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Here we discuss the life expectancy and warranty periods of tankless water heaters, also called instant water heaters or "on demand" water heaters.

We list typical and special applications of tankless or instantaneous water heaters in a variety of uses. Page top sketch of a point of use tankless water heater courtesy of Carson Dunlop.

© Copyright 2009 Daniel Friedman & Carson Dunlop Associates, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

List of Typical Tankless Water Heater Applications

Thermostatic Hot Water Booster Applications

A single point of use tankless water heater is installed where a boost in hot water temperature is needed such as

• Long pipe runs, slow hot water: In a building with long water piping runs the heat loss during delivery of hot water to distant fixtures as well as the delay in delivery of hot water are eliminated if a point of use tankless water heater is installed. If your concern is only the hot water delivery time, see How to Speed Up Delivery of Hot Water.
• High temperature applications: such as in restaurants, food processing, or other facilities where dishwashing requires a specific and high hot water temperature

Single point of use tankless water heater

• Limited hot water need: To support limited-requirement hot water flow requirements such as a low-usage restaurant bathroom
• Intermittent hot water need: to support delivery of hot water that is only occasionally needed in a building, avoiding conventional water heater standby energy losses.
• Home heating systems - water to air: Tankless water heaters may also be used to heat the home, either as part of a forced air combination system, or a radiant heating system.
• Driveway ice melting: Demand water heaters are also used for heated driveways.

Whole house tankless water heater

• To address the limited hot water flow capacity of tankless hot water heaters in a building where lots of hot water is run at once people may install a large unit - which may not be the most efficient design if you do not usually run lots of hot water at many fixtures at once.
  
  If the required hot water volume is large (serving multiple apartments or laundry facilities at once, for example) no single tankless water heater is likely to be sufficient.

Multiple or ganged tankless water heaters

• Install two or more individual and smaller tankless water heaters, possibly closer to their point of use - a more efficient design but possibly with a larger equipment and installation cost.

Indoor vs. Outdoor Tankless Water Heaters

Tankless water heaters are made in models designed to be installed outdoors, exposed to weather, or indoors in a protected area such as a basement or utility room or near a point of use.

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ALTERNATIVE HOT WATER SOURCES
  High Efficiency Water Heaters
  Indirect-fired Water Heaters
  Instantaneous Water Heaters
  Multiple water heaters in parallel
  Multiple water heaters in series
  Range Boiler Water Heaters
  Side Arm Coil Water Heaters
  Solar Water Heaters
  Tankless Coil for Hot Water
  Tankless Water Heaters
    Guide to Tankless Water Heaters
    Operation & Characteristics
    Problems & Defects
    Hot Water Delivery Speedup
    Installation Requirements & Costs
    Should I Convert to a Tankless Heater?
    Calculate Water Heater Requirements
    Capacities of Tankless Water Heaters
    Life Expectancy & Applications

• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Consumer Reports offers an article on the efficiency versus the economy of tankless water heaters - see http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/water-heaters/tankless-water-heaters/overview/tankless-water-heaters-ov.htm
• Bosch Tankless Water Heaters - http://www.boschhotwater.com/
• Chromolite Tankless Water Heaters
• Bradford White Everhot Tankless Water Heaters - Bradford White offers this step by step hot water retrofit installation file (large, slow PDF) - www.bradfordwhite.com
• Eemax Tankless Water Heaters - http://www.eemaxinc.com/
• Noritz Tankless Water Heaters - http://www.noritz.com/
• Rheem Tankless Water Heaters - http://www.rheemtankless.com/content/
• Rinnai Tankless Water Heaters - http://www.rinnai.us/tankless-water-heaters/
• Stiebel Eltron Tankless Water Heaters - http://www.stiebel-eltron-usa.com/
• Takagi USA Tankless Water Heaters - http://www.takagi.com/
• Titan Tankless Water Heaters - http://www.titanheater.com/
• U.S. Department of Energy on Tankless Water Heaters - http://apps1.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=12820

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