All about the water accumulator for diesel oil boilers

The immersion heater is one of the best inventions ever. Installing a container that constantly makes hot water available so that it is always ready when needed, favours great home comfort, in addition to helping to save fuel, reduce polluting emissions, protecting your pocket and extending the useful life of your boiler. In this article we will discuss all the details about the water storage tank for a diesel oil boiler: what it is, how it works, what types there are, its advantages, and some tips on how to install one correctly.

What we call a hot water accumulator for boilers

A hot water storage tank is an almost essential component of the heating system. And we say “almost” because not every boiler has an accumulator, despite the fact that the accumulation of hot water is one of the most efficient methods on the heating market. Its basic objective, as its name suggests, is to accumulate hot water for hours, in order to then be able to maintain a comfortable temperature in the home or on the premises.

From the point of view of autonomy, we can say that there are two types of accumulator: one is the tank that is added to the boiler, and another is the tank with its own capacity to heat the water without the need to be connected to a boiler. The first is called a hot water accumulator, and the second is called a thermal accumulator, or immersion heater:

  • Hot water accumulator: Water tank connected to a boiler, with the aim of storing hot water until there is demand. Its heat source is the heating boiler. It is considered a better energy saving resource.
  • Thermal accumulator, or immersion heater, is an autonomous water tank. It does not need to be connected to a boiler, since it heats the water by itself and distributes it through the home’s sanitary system. It incorporates a resistance isolated from water. It is thought that this uses more energy and costs more money than a hot water accumulator. However, as it does not require the resources of a heating boiler, it is a highly recommended alternative during the summer or at other times when the demand for domestic hot water is not as great.
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As we said above, a heating system does not have to include an accumulator. There are those that heat the water instantly. But the accumulator guarantees a supply of hot water without interruptions and without large investments. These are its greatest advantages compared to the thermal accumulator or heating without an accumulator.

How does a hot water accumulator for a boiler work?

Domestic hot water (DHW) has become an essential requirement for home comfort, and hot water storage tanks are very common in homes, because they help to minimise the electricity bill. Now we will talk about how this device that is present in so many homes works.

We have already said that the accumulator is a water tank (connected to the boiler). To this we must add that said tank is designed with a thermal insulating material that helps to conserve maximum heat over time. The water is heated by a coil whose energy comes from the boiler. The stored hot water is always available, at the exact moment it is required for sanitary or heating purposes.

The operation of a water accumulator is very simple but exact. It is based on the succession of charge and discharge cycles. Hot water loading usually occurs at night, while flushing cycles occur during the day, when hot water demand is much higher.

03 Schematic diagram of the relationship between the boiler.webp

One of the most effective ways to save

As we know, installing a thermostat is the most traditional way to make the boiler more efficient . But in addition to the thermostat, installing a storage tank in a boiler is also an effective means of saving: saving fuel, money… and environmental pollution. If the boiler does not have an accumulator, it will have to be running almost all the time, which will cause enormous energy consumption, large electricity bills, and great environmental pollution.

Instead, the stored hot water prevents the constant firing of the boiler, thus saving fuel and protecting the equipment from being overworked. For this to be more effective, the type and quality of thermal insulation that the accumulator has must be taken into account.

Poor or insufficient insulation will cause heat to escape into the environment, forcing the heater to use more energy to recover temperature. Adequate thermal insulation will be something that your economy will appreciate.

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Types of accumulator for boiler

There are several types of accumulator, and they can be classified from various points of view. One of them is the one we have already seen, which depends on the level of battery autonomy. Another point of view, closely related to the previous one, is the type of energy source used to heat the water.

Both the boiler heater and the autonomous heater or thermal accumulator can receive heat energy from different sources: a resistance current, gas, diesel, heat pump, biomass, or even solar energy. Some of these energy sources are more environmentally friendly and renewable than others. The boiler accumulator receives heat energy through a circuit that conducts a heat transfer liquid (water), but in the autonomous heater the water is heated directly.

From the point of view of where the energy source and heat exchanger of the accumulator are located, accumulators are classified into:

  • Direct accumulators (with internal energy source: electrical resistance, gas burner, etc.) They are not recommended for constant and prolonged use, because they are not economical. But they have the advantage of having a simple installation process and being able to meet large simultaneous demands.
  • Indirect accumulators (with external energy source: the boiler). In addition to the energy provided by the boiler, this type of accumulator requires an extra heat exchanger. The water tank has to be connected to the exchanger, and its capacity will promote a more dynamic operation. This equipment is capable of satisfying both punctual demands and longer consumption. As it accumulates hot water, it continues to heat more water.

There may be some differences between water heaters depending on the type or brand of boiler. For example, the water storage tank for a Ferroli diesel boiler is not identical to the water storage tank for a Roca diesel oil boiler. But the main characteristics of a hot water accumulator for boilers are maintained from one brand to the other. The storage capacity of the tank and its level of insulation can also vary depending on the manufacturer. There are 15 L and there are 1000 L, with all intermediate volume ranges.

