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Guide to Electric Shower Heads - Instant Hot Showers
Shower Water Heaters
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Point of use electric shower heaters: Dur-o-Matic, Marey, Steibel Eltron, other hot water brands.
Tankless water heaters = demand water heaters = instantaneous water heaters
Detailed explanation of how tankless hot water heaters work, what they cost, what are their operating characteristics, pro's and con's.
Questions & answers about electric shower water heater heads: choices, installation, performance, safety

Electric shower heaters: this article explains the operating characteristics of electric shower heaters, also called instant water heaters or "on demand" water heaters for point of use at shower heads.

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Readers should also see Tankless Water Heaters. Photos of electric shower heaters are courtesy of Arlene Puentes.

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A Guide to Electric Shower Water Heaters

An instant hot water point of use system like the shower heaters we show here are a very different approach to making hot water for bathing than the tankless water heaters discussed above. These electric shower heads work where the incoming water temperature is pretty high to start and where the water flow rate is modest.

Electric shower water heaters are typically used where a central hot water heater is not installed. The heater is installed directly on the shower water piping at the location where a conventional shower head would otherwise be found.

Several companies, including Dur-o-Matic and Marey (shown below) and Steibel Eltron produce point of use electric heaters such as the electric shower heaters shown here.

These electric point of use water heaters are typically installed in buildings where no water heater or hot water source has been provided.

When a sensor in the shower head detects water flowing, the electrical heating element turns on. An electrical element heats water as it enters and flows through the unit, drawing typically about 23 amps (when wired at 110V 2400 watts) or 13.5 amps (when wired at 220V 2900 watts).

The temperature of the hot water received depends on the flow rate through the heater.

Slower flow rate yields hotter water. Flow rates are limited, however, with a maximum water pressure of 2 gpm and a minimum water pressure (to activate the unit) of 0.83 gpm. The average water temperature increase across this range is 10-25 degF.

That means that if the incoming water temperature is 42 deg.F. (northern U.S. and Canada) your hot shower might reach 67 deg.F. at the slowest flow rate of less than 1 gpm. Not a hot shower.

These point of use electric showers are intended to work in areas where the incoming water is already not very cold, such as the more tropical climate of Puerto Rico, where Duro-Matic is based.

The Mini Marey tankless shower heater (photo at left) is advertised for use in boats, cabins,campers, recreational vehicles (RV showers), mobile homes, apartments where no central water heater is provided.

Puentes, who inspected a large number of electric shower installations in Puerto Rico in 2009 reported that perhaps because these devices were installed in homes of people of limited means, many of them were simply turned off entirely in an effort to reduce the occupant's electrical bill.

We found the exposed electrical wiring at some of these point of use electric shower heaters disconcerting and a possible electrocution hazard, particularly where the wiring was not GFCI protected. Be sure that your electric shower heater is wired according to local and national electrical codes.

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ALTERNATIVE HOT WATER SOURCES
  Electric Shower Heaters
  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 Arlene Puentes for photographs of a variety of electric shower heaters in use in Puerto Rico and for technical contribution to this article - 07/15/2010. Arlene Puentes is a licensed home inspector, past chapter president of the Hudson Valley chapter of the American Society of Home Inspectors, an educator, and building failures researcher in Kingston, NY who can be reached at ap@octoberhome.htm or at 845-339-7984. Ms. Puentes website www.octoberhome.com contains additional information.
Dur-o-Matic point of use electric shower heaters - Duromatic of Puerto Rico Inc - Rio Piedras, Puerto Rico, 787-764-4490
Marey electric point of use shower heaters: http://www.marey.com/english_/home.htm "Marey electric shower water heaters are installed directly on the shower water pipe. These heaters are commonly used where central hot water is not available."
Marey electric point of use shower heaters (and also Marey propane gas tankless water heaters) are distributed in North America by Mark Brant at www.tanklesshq.com where you can view their Marey electric shower water heaters at http://tankless-water-heaters.ecrater.com/category.php?cid=292215
Stiebel Eltron Tankless Water Heaters - http://www.stiebel-eltron-usa.com/

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A Guide to Electric Shower Water Heaters

Questions & Answers regarding this article

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Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair