What Is Better A Two-Circuit Or Single-Circuit Gas Boiler: A Comparative Design Review

Choosing a gas boiler for an independent heating system in a private house or an apartment? Agree, you want to choose the best equipment that can provide you and your family with hot water and heat in the cold season. But you can not decide what is better to buy - two-circuit or single-circuit gas boiler?

We will help you to understand this question - in the article the features of two-circuit and single-circuit equipment, their main advantages and disadvantages, subtleties of using each of them are considered. Also a comparison of two types of boilers is made, thematic photos and video recommendations on the choice of the best option, based on the individual needs of the potential buyer are selected.

Content of the article:

  • Design and features of boilers
    • Differences in the construction of single and two-circuit units
    • Comparative review of gas boilers
  • Benefits and drawbacks of equipment
    • Pros and drawbacks of single-circuit units
    • Defects and drawbacks of two-circuit boilers
  • Which boiler is better to choose?
  • Conclusions and useful video on the topic

Boiler design and features of operation

Modern gas boilers, depending on the number of circuits, can be single-circuit and double-circuit. They are externally and structurally similar, but are designed to solve different problems, and in different conditions.

As a result, we can say that both types of equipment are equally useful and effective, so there is no best among them. And therefore everything depends on the right choice. Next, let's understand in detail what is the difference between the single-circuit type of gas boiler and its double-circuit counterpart.

Differences in the construction of single and double-circuit units

Products that belong to both types of equipment in most cases consist of the same components.

Detailed design of a modern wall mounted single circuit boiler and the device diagram of its two-circuit \"brother\" are shown in the following pictures:

What is better a two-circuit or single-circuit gas boiler: a comparative design review

Any single circuit boiler is characterized by constructive simplicity. That makes them more reliable and affordable. But these advantages are leveled by the necessity to buy a boiler

What is better a two-circuit or single-circuit gas boiler: a comparative design review

The presence of a double circuit unit with a complicated heat exchanger and three-way valve makes it fundamentally different from any single circuit analogue

The basic nodes of the two types of boilers are similar - both in name and in purpose.

Such as the similarities between the single and double boiler types:

  • cold water piping;
  • gas burner;
  • membrane tank;
  • flue gas duct.

Even the construction element intended for water heating is called in the same way - a heat exchanger.

But if we look into it, it turns out: this name is the only similarity between the types of boilers - the heat exchanger of a single-circuit unit is a tube, which serves for efficient transfer of heat, released during gas combustion, to water.

What is better a two-circuit or single-circuit gas boiler: a comparative design review

The important difference of two-circuit boilers is that they are equipped with everything necessary for space heating and hot water supply. Therefore, there will be no additional costs, for the purchase of equipment, and they also allow saving space

And in the case of its two-circuit counterpart, everything is not so simple, since its heat exchanger is structurally more complex. And such products are divided into separate subspecies and are bithermal and dual.

In the first case, the construction is a pipe placed in a similar product of larger diameter. This feature allows the creation of two circuits, one for the transfer of the heat of the fluid used for heating and the other for the hot water system.

The dual heat exchanger consists of:

  • pipes that provide heating water for heating;
  • platesthat transfer heat to the water supply.
That is the structural complexity of the heat exchangers of two-circuit boilers differ solely because of the need to solve 2 problems.

But still the most significant difference between the single-circuit and two-circuit products is the presence in the construction of the latter three-way valve. Its task is to change the direction of hot water.

So in the standard position the valve is in a position where the heating medium is only supplied to the radiators. This changes when the hot water tap is opened. Because the three-way valve, having received the appropriate signal, moves to a different position. Namely in the position providing hot water supply.

In this case the coolant supply to the radiators is stopped, and in full - the premises will not be heated throughout the use of hot water for domestic purposes.

I.e. the design of double circuit boiler allows it to supply hot water only in one of the two modes. But still this feature should not be considered a weak point of the equipment.

Comparative review of gas boilers

Both presented types of equipment serve for heating the heating medium for heating premises, buildings. And on this point the functionality of single-circuit boilers is limited.

What is better a two-circuit or single-circuit gas boiler: a comparative design review

The single-circuit gas boiler serves exclusively for heating the heat carrier, supplied to the heating system radiators. But if one adds a boiler of indirect heating, then it, like its two-circuit analogue, can also provide hot water

These two-circuit analogues are additionally used for providing hot water in order to solve any domestic problems. That is, they allow to take a shower, perform any other hygienic procedures, wash dishes, etc.

Let's carry out a comparative review of single-circuit and two-circuit boilers according to a number of criteria.

 Критерии сравнения Одноконтурный котел Двухконтурный котел
 Тип установкинапольный; wall-mountedfloor; wall-mounted
No additional
capital investment
is required if there is no demand for
HW; if there is a DHW requirement, a buffer tank must be purchased
Hot water
None if there are no more than 2 extraction points and they are near the boiler
EconomyIt is activated when the water temperature in the boiler is cooled below the permissible
level
the heating circuit is activated when the water cools below the permissible level;
the DHW circuit switches on every time the water extraction starts
Compactnesswhen used together with
a boiler, the occupied area actually doubles
compact than a single circuit; wall-mounted models suitable for limited spaces
                      &nbsp     Convenient to usewhen used in conjunction with a boiler
the hot water will have the same temperature at all extraction points; the heating medium in the heating system is supplied evenly
when the boiler has insufficient power and there are many water intake points, the water and water-carrier temperature
will fluctuate,
with sharp changes; the water is not supplied to the

When a single-circuit boiler is used, one should buy additional equipment for hot water supply. For example, a boiler for indirect heating. And that is additional costs

More than that, after buying a boiler it has to be properly installed and connected. And how to do it correctly and what to take into account when operating such devices we have described in detail in this article.

