Clean Your Coils

Most people think that it’s only the filters that get dirty. That’s almost right. Almost. Your filters are going to be the first thing you notice being incredibly gross, but the entire HVAC system is exposed to the same types of dirt, pollen, and mold. These can sometimes get past the filter, but that’s not where the biggest problems lay. Efficiency The key parts to your HVAC system are often radiators of some sort (depending on the type of system). If you have hot water heat, you probably have baseboards, which are essentially radiators. Your air conditioner has two radiators, a condenser and an evaporator (these usually called Coils). The job of these devices is to move heat from one place to another. In some places we take heat from the air and put it into a refrigerant. in other cases we take it from the refrigerant and put it in the air. When these things are designed, engineers use materials that are known to have incredible thermal conduction capabilities. We know that paper is an awful thermal conductor and that metals tend to be amazing conductors. Beyond that, we know that specific metals are better conductors than others, conduct into the air better, and we know the number of fins and distance between them necessary to get amazing performance. Under ideal circumstances, especially when these products are fresh and new, they will work flawlessly. When the coils are all […]

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Why Steam Heat?

There are a lot of ways to heat your building. Forced air and hot water heat are the most common today, but it’s also possible to use steam.  You might think that steam and water based systems would be almost the same, but they’re actually very different. The Cheap Installation In a traditional hot water system, water flows from radiator to radiator, then back to the furnace to be reheated and recirculated. In a steam system, you don’t need that return pipe. When the steam condenses, it’ll collect at the bottom of the pipe and drip its way back to the furnace the same way it came. The hot steam meanwhile will fill the top of the pipe. This sort of system has traditionally been incredibly popular in tall buildings, such as the skyscrapers in New York city. Being able to use just a handful of stand pipes to provide heat to the entire structure was a massive cost savings. You could essentially build a heating system with half the pipes involved. At the same time, steam heating could be incredibly efficient for a zone-like installation. Many radiators featured shut off valves, allowing a room’s occupant to manually manage the heat. Unused room? Shut off the valve. Too hot? Shut off the valve. It was manual work, but in the right setting, it saved on heating needs. Once one of these radiators became heated, they would also provide heat for […]

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Why is There a Belt in the Furnace?

Is it weird that we use belt drives in furnaces? Belts aren’t necessarily known as the most durable or flame-resistant thing in the world. Why would we put a belt next to a roaring inferno? It’s 2018, why don’t we just bolt the motor straight to the fan, blower, or whatever it is we’re driving?   Gear Reduction Spinning blowers, fans, and other equipment requires a lot of mechanical power. At the same time, it can take more power to overcome the friction on a resting object, especially for heavier parts or equipment that’s not perfectly supported. There can be additional friction by such offset loads. Providing enough force to move this equipment requires bigger and bigger motors. Or does it? Physics is full of tricks. We can use a concept called Gear Reduction so that a smaller motor can get the job done. Instead of outputting a lot of power at once, we output less power, but more revolutions of the motor. For every 2 rotations of the motor, the blower might only spin once. This reduction requires the motor to spin faster to achieve the same result as a bigger motor, but it won’t need as much torque to do that work. The easiest way to see this concept in action is to look at a multi-speed bike. Your gears are different sizes to allow for different speeds. In low gear, it is incredibly easy to spin 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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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 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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We still use Ice in AC TODAY!?

