PDF《Design Guide》

s effectiveness. Therm is a unit of heat energy that is used for converting a volume of gas to its heat equivalent to calculate the actual energy use. Thermal efficiency is a dimensionless performance measure of a water heater;

expressed as a percentage it is heat (energy) output divided by heat (energy) input. Improving Hot Water System Performance Design Guide C Energy Efficient Water Heating, Delivery and Use C 3.26.10

4 Design Path for Savings: A Systems Perspective Designing in a reverse direction, starting with the hot water using equipment and moving back to the water heater, is an effective thought process to achieve high system efficiency and performance. Reducing hot water consumption not only results in lower water and sewer costs;

it is the most effective way to reduce water heating energy. This simple tactic is overlooked as operators do not receive a dedicated bill for hot water use C they just don'

t see the dollars going down the drain. Step 1: Designers should start by specifying high-performance equipment and accessories that use less hot water. The best location in the kitchen to achieve savings is the dish room, where the largest portion of hot water is consumed. Reducing the water use per rack of the dishwasher and flow rate of the pre-rinse spray valve is the foundation of an optimized hot water system. Step 2: The distribution system is the second target. Delivering hot water more efficiently yields permanent energy savings and improved system performance. Once the fixtures and the sanitation equipment are specified, the placement of sinks and equipment in relation to the water heater is a key factor to the efficiency and performance of the distribution system. Step 3: The heart of the system is the water heater. If natural gas is the energy choice, specifying high-efficiency [condensing] water heaters, either storage or tankless, is imperative. Step 4: Before the hot water system design is finalized, consider integrating pre- heating technologies such as refrigerant heat recovery, dishwasher heat recovery or solar. Step 5: Proper installation and simple monitoring equipment can play an important role in commissioning and maintaining the system. Verify that the blueprints enable the contractor to build to the specifications. Requiring that the contractor take digital photographs of the entire hot water distribution system (before it is concealed by drywall) is one way to secure pipe layout and insulation specifications. Design Path for Savings Specify efficient hot water using equipment and fixtures. Specify branch and twig sizing and pipe insulation to meet plumbing codes and satisfy water flow requirements including: time to tap, volume, temperature, and water velocity. Optimize posi........