White Paper – Cure for the Cold Water Sandwich Effect

Electric Mini-Tank Water Heater…A Key Ingredient for Ideal Hot Water Blend

By Jens Bolleyer

In a home, the introduction of cold water into the hot water supply line can be bothersome –as well as costly – when water is wasted down the drain. Fixtures are turned on and off quickly and frequently throughout any given day. Typical hot water daily usage includes: 10 to 12 minutes in the shower, washing hands in the sink, washing the dishes by hand or running the dishwasher, and the occasional load of laundry on the hot setting. There is a need throughout the day for hot water on demand.

What causes the Cold Water Sandwich Effect? When a sink or shower is turned on, the water flows through the gas tankless water heater detecting the call for hot water. Water flow and temperature is monitored to adjust the flow of gas to the burner. A signal is sent to the control board, which then looks at multiple factors, including: incoming water temperature, desired water temperature as set on the thermostat, and calculated difference between the two temperatures. Then, the electronic ignition sequence begins. Water is heated to the desired temperature as it circulates through the heater. When the hot water tap is turned off, the gas tankless water heater shuts down. It takes about 10 seconds for the ignition sequence in most gas heaters to restart, and this is when cold water is introduced into the home’s hot water system. When hot water is stopped, then started again, the ignition sequence is repeated. This small, yet noticeable amount of cold water passing through the heater during the sequence creates the “Cold Water Sandwich Effect.”

A Perfect Blend

Utilizing an Eemax Mini Tank Water Heater as a mixing tank to blend cold and hot water is a simple and cost-effective solution which will eliminate the Cold Water Sandwich. Integrating the Mini Tank into the hot water outlet of a gas tankless heater (as indicated in the diagram below) removes the Cold Water Sandwich Effect. The Eemax Mini Tank eliminates the cold water flow from the fixture, delivering the perfect hot water temperature that is expected when the faucet is turned on.

They may be small, but deliver BIG results…Eemax Mini Tanks fit virtually anywhere and go where larger water tank heaters can’t. They are ideal for under-the-sink hand washing and kitchen areas in residential, commercial, or industrial settings. An Eemax Mini Tank is easy to install, offers great cost value, plugs directly into a 110/120 volt wall outlet, and is floor or wall mountable. For medium to large applications, use a 6 gallon (EMT6) or a 4 gallon (EMT4) heater. For smaller applications, use the 2.5 gallon (EMT2.5).

With unbeatable recovery times, the Eemax Mini Tanks ensure hot water where and when it’s needed, eliminating the cold water sandwich effect.

        Eemax Mini-Tanks At-a-Glance:

•    Utilized in conjunction with a gas tankless water heater to eliminate the Cold Water Sandwich
•    Point-of-use, ideal for under the sink
•    Easy installation with 120V outlet plug
•    Small, compact, wall or floor mountable
•    No need for costly re-circulating lines and pumps
•    Adjustable temperature range 50°F to 140°F
•    Glass lined for long life
•    Quick recovery time

To learn more, please visit www.eemax.com/PointOfUseMiniTanks

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