What type of boiler do I need?

You were so happy with your old gas boiler until one day it just stopped working! You ask yourself.. “did I maintain it sufficiently?”  But it’s too late now and after getting several quotes for a full repair, you decide rather than throwing good money after bad it is best to change it completely.

What boiler should I install?

This is a common question and first it is important to establish your definition of boiler and what you want to achieve!

Boiler jargon. What is a boiler?

“Boiler” is a word often used to describe an apparatus that supplies hot water. In the plumbing world, however, a Boiler describes an appliance that provides both domestic hot water and supplies heat for a central heating system.

Types of Boiler and water heater

There are several types of boiler and water heaters that we regularly install on the Costa Blanca with functions that include supplying hot water but it is important to distinguish between them as they are all very different.

Electric boiler = also known as;  Electric Immersion Heaters; Electric hot water cylinder or Spanish “Thermo electrico” pronounced “termo……”

This only produces hot water.

Our preferred brands:   Ariston, Aparicci, Baixi

Gas boiler =  also known as geiser; Instant fired gas water heater or in Spanish “calentador a gas”

This only produces hot water.

Our preferred brands: Ariston, Junkers, Vaillant

Combi Boiler or just, Boiler = Combi Boiler / Boiler or in Spanish Caldera or Caldera mixta.

These can be gas-fired or oil-fired and will provide hot water for a central heating system. Some also provide hot water for domestic use (the combi models).

Ariston, Junkers, Vaillant or oil; Ferroli, Domusa

Indirect cylinders = Indirect hot water storage tanks or indirect immersion tanks or (in Spain) interacumulador.

These units provide hot water for domestic use or central heating depending on the system design and are heated by an independent heat source eg. Solar installation, Central heating boiler, or Air flow heat pump.

Our preferred brands: Ariston

Air source Heat pump = Air source Heat pump or (in Spain) Bomba de Calor Aerotermia.

Provide hot water for central heating or for domestic hot water supply.

This is the latest technology providing and is most efficient. It works with Electric.

Our preferred brands: Daikin, Panasonic, Mitsubishi

Domestic hot water heat heat pump = Air source or (in Spain) Accumulador aerotermia.

Provide hot water only for domestic hot water supply.

Our preferred brands: Daikin, Panasonic, Mitsubishi

Airflow technology is the latest technology providing and is most efficient. It works with Electric.

Electric Immersion Heaters

How to choose an Electric Immersion Heater?

Electric immersion heaters are characterized by operating by electricity! Amazing! This type of boiler is used solely to provide a limited source of hot water. Yes limited… the size of the tank will dictate the volume of hot water available. This conventional style of water heater is typically the most affordable style and is also easy to install.

Among some of the features that your electric boiler can incorporate are external temperature control thermostat although these are found on more expensive models and safety valve which is a safety feature of all immersion heaters. Some heaters may also be equipped with an eco setting.

Advantages of an electric water heater

  • The electric water heater does not produce any noise or fumes.
  • There is little or no maintenance required by electric boilers which are generally very user friendly.
  • An electric boiler will not give you supply problems unless there is a power cut or power surge. Electric boilers are generally equipped with surge protection and can often be brought back to life after pressing the reset button.
  • Outside of wet areas, an electric water heater can be installed wherever there is a power supply without safety concerns as they cannot leak gas, carbon dioxide, or give ventilation problems.

TOP TIP: It is important to hang your hot water heater on a supporting wall with solid and secure fixings. As once full of water a larger capacity heater will be very heavy.

Disadvantages of an electric water heater

  • Electric water heaters come with between a 2 – 8-year guarantee. This applies to the tank only. In Spain electronic components have no guarantee.
  • Guarantees can be expensive to maintain. Our experience is that your heater will generally fail a few months after the guarantee period has expired!  However if your heater does spring a leak during the guarantee period it will only be valid if you have changed the sacrificial anode annually. Although this is rarely complied with, it is a manufacturers requirement especially in our area where the water is hard. If compliant this means that to maintain your guarantee requires a considerable additional annual expenditure.
  • For a family home, the electricity bill can be quite high for simple water heating.  You need to keep an eye on how long your teenagers spend in the shower!
  • The electric water heater is fitted with a safety valve which releases pressure by means of a release of water. This can be a source of great annoyance if the valve is particuarly sensitive especially as water heaters are often installed in cupboards in bedrooms and linen cupboards. Solutions for an intermittent leaking safety valve include installing a pipe from the valve to a waste outlet, or a separate pressure vessel or pressure regulating valve to absorb the fluctuations in the incoming water supply.
  • Larger volume units can take up valuable space.

Instant gas-fired water heaters

What is a gas-fired water heater?

An instant heater, also known as a circulating or passing water heater, is a device used to instantly raise the temperature of the household water. Unlike heaters with a tank, it heats the water as needed: when the tap is opened, when the shower works, etc. In this way, it is not necessary to store hot water.