Benefits and disadvantages of equipment

Both varieties of gas boilers are distinguished by simplicity in operation, efficiency and durability. And they also have an attractive appearance.

The design of each type of gas boiler is designed to meet the needs of different categories of users, which clearly demonstrates their advantages and disadvantages. And they also make it possible to understand the differences between a single-circuit gas boiler and its two-circuit counterpart, helping the potential buyer to make the right choice.

Pros and cons of single-circuit units

Such products can provide stable heating of premises of any area, floor area, distance from the heat exchanger.

And besides this, single-circuit boilers are:

  • more reliablethan their double circuit counterparts, whose construction is more complex, leading to a slightly higher number of damages
  • easy to maintain, what is also caused by construction features;
  • cheaper.

A significant advantage is that the single circuit units can be the base for connection of other equipment. That will expand their functionality and increase comfort of living.

When it is necessary to provide in the premises a hot water supply together with a single-circuit boiler it is necessary to buy a storage boiler. And this will lead to a lot of additional costs. A set of the listed equipment will also take up considerable space, which can be critical for small flats

What is better a two-circuit or single-circuit gas boiler: a comparative design review

The connection of accumulation boilers allows supplying premises with hot water. And the water will be hot at any moment, which cannot always be achieved by two-circuit counterparts

This kind of equipment has no pronounced disadvantages when there is no need for hot water supply. But otherwise the lack of versatility immediately affects. Which leads to the need to purchase an additional electric heating device.

As a result, its combined operation with a single-circuit boiler leads to:

  • higher purchase, installation, maintenance costs;
  • limited water volume for domestic needs - for joint use with single-circuit units, boilers are most often purchased, so there may be a question of rational water consumption, whose volume depends on the storage capacity;
  • more load on wiring.

The last disadvantage is relevant in cases where the house or apartment has old wiring or powerful electrical equipment is used in parallel. Thus, it may be necessary to upgrade the electric wiring and select a cable with a larger cross-section. And with limited space it can be a significant disadvantage.

Benefits and disadvantages of two-circuit boilers

Aggregates, which belong to the specified type with some limitations, but still capable of providing hot water for two systems at once (heating, hot water). And they also take up less space than their counterparts with boilers. As a result, two-circuit boilers are more convenient to use.

What is better a two-circuit or single-circuit gas boiler: a comparative design review

Other varieties of gas boilers are easy to operate, efficient and long-lasting. And they also have an attractive appearance

In addition, the competitive struggle of manufacturers has led to the fact that the difference in cost of both varieties of units is gradually leveled.

So today you can find a two-circuit boiler whose price exceeds the similar indicator of a single-circuit product insignificantly. That in some cases can also be considered an advantage.

If we talk about disadvantages of two-circuit boilers, the most important is the impossibility to instantly provide hot water of the same temperature to all points of water consumption in the house or apartment.

So, in their heat exchangers heats the amount of water that is needed right now. That is, no reserve is created. As a result the water temperature can differ from what is expected or change over the course of its use. This happens in case of pressure or flow changes, e.g. after opening/closing the second tap.

What is better a two-circuit or single-circuit gas boiler: a comparative design review

When using a two-circuit boiler the water temperature often differs in two different intake points - the hot water is delivered to the right point with a significant delay. What is inconvenient and leads to additional costs

With regard to installation, the installation of two-circuit boilers - is a more complicated procedure, especially at the design stage. Since you will have to comply with numerous manufacturer's recommendations

Which boiler is the best to choose?

When choosing the best boiler you should take into account that each type of equipment is designed for certain conditions. When complying with which they will show the maximum efficiency, allow to achieve the expected result and level out the drawbacks.

That is why it is so important to define your requirements and take into account the living conditions. So, if the equipment is chosen in an apartment and there is no extra space for installation, then the ideal option will be a two-circuit wall boiler. Even though he is inferior in power floor models, but quite able to meet the needs of residents.

For summer residences or private houses, where there is a separate room under the arrangement of the boiler room, a great solution would be the installation of floor standing single boiler on the gas in conjunction with a boiler of the desired volume. What will provide the family needs in hot water and heat.

What is better a two-circuit or single-circuit gas boiler: a comparative design review

When installing any model of floor standing single boiler with a boiler will require an order of magnitude more space than for two-circuit analogues. And the load on the equipment in this case will be higher, so it is important to choose the necessary boiler power

If you are choosing a heating unit for a country house or cottage, in this situation it is better to choose a powerful two-circuit floor boiler with a built-in large volume heater.

Gas floor boilers with one and two circuits differ more power from their wall mounted \"brothers\". They are also most often independent power. This is quite convenient, especially if there are power outages in the region.

More recommendations and important criteria for choosing gas boilers we have given in the next article.

Conclusions and useful video on the topic

This video will help to understand the features of different varieties of gas boilers:

The video material is intended to deepen knowledge on the topic and help make the right choice:

When choosing between a two-circuit boiler and its single-circuit counterpart, you should not wonder what is better. Since all of the above equipment is modern, productive and durable, but, as indicated above, is designed for different tasks. That is why it is so important to consider personal needs and living conditions, so that the equipment will not disappoint you.

And how many circuits does your gas boiler have? Share your impressions of using your heating equipment - tell us whether your chosen boiler meets all your needs, or for some reason you think your choice is wrong? Add photos of your gas boiler, indicate its pros and cons found during operation.

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