From the design instructions for condensing boilers Buderus(Germany).
Corresponds SNiP 41-01-2003 p. 6.4.1 PIPELINES
: "...Polymer pipes used in heating systems together With metal pipes(including in external heat supply systems) or with instruments and equipment that have restrictions on the content of dissolved oxygen in the coolant, must have an oxygen permeability of not more than 0.1 g / (m3
∙day)..."
VITODENS Gas condensing boilers
Design Instruction
Bosch Condens 3000W
- Possibility of direct connection to the underfloor heating system
Other model
BoschCondens 5000W Maxx
Possibility of direct connection to the underfloor heating system
Without required minimum flow circulating water
High quality components such as plasma cured aluminum heat exchanger and robust construction make the Condens 5000 W Maxx not only extremely reliable, but also exceptionally robust. Thanks to innovative Flow Plus technology No minimum value water pressure through the heat exchanger . For this reason, complete hydraulic system not required.
About the anti-diffusion layer (oxygen barrier):
"... This result once again confirms the erroneousness of the widespread statement: “Pipes of small diameters do not have to be reinforced or protected from the ingress of oxygen into the coolant, since the flow of oxygen through the wall of such pipes can be neglected.” Supporters of this point of view urge not to reinforce with aluminum and not to cover with a layer of AVOH (anti-diffusion layer for PEX pipes)
and PPR pipes of small diameter. However, it is precisely such pipes that stand, for example, in front of steel panel radiators (steel wall thickness - 1.2 mm). Therefore, to reinforce pipes of small and large diameter required for heating systems. Moreover, for pipes of small diameter, this rule is more important than for pipes of large diameter, where calculation and binding to a specific application scheme is necessary.
For example, at D=2х10-11 m2/s (oxygen permeability of polypropylene) and ∆сО2 MAX = 270 g/m3 (approximate oxygen content in the atmosphere)
Q/V=1.9٠10-8/DN2 (g/s٠m3) or 1.6٠10-3/DN2 (g/day٠m3)
for DN20mm, we get 4 g / m3 of oxygen per day - in other words, the formation of 30 g of rust is possible. One meter of pipe DN20 PN20 (SDR=6) contains 2.2x10-4 m3; respectively, through this running meter pipes into the coolant will pass to a maximum of 8.8x10-4 g / day. oxygen.
For example, if the heating system is made of polypropylene pipe PN20 (non-reinforced or fiberglass reinforced), the volume of the heating system is 100 l, there are wall-mounted boilers with aluminum-copper heat exchanger and a heating temperature of 80 ° C and steel panel radiators, and the pipe capacity is 50 liters, then per day for a typical set of pipes different diameter with SDR=6, about 0.1 g of oxygen will pass into the coolant; in terms of per year, this is 37 g of oxygen, or 250 g of rust obtained in steel panel radiators(which is very likely to leak after a year or two of operation).
The scope of this article does not include the exact quantitative analysis oxygen permeability, however, this example allows us to resolve the frequently asked question: “How much oxygen does plastic pipe? Is it a lot or a little? I think we have given a very specific answer. In conclusion, we note that a lot of substantial works have been written on this topic, but the conclusions of readers or companies supplying such products to the market do not always correspond to the analysis carried out in these articles...."
It's time to consider and deal with the features of condensing gas boilers ...
Condensing gas boilers: principle of operation, types and advantages
Thanks to their high-tech design, condensing boilers make the heating system much more convenient, comfortable, and economical. If in conventional devices the products of combustion give only a part of the thermal energy, then in this case this is done to the maximum. The Luch Tepla company presents boilers of all types in a large assortment.
Design
By their structure, condensing boilers are indistinguishable from typical heating appliances. Available in several versions:
- wall-mounted (more traditional, focused on individual systems heating of private houses);
- floor (increased power, designed for use in office and industrial premises).
Their design includes a non-standard heat exchanger made on the basis of acid-resistant materials. Usually - from steel-stainless steel or silumin. It looks like a pipe with a complex section and spiral fins. All this increases the heat exchange area and makes the gas boiler more efficient.
Besides, condensation device equipped with a fan placed in front of the burner. It "sucks" the gas from the gas pipeline, mixes it with air and directs it directly to the burner. The boiler also has an electronically controlled pump, which allows you to optimize the heating power, reduce noise from the coolant passing through the system and save on electricity.
