The most important question that owners of country houses have when installing a new heating system or reconstructing an old one is how not to make a mistake when choosing a boiler and where to put it. Wall-mounted or floor-mounted, conventional (convection) or condensation, single/double-circuit, with natural draft or coaxial chimney. The choice is actually huge. And for it to be correct, you need to have a rough idea of the design features and basic operating algorithms. Therefore, we will figure out which one is better and why.
Design features, fundamental differences
A single-circuit boiler is used for heating premises by heating the coolant using 1 heat exchanger built into the boiler. Gas boilers, the design of which involves two heat exchangers, i.e. separately heating the coolant water for heating and hot water supply - called double-circuit.
Photo from ktl.by
Devices are classified:
- by location - floor and wall;
- in terms of energy efficiency: conventional, using a low calorific value and condensing, designed to consume a higher calorific value of fuel with the additional use of thermal energy released with condensate from water evaporation;
- according to the design of the gas burner - with an open and closed combustion chamber.
We also recommend reading: floor-standing or wall-mounted gas boiler, which is better and Top 10 best floor-standing gas boilers
When operating a gas boiler room, it is necessary to remember that gas is not only a benefit, but also a source of increased danger. Therefore, independent installation of equipment can lead to gas leaks and irreparable consequences.
To put it into operation, you must obtain a package of permits and consult with a specialist. It’s even better to entrust heating installation to professionals. You should not save on the health of your loved ones.
Answers from experts
Andrey Lukin:
single-circuit for heating only. double-circuit for heating and heating hot water (taking a bath). but what you were told is different. if the boiler operates without electricity (on natural draft) it is ATMOSPHERIC. if there is a SUPERCHARGED burner, then you need electricity
Dostoevsky and the cerebellum:
Single-circuit current heating, and double-circuit also heats water. And everything depends on electricity - there’s a pump that pumps water through pipes, and in some boilers there’s a lot of electronics themselves...
Verethragna Mitra:
electricity for the fan - blower, which supplies air to the nozzle, where it is mixed with gas and then ignited in the combustion chamber. For smoke extraction fan. Also, electricity (already autonomous) is used for safety, a thermocouple is installed (flame control), it generates an EMF, then through an amplifier and turns on the gas damper coil, when the flame goes out, the circuit opens and the damper falls, bimetallic plates are also used (switching off by temperature max. ) when heated, they bend and open the circuit; the circuit can also include an air pressure sensor on the burner, a pressure sensor. gas to the mountains , sensor on suction, pressure meters - sensors, off. boiler at min-max. gas pressure, shut-off valve, electromagnetic valve, etc. There are a lot of boilers... and everyone is different!
Hmansy:
The difference is whether you have hot water or not.
Alex Sharp:
single-circuit: drives water through only one set of pipes. In winter you have both heating and hot water. In the summer, if you want hot water, you have to turn on the heating and fry.
Double-circuit: There is a short pipe and valves on the primary circuit (two: at the inlet of the primary circuit and at the outlet. Additionally), by closing the valves, the boiler does not heat water in the entire system, but only in a small circuit. Without heating the house you have hot water.
There are boilers without electricity. I have a double-circuit Zhitomir. The water moves there thanks to the slight slope of the pipes and the law of physics (hot water rises to the ceiling and goes through the apartment, eventually dropping 12 m to 15 cm, then through radiators (like Soviet central heating batteries) it goes back to the boiler). No pump, no electricity! When lighting the torch (starting the boiler), there is a piezoelectric button on it (you can also light it with cotton wool in alcohol on a long rod, as I did, because the button is dead, and it’s expensive to buy it for ignition once a year...
alexm66:
A double-circuit boiler is smaller in size and easier to install: it has everything to connect the heating system. The downside is the overestimated heating power: the power is selected to heat water for hot water supply - they are rarely less than 24 kW (this power is enough to heat at least 240 sq. m of house area). Also, in a 2-circuit boiler, the heating system does not work while heating hot water. The single-circuit boiler + gas water heater system is very rare, except perhaps if the heating system is gravity-based - without a circulation pump. It is much easier to install a single-circuit boiler with an external boiler. The boiler smoothes out the need for boiler power - abroad they generally install special timers so that it heats up only at night: at this time they reduce the air temperature in the rooms. In terms of gas consumption, you won’t notice much of a difference. It will be more helpful if you insulate the house itself.