In the early days, perhaps up to the 1950s or so, Ice was your standard cooling solution. If you didn’t have a refrigerator, you had an ice box. This solution wasn’t as on-demand as modern AC, but it had a nice benefit: no high electricity bills. Every summer as we turn to AC to avoid sweating to death, we’re faced with our soaring cooling bills. With this in mind, some manufacturers actually still use ice in HVAC systems today.   Why ICE? Prior to the invention of air conditioning, ice was pretty much the only cooling thing available. Today, we have a million and one ways to cool things, but they don’t entirely hold up to ice. Water by itself is amazing at storing and conducting energy. Just think of the last major snow storm and how long it took for that to melt off afterwards. North of Philly here, our last major storm dropped eight inches or so that actually stuck to the ground and it took days of 50+ degree weather for it to melt. This makes Ice an excellent way to store “coolness”. On top of that, water is non-toxic, abundant, easy to store, and easy to cool. The other famous alternative might be liquid helium or liquid nitrogen, both of which are used in industrial cooling applications such as MRI machines and particle accelerators. The problem is that they’re not easy to cool, can involve vast […]

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Blizzard Testing Your HVAC System

Can you tell it’s winter yet? Is it safe to come out yet? Here in the North East, Mother Nature has just finished her first major storm of the season. We can confirm that no one at Procure is interested in living in the far, Arctic North after experiencing days-straight of subzero temperatures. We were within spitting distance of water being able to freeze before it hits the ground. Along the way, we also got to push our heating systems to their edges and see where we really should’ve built things differently. Edge Case Testing During normal operation, it’s doubtful you’ll ever see something out of place in a well designed heating system. If you engineered a system for an average winter, then chances are you can turn your home or office any temperature you like during average weather. It can be ten degrees outside, but a sweltering 92 inside. When nature throws you a curve ball you get to see where the weaknesses are in your heating system. More extreme weather, is more stress on the system. More stress is going to show you what parts can’t keep up. This breaks down to a problem of numbers. The sum-total of heat you can put in the air is XX. Your building loses heat to the air at a rate of YY. Severe winds increase this rate by ZZ. In order to stay warm XX needs to be greater than […]

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Why is my 2 Stage Furnace Always Running?

After our talk on short cycling, we came across people with the opposite complaint: their furnaces were running constantly. As opposed to constant short cycling, these people were experiencing some form of long cycle. Their furnace would fire up, warm the office, and then keep running. There would be constant, mechanical sound from the machine. This is exactly what it’s supposed to do.   Wasted Heat In a single stage furnace, the thermostat calls for heat, the furnace runs, and once the target temperature is reached, it all shuts down. This is horrendously wasteful. Your furnace has just  burned fuel or used electricity to get a heat exchanger red hot. When the furnace shuts down, that heat exchanger is still roasting, glowing red, but its not using that heat. The heat exchanger will just sit there, cool down, and an extra ten, twenty, or even thirty minutes of warmth has just been completely wasted. The excess heat in the exchanger will go into the ambient air in the furnace. It might heat some of the basement or perhaps the furnace will have a tiny bit less work to do next time. In any event, it’s resources spent that aren’t making you more comfortable. This situation is analogous to approaching a red light, flooring the car, and then slamming on your brakes. All that gas to speed up is probably being burned for nothing.   Using Idle Heat There’s not really much […]

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The Origins of the HEPA Filter: Nuclear Research

There has been some… grim news recently about a possible war between the US and North Korea over their developing nuclear capabilities. There is a ray of light though, in this grim news. It gives us an excuse to talk about HEPA Filters. It turns out, they were created specifically because of nuclear research and the fall out of nuclear weapons.   Filters Before HEPA Air filters have been around for a long time. The first air filters can be traced all the way back to the 1500s, a primitive respirator to protect the wearer from gases, dust, and fumes. Damp-cloth respirators started to come around in the 18th and 19th century. These used damp wool and valves to filter dust out of the air. The liquid-based approach would end up expanding to water and oil bath systems that essentially washed the air. Most contaminants would end up dissolved or pushed down in the water, while the air could eventually pass through. This technology was used on cars, trucks, tractors, and even some early air conditioning systems. It was pretty much the only known way to clean the air. At the time, there were no electron microscopes and the concept of cells and bacteria was still pretty new. There simply hadn’t been research into all the little things in the air and how effective or ineffective the existing filters were beyond subjective opinions. In the 1940s, there came a very […]

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