5. OPEN FORUM HANDOUT 10-20-2014

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New high efficient ,boiler have helped the Sherburne County Government Center reduce its natural gas consumption by 12 percent. Case Study. Sherburne County Government Center New high efficient- boilers sane $1 o,000 in 2012 Aims and objectives. Struggling to maintain and keep two 2- million Btu per hour aging and inefficient boilers supplied with natural gas, the Sherburne County Government Center in Elk River sought improvements to save energy and reduce utility bills. It decided to replace the aging hot water boilers with high efficiency units. Implementation. The existing boilers` efficiency was estimated at 75 percent. Sherburne County installed two 91 percent efficient condensing boilers at the 160,000 square -foot Government Center, built in 1965. Kevin Anderson, Sherburne County building facilities manager, says they are now able to run the heating system at lower temperatures so that the return temperature to the boiler is 130 degrees F or below. With the new equipment the county no longer needs to pay for expensive repairs to the old boilers; just a little preventive maintenance is needed, he says. Key to efficient boiler operation —low return water temperatures. Condensing boilers require a low return water temperature to operate at their highest efficiency, according to several sources, including information from the Center for Energy and Environment. In general, heating systems must be able to perform adequately at return water temperatures below about 130 degrees F in order to obtain boiler efficiencies above 87 percent (see Figure 1). Thus, the more hours during the heating season that the temperature of water returning to the boiler can be kept below that value, the higher will be the average seasonal efficiency. High - efficiency boilers are especially well suited to applications such as snow melting and in -floor radiant heating, because those applications typically have a large temperature drop and low return water temperatures. 27