Electric hot water heaters covered here are mainly for residential water heating use and we will guide you through the main categories, popular brands, advantages, disadvantages and the main parts.
Depending on the size of your house and your needs, you can find electric water heaters different in size, small like point-of-use or lowboy, medium size like tankless and big tank-type used for commercial and residential domestic water and radiant heating.
Water heating process in tank-type electrical hot water heaters is very simple. There are usually two heating elements, submerged inside the water, one in the middle of the tank and one at the bottom, and two thermostats, one for each heater.
Cold water enters the tank heater through the dip tube and fills it from bottom up.
The top thermostat which is pressed against the tank, controls the upper heating element and turns it on when there is a need.
Cold water is becoming warmer and when it reaches the pre-set temperature the power is switched from the upper to lower heating element.
Now the bottom thermostat, which controls the lower heating element, turns the element on until the water temperature reaches the pre-set value.
Safety device, high-limit switch, reacts if the water becomes too hot, cutting the power to heating elements.
Once you open hot water tap, hot water is drawn from the top of the water tank, at the same time cold water enters the tank, drops the temperature that triggers the thermostat. The whole water heating process starts all over again.
If there is an excessive pressure in that tank, because of the high water temperature, another safety device called pressure relief valve reacts.
Thermostat is a switch and it can sense a change in water temperature. The switch closes to allow current flow and it opens when the temperature of hot water reaches its preset limit.
The current passes through electrical-resistance heating elements, power is delivered and it heats the water to the correct pre-set temperature.
The heating elements continue to carry current until the thermostats are satisfied. These heating elements are very efficient, providing about 99 per cent of the available heat to the surrounding water.
On some tanks the thermostat has a mark showing a maximum temperature and where to set the temperature that provides energy savings and scald protection.
The advantage of electric hot water heaters over gas or oil fired is that heating elements have longer life expectancy as they wear and tear less.
Money saving tips:
To reduce the heat loss through the bottom of the electric water tank heater, place the tank over a thick layer of firm thermal insulation.
Reducing the temperature setting by 10 degrees F you can save between 2-5% of your electricity costs.
Note: An electric water heater is typically a better selection than fuel fired units if the installation is limited to the middle part of your home. And the price is better.
Electric hot water heaters with the tankless technology provide hot water on demand, meaning that water never runs out. They have a compact, small design that saves a lot of space. Stiebel Eltron and PowerStar from Bosch are good examples.
You can put them anywhere, bathroom, kitchen, closet, even under the sink.
As they are far less to leak, prone to the hard water and sediments, they maintain the efficiency for a very long time.
Tiny point-of-use electric water heaters, tank type, like Ariston from Bosch, are with small capacities usually installed in the kitchen, bathrooms and above the sink and good enough for small hot water jobs, like hand-washing, shaving and dishwashing.
Cylindrical steel tank holds the hot water. Typical sizes for residential electrical hot water heaters are 40, 50, 60 and 80 gallons.
To keep the rust out of the water, steel tank has a bonded glass liner.
Insulation - helps to keep heat inside the tank longer.
Cold water inlet and hot water outlet, or pipes.
Thermostats to control the water temperature inside the tank.
Heating elements to heat the water, usually two of them.
Drain valve that allows you to drain the tank.
Temperature and pressure relief valve (TPR) - safety feature.
Even with low recovery rate, their advantage is high tank capacity.
Can be installed in many areas of your home.
Can be installed close to the actual point-of-use.
Various sizes and models.
No venting needed, there are no exhaust gases.
Pricing electric hot water heaters; they cost significantly less than gas heaters.
Longer service life.
Energy efficiency goes to 99%.
Electricity reaches more households than gas.
Electric tankless water heaters are one third of the size than gas heating systems.
Very little maintenance needed, easy to clean.
Much easier to diagnose the problem, troubleshoot and repair.
They are safe.
Expensive to operate, electricity is more expensive than gas.
Low recovery rate.
Electric tankless water heaters are high amperage devices and when the hot water is used during the peak times its operating cost increases.
Even with the lower cost for installation, you have to consider an adequate electrical supply, to support this high output hot water heating appliance.
The biggest problem with electric hot water heaters is that they lose heat through the surface of the tank, as a result of standby losses.
They fall into the category of water heaters with low recovery rates (the lowest actually) meaning that it takes longer to heat the water.
Solution for this problem is to cover them with a specially designed insulation blanket or "jacket".
Bosch - PowerStar electric tankless are designed to replace tank-type electric hot water heaters, with 90 % efficiency rating.
Bosch - Ariston point of use electric hot water heaters, modern Italian design; mini tank electric heaters with one of the highest recovery rate.
German quality, Tempra from Stiebel Eltron, is one of the most technologically advanced and top selling electric tankless water heaters available.
Rheem/Marathon electric water heaters; 40 and 50-gallon.
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