Mikhail Savelyev:
the ability to simultaneously heat water and heat the room using the same amount of gas
Grey:
single-circuit ones are simpler in design and maintenance, the column heats the water faster, which means gas savings,
Savva Schultz:
N***N:
there is an advantage. firstly, it is heating the water and there is no need to install a water heater or water heater; this is an extra expense and at the same time you save gas, which is still cheaper than electricity (if you have an Ariston) and spend money separately on the water heater!! ! Or better yet, buy a wall-mounted boiler, everything is there!!!
Rus Ivashkevitch:
The gas consumption of a double-circuit boiler definitely does not exceed the gas consumption of a boiler + column set. It has one heat exchanger, one burner, and a special valve that switches to water for washing hands or for heating. And the efficiency is definitely higher than that of a dual-circuit one. And the size of the double-circuit boiler is the same as the Neva column.
Sergey Telyshev:
Two in one is always worse. The advantage of a double-circuit boiler (IMHO not significant) is that it saves space. I’ve been using the boiler and heater for 7 years, I repair it and maintain it myself – I’m very pleased.
Dimon Rumyantsev:
With a 2-circuit boiler, hot water at a constant temperature will not flow. heats up slowly
Differences in the design of single and double circuit units
What is the difference between the design of units with 1 circuit and with 2 circuits? If we talk about the main components, then the basic principle of operation is the same for both types of equipment:
- pipelines through which water is supplied from a well (water supply);
- expansion tank;
- smoke exhaust or coaxial pipe and burner.
One of the main things that distinguishes a single-circuit gas boiler from a 2-circuit one is the design of the heat exchanger.
If in a 1-circuit it is a pipe through which water is heated due to the exchange of heat from a gas burner, in a 2-circuit it is two double heat exchangers made of pipes and plates or one bithermal (to make it clearer, this is a pipe inside a pipe).
- primary, heating heating circuit;
- secondary or plate, responsible for heating the water.
Photo from https://teplowood.ru
However, the key difference is the 3-way valve, which is responsible for the direction of water. When the heating circuit heats up, the valve is in its normal position. However, when the DHW tap is opened, the device’s automation is activated due to the pressure difference. The valve blocks the access of hot water to the heating circuit. Then the coolant begins to circulate inside the boiler. At this moment the room is no longer heated.
Dependence of the heating system on piping and power supply
To ensure the functionality of boilers, all types of boilers are provided with a standard set of equipment sufficient to generate heat from the fuel consumed. Each model has a combustion chamber and a heat exchanger.
Boilers can be powered by a solid liquid or gaseous energy source. Depending on the type of fuel used, the design of the combustion chamber changes. The heat exchanger is also undergoing some improvements to increase the efficiency of the entire device.
The boiler model is selected taking into account the heating system with which the house is equipped. Or vice versa - pipes and radiators are installed taking into account the capabilities of the already purchased boiler. In this case, maximum efficiency of the equipment is ensured.
For a heating system with natural hydraulic circulation of coolant, it is enough to purchase a boiler of the simplest design. Once you have set the fuel combustion mode and adjusted the coolant flow using valves on the pipes, you obtain acceptable temperature conditions for the entire season. Boilers with increased functionality are equipped with thermostats, heat sensors, and automatic room temperature controllers.
Depending on the type of heating system connected to the boiler, it may contain a circulation pump that pushes water into the heat exchanger. In this case, the device must be provided with an uninterrupted power supply. Stopping the circulation pump will stop the migration of water in the system. To eliminate dependence on power supply, a pipework with natural coolant circulation is installed.
Comparative review of gas boilers
Boilers with one heat exchanger are responsible only for supplying heat to the room; organizing hot water supply is not their task. In this regard, they are inferior to devices with two heat exchangers. The installation of an indirect heating boiler will allow you to expand the functionality, but then additional expenses are inevitable.
Also read with this article: Connection diagram for a single-circuit and double-circuit gas boiler with an indirect heating boiler
For clarity, we structure the information according to comparison criteria and present it in the form of a table.
| Single-circuit | Single-circuit with indirect heating boiler | Dual-circuit | |
| Possibility of installation (floor/wall) | +/+ | +/+ | +/+ |
| Additional expenses | – | + (for the purchase and connection of a boiler) | – |
| Economical | + | + | – (constant operation of the second DHW circuit when using water) |
| Compactness | + (in the absence of a boiler) | – (requires additional space for the boiler) | + |
| Comfort | – (when connecting the DHW circuit, the DHW and heating temperatures are not regulated) | – (temperature does not change at all points of DHW use) | – (when using more than two points, the water temperature may change sharply) |
Read about saving blue fuel in the article: How to save gas when heating a private home
About ease of use
What to choose for those who are not used to putting up with discomfort, but still want to comfortably use the benefits of civilization? For these purposes, single-circuit boilers are created as opposed to double-circuit boilers. Such a device is designed to heat heating fluid, but if you connect an indirect heating boiler to it, you can get a modern, efficient hot water system.
