of 80 degree weather if we’re not seeing it already. That means we need to talk about shutting down the AC. In most cases, you can’t run the air conditioning through a North Eastern winter. Cold weather can, and will destroy your central air, split system, rooftop and window units.   The Water Problem The air conditioners we have today have a dangerous relationship with water. Back in the early 1900s, air conditioners started out as enormous, expensive dehumidifiers. The fact that these machines cooled the air was just a side effect until people started to like the idea of comfortable work places. This means that air conditioners collect water. Water vapor in the atmosphere will condense on anything cold, such as the evaporator coil in the home or the tubing connecting indoor and outdoor components together. This isn’t normally much of an issue. In fact, during the summer it’s a good thing. The water collecting on the system helps it to better conduct heat and ultimately operates more efficiently. During the winter however, things become more problematic. Between the cold air and the cold AC, all that condensed water is going to freeze somewhere along the line. It becomes an issue of keeping the air conditioner warm with the air from […]

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Albert Einstein Designed a Fridge

We all know Einstein as the man who invented E=MC2. He also used experiments to find Avogadro’s Number, proposed that light was not just a wave but also a particle (a photon), created the General Theory of Relativity, and among all his accomplishments, designed a fridge without a single moving part. As with all things in our industry, this relied on cheating the laws of physics into doing our bidding.   Motivation The first refrigerators were deadly machines. They used a similar compression system to what we have today, but there was a catch. The new technology had a short lifetime before failure and when it did fail, it failed deadly. At the time, there were three major refrigerants: methyl chloride, ammonia, and sulfur dioxide. Methyl Chloride can disrupt the central nervous system, starting with drunken symptoms and ending at paralysis, coma, and death. Ammonia is incredibly corrosive and will cause irritation of the skin, eyes, and lungs before more severe symptoms such as blindness and death by lung failure set in. Sulfur Dioxide is similar to ammonia, it attacks the skin and mucous membranes, and with the right circumstances can damage and destroy the lungs, and even interfere in the heart. The seals on early fridges would fail at random due to the newness of the technology, variations in product quality, and perhaps even outright design flaws. When such a failure occurred, toxic gasses got into the air, and […]

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