One of the most frequently asked questions we receive from potential residential Zeta Rod customers is whether the Zeta Rod will help protect their Tankless Water Heater from scaling. The answer is: "Yes, the Zeta Rod will prevent scale deposits from forming on the tankless water heater pipes".
The following is a brief description on how tankless water heaters work and why are they susceptible to scale deposits forming on their pipes.
Tankless water heaters are gaining popularity over the older tank water heater model. Some of the advantages that tankless water heaters offer over the older tank design include: reduced floor space, lower energy consumption and endless hot water available on demand .
Tankless water heaters work by rapidly heating the water in a heat exchanger to the desired temperature as the water flows through the heater. The burner of the unit only turns on when there is demand for hot water, this is how it is able to use less energy while providing endless hot water. Older model hot water heaters store water in a tank and heat it up with a burner (or electric heating elements) when the water drops below a certain temperature. This has the inconvenience that the burner may turn on even when there is no demand for hot water. The following diagram shows a simplified version of a tankless water heater.
Because of the design of the tankless heaters, the water is heated at a very fast rate, forcing the water to come in contact with very hot surfaces on the pipes as it goes through the heat exchanger. This provides conditions that favor minerals in the water to precipitate and form scale deposits on the tube walls. In places with hard water the problem is exacerbated and precautions must be taken to prevent scaling of the heat exchanger tubes.
Mineral scale is primarily composed of calcium carbonate (hardness in the water) which precipitates from the water under certain conditions (such as high temperature, high pH or high concentrations). Scale has a very low heat transfer coefficient, or thermal conductivity. The thermal conductivity of copper is 384 W/(m*K) and the thermal conductivity of scale is 2.6 W/(m*K). This means that scale is about 140 times less efficient in transferring heat than the copper which is used in the tankless heater pipes. The following graph shows the amount of energy increase that would be required to overcome a layer of scale.
The lower thermal conductivity of scale has a direct negative effect on the performance of the tankless water heater. Since the amount of heat transfered to the water is reduced, the unit would have to operate at a higher rate in order to try to get the water to the design temperature, which in turn would result in higher energy consumption. If the scale is thick enough, the unit may not be able to heat the water to the desired temperature at all. And if scaling is very aggressive, water flow can be restricted through the unit and it eventually could lead to tube failure.
The Zeta Rod is an ideal low cost and environmentally friendly option to prevent scale formation in tankless water heaters. A Zeta Rod installed in the main water line entering a home will protect the tankless water heater as well as all the fixtures in the house. The following pictures are courtesy of R&G Sales and show a Zeta Rod displayed with a Noritz Tankless Water Heater at Central Arizona Supply. At this show room's display the Zeta Rod protects the tankless heater and the shower fixtures. This picture shows the small floor space that both the tankless heater and the Zeta Rod take.
