It’s getting colder out, and most homes are starting to rely more and more on that big tank of water pumping out heat: your boiler. Maybe it’s tucked away in a tight closet, or maybe it’s out for all to see in your laundry room or basement. Either way, there’s no doubt it’s getting more use now, so it’s not a bad idea to get it inspected by a technician before you can’t go a day without it.
While that boiler is chugging away, what exactly is it doing? In this article, we’ll talk about the various parts of a boiler system and how they all work together to bring comfort to your home, office, or other building structure. While we’re at it, we’ll throw in a few tips on how you can increase energy efficiency and save some money this winter. Maybe you can use that money to take on that bathroom remodeling project you’ve been waiting on (see our other article this month for some bathroom DIY tips). Or maybe you could buy a nice coat and stay warm outside too! It’s always good to get some fresh air…
So first off, let’s come up with a simple, yet descriptive description of a boiler: A boiler is a closed tank in which water is heated under pressure. Pressure in the tank is helpful for easing pumping and driving up temperatures. This pressure is created just by the fact that the tank is completely closed, which also leads to less corrosion, since there’s minimal exposure to oxygen and other elements/particles in the air. Now how does a hot tank of pressurized water help heat our homes? To answer that, let’s explore what other parts there are in a boiler and how they work together to create a complete heating system.
In order to heat the water, we need a fuel source. The flow of that fuel source will typically be controlled by a valve (the above picture is of a gas boiler, so it has a gas valve). The fuel is then burned by the burner, which controls the amount of air that mixes with the fuel to maximize the efficiency of the combustion. The hot gases produced from the fuel burning are then sent through a heat exchanger, which transfers heat from the gases to the water in the tank. Depending on the type of boiler, that water might turn into steam or just remain as hot water, but we’ll get to that in a minute. After heating the water, the combustion gases are then vented out of the house using a chimney or other venting system. If the venting system is not properly designed, installed, and maintained, it may cause carbon monoxide to build up in the home or be a fire hazard. Meanwhile, the hot water or steam travels through a piping system to deliver heat to where it is needed and then makes its way back to begin the process again. In addition to these parts, every boiler has external controls that can be used to manually or automatically regulate temperature and maximize efficiency. Soon we’ll talk about how these controls can save you a good deal of money, especially in climates where the temperature likes to fluctuate.
As mentioned above, there are two ways that a boiler can deliver heat. One way is to heat the water in the boiler until it boils, creating hot steam. Since steam is lighter than air, it rises without any mechanical assistance to the highest point in the system, usually a radiator. The radiator acts as a heat exchanger, and the steam gives off its heat to the surrounding air and condenses back to water (see our heat pump article for details on this heat exchanging process). Since this water is heavier than the steam surrounding it, it falls through the piping system back to the boiler where it is heated until it turns into steam and begins to rise again. Another way to deliver heat is to heat water up to a selected temperature below its boiling point and send the hot water itself to radiators around the building. Because hot water will only rise very slowly, this type of delivery system requires a pump to circulate the water from the boiler to the radiators. As in steam delivery boilers, once the water has given its heat to the air, it returns to the boiler to be heated again.
With a solid, basic understanding of how a boiler system works, let’s talk about how you can manage the efficiency of your boiler. One way is by making sure that you are only producing the amount of heat that you need and not more. Some boilers only have one stage, meaning they are either off or firing full at power. Some boilers, though, have multiple firing stages, which are controlled by your thermostat. When your thermostat determines that less heat is needed to reach a desired indoor temperature, the boiler will only fire at partial power. When you need more heat, the boiler will boost its firing rate to the next stage, and so on until the boiler is eventually firing at 100% power. While staging boilers have only a few discrete firing levels, modulating boilers allow for the adjustment of firing rate on a continuous scale for even more efficiency. The range of the scale is predetermined and typically not all-inclusive, but modulating boilers allow you to more finely tune the output of your boiler to match the needs of your home.
One way to further match a boiler’s output to actual conditions and increase efficiency is through the use of an outdoor reset control. Both staging and modulating boilers will adjust their firing rate based on the current and desired indoor temperature, as described above. Outdoor reset controls add one more important piece of information to the equation – the outdoor temperature. It will take less energy to heat a space by a given amount if it’s warm outside than if it’s cold outside. To take advantage of this, an outdoor reset control selects the lowest possible water temperature necessary to deliver just the amount of heat required to heat your home and no more. The colder the water leaving (and therefore returning) to a boiler, the more efficiently it is able to operate. In fact, outdoor reset controls can save you about 10% per year on energy costs. Considering that they are simple to add on to your existing boiler, making your boiler smarter with an outdoor reset control is almost a no-brainer!
If you’re looking into getting a new boiler altogether, consider a boiler that takes advantage of condensing technology, such as the Vitodens 200 series by Viessmann. When standard boiler fuels, such as natural gas, propane, or oil, are burned in the presence of oxygen, the combustion produces a variety of gases including water vapor. Conventional boilers allow the combustion gases to leave through the vent after passing through the heat exchanger, letting out all of the energy not captured by the heat exchanger. Condensing boilers save some of that wasted energy by capturing water vapor before it escapes through the vent, condensing it back to water, and using the latent heat from that phase change to support the heating system. While they cost more than conventional boilers, condensing boilers can save you another 10% in energy spending every year. That’s 20% in savings when combined with an outdoor reset control! Getting excited about remodeling that bathroom yet?
Hopefully at this point you’ve learned enough about your boiler to garner a greater appreciation for what this big, complex system is doing in your home. As they say, knowledge is power, and you now should have the power to save money on your heating bill this winter. First, get your boiler checked out by a technician to make sure it’s safe and ready for the long winter ahead. If you need a new boiler, look into getting a condensing boiler and save 10% on your energy bill. If you don’t need a need a new boiler (or even if you do), don’t forget to include an outdoor reset control to improve you boiler’s efficiency another 10%. With so much potential savings, you can feel confident that you’re going to stay comfortable all winter long.