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NORA Advanced Efficiency

when it is off. That means there are virtually no stand-by losses. Be sure to consider how the entire system is operating and make any needed changes that minimize heat loss. Don’t forget to use combustion test instruments when installing the new unit. It is the only reliable way to reach the highest possible operating efficiency. Boiler Water Temperature Reset, and Electrically Commutated Magnetic Motors The ideal heating system would operate continuously, supplying only the heat needed to replace the heat lost through the building envelope. The room temperature would never change. However, heating systems provide short bursts of heat followed by periods of no heat. As a result, room temperatures go up and down. Manufacturers have developed a number of strategies to try to keep the house at a fairly uniform, comfortable temperature. Electrically Commutated Magenetic Motors (ECM) on blowers and circulators vary the speed the air or water moves through the heating system, 26 National Oilheat Research Alliance better matching the heat delivered to the room to the heat lost through the envelope. Temperature Reset is a control strategy that adjusts appliance water temperatures to provide more heat when it’s colder and less heat when it’s warmer. There are two types of boiler temperature reset controls available today: indoor and outdoor. Outdoor reset controls adjust the temperature in the boiler based on the outdoor air temperature. As the outdoor temperature rises, the control lowers the boiler water temperature to meet the reduced space heating demand, lowering off-cycle heat losses for most of the heating season. Indoor reset controls adjust the boiler temperature to meet the actual heating needs of a home, based on how cool the water from the radiator pipes is when it returns to the boiler. Fuel saving for temperature modulation controls depends upon the initial off-cycle heat loss and the degree to which the boiler temperature is reduced. Typical savings of 10% are expected for older burner-boilers with large heat losses when automatic controls are applied. Thermal Purge Controls Thermal purge controls anticipate the end of a thermostat call and keep the zone valve open to send the energy left in the boiler to the building or domestic water heater, similar to the way the fan on a furnace continues to run after the thermostat shuts off the burner. These controls are most effective with boilers with low water volume, as they have very little energy left to purge when the thermostat is satisfied. This greatly reduces both off-cycle losses and losses caused by oversizing. Laboratory studies show that this type of integrated operation can save 20% to 40% over Consider the Heating System Factors The following heating system factors affect overall efficiency: • Proper boiler or furnace sizing • Chimney draft • Source of combustion air • Burner design and static air pressure • Zoning of the distribution system • Pipe and duct insulation and air duct leakage • Source of domestic hot water.


NORA Advanced Efficiency
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