05 Bathroom with boiler and hot water storage tank

Accumulators are often made of (stainless) steel, and include thermo vitrified and enamelled material, which maximises water quality and protects the equipment against corrosion or weather conditions. The insulation can be made of rigid polyurethane foam, which helps reduce the dissipation of thermal energy and makes the process of heating water and serving it to the home more efficient.

Accumulators can have horizontal or vertical design. Vertical models are well known and frequent, but horizontal models should not be ruled out. They are specially designed to be located just below the boiler, providing a sleek and compact overall design.

Differences between accumulator, inter accumulator and buffer accumulator

We have been talking about the accumulator so far. Let us only emphasise its mission of receiving the water from the boiler, accumulating it for as many hours as possible, and then being able to maintain the set temperature.

Now, the basic difference between a storage tank and a water storage tank is that the latter incorporates a coil inside, although it always needs to be connected to an external heat source (heating-only boiler, solar panels, or even wood stove). Thanks to this integrated coil and an internal thermostat, the storage tank is able to control and monitor the temperature of the sanitary water that is stored inside it, and remains ready to give the activation order to the external energy source when required.

Another accumulator variant is the so-called buffer accumulator. This type of accumulator is mainly used in pellet or biomass boilers. As these boilers do not produce domestic hot water directly, they need an accumulator. And since they turn off and the fuel can continue to burn, the best accumulator they can use is the inertial one.

The inertial storage tank allows us to manage the hot water demand in a very efficient way. It will only be necessary to turn on the boiler once every 2 or 3 days, and that will be enough for it to provide service and load the buffer tank with hot water.

Advantages of installing an accumulator to the boiler

  • The hot water accumulates, and thanks to that it is not necessary to turn on the boiler every time.
  • The heated water is kept at a constant temperature, without the typical rises and falls of when there is no accumulator.
  • The accumulator allows hot water to be used at 2 points in the home at the same time, without the temperature suddenly dropping in one of the points. This is so thanks to the fact that the water is already hot and previously accumulated.
  • It is more economical and less polluting to heat water from the energy of the same heating boiler than by means of electrical resistance from a thermos.
  • The accumulator is easier to adapt to solar energy heating systems, since the water can be heated during the day (or when there is sunshine) and stored for later use.
06 Man installing a heating boiler

Tips for installing a water accumulator for boilers

Installing a hot water tank is a complex and detailed procedure. Which means that the safest thing is to hire qualified personnel to do it. Hydraulic and electrical connections vary from brand to brand, and are best done by a technician or professional. These tips we give are very general.

Place the accumulator in a suitable place

The accumulators are usually made of very good material (that also depends on the brand), but they are not unbreakable. Therefore, to install your accumulator, choose a fairly dry place, away from the elements, wind, rain and snow. If your equipment is noisy, it should be located a little away from the most inhabited areas of the home, or in a room that can be closed and that is quite isolated in the sound sense.

» Locate it far enough away… but not too far

The location site must be selected according to the distance from the boiler and close to the areas where the hot water will be used in the home or the premises. In this way, temperature losses due to travel through the pipes are reduced and load losses are reduced to a minimum. The accumulator can be placed directly on the floor, or in a wall position using the included design details for it. If it is placed directly on the ground, it would be better if it is on a special base.

» Use proper tools to handle it

Always use suitable tools for the installation of the hot water accumulator, and in general for any type of installation or maintenance work on boilers. This will avoid unnecessary risks, such as breaking the part during installation, damaging the boiler by using imperfect or inaccurate tools, or promoting future breakdowns due to the part being installed incorrectly.

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Use the manufacturer’s connection kit

In order to simplify the process of installing the accumulator to the boiler, manufacturers usually include a special connection kit in the purchase. The kit (depending on the equipment) may include flexible pipes and connectors of the indicated diameter, joints, nipples, diverters, and sometimes Teflon. Use the kit, because it will always be the most accurate.

» It is mandatory to include protection against Legionella

Legionella is a bacterium that lives in natural or artificial water reservoirs, including hot water tanks and accumulators from DHW systems. Special care must be taken to implement anti-Legionella methods, especially in the case of heating accumulators in buildings. It is something that has been stipulated by law for a long time. The technician who installs the accumulator must include an anti-legionella disinfection system, and the accumulators must be installed in such a way that they always remain accessible for cleaning inside and out. (See more details in the IDAE manual .)

» Other safety measures: overpressure valve and valve for emptying

Something that must also be incorporated when installing a hot water storage tank is an overpressure valve that empties into the drain, and a key enabled to guarantee emptying whenever it is needed. They are both safety and hygiene components. In any case, they will facilitate the maintenance processes of the boiler and the heating system.

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Wide assortment of accumulators in Suner

If the time has come to replace your accumulator with a new one, or if you are thinking of buying a hot water accumulator for the first time, at Suner you have equipment from the most prestigious brands on the market, with very good sales and after-sales services .

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