Which wall-mounted gas boiler is the most economical?

Which gas boiler is considered economical?

The main characteristic of any fuel is the amount of heat released during combustion. The most economical gas boilers are those that spend all combustion energy on heating the coolant, and its losses are minimized.

The combustion process involves gas and air. When heated, they react and produce carbon dioxide and water. The released energy goes:

• for heating the coolant;
• into the chimney along with combustion products;
• for water evaporation.

Economical gas boilers are designed so that the second and third components are minimized.
The efficiency of such heating devices varies between 90-99%. Note! The lowest efficiency is for models with an open firebox, the highest is for condensing type models.
For gas boilers, the temperature of the exhaust gases should not exceed 150ºC. For condensing units this indicator is at 70ºC. If the gas temperature rises to 200ºC, then it is better not to purchase such boilers, as they consume a lot of fuel. Another important indicator is the amount of water vapor that comes out along with the smoke: for average boilers it is 6%, for condensing boilers it is 0.5%.

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Based on the presented indicators, it is clear that condensing units are the most economical. They have a cylindrical stainless steel burner, around which a heat exchanger is concentrated, made in the form of a coil with closely spaced turns. Drops of steam condense on it, which transfer heat to the coolant. In conventional boilers, the heating circuit has a simple shape; as a result, the steam does not have time to condense and exits into the chimney along with the exhaust gases.

You can learn more about the design of condensing boilers by watching the video.

What affects the efficiency of a boiler?

In order to learn how to correctly choose the most economical gas boilers for specific conditions, you will first need to understand how thermal energy is produced and distributed during gas combustion.

The calorific value of the gas used for heating must comply with regulatory requirements. Of course, it is not consumers who are responsible for this, but gas supply organizations, but only high-quality fuel can help a gas heating boiler achieve its design efficiency.

An important economic role in the individual heating system is played by:

• type of boiler;
• installed installation materials;
• environmental conditions and geometry of the heating object.

The calorific value of a fuel is an indicator that determines the amount of heat released when a unit volume of gas is burned. The efficiency of the device shows the portion of the useful heat of combustion used in different heating and hot water modes.

Efficiency and economy are interdependent values ​​- the more complete the use of gas, the lower the specific consumption for generating a unit of heat and, therefore, the less money spent on its purchase, and the heater will be economical.

An economical heating boiler must first completely and efficiently burn natural or liquefied gas, and effectively use the released energy to increase the temperature in the heating system.

In real conditions, combustion and heat transfer processes do not proceed so well:

1. To completely burn the fuel and obtain maximum power, you will need to mix the gas-air mixture in a ratio of 1 to 10, but not all heat generators can do this.
2. The oxidation reaction of methane occurs with the release of CO2 and water, the latter instantly evaporates, thereby taking away part of the heat generated during fuel combustion.
3. The heated combustion products are not able to transfer all their temperature to the coolant, since part of it is carried away by the exhaust gases into the chimney; the size of such losses depends on the design of the device and the gas-air path.

Thus, one part of the gas energy is irretrievably lost during combustion, and the second - during thermal convection. The smaller the total amount of such losses, the more economical the device for homestead housing construction.

The most economical boilers for heating a private home are selected according to their efficiency, which must be specified in the boiler passport and ranges from 90 to 96%. If the efficiency is indicated above the upper limit of this range, then we can safely say that such data is not real, and the seller is deceiving the buyer.

The main parameters influencing the efficiency of boiler equipment are the type and design of the boiler unit. They can be volatile or autonomous. The former have a closed combustion chamber and forced air supply from an external powered fan.

Many types of wall-mounted devices belong to this class. The second type is an open-type floor-standing gas boiler that operates on natural ventilation of air and flue gases in the gas-air duct of the unit.

It is much more economical than the previous one, although it has a more complex design with large dimensions, so it is usually designed as a floor-mounted one.

The next parameter is the material of the boiler heat exchangers: copper, cast iron or stainless steel. Copper and cast iron have the highest heat transfer; they are more economical because they significantly reduce fuel consumption.

Another important parameter is related to the technology of the heating process. For example, in condensing boilers, in addition to water coolant, steam is additionally produced.

Despite the increased market price, they consume less fuel to produce a unit of thermal energy and, therefore, have a short payback period.

Particular attention in the energy efficiency package of a boiler heating system must be paid to compliance with the operating rules of gas boilers; users need to know how to set up the efficient operation of the entire heating complex.

If the heating facility and heating networks are not properly prepared for operation in winter (thermal insulation, cleaning, flushing, pressure testing), the costs of operating the equipment will increase exponentially, and equipment operating in emergency mode may fail.

Therefore, the concept of an economical operating mode is much broader than simply purchasing an efficient unit; it is important that it also corresponds to the heating characteristics of the house and is suitable for the existing heating system.

Rating of the most economical boilers

How to determine the efficiency of a boiler?

Before we give specific recommendations on choosing an economical heat generator, let’s clarify some points. The efficiency of modern installations burning natural gas is in the range of 90-98%. The lowest indicator is for inexpensive non-volatile models that have a one- or two-stage burner device. Modulating burners with electronic control and forced air injection work better, where the power is controlled smoothly rather than stepwise. But you need to understand that the burner only burns fuel, and heat transfer is the task of other elements of the boiler.

Initially, the heat generated in the firebox directly heats the water jacket of an economical gas boiler. The remaining heat, along with the flue gases, enters a steel or cast iron heat exchanger. This is one of the most important stages, it is here that the combustion products transfer part of the remaining energy to the water, after which they flow into the chimney. The fraction of heat that gets there is irretrievably lost, escaping into the atmosphere.

How large this proportion is is shown by the temperature of the flue gases, which indicates the efficiency of the boiler. If the gas temperature at the outlet pipe of the unit is 200 degrees or more, then you have a not very successful heater design. It allows too much heat to escape outside. If the temperature of combustion products is in the range of 100-150 ºС, then this boiler can already be considered as an acceptable option.

The best indicators for flue gas temperature are produced by gas condensing boilers. This is realized by removing the heat of vaporization of water. In the previous section, we said that the water released as a result of a chemical reaction evaporates, taking away part of the heat of combustion of natural gas. So, the most economical boilers are able to take this energy back by condensing the resulting water vapor.

For this purpose, the unit uses a cylindrical burner installed inside a stainless steel heat exchanger. The latter is a coil, where the coils are close to one another, and the coolant circulates inside. The steam has no other way but to pass through this coil and condense on its surface, giving off heat. The temperature of the flue gases of condensing heat generators is record low - from 45 to 70 ºС, and the efficiency reaches 98%.