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By Rani Fischer, Eng. WaterPath Engineering Consultant
Limescale settles and forms in water systems when the concentration of salts in the water is greater than its solubility in given conditions. Most of the salts that settle are, of course, insoluble salts.
At high temperatures (above 50 degrees Celsius), the calcium in the water crystallizes into a kind of hard stone known as limescale, which previously appeared as water-soluble calcium. Limescale can settle and accumulate not only in high temperature conditions, but also when there is a change in the turbulence of the water and it is penetrated by air (desalinated water), and when there is a change in pressure. This limescale buildup manifests itself both in the pipe system and the various heating elements in household appliances: kettles, boilers, washing machines and solar collectors.
The problem of limescale buildup in household appliances manifests itself in two main ways:
a) Decreased capacity for water conduction of the domestic pipe system due to a buildup of limescale on the pipe walls, consequently reducing their diameters and conduction capacity.
b) Limescale buildup on heating elements constituting an insulator that keeps them from properly doing their job, i.e., heating the water. This leads to financial expenses to pay both for the extra ongoing energy consumption required for heating as well as for replacement of those heating elements more frequently than is necessary.
Calculating the Projected Savings from Limescale Removal
The calculation is divided into two parts:
a) Removal of limescale from heating elements in boilers -
energy savings
The following calculation shows the expected savings in three different situations involving limescale buildup on a boiler heating element, after the limescale is completely removed and the element is cleaned.
Calculation assumptions:
1) Limescale thickness and its effect on energy consumption:
In our examination, we will relate to three situations:
| Limescale Thickness (mm) |
Added Energy Consumption (%) |
| 1 |
7% |
| 3 |
22% |
| 6 |
38% |
2) An electrical boiler has a capacity of 2.5 KW.
3) The average family (5 people) operates the boiler an average of
about three-and-a-half hours a day per year.
4) Therefore, the theoretical average electricity consumption for
operating a boiler (without limescale) is:
3.5 hours x 2.5 KW x 365 days = 3,193 KWh/year
5) Cost per KWh of household consumption: KWh/NIS 0.425
Projected Savings:
The theoretical average annual energy consumption:
3,193 KWh X NIS 0.425 = NIS 1,357/year
| Limescale Thickness (mm) |
Annual Savings (NIS) |
| 1 |
95 |
| 3 |
298 |
| 6 |
516 |
Obviously, the more limescale removed, the greater the savings.
b) Removing limescale from heating elements in boilers saves wear and tear
Removing limescale from water pipes directly affects their conduction capacity and extends the life of the boiler, in general, and the solar collectors, in particular.
Assuming that an electrical boiler system plus collectors costs about NIS 4,000 and its average lifespan is about 8 years, each one-year extension to the life of the system will save the owner about NIS 500/year
(without interest calculations).
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