Oil-fired condensing boilers are uncommon in the U.S. Some controls are standard features in new boilers, while others can be added on to save energy (see the “Modifications by Heating System Technicians” section on the heating maintenance page).Īs with furnaces, condensing gas-fired boilers are relatively common, and significantly more efficient than non-condensing boilers (unless very sophisticated controls are employed).
#Steam radiant heating system install
Although the cost is not trivial, it is generally much easier to install “zone” thermostats and controls for individual rooms with a hydronic system than with forced air. Important boiler controls include thermostats, aquastats, and valves that regulate circulation and water temperature. Some hot water systems circulate water through plastic tubing in the floor, a system called radiant floor heating (see “State of the Art Heating”). Instead of a fan and duct system, a boiler uses a pump to circulate hot water through pipes to radiators. In steam boilers, which are much less common in homes today, the water is boiled and steam carries heat through the house, condensing to water in the radiators as it cools. Residential boilers generally use natural gas or heating oil for fuel. Hot water systems are often called hydronic systems. The cooler water then returns to the boiler to be reheated. While furnaces carry heat in warm air, boiler systems distribute the heat in hot water, which gives up heat as it passes through radiators or other devices in rooms throughout the house. Boilersīoilers are special-purpose water heaters. The higher the AFUE, the more efficient the furnace or boiler. AFUE is like your car mileage between fill-ups, including both highway driving and stop-and-go traffic. AFUE accounts for start-up, cool-down, and other operating losses that occur in real operating conditions, and includes an estimate of electricity used by the air handler, inducer fan, and controls. AFUE estimates seasonal efficiency, averaging peak and part-load situations. In the U.S., furnace efficiency is regulated by minimum AFUE (Annual Fuel Utilization Efficiency). Combustion efficiency is like the miles per gallon your car gets cruising along at 55 miles per hour on the highway. Combustion efficiency is the simplest measure it is just the system’s efficiency while it is running. The efficiency of a fossil-fuel furnace or boiler is a measure of the amount of useful heat produced per unit of input energy (fuel). The best gas furnaces and boilers today have efficiencies over 90% But, there are other internal controls in a heating system, such as “high limit” switches that are part of an invisible but critical set of safety controls. A typical forced air system will have a single thermostat. The most important control from your standpoint is the thermostat, which turns the system - or at least the distribution system - on and off to keep you comfortable. Heating system controls regulate when the various components of the heating system turn on and off. The current furnace standards have not been updated since 1987. Department of Energy, and are due to be finalized in the spring of 2016. New furnace standards are currently under development by the U.S.
These typically vent through a sidewall with a plastic pipe. This is the primary feature of a high-efficiency furnace (or boiler). “Condensing” furnaces are designed to reclaim much of this escaping heat by cooling exhaust gases well below 140☏, where water vapor in the exhaust condenses into water. Current minimum-efficiency furnaces reduce this waste substantially by using an “inducer” fan to pull the exhaust gases through the heat exchanger and induce draft in the chimney. Older “atmospheric” furnaces vented directly to the atmosphere, and wasted about 30% of the fuel energy just to keep the exhaust hot enough to safely rise through the chimney. At the furnace, combustion products are vented out of the building through a flue pipe. Air is pushed through the heat exchanger by the “air handler’s” furnace fan and then forced through the ductwork downstream of the heat exchanger. The flames heat a metal heat exchanger where the heat is transferred to air. Inside a gas- or oil-fired furnace, the fuel is mixed with air and burned. It can be powered by electricity, natural gas, or fuel oil. This type of heating system is called a ducted warm-air or forced warm-air distribution system. A furnace works by blowing heated air through ducts that deliver the warm air to rooms throughout the house via air registers or grills. The majority of North American households depend on a central furnace to provide heat.
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