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Electric shower heater (C) D Friedman A PuentesGuide to Electric Shower Heads - Instant Hot Showers
Shower Water Heaters

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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- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

A Guide to Electric Shower Water Heaters

Electric shower heater (C) D Friedman A PuentesAn 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.

Marey electric shower heater (C) D Friedman A Puentes

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.

Question: how do I choose & set voltage for an electric shower heater?

I want to buy one does products but I don't know how many volt it - Elid Barahona 11/5/11

Reply:

From an anonymous reader:

For Elid Barahona, Answer is: The Duromatic Electrical Instantaneous water heater is powered by 120 volts.
El calentador de agua eléctrico instantáneo Duromatic utiliza 120 voltios.

It's an excellent product. We installed it inside the wall May of 2008 & never a problem.
Es un producto excelente. Lo instalamos dentro de la pared en Mayo del 2008 y funciona bien. - Anon

We add that the voltage choices (120V or 240V) depend on

- what voltage you have at the building (in the U.S. usually 240V but certainly not everywhere)

- choice to spend a little more on wiring or on the device to save on hot water heating costs (240V is generally more efficient)

Photos of electric shower heaters used in the article above are used with permission and were provided courtesy of Arlene Puentes.

Electric Shower Heater Sources & Guides

Drakken iHEAT electric shower head cited & discussed at InspectApedia.com

Illustration: Drakken's iHEAT electric shower head cited below.

Electric shower heater sold at Amazon

Above: an electric shower heater-head made in China and sold on Amazon (4/27/2020) - no IO manual found.

Below: Marey Electric point of use electric shower heaters in the company's two current models, the Marey Mini and the Marey Aquamatic electric shower heaters.

Marey mini electric shower heater at InspectApedia.com ... Marey electric shower water heater at InspectApedia.com

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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-11-15 by Inspectapedia Com Moderator (mod) - proper electrical receptacle for a tankless electric shower water heater

@Anonymous,

Thanks for that helpful question on the ampacity required for electric shower water heaters.

A quick look at a typical Marey shower water heater like the Aquamatic Manual given above on this page shows us that the 110VAC model of the shower heater draws 23.5A so you'd need a 30A circuit to support the heater.

Two types of 30A electrical receptacles - at InspectApedia.comI agree that the use of what looks like a typical 20A electrical receptacle is confusing, but keep in mind that the company is telling you that the receptacle must be on a dedicated circuit - so nothing else ought to be plugged in there. And notice also that it's a single receptacle, not a duplex one.

You'll see in our illustration below, looking at the Bryant 30A receptacle, that there are, in fact, 30A electrical receptacles that look much like a conventional 20A device.

But watch out: the Marey illustration may be confusing or misleading.

In the U.S. the NEC 210.21(B) specifies that you can NOT use a 30A breaker to power a 20A receptacle. The receptacle must itself be rated for 30A.

US NEC 210.21(B) Receptacles.

(1) Single Receptacle on an Individual Branch Circuit.

A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

So if you have a Marey document that says otherwise, please let us know, or use our page top or bottom EMAIL contact to send us the document.

On 2021-11-1 by Anonymous

Marey electric shower heater plug receptacle at InspectApedia.com

why does the Mini Marey 110 V electric shower head use a plug for a 20 Amp receptacle, but requires a 30 Amp circuit?

On 2019-05-08 by (mod)

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.

On 2019-05-06 by Elvis King

I am trying to source some elements for my Dur o matic system. I am in Barbados and bought this system which works very well I must admit from Puerto Rico a while back but never used it until now. Can you tell me where I can source some elements for a 110/120 V system?!! Thanks in advance!!

On 2019-05-06 by Afternoon sir,

I need to get some elements for the Dur o matic 110/120V system. Can you point me as to where I can source some of these elements?!!

On 2018-02-20 by (mod)

Here's a packaging example provided by reader

IMAGE LOST by older version of Clark Van Oyen’s Comments Box code - now fixed. Please re-post the image if you can. Sorry. Mod.

On 2018-01-25 by (mod) - contact information for Dur-o-Matic shower heaters

Depending on where you live Duromatic shower heaters are sold in Puerto Rico
Dur O Matic Of Puerto Rico Inc
1005 Ave. Americo Miranda
San Juan, PR 00921
Tel: (787) 764-4490 / (787) 764-4780

Similar products in the UK are sold by Triton http://www.tritonshowers.co.uk/

Similar products are available from Marey - https://marey.com/

On 2018-01-24 by Bryan G

Wow, we are both trying to find the part or the company's contact information

On 2018-01-24 2 by Ken

I need an element for a Duromatic but can't find one. How do I contact them?


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