Why The Thermostat’s Wrong

Thermostats are a great technology in principal. They automate a simple issue: if cold, turn on the heater. Before thermostats, someone would have to either stoke a fire or open a valve for hot water to flow. By comparison, any automation should seam brilliant, but there is a slight flaw.   Single Point of Reference In most homes and even small businesses, there’s a single thermostat, and it measures the temperature in a single place. Even in a smaller home, this can lead to drastically different temperatures across the building. Typically a thermostat’s in the center of the building to get the best ‘average’ temperature. This average however, is almost never correct. In the case of my own home, we can actually measure the temperature difference between rooms. My room is the second on the heating loop, and consequently has some of the hottest water delivered to it, the most available energy. By the time this water has reached the kitchen and living room at the end of the loop, the water’s significantly cooled, resulting in a potentially 10 degree temperature difference. These differences can be exacerbated by design flaws. The bedrooms in this house, for example, have base boards that are about half the circumference of the rooms. This allows for a ton of heat to be left in these rooms. The living areas of this house however, have a much, much lower ratio. Those baseboards are only able […]

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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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How to Pick a Thermostat

We talked about installing a Thermostat and a little bit of the install process. Today, we’re going to look a little deeper into the factors and reasoning behind picking the perfect thermostat for your needs.   The Key Factors What type of HVAC System do you have? Heating, cooling, multizone? What can your existing system support? What do you want out of your new thermostat? Efficiency, ease of use, programmability, automation? If you can answer these questions, you can begin to narrow down what type of thermostats will fit your needs. There is a wide range of options out there, from simple, old fashioned set it and forget it units straight up to smart thermostats that detect and learn the building’s occupancy over time. Let’s dig a little deeper.   The Existing Hardware Your first concern is going to be making the best out of the hardware you’re already using. If you own a multizone system, it would be a tremendous step backwards to install a single, old fashioned thermostat for the whole building. If you own a simple hot water furnace with some radiators in a single zone system, a multi-room thermostat is probably going to be overpriced for the limited returns it can deliver. If there’s a full heating and cooling system, that too needs to be factored in. There are thermostats out there which are heating only. There’s probably even thermostats out there which are cooling only […]

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Gas Furnace Ignition

We’ve talked a lot about the safety systems keeping your furnace from burning down the building or blowing up your building. This all begs the question: how do we get the flame started in the first place? It’s actually not a fully straight forward answer, and it varies by fuel source and furnace design.   The Old Fashioned Pilot Light In days long-gone, a furnace needed a constant flame to light it’s burner. This was called a Pilot Light. It was just a tiny, constant little flame like a lit candle. When the burner started, it simply had to turn the gas on and the pilot would ensure that the whole burner lit afterwards. The solution worked well enough, but by modern standards is an incredibly wasteful way to run a furnace. In systems with an always-on pilot light, fuel would always be getting burned, even if there wasn’t heating anything. Overtime, this adds up to hundreds and thousands of gallons of wasted fuel. It certainly worked for a time when we had no better alternatives but it’s a relic in today’s high-efficiency world.   Intermittent Pilots One of the major hurdles of moving on from a pilot was creating enough energy to light the fuel. It takes more than just a spark for ignition, it can take significant voltage. Between the fuel mixture, spark size, spark temperature, and everything else, it’s a difficult ballet to directly, electrically light a […]

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Measuring the Heat

Have you ever wondered how your heating system knows to turn on? Or to turn off? You could say “the furnace controller tells it to” and “the thermostat tells it to,” but that’s not the whole picture, is it? We need a way to measure the temperature inside the furnace and inside our homes. It has to be durable, reliable, and affordable. It doesn’t have to be precise, but it must be right every time it’s measured.   A Complex Web of Technology There are a staggering number of ways to control a furnace through temperature input. A brief and nowhere near all-inclusive list of techniques include: Gas Expansion Tubes, Bi-Metal Switches, Bi-Metal Coils, Thermocouples Driven by a Pilot-Light, Thermistors, and of course modern IR Temperature Sensors found in your enthusiast-chef’s kitchen. These devices are all in some way sensitive to the heat. Bi-Metal systems expand as temperatures change. Measuring the expansion reads the approximate temperature. Gas Expansion Tubes have an internal change in pressure as temperature changes. The pressure can be used to calculate temperature. Thermocouples generate an electrical current when they’re heated. Measuring the current allows you to determine the temperature. Inside a furnace, they’re often heated directly by the pilot light or burner to read flame temperatures. Infrared Thermometers measure “Blackbody (Wikipedia Link)” radiation, but aren’t all that effective around metals or the air. And lastly, we have the humble Thermistor, which varies it’s resistance based on […]

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Why Use an Electric Actuator?

In many ways, electric actuators are the holy grail. They are precise, efficient, fast to respond, have low support requirements, can be bought cheaply, can be easily retrofitted into existing environments, and in principal can be configured for absurd output torque. There aren’t a lot of downsides here. We’ve harnessed hydraulic and pneumatic power to move things, but that was always a multi-step procedure. With electronics? Nearly everything is built right into the actuator.   Minimal Install Requirements Facilities using hydraulics and pneumatics need to provide hoses, valves, pumps, compressors, reservoirs, and more. It’s a lot of hardware just to make something move. That’s a lot of money, maintenance time, and space just to have your fully automated, multi-zone heating system. It’s a lot even if you’re automating a brewery or bakery, where the equipment will ultimately save time and money. Facilities using electrical actuators however, need only provide power and control signals. In some cases, multi-phase power is required, but that mostly boils down to some extra electrical panels and service wires. Each actuator is pretty much independent and will operate regardless of what the rest of the facility is doing. That’s less hardware to keep track of, fewer failure points, and overall easier maintenance. In terms of a retrofit in existing facilities, that pretty much means you remove the old actuator, install the new one, and plug it in. In principal, it’ll just plugin and work. It’s hard […]

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Multizone Systems: The Single Flow Problem

Over the past several posts, we’ve been hitting on the big deal with multi-zone HVAC Systems. You can attain amazing levels of control over how hot or cold any given room is. That is, except for one problem: you can only really push one “direction” at a time without making things incredibly complex.   One Temperature Change Suppose most of your building is set around sixty eight degrees. Maybe one room wants seventy four and another sixty. The temperature outside is a warm but not unbearable eighty seven degrees. Our multi-zone system kicks in and sends exactly the right amount of cold air to exactly the right rooms as needed to achieve those desired temperatures. All sounds good, right? What if someone wanted their room to be ninety eight degrees? Maybe they’re curing concrete or they’re homesick for some equatorial inferno. This shouldn’t be a problem for our amazing system, right? Just raise the thermostat and hot air will come pouring into the room? We’ve been presenting the most straight forward, affordable, and common multi-zone system: one set of ducts, and one set of pipes. In order to heat that one room above the outdoor ambient temperature, the furnace and cooling system would be running at the same time. They would both be pushing hot or cold material into the building’s one distribution system. The air or water would mix and become the median temperature, something neither hot nor cold […]

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Multizone HVAC: Forced Air Systems

Forced Air HVAC systems are an ideal candidate for a multizone installation or even retrofitting the necessary controls to an existing system. With air-based systems, leaks are easy enough to fix and it’s pretty straight forward to add in dampers, sensors, and the central control hardware without majorly disrupting the system. In contrast, water based heating systems require the lines to be drained, soldering, and a lot of effort to seal leaks in tight spaces.   The Basics Your standard, single zone/whole building forced air system is going to come down to the furnace/air conditioner, a bunch of ducts, some sensors, vents where it feeds into the rooms, and probably a single thermostat. By adding some sensors and controls, this easily turns into a multi-zone system. All we have to do is block the flow of air in strategic locations and have some central hardware manage the strategy for where air should and should not flow. Blocking the air flow is achieved with a damper and an actuator to control it. These come in a variety of shapes and sizes to accommodate near any system. They fit in over other pieces of duct work and get wired into a central control that sets how opened or closed that damper needs to be, to achieve the desired temperature. In principal, these can simply be added as part of a new installation, or put in place of an existing piece of duct […]

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Multizone HVAC: The Ductless System

Multizone systems can be big, complicated, and a challenge to cram into small spaces. If you’re using hot and cold water for your heating and cooling, you need to install valves and actuators everywhere, possibly install a whole second set of pipes for a “dual pipe” system that meets any need, and make sure you can pump enough water to satisfy the beast. In forced air applications, you would have to tear apart your ducts to add the controls and fans, then spend ages locating and sealing every leaking part. This nets you a working system, but it could be better and easier.   The Central Problem We tend to centralize our HVAC hardware as much as possible. You do all your heating and cooling in one place, then send the air or water around the building. It makes a lot of sense. You only need one or two boilers for most places, even industrial settings. Put it all in one place and save on energy costs and complexity, except when you want granular control. With a central heat or cooling source, you need to add tons of controls to manage the flow hot and cold air. You’ll lose a lot of energy by sending air and water around too. Leaks in air ducts and pipes radiating heat into the open air pose annoying losses in efficiency. There’s only so much you can do to fight nature’s hell-bent desire to […]

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What is a Multi-Zone System?

Most residential and older HVAC Systems have one enormous flaw: They don’t provide a uniform or even well controlled environment. These simpler systems have one point of measuring temperature, and generally have to just hope that the single thermostat is a good representation of the temperature in the house. In practical terms, this means one room can be twenty degrees hotter than the rest of the building or a good draft from a single window can fool the thermostat into roasting everyone. This is the old way of doing things, from before we had cheap electronics and a mature industry to deliver on our comforts day and night. Take for example, my house. It was built probably in the late 1940s or early 1950s with hot water heat, two floors, and a single thermostat in the center of a house. This proves to be a challenge in the winter. The rooms first on the heating loops will become scorching hot. You open a window in those rooms and they become comfortable. The cold draft blows into the other rooms and they’re suddenly not comfortable. We might bake in the kitchen one night, whipping up a lovely ten to fifteen degrees of extra warmth, which happens to heat the thermostat. The kitchen eventually becomes comfortable, but the bed rooms freeze over.   Single Zone Systems This single-thermostat arrangement is called a Single-Zone system. There’s one data sample and one place all […]

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