Don’t Clean Your Coils

With a Pressure Washer We previously mentioned that clean evaporator and condenser coils are happy coils. Dirt and debris builds up, restricts airflow, and prevents the coils from doing their job. Recently we realized, while there is a right way and a wrong way to do everything, there is a really wrong way to clean your air conditioner. High Powered Cleaning Suppose you need to clean something that’s incredibly ground in. You might scrape at it, or find someway to break up its edges and get under the layer of dirt to pry it up. It’s going to take forever, require a lot of work, but eventually gets the job done. What if you could instantly apply all that force to every weak spot in the dirty build up, and just blast it apart? This is in part, how a pressure washer works. On the one hand, we’re applying a massive amount of force in a small area. Any imperfections or weak points are going to make the substance fracture. The water will shoot through the dirt, and then blast outwards and send it to bits. On the other hand, water isn’t exactly abrasive like sand, BUT it will carry away a little more material with every drop that hits. Detergents can be added to the mix to chemically breakdown whatever it is that’s getting sprayed. If there’s an especially solid build up, you can essentially blast and melt it […]

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Glas’s Growing Pains

The smart thermostat market is a crowded, complex mess of competing designs, features, and ideas. Some designers are integrating popular assistant tools like Alexa. Some are integrating with smart home standards like Z-wave to expand their ecosystem. There’s some out there that are just trying to enter the market before it becomes too crowded, regardless of how ready they are to do it.   Johnson’s Glas Last spring, Johnson Controls released a new smart thermostat of their own: Glas. They created a cool, futuristic design. There’s a transparent screen, support for multiple assistants, and a rare sensor in these thermostats: an air quality sensor. On paper, this sounds like a winner in the smart thermostat market, but there’s a catch: the software’s not quite perfect yet. Johnson has managed to put out the hardware of a really cool device, but it’s real promise is in the future, the features yet to come. Right now, reviewers and customers alike have come across some short comings we all hope Johnson will address in software updates in the months to come. Users have complained about the lack of support for remote sensors, the lack of custom events, and other shortcomings in just how much of their smart thermostat they can control. We’ve already seen over the past few months some improvements. Customers’ complaints have gone from the thermostat having bugs or being slow, to a desire for new features instead. The good news […]

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The Air Conditioner is my Heater?!

Air Conditioners don’t necessarily just cool your building. An air conditioner essentially moves heat from one place to another. In the case of your typical AC set up, we absorb the heat in your office and we put it outside with a gigantic condenser coil. What if we did the opposite?   Air Conditioning the Outside Speaking in terms of pure-physics, there’s pretty much always heat outside. To us living, breathing creatures, 0 degrees may seem like there is no-heat, but to a physicist, that’s orders of magnitude above the coldest cold possible “absolute zero.” That means we can put that ‘heat’ to use. In a configuration like this, the outdoor coil will become incredibly cold. This will allow it to absorb heat from the outside air and bring it indoors. Inside, the refrigerant is condensed and we basically get heat. We’re literally switching the roles of a traditional air conditioner. Systems such as this are often called Heat Pumps. Technically speaking, anything that moves warmth is a heat-pump, even an air conditioner or a fridge, but the term in particular is related to using air conditioning hardware for heating purposes.   The Extra Hardware Achieving this requires some special tweaks. If we’re going to have an air-conditioning-heater, we need some extra valves, control logic, and tweaking the design of your coils. Your coils will now both be able to function as evaporator and condenser coils. There’ll be two expansion […]

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Fall AC Maintenance

It’s getting cooler outside. The high today in Philly isn’t even 80 degrees. Just a week or two ago we couldn’t go a day without seeing 90. In another few weeks, we’ll be struggling to see the 70s and we’ll be turning to warmer clothes for the start of fall. As with all things, that means now is about the best time to prepare for winter with some pre-emptive maintenance and cleaning.   We’re Going to Maintain Something… We Won’t Be Using? It’s always best to work on things when you don’t need them and better still to work on them just a little ahead of time. The weather outside is nice and pleasant right now. You can walk outside in a T-shirt and not feel like your arms are going to freeze off. It’s a good time to do any outdoor work before mother nature gives you a nice, awful cold for your troubles. In the case of your air conditioner, there’s a fair bit you can do to get ready ahead of the season. You can clean the area around your condenser, your HVAC contractor can clean out the drainage connections for the drip pan, you can order a protective cover to keep your condenser free of debris throughout the winter, and you can do one last inspection for any worn parts. There is some logic to all of this. Debris is going to trap water from rain […]

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Evolution of Air Conditioners

When Air Conditioners first came out, they were a commercial-only piece of equipment. They were almost always custom designed and installed equipment. The first major system was built by Willis Carrier to regulate humidity for a printing company. There was no going out to the store or your contractor to buy this technology. It was made from scratch.   Public AC The first air conditioners were installed in factories. These started out with textile mills and pharmaceutical companies in the 1910s. In the 1920s, department stores and movie theaters would start investing in air conditioners. In these days, a large department store could get hot enough for customers and workers alike to faint. Cool stores attracted customers looking to escape the heat. The Milam Building, in San Antonio, Texas would later be built specifically to be air conditioned from top to bottom. The entire building had special accommodations built-in to ensure consistent airflow to every floor, room, and store. This custom system was first put to use in 1928 and would not be retired until 1989 after a full 60 years of service. These innovations all lead to better technology, but it still was not accessible. These 1920s systems were hand-designed, in many cases by Willis Carrier himself. His sales team could pitch an air conditioner to any client for any purpose and he would design whatever it took to make it work. This isn’t entirely unique today, but at […]

