National Oilheat Research Alliance 23 are idle losses. The Energy Factors for new oil direct-fired water heaters range from .5 to .68. This means that 50 to 68 percent of the potential energy in the fuel is converted into hot water and stays in the hot water until it is used. Water heaters are also rated by the First Hour Rating. This indicates how many gallons of hot water that can be produced by the water heater in one hour of operation. To understand the efficiency of indirect water heating (where boiler water is used to heat domestic water) requires an understanding of the efficiency of the boiler. The secondary considerations involve heat transfer and storage. There is no government or industry-wide sanctioned way to measure the efficiency of indirect water heaters. Integrated Space and Water Heating Systems Many boiler manufacturers offer an integrated system, featuring an external plate-type heat exchanger and storage tank or hot-coil water heater. They use a low, or at least lower, mass boiler combined with a control system. Systems that are designed to do both space and water heating offer efficiency that is far superior to any of the other systems. Water Heater Energy Conservation Strategies Insulate the pipes Insulating hot water pipes can save energy. Savings depend upon the location of the tank and pipes in the building. If the tank and pipes are located in the living area, then any heat they lose helps heat the building. However, in the summer, they are making the air-conditioning work harder. Installing heat traps on the inlets and outlets of non-circulating water heaters and tanks reduces buoyancy-induced flow (hot water rises) of hot water through the piping, where it loses heat to the building interior. These simple pipe loops reduce unintended hot water circulation for a small installation cost, with typical paybacks of less than a year. Heat traps are already built into many high-efficiency water heaters and the addition of external traps is redundant. Also, insulating the cold water intake piping next to the water heater connection reduces losses from the hot water heater conducting heat to the cold water pipe. Recommend Water Conditioning Hard water is very tough on any water heating system. Hard water causes lime (calcium) deposits on heat exchanger surfaces, in lines and valves. The lime will cause reduction in performance and can lead to insufficient hot water and wasted energy. This calcium build up must be removed periodically. Over time, calcium will build up and it is necessary to flush the sediment out of the bottom of the water heater tank. To eliminate the need for coil cleaning, recommend that customers with hard water install water softeners. Acidic water will attack pipes and tanks. In such cases, you should recommend acid neutralizers to customers. Hot Water Conservation Low-flow showerheads and faucet aerators, cold-water rinse cycles for the washing machine and fixing leaking faucets can save significant amounts of hot water. Which water heater is best? For a furnace or large hot water demand relative to the heat load, the best option is the high-recovery, direct-fired, oil-powered water heater. If the customer has a reasonably efficient boiler, they are better off with a storagetank type indirect water heater because there is only one burner heating both the space and the water. The best system of all is an integrated boiler with an indirect water heater and a storage tank system.
NORA Advanced Efficiency
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