Further, with the use of a boiler, the following can be noted: the boiler begins to heat the water only from the moment it begins to cool for some reason. This means that it is possible to create a special recirculation system, i.e. movement of hot water in a circle. The water will bypass each tap and return to the boiler for further heating. In this case, we get hot water immediately after opening the tap - because the water will already be there. This is very important if you plan to build a large house with several bathrooms, and they are quite far from the boiler room
Advantages and disadvantages
When installing autonomous heating, gas equipment becomes the optimal solution. This choice is explained by its high efficiency (90%), variety of models and manufacturers, versatility of use, compactness, ease of maintenance and relatively quick payback.
Before deciding which is better - a single-circuit or double-circuit gas boiler, let's consider the pros and cons of each of them.
Single-circuit units
The main advantage of this type of equipment is its simplicity of design, therefore, unlike double-circuit equipment, it is characterized by higher reliability and fewer breakdowns.
The operation does not depend on the pressure in the water supply system. The advantages include low equipment cost and excellent performance.
When there is no need for hot water, there are practically no disadvantages, but then versatility and functionality are reduced.
If for a comfortable stay you need to provide access to hot water, then there will be a need to purchase and install additional equipment. As a result, the area for its placement will increase and it will be necessary to equip the boiler room.
Double-circuit boiler
This may seem strange, but a 2-circuit boiler is cheaper in price. The difference in cost is small, but it is there.
Such devices are usually low-power and compact. They can be installed not in separate special boiler rooms, but, for example, in the kitchen or hallway. The main thing is that the status of the premises is non-residential. This prevents installation in the kitchen - living room, for example.
The living room is a living space.
There is a huge variety of dual-circuit gas units on the market.
Read more: Top 10 best double-circuit boilers.
This allows you to select the desired power option. At the same time, they fit quite well into the interior. There are consumers who are concerned about the noise when the device operates. However, all the worries are really in vain. The volume of the boiler is comparable to that of a refrigerator. A little time will pass and additional extraneous sounds will be in order.
We recommend reading: Requirements for the room for installing the boiler
Additional advantages of a 2-circuit boiler include the possibility of complete autonomy. You just need to set the temperature, set the time, and the boiler will turn on and off automatically according to the specified settings. Plus, the device informs about any malfunctions and performs an emergency shutdown. See the table below for convenience.
| Advantages | List of disadvantages |
| The device is compact and takes up little space | if the family is more than two people, then prepare for the fact that there will not be enough hot water |
| there is a separate circuit for DHW | water temperature is not adjustable |
| The delivery set includes a circulation pump and a membrane tank | if the cold water pressure is low, then the hot water pressure will be the same |
| with the same parameters, the equipment has higher power | When you open the tap, cold water flows for a few seconds, and only then hot water. You need to get used to this too |
| ease of installation and connection | since heating of the room stops when the hot water system is turned on, then with prolonged use of hot water, the temperature in the heating radiators can decrease noticeably |
| Possibility of use in the warm season without turning on the heating |
However, issues with the order of water procedures can be resolved. As for the rest, if you monitor the technical condition and change components on time, the equipment will last for many years.
Which boiler is better to choose: comparison of differences between single-circuit and double-circuit models
The durability of its operation, the comfort of residents and heating costs depend on how correctly the equipment is chosen.
When the question arises, which boiler is better, you must take into account its power. Most often they start from the fact that for heating 10 square meters. meters requires 1 kW. However, these figures are averaged, and first of all, the heat loss of the building must be taken into account.
Dimensions
Based on the type of installation, they are classified into floor-mounted and wall-mounted. The floor-standing equipment uses a volumetric cast-iron heat exchanger. Although they last longer than wall-mounted ones, they have greater weight and dimensions. In addition, their installation is more difficult. If we talk about the characteristics, the wall-mounted version is better, while the floor-mounted one is simpler, without complex automation.
What nuances should you pay attention to?
Also important points to consider when purchasing are:
- Dimensions. Double-circuit models are more compact and allow installation even in small spaces.
- Installation location. While the installation of a single-circuit boiler is carried out in a separate room, the installation of a double-circuit device differs in some nuances. Thus, the use of a double-circuit gas appliance is possible only in a building where water points are located at a short distance from each other. And the heating device itself must be placed at an equal distance from the main water sampling points.
- Power. To select the correct parameter, you need to calculate in advance the expected hot water consumption, heat loss of the building, and also take into account the maximum temperature in winter.
