Condensing boilers: hot water at low cost

Condensing boiler

In the last years the need to reduce energy consumption and environmental pollution was the push for research and development of new technologies, with the definition of a precise number of hours of power for the heating of buildings and offices, depending on the locality of reference.

Besides the usual existing boilers which are in use in four out of five families, few are aware of condensing boilers.

The latter means a significant innovation, it is currently completely replacing standard boilers.

Quite simply we will try to explain what they are, what are they for and what are the benefits they bring to the environment and to our pockets.

What is a Condensing Boiler?

During the winter, spending on heating bills means more gas and electricity.

To heat the water with lower costs than those to which we are normally accustomed to, we can use condensing boilers.

First, however, we should explain what is the latent heat released from boilers.

To cope with the needs for heating and hot water of a standard apartment of about 100 square meters, occupied by four people, with reference to mild weather conditions, it is sufficient a standard boiler of 24 kW which must have a yield not less than (88 +2 logPn) -1 Pn with nominal boiler (reference Legislative Decree 192/05 adequate to Legislative Decree 311/06 and amended by Ministerial Decree 26.06.2009).
This value is approximately of 90%.

According to the same references a condensing boiler must have a yield of not less than (90 +2 logPn) -1, a value significantly higher than the 90%.
Condensing technology allows to transfer to the water to be heated, through a heat exchanger, the heat produced during the condensation of the exhaust fumes.

The latent heat of condensation is supplied to the return water of the boiler, that is the water to be heated.
Furthermore, a lower temperature of exhaust smoke from the condensing boiler, generally 80 C compared to about 100 C for standard boilers, also allows to reduce the amount of heat loss through the mantle of the same boiler.

The lowest value of the flue gas temperature compared to standard boilers allows the use of fume systems in PVC, cheaper and handy during the installation phase.

Installing or replacing a condensing boiler

Install a condensing boiler is much easier than with a common boiler.

By replacing a standard boiler with a condensing boiler and respecting the legislative references mentioned above, you can take advantage of the deductions of 55% of the incurred costs, untill 31.12.2012.

However, when replacing an old boiler, you must take into account the type of fuel available.
As a matter of fact, the advantages of condensation are bigger if using methane as fuel gas, in comparison with other combustible gases.

Each fuel has its own heater power, defined as the heat produced as a result of its complete combustion.
The lower calorific value does not take into account the phenomenon of condensation, while the gross calorific value takes also these into account.

The greater is the difference between the lower calorific value and the higher calorific value, the greater is the amount of recoverable heat with the condensing technique.
For the main fuels, the difference between lower and higher calorific value turns out to be of 11% for natural gas, of 6% for diesel and of 8, 4% for butane.

In addition, when installing a condensation boiler you should consider the condensing discharges, suitably conveyed; consider also evaluating the type of heating system that you have.
The major advantages with a condensation boiler are obtained with systems at low temperatures.

The ideal coupling is a condensing boiler and a radiant panels system, they work with supply water at 40/45° C and return water temperatures of 30/35° C, the use of a solar thermal panel gives place to a real integrated system capable of exploiting fossil fuels and solar energy as alternative and renewable energy resources.

The old heating systems were designed to work with the supply and return water temperatures respectively of 80/85° C and 70/75° C.
In the presence of an old radiator system the technique of condensation can be exploited only in the less rigid winter period, when the system can work with relatively low temperatures.

However, many old radiator systems, oversized in the number of elements, provide a surface larger than necessary to get the design temperatures, thus you can consider the possibility of making them work with lower temperatures and take advantage of condensation.

Disposal of moisture from a condensing boiler

The disposal of moisture, a substance that has an acid profile, produced by condensation boilers, it is a threat for the environment.

The most common solution for the disposal of the moisture is to convey it in the waste water used in buildings.
These latter thanks to the presence of soaps and detergents and their basic profile should neutralize the acidity of the moistures.

The evolution of the existing rules about moistures, over the years has embarked on a road with complicated instructions that are not easy to implement.
For systems with a power of less than 35 kW, on average, in the discharge of moistures there are no particularly high contents of poisonous substances, it is in fact in principle allowed by the rules in the direct discharge of sewage collection systems and surface water.

With reference to UNI 11071/03, would have required the adoption of a system of neutralization or passivation of moisture prior to placing in collection system of sewage or surface water for a power from 116 kW.
However, even in such a case the possibility of neutralization with soapy discharges and with detergents of daily use, it is not excluded.

Even in Europe, if we consider power systems of less than 200 kW, there are no clear guidelines to follow.
The lower limit of the power below which it is not mandatory the use of a neutralizer according to European standard is 25 kW thermal, against the 35 kW in force in Italy.

Practical example of saving with a condensing boiler?

As ecologists we can be, if we do not find a purely economic advantage in things, we are hardly going to change our boiler supporting a much more burdensome expense.

In addition to the huge gas reduction unpleasant for the environment like the aforementioned Oxides of Nitrogen and Carbon Monoxide, we could get a cut of the gas costs up to 60%.

LPG has a lower calorific value equal to 21,750 kcal / mc while methane has a lower calorific value of 8,250 kcal / cubic meter.
Considering as indicative prices 2.50€/ mq for LPG and 0.80€/ mq for methane, the cost of 1000 kcal turns out to be:

2,50 / 21750 -> 0.115€ in the case of LPG

0.80 / 8250 -> 0.097€ in the case of methane

For an apartment of about 100 square meters considering about 80-100 W per square meter of thermal power needed for heating and domestic hot water, with a methane boiler and with the references of these, the expense would be of about 500€ per year, while the LPG of about 600€.

The corresponding efficiency with the condensation would be of about 150€ and 180€.

How Much do the condensing boilers cost?

The price of regular boilers varies between 500€ and 1000€.

Condensing boilers have a slightly higher cost: according to the power, in fact, prices can fluctuate between 1,000€ up to 2,100€.

Who to contact:

Some price lists of condensation boilers, area of Turin, Cuneo and Asti click here .