Types of Condensing Gas Boilers :
Condensing boilers are of several types:
- single-circuit;
- double-circuit;
- heating;
- water heating.
At the same time, their power can vary from 20 kW to 100 kW, which is quite enough for domestic boilers. For office and industrial premises, they are produced with greater power and in the floor version.
Operating principle of condensing gas boilers :
In standard boilers, hot exhaust gases are simply thrown into the atmosphere through the chimney, losing a significant proportion of unused heat. It is discharged to the outside along with the waste products in the form of water vapor, which is formed at the time of fuel combustion. It is in the pair that the additional thermal energy, which condensing boilers store and then transfer to the heating system.
Cooling, the vapor condenses, that is, it becomes a liquid, and releases a certain amount of heat. This process takes place in a special heat exchanger with an expanded area. It is he who “takes away” heat for transfer to the heating system. This approach has been known before. But it began to be used relatively recently due to the emergence of corrosion-resistant alloys, which form the basis for the production of condensing boilers.
Features of operation of CONDENSING gas boilers:
The efficiency of such gas devices largely depends on the characteristics of the heating system. The lower the water temperature, the more complete the process of condensation of water vapor. Therefore, the higher the amount of latent heat that is returned to the system.
In this way, the condensation mode is maintained throughout the entire heating period. Therefore, the most important condition for the functioning of the condensing boiler is the average temperature of the coolant. For example, at the entrance to the boiler, it should be less than 60 degrees (ideally, up to 57 degrees). This will give better condensation and increase the efficiency of the heating device.
But even if you combine a condensing boiler with an old system, it will still bring tangible savings, as it will be more efficient than the old equipment. This is due to the fact that in our climatic zone the most frosty days in total occupy a little more than 10 percent of the duration of the entire heating period. On other days optimal condensation is possible.
Advantages
Among the basic advantages of this type of boilers - high efficiency. In this case, it is equal to 108-109 percent, when compared with other boilers. Another advantage is their increased economy. It is approximately 15-20 percent more than standard heating appliances.
It must be made of materials with increased resistance to acid corrosion. It is one thing when hot combustion products pass through the pipe, and quite another when condensate forms in it, a concentrated acid with a pH of 3 to 5.
2. The chimney must provide free discharge of condensate into a special reservoir
This tank (boiler) must be equipped with a siphon water seal filled with water to avoid flue gases into the drain pipe.
Insulated. Photo: Navien
3. It is necessary to provide forced draft
The flue gas temperature is low (approximately 55 C), three times lower than the flue gases from a conventional boiler (180 C). Because of this, the natural draft of the chimney is usually not enough, so forced draft is used. The boiler fan facilitates the removal of flue gases from the boiler.
4. The chimney must be airtight
Due to forced draft, the chimney must be sealed along its entire length (for example, lip seals are used). Otherwise, part of the flue gases will enter the room.
Coaxial. Photo: Protherm
5. A constant supply of air is needed
For normal operation condensing boiler needs to be arranged constant inflow air to him. This can be done in several ways, for example, by taking air from the room if there is a sufficient supply of it. If a supply air is not enough, the air flow is organized through the same chimney, which is usually made for this in the form of a concentric pipeline ( coaxial chimney). By inner tube outside air enters, and flue gases are removed through the outside.
Compact boiler with coaxial chimney. Photo: Boris Bezel
6. It is necessary to correctly determine the length of the chimney
The length of the chimney cannot be arbitrarily large, it is determined by the fan power of a particular boiler model. For each model of a condensing boiler, it has its own, and is indicated in technical specifications products. For example, the De Dietrich VIVADENS MCR-P 24 model is recommended to be connected to a coaxial chimney with a horizontal ending and with an air duct diameter of 60 mm and for flue gases of 100 m. And the length of this chimney should not exceed 6 m if it has a horizontal ending (outlet pipe section goes horizontally through the wall of the house) or 20 m if the coaxial chimney has a strictly vertical structure.
The editors would like to thank De Dietrich for their help in preparing the material.
It should be your desire when installing a condensing gas heating boiler to follow the latest developments in design thought. The point is that ordinary gas boilers, without which no serious system is conceivable autonomous heating country house, do not fully use the full potential of such an energy source as gas. That is why even best models gas heating boilers have an efficiency of no higher than 80%. Part of the energy has to be brought out and simply thrown out through the collector.
