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It is now possible to combine a gas condensing boiler with renewable energy, such as solar for hot water production or heat pump heating for more savings. State of play...

Which model of gas boiler to choose

5 questions about new gas boilers

Responses from ValérieLaplagne, Renewable Energy Manager at Uniclima (Association of Thermal, Aeraulic and Refrigeration Industries)
Are gas and renewable energies reconcilable?
Today, you can fully connect a condensing boiler to solar collectors or a heat pump. There are also boilers called "hybrid", which combine under the same body a boiler, a heat pump and a regulation. With regard to solar energy, there are systems for the sole production of DHW (domestic hot water): it is the CESI (individual solar water heater). The heating function can also be added: it is called a SSC (combined solar system). These systems operate with a supplement, either electric or with a condensing boiler, usually gas. In renovation, it is better to move towards these SSC when it is necessary to change the boiler because one optimizes then better its investment.
What is the ideal solution?
The most recent are the very compact solar columns, whose size is comparable to that of a high fridge and which integrate in the same envelope the boiler and the balloon, to which is added the hydraulic connection. This system allows you to equip yourself in stages: you start with the column, which offers heating and hot water from the gas energy then, in a second step, it is associated with the solar collectors. If proceeding in stages is not the least expensive solution - it is cheaper to move the installer only once - it allows staggering expenses. With these columns incorporating a condensing boiler, the emitters will preferably be at low temperature (floor heating or radiators soft heat).
Is this choice profitable?
The investment is important: it requires a real environmental determination. However, with this equipment, we make sure that in the future much of the energy bill will remain stable, which is not true for a conventional solution whose cost will only increase. In addition, the rate of the tax credit is increased in the event of complete equipment. Thus, it is 10% for the boiler alone, 32% for the solar ECS and 40% for a solar column. Finally, in terms of physical possibilities, it will be up to the installer to define whether the installation of solar collectors is possible or not (well oriented roofing, possible shadows, etc.).
What about the gas boiler + PAC couple?
If the boiler is not too old, we can install a PAC in "relief". The advantage of this system is obvious: the CAP, which draws its calories on a renewable energy (air) works as long as the outside temperature is not too low, thus generating savings. However, it is important to monitor certain points, such as the temperature level of the heating system: if you have a standard boiler, the emitters are surely at high temperature (and not at soft heat). It must then move towards a high temperature heat pump capable of supplying water at the corresponding temperature. As for the power, it depends on the size of the house. The installer must observe precise sizing rules. It must, for example, take into account the coldest temperature of the region in which the house is located, the power of the heat pump to be sized between 80 and 120% of losses at this minimum temperature. It is of course highly recommended to use a qualified QualiPAC installer for heat pumps and QualiSOL for solar energy. Moreover, from 2014, the individual will be in the absolute obligation to go through a professional in possession of these qualifications to be able to access the various financial aid.

Gas boiler: which costs and what return on investment?

According to the Uniclima union, the CESI (individual solar water heater) only provides domestic hot water with the sun. The SSC (combined solar system) is more expensive, but it can cover a higher proportion of the energy bill, including heating and domestic hot water (DHW). Overall (excluding aid but including installation), a CESI, with 4 m2 of sensors, costs about 6 000 € HT with an electric booster (a pin in the ball), and instead 7 000 € HT with a gas make-up (in general an exchanger coupled to the gas boiler). This configuration is suitable for a family of 4 to 5 people. A column costs about 10 000 € HT, including pose. The return on investment is of the order of 20 years without the aid and 10 to 15 years with help. For a SSC, the cost is from 11 000 to 16 000 € including VAT, including 10 m2 of sensors. These prices are only indicative: each project requiring calculations according to the dimensioning, the region, the insulation, etc.

Services for LPG and propane

Services for LPG and propane

LPG and propane suppliers such as Totalgaz, Butagaz, Primagaz or Antargaz offer a range of services for underground tanks. These services take different forms. These can include 24-hour, 24-hour advisors to help the customer determine the best location for the tank or give tips and tricks to reduce their energy bills and extend the life of their facility.
These suppliers also help their customers to schedule deliveries as quickly as possible, provide periodic inspections and checks, leakage control of the installation and its safety, maintenance and upkeep, parts and labor warranty etc. Note: deliveries can be made to order, or be automatic or forecast. Finally, websites offer "customer spaces" to obtain a duplicate invoice, the ability to report an exact consumption statement at any time...

Some models of gas boilers: models

Here, the condensing gas boiler combines with the hot water accumulator and operates virtually without any loss, unlike conventional boiler / balloon installations.

The 4 strengths of gas boilers

1 The power of the boiler It is dimensioned in relation to domestic hot water needs because these are generally stable, while the heating needs decrease a lot due to a building increasingly insulated at the moment.
2 A condensing boiler has a yield of 102 to 108%. Its installation provides savings of 15 to 20% compared to a modern standard boiler while producing less pollutants and releasing less CO2.
3 For more savings the boiler can be "modulating". This means that a 25 kW generator can vary its power from 2.5 to 25 kW, which makes it possible to better adapt to heating or domestic hot water needs (this ratio of 1 to 10 is a maximum).
4 GDF Suez offers the DolceVita ZenBox A solution that allows the user to track their energy consumption. It can receive alerts in the event of exceeding the threshold, the risk of fire, the freezing of pipes or the breaking of the cold chain. It even protects housing against intrusions!