Advantages of the instant gas-fired hot water heater

  • Its production of hot water is unlimited, unlike storage boilers where hot water will end when the tank is emptied.
  • It occupies less space since its size is smaller because it does not have a storage tank.
  • The instant heater remains off until a sensor detects that there is demand for hot water. Therefore, it consumes less energy. This is especially true with the battery or hydropower units which operate without a live flame pilot light.
  • Its consumption is very efficient since little energy is lost in the process of heating the water.

Disadvantages of the instant gas-fired heater

However, there are also certain disadvantages to its use.

  • The instant heater has a lower flow capacity, so boilers with a hot water tank are more convenient when the water consumption is high. It is possible that, for example, if two hot water taps are opened from different points of the house the hot water flow rate will be significantly reduced to just a trickle!
  • A gas supply is required.
  • It must be maintained periodically and, in addition, it must meet gas safety and evacuation requirements.

If you have decided that you want to install an instant heater, keep these considerations in mind. They will help you choose the most appropriate.

  • What type of fuel is used in your home? If there is no gas installation (natural or butane) for a gas water heater, you will have to opt for an electric one.
  • How much hot water are you going to need? You need this data to be able to calculate the capacity and flow that it can provide you.
  • How many hot water points do you want to cover with the instant heater?
  • Where can the heater be placed? They need to be positioned in a well-ventilated spot with available gas supply.

Storage gas water heaters

This style of water heater is the most popular and probably the most suited to larger properties with several bathrooms.

What is a conventional storage tank water heater?

This style of water heater has a tank that contains water for heating. This means that the capacity of the tank determines how much hot water is available at the same time. The tank is insulated so that when the water is heated, it remains hot until it is needed.

This is the most common type of water heater among family homes but is limited to the amount of hot water it can contain. If your tank is too small or if you need an excessive amount of hot water in any one day, you may run out and have to wait for the next tank to heat up.

The typical shelf life of a conventional storage-tank water heater is around twelve years.

What are the benefits of this style of water heater?

  • A good supply of hot water for two or more showers simultaneously.
  • More economic to run compared with electric storage hot water heater.

What are the disadvantages of buying a conventional storage-tank water heater?

  • Limited supply of water at a time. This should not be a problem if the unit is sized correctly to your demand.
  • Less user friendly. Storage hot water tanks have their living flame pilot lights and ignition at floor level, because of this can be difficult to light especially for someone with mobility issues. Re-lighting requires you to crouch down.
  • Can provide a safety hazard if unburt gas accumulates during the lighting procedure it can produce a small explosion.
  • Requires space for installation, as tanks can be large.
  • Requires a gas installation with its safety constraints including ventilation and evacuation of fumes.


If you have difficulty in lighting your gas storage heater always ensure the area is well ventilated and that a time pause is allowed between lighting attempts.

Combi Boilers

A combined boiler is both a water heater and a central heating boiler combined in a single compact unit.

Combined boilers account for more than half of domestic boiler sales in the United Kingdom, the condensing models are energy efficient, which helps reduce energy bills.

Not only does a combi boiler supply your heating system but many also heat water directly from the mains when a hot water tap is opened for domestic use. This means that an external hot water bottle or a cold water storage tank is not required which frees up space in your home. A disadvantage is that they can struggle to generate large amounts of hot water at the same time and this can often lead to a drop in water pressure if  hot water is called for simultaneously at different parts of the house. This can be a problem in a larger house with several bathrooms where there is likely to be an overlap with the use of hot water.

Larger flow capacity units are available so it is important to check the hot water capacity and size it correctly to your needs. Combi boilers are also available with a small water deposit, normally 50Lt which helps to exacerbate this problem of reduced flow.

Advantages of the combi boiler

  • Its compact size makes it an ideal choice for smaller properties.
  • Instant access to hot water, without waiting for the tank to heat up.
  • No hot or cold water tank is required to free living space and loft.
  • Energy efficiency as no store of hot water and energy is not needed to maintain water temperature.
  • Combined boilers are available in both gas and electric.

Disadvantages of the combi boiler

  • Not ideal for larger homes or houses with multiple bathrooms (see system boilers) as water pressure may be affected when multiple exits are used at once
  • There is no access to stored hot water if a problem arises with the boiler
  • Often a brief delay in heating.

System Boilers

These operate in much the same way as a Combi boiler however only supply heat for a Central heating system and have no domestic hot water function. A system boiler is commonly installed in an oil fired system or a large domestic system with a large demand for central heating. System boilers are normally installed in conjunction with a gas or electric storage hot water tank.

Solar Hot Water

How to generate domestic hot water with solar energy?

Here we are on the Costa Blanca with more than 300 days of sunshine every year so solar water heating seems like the ideal solution and an alternative not only respectful of the environment but also very attractive and with a lot of future.

This is a very cost-effective and easy solution to get hot water for free!  Did you know that with a simple installation you can get 100% of the hot water consumption of a home even in winter, saving energy and money?