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History of Refrigerants

The concept of mechanical refrigeration starts back in the 1750s. Researchers knew nothing about cooling except that pressure and gasses somehow played a key roll in absorbing and removing heat. In these early days, everything was tried as a refrigerant: ammonia, alcohol, air, carbon dioxide, and more. It was the days of trial and error to create the robust understanding of physics and chemistry we have today.   Low Temperature Boiling The first experiments in refrigeration used Ether and Alcohol, which are readily evaporated. At sea level, Ether boils at 94F and Alcohol can boil as low as 151F, depending on the exact chemical form. Sea level is important here, as pressure changes the boiling point. Lowering the pressure causes a decrease in the boiling point. These gasses with low boiling points were ideal for early experiments. The first experiments used vacuum chambers and potentially some custom hardware. There isn’t a lot needed to build a basic vacuum chamber. A jar with a good seal, a hose, and a pump can create a vacuum. An observable refrigeration can be done with almost no special equipment at all. At this scale, cooling was possible, but not feasible. Alcohol, Ether, and other chemicals were common and easy to acquire, but no one was going to put a chunk of meat in a vacuum chamber, cover it in alcohol, wait for it to freeze, and try to store it somewhere. There had to […]

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The Fridge Came First

Every now and then, we discover the weirdest facets of fate and history. We’re all familiar with Carrier’s major break through in creating air conditioning in the early 1900s, but it turns out, he wasn’t exactly the first. There were working, mechanical refrigerators before we had working air conditioners.   The Ground Work The first artificial refrigeration was done by a Scottish professor in the 1755. He used a vacuum chamber and ether to lower the temperature inside the chamber. When the ether boiled, it removed energy from the chamber, cooling it down. The effect was just powerful enough to produce some ice inside. In 1758, Ben Franklin and John Hadley at Cambridge University would conduct similar experiments with volatile liquids. They were able to cool a  chamber now to 7 degrees fahrenheit, from an ambient 65 degree starting point. Franklin wrote, “From this experiment, one may see the possibility of freezing a man to death on a warm summer’s day.” At that point in time, there wasn’t yet a practical way to actually freeze anyone. This refrigeration involved a vacuum chamber. Anyone cooled down would be all but freeze dried in the process. Further refinements would come over the next century. In 1820 there was a closed-cycle system that could continuously cool a chamber and condense it’s refrigerant, it would be able to keep cool indefinitely. In the 1860s, German researchers began work on refrigeration for breweries. During the […]

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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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High Voltage in AC

Your air conditioner (and whole HVAC system) are a strange mix of parts. On the one side, we have low voltage, DC electronics that couldn’t tickle a fly. On the other, we have high voltage, AC equipment that could turn an ill-prepared reptile or rodent into a charred chunk of bones. How exactly do we mate these two, different systems together safely?   The Safety Issue In all electronics, we strive to separate high voltage and low voltage. We don’t want them to touch each other. In some systems, you have no choice but to put high and low voltage equipment on the same board, in other cases you try to keep them on separate boards altogether. If there’s any sort of electrical short between high voltage and low voltage, the low side is going to get destroyed. That’s your best case scenario. 240 volts or 440 volts blasting into some tiny microprocessors and capacitors, which then explode in a terrifying, but mostly harmless show of pyrotechnics. If the board is really well built, a diode will take the brunt of the failure before anything scary does. Sometimes though, these shorts don’t go like that. Some older equipment or equipment which never passed any reviews like Underwriters’ Laboratories can send high voltage straight to frame components, a button, or other areas where a user could come in contact with it. 220 Volts is not a pleasant experience, let me tell […]

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Why Are There So Many Fins in a Coil?

If you look really close at your air conditioner’s evaporator or condenser coil, you’ll see a ton of tiny fins sandwiched between two tubes. You might ask yourself, why are we making this so fragile. A screwdriver could puncture these fins with just the smallest bit of force, let alone what some ice could do. Why are we using such tiny parts instead of just a few, massive fins or something more robust?   Old Radiators Let’s start with a trip to the past: the classic heating radiator. A radiator like this is just another type of heat exchanger, almost the same thing as your air conditioner’s coils, but designed to heat the home or office. These were massive, robust pieces of equipment. They weighed hundreds of pounds of cast iron and could break your foot, leg, and back all at once during a botched installation. These work on the same principle as other heat exchangers: we change the temperature of the heat exchanger, and it in turn changes the temperature of the air. With such beefy components though, it requires a lot of water or steam to make any significant changes. Sure, the radiator will get hot enough to fry an egg or reduce just about anything to a piece of charcoal, but it doesn’t have a lot of contact with the air. It ends up being slower as a result.   Surface Area When we radiate or absorb […]

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