Devices outside the school postulates of physics
But, there is an opportunity to squeeze additional dividends out of gas in the form of kilocalories of energy.
The essence of the process
The idea is the following postulates:
- gas is a heterogeneous heat source, in its composition it also has water vapor;
- turns out, when burning gas, we throw out not only combustion products, but also this very steam;
- and an idea arises - why not condense this steam and the resulting hot water also not to be used for heating the coolant in the heating system.
And so it was done - the newest gas heating boilers condensation type. Boilers that are gaining popularity so widely that, according to statistics, more than 30% of all gas boilers in Germany are compensation boilers.
Born at a time when high demands were placed on the products created in the world in terms of design, condensing boilers are developed with an emphasis on this characteristic - they all look terribly attractive.
Well, what is hidden inside, thanks to such a “double cleaning” of the gas, makes it possible to achieve a real calculated efficiency from 105 to 110%. In other words, condensing boilers, in fact, are double-circuit boilers.
Useful advice! Unfortunately, we cannot say about the same prevalence of the presented boilers in our country as in Germany. Therefore, if you decide to install such a boiler, first of all choose a worthy model, and most importantly, a worthy supplier and installer of the purchased boiler. Frankly, the vast majority of companies have neither experience with such boilers, nor the appropriate personnel for its further maintenance.
Benefits of condensing boilers
Among the benefits are:
- they have the highest efficiency of all possible devices similar purpose - and, therefore, you have the opportunity to reduce gas consumption with the same calories of generated energy; according to statistics, gas consumption of condensing boilers is 15-20% less than that of conventional ones;
- a much larger range for adjusting the temperature of the coolant - such an adjustment is possible on all boilers, but those working with gas and “associated” steam have a maximum range of 30 to 85 degrees (by the way, such a maximum, as a rule, does not need to be supplied to the system, the usual temperature of the coolant in heating systems does not exceed 40 degrees);
- smaller output harmful substances in atmosphere - gas mixture burns in a much larger volume;
- innovative technology spurs both designers and technologists - all condensing boilers are manufactured according to the most advanced technologies, which provides them with a much longer service life under the same loads.
Of the shortcomings
But we must be aware that such boilers also have some disadvantages, more than an everyday plan:
- most importantly, they cost at least twice as much as conventional gas boilers; and this is today the main brake on their mass use;
- secondly, such units are very picky about the material from which the chimney is made - it is necessary to use only high-quality plastic and ceramics;
- thirdly, it requires a special calculation of the heating system for lower internal temperatures (not higher than 70 degrees) - this requirement already puts forward the need for condensation of steam inside;
- fourthly, a special conduit is required to bring it outside, usually into the sewer, accumulated inside the water (usually no more than 30 liters per day with permanent job boiler); here it should be noted that in the same Germany there are restrictions on the withdrawal of such water into the general sewer system;
- fifth, it requires experienced personnel to install and maintain them.
Despite the fact that these boilers were originally developed as double-circuit boilers, there are also single-circuit models. But most importantly, several modifications of condensing boilers have been developed, depending on the place of their installation.
There are modifications:
- floor- the most powerful and widespread; the power of such boilers can be 100-120 kW;
- - very elegant looking devices with a power of 30-40 kW, which is often more than enough.
Useful advice! If you decide to purchase a gas condensing boiler for industrial use, most likely, you will need to choose a model of direct, or they say, "wet" impact on the coolant flow. The efficiency of such boilers is even higher, but their use is still limited to a small supply market. At home, boilers of indirect, or “dry”, impact on the coolant are used without contact with it.
On the crest of a wave
With your own hands, you are unlikely to succeed. This is too responsible technique, serving for too responsible tasks. Even despite the fact that you will have installation and operation instructions at your disposal, even despite the fact that you view all the photo and video materials on our website, you still have to seek detailed advice from professionals.
But to understand the algorithm of operation of condensing boilers and choose the necessary one, according to the power and appearance, this is for you. In any case, take the choice very responsibly, the price of a mistake is quite high and is expressed not only in the quality of heating your home, but in considerable lost financial means, but also in discrediting such an important thing as the introduction of the most advanced achievements of constructors and designers into our lives.