Advantages of solar thermal energy for hot water

Domestic hot water supply requires an ideal temperature between 37ºC and 42ºC. The use of the Sun’s thermal energy is extremely effective for heating water. Generating hot water from solar energy has many advantages:

  • Possibility of receiving subsidies.
  • It saves up to 95% of the energy for the production of water throughout the year.
  • Energy-saving implies the consequent cost savings.
  • It is ecological.
  • It does not pollute or emit CO2.
  • It is the most practical way for you to contribute to the environment.
  • Long service life: about 25 years.
  • Easy use: everything works automatically and the user should not worry about anything.

What solar systems can generate hot water?

If you are thinking of a solar installation for the generation of solar hot water in the home, we should focus on the following two large groups:

Thermosyphon systems

Thermosyphon systems or compact systems are the best known solar thermal systems (typically seen on single-family homes with the tank on the solar panel) since they are the most economical and easy to assemble.

The movement of the fluid through the primary circuit is produced by natural convection, where the fluid when heated as it passes through the solar panel expands increasing its volume, and therefore decreases its density. Weighing less, the fluid rises to the upper part of the circuit where the accumulator is, while the colder fluid contained in the accumulator, with greater density, moves to the lower part of the installation through the inlet pipe to the panels.

This creates a natural circulation of the fluid, which is maintained whenever there is a temperature difference between the collector fluid and the one located in the upper part of the installation inside the hot water tank. It is there, inside the tank, where heat transfer occurs via a heat exchanger (copper tube coil) located inside the storage tank.

This water from the tank, once heated, passes to the internal circuit to be consumed at the points of consumption (showers, sinks, washing machines, dishwashers, etc.). This system, of gravity flow, makes the thermosyphons easy to install, and in addition to being very economical, they are the most popular.

However, in thermosyphon systems the driving force of the movement is small and, therefore, special attention must be paid to the design and assembly of the installation to always favour the natural movement of the fluid. For this, the accumulation tank must always be placed at a level higher than that of the solar collectors to allow natural convection due to the difference in temperature.

Forced circulation systems

The forced circulation systems are more efficient than the thermosyphon system, but also more expensive. The movement of the heat transfer fluid is carried out through a circulating pump regulated according to the thermal demand. When using a pump for the circulation of the solar fluid, it is no longer necessary for the heat exchanger to be located above the panels, so the accumulation tank, which contains the exchanger inside can be placed in a protected place inside the building on the ground, which allows the use of greater capacity tanks.

Forced circulation systems obviously require an electric pump as well as a control unit which makes them less green.

How many solar panels do I need?

You will need varying numbers of panels depending on the number of people in the house and the consumption that you have.  With a normal consumption 1-2 panels are normally sufficient. 3 panels for a higher consumption would require a larger volume solar hot water tank.

Air to water heat pumps or Airflow heat pumps (Aerothermia) for heating and hot water or stand alone

Air flow energy is a renewable energy source that uses energy stored in the air around us and converts this to heat or cooling for your home and domestic hot water – up to 80% of the heat energy is taken from air – even in low temperatures. This is passed through a circuit full of ecological refrigerant.

A heat exchanger is then responsible for transmitting the energy generated to the heating and domestic hot water circuit of your home.

The elements that make up an installation are:

  • Outdoor unit, regulator and compressor.
  • Air flow heat pump
  • Heat / cold distribution network; radiators, fan coils or underfloor heating, which allows the optimum temperature to reach every place inside the building.

A reversible heat pump, by reversing its operation, can be used as heating in winter as well as cooling system in summer.(offering a chilling function for heating systems eg. underfloor heating)

Advanced technology leads to significant savings of up to 80% of a traditional fuel system. In addition, an inverter unit can operate at different speeds, eliminating stopping and starting, greater energy efficiency is obtained, improving the performance of the heat pump and achieving greater comfort while maintaining greater stability in the temperature of the room.

So, in summary, the main advantages of air flow energy are:

  • With the airflow system, the demand for heating, domestic hot water and cooling can be met with the same equipment
  • It is a natural, renewable and inexhaustible energy, which does not pollute and with high return on investment.
  • Installation and commissioning is simple and safe.
  • It is a compact system. It occupies the same space as a wall-mounted boiler but with the distinct advantage of not requiring any fuel storage tank or inertia tank. Although separate hot water tanks can be incorporated into the system depending on system design.
  • An aerothermal system does not require a gas, oil supply or evacuation duct, thus no chimney is required on the facade or roof of the house.
  • It can be installed and adapted to existing conventionally fuelled systems.

Disadvantages of an Airflow heat pump.

  • The initial investment can be considerable however the airflow heat pump will quickly pay for itself in the medium to long term.
  • The process used to extract energy from surrounding air produces water, so some consideration needs to be given to water discharge.

Aerothermia represents the future, clean, ecological, safe and simple.

For More Information please contact

Tracy & Mike Smeed
100% Plumbing
+34 96 583 5939
+34 607 415 520
Email: info@100percentplumbing.com