TO KNOW:

For advice and technical information, GDF Suez DolceVita has created an "Energy saving" section on its website gdfsuez-dolcevita.fr and a dedicated telephone line (0810 124 125) for direct dialogue with an expert.
The online simulator "Financing your work" makes it possible to identify aid, tax credits and other financing solutions that you can claim to carry out your energy efficiency work.

Some models of gas boilers

(topic published in October 2013 - the prices and the models are likely to have evolved at the time of the reading of this article):

SOLAR AND HYBRID

SOLAR AND HYBRID

Combined with an integrated 220-liter solar storage tank, this hybrid gas condensing boiler is available in two power ratings of 14 or 20 kW. A program ensures a minimum flow of hot water (DHW) in case of insufficient sunlight. "Solar hydroconfort", Frisquet. Public price: € 6,200 excl.
HIGHLIGHT: in addition to the production of DHW, it can manage three heating circuits.

IDEAL IN RENOVATION

IDEAL IN RENOVATION

With its 60 cm wide, this gas condensing boiler on the ground is equipped with a modulating burner which adapts the power constantly, as needed, over a wide range of 18 to 100%. We can add a solar system or a PAC "8 0 0 0 F Condens", Bosch. Public price: from 2 995 € HT.
THE STRONG POINT: it replaces very easily an old gas boiler.

BOILER + CAP IN MONOBLOC

BOILER + CAP IN MONOBLOC

The condensing gas boiler is associated with a small air / water heat pump to ensure the heating and the production of domestic hot water, in instantaneous as in accumulation. Modulating, its power ranges from 4 to 24 kW. "Megalis Condens Hybrid", Elm Leblanc. Public price: € 4,523 excluding tax.
STRONG POINT: its three modes of operation to choose from. Boiler only (winter), boiler + heat pump (mid-season), heat pump and booster boiler for DHW (summer).

FOR NUMEROUS FAMILY

This hybrid solution combines a heat pump (PAC) of 3 kW, a gas condensing boiler of 24 kW and a balloon of 120 liters. It ensures both the heating of all rooms and the production of domestic hot water (DHW). "Hynea Hybrid Duo", Atlantic. Public price: 6 450 € HT all.
STRONG POINT: the set fits in less than 0.5 m2 on the ground. The boiler takes over from the heat pump if the weather is too cold.

COMPATIBLE WITH DIFFERENT TRANSMITTERS

COMPATIBLE WITH DIFFERENT TRANSMITTERS

This system includes a heat pump relayed by a condensing gas wall boiler. It offers a hybrid control with external sensor and remote control. It can be connected to a DHW tank (115 or 300 l). "Talia Green Hybrid 3-30 FF", Chaffoteaux. Public price: 5 866 € HT.
HIGHLIGHT: its compatibility with a floor heating and radiators.

FOR TWO HEATING CIRCUITS

FOR TWO HEATING CIRCUITS

It can supply two independent circuits (radiators and heated floors). This condensing gas boiler is available with or without domestic hot water production. Modulating power up to 23.9 kW. "THRi DC", Geminox. Public price: € 2,520 excluding tax.
THE STRONG POINT: it is very easy to replace an old gas boiler.

SUPER REGULATION

SUPER REGULATION

Wall-mounted, this condensing boiler offers a built-in double boiler for heating and DHW. A low temperature function allows connection to a heated floor. Power: 30 or 35 kW. "Isomax Condens", Saunier Duval. Public price: from 3 600 € HT.
HIGHLIGHT: self-regulation by wireless room thermostat and radio outdoor sensor.

INTEGRATED PREPARER

INTEGRATED PREPARER

Operating on natural gas, LPG and authorized biogas, this condensing boiler forms a compact unit with its integrated hot water cylinder with a plate or coil heat exchanger of 100 liters. "Thermo Condens WTC-GW K", Weishaupt. Public price: 4 198 € HT.
STRONG POINT: control and configuration managed by a remote control.

COMPATIBLE MULTI-ENERGY

COMPATIBLE MULTI-ENERGY

For heating alone, this condensing gas boiler from 5.4 to 35.9 kW can also provide DHW by stratification, coil or solar. Its heating body then integrates boiler modules and balloon columns or juxtaposed for a suitable space. "Modulens G", De Dietrich. Public price: from € 3,543 excluding tax.
STRONG POINT: true brain of the installation, the control panel incorporates a programmable control.

DETECTION TESTER

DETECTION TESTER

This wall mounted gas boiler for heating alone is available in two models from 3.8 to 19 kW and from 5.6 to 35 kW. Its modulating burner has a combustion regulator that optimizes the latter. "Vitodens 300 W", Viessmann. Public price: from € 3,029 excluding tax.
THE STRONG POINT: it is equipped with a tester detecting the operating deviations.


Video Instruction: A QUICK GAS FIRED MODEL BOILER TEST - IN THE WORKSHOP