Chimneys of condensing boilers
There are many options for connecting the chimney to the condensing boiler. The main requirement for chimneys for condensing boilers is the tightness of joints of the chimney elements.
In general, the chimney design of condensing boilers is not much different from that of conventional gas boilers.
Features chimney for condensing boilers:
- The material from which they are made. The chimney for condensing boilers must be made of acid-resistant materials, such as stainless steel or plastic. This is due to the fact that the condensate that runs down the chimney is a mild acid, so the chimney material must be protected from corrosion.
- The chimney for a condensing boiler must be located at an angle, so that the resulting condensate flow back into the boiler, but it does not get there precipitation. Precipitation in the boiler can cause a short circuit or boiler breakdown.
Chimney for a “condensing boiler
If all the instructions of the boiler manufacturer for arranging the air intake and flue gas evacuation have been followed, the problem of winter frosting usually does not occur. Most often abnormal situations in the boiler arise when the gas condensing boiler is replaced by an old conventional boiler without significant alteration of the existing chimney. Typical boilers have a high temperature of the flue gases, and this is enough to create a draft in the chimney because of the temperature difference in the density of hot air after the boiler and the cold air outside. Condensation, however, have a forced removal of exhaust gases with a fan and a completely different temperature-humidity mode of smoke removal.
The normal flue gas temperature is 57 63 ºС. Condensation of the flue gases is not limited to the boiler part of them manages to leave the condensation zone inside the boiler, and they condense already in the chimney. There is quite a lot of condensation. Typically, a condensing boiler of average output (3040 kW) produces 5-7 liters of condensate per hour. In addition, the condensate from the flue gases has some acidity (
condensate (pH = 4) and contains aggressive organic compounds, i.e., when subjected to prolonged exposure this mixture can corrode the walls of the old chimney. Therefore, only high quality chimneys made of special heat resistant polymers, acid resistant stainless steel or special passivated aluminum alloy are used for flue gas extraction from condensing boilers.
Some options for connecting flues to condensing boilers are shown in Fig. 2.
To ensure that the condensate formed in the chimney flows back into the condensing boiler, the slope of the chimney is made towards the boiler at least 23. The chimney cap must be protected against the ingress or the blowing of precipitation water. The joints of the chimneys are assembled with their sockets facing the condensate, so the joints do not interfere with the free flow of condensate.
The chimney outlet scheme is vertical (Fig. 2, a)), with the intake of combustion air from the boiler room, it is necessary to provide a chimney cap, protecting the chimney from precipitation of water. A supply air must be arranged in the boiler room at the rate of 10 m3 of air per each cubic meter of flue gas.
When extracting the flue gases from the boiler into the existing chimney of the building with air intake from the boiler room (Fig. 2, b) the slope is taken from the condensing boiler, similarly to the chimney slope for a normal boiler. It is necessary to provide a water trap for condensate drainage. The boiler duct below the chimney connection, where the condensate flows down, must be made of acid-resistant materials (or bunged). The supply air rate is similar to point a).
Standard coaxial flue of a condensing boiler (Fig. 2, c)) is installed so that its inner pipe, through which the flue gases are drained, has a slope to the boiler.
Horizontal flue led into the wall (Fig. 2, d) is also arranged with a slope to the boiler. It is important to protect its head from precipitation. The requirements for boiler room ventilation are the same as indicated for the diagram in Fig. 2, а).
To protect against condensation
The problem of safe drainage of condensate formed as a result of boiler operation has become particularly relevant in improving the energy efficiency of boiler equipment, of which the highest thermal efficiency is characterized by condensing boiler models.
Condensation is formed when the outgoing gases, consisting of excess combustion air and products of fuel combustion in the boiler furnace, cool down. It is formed as a result of the phase transition of water, when the temperature of the escaping gases falls below the dew point. The more efficient a boiler, the higher its thermal efficiency, the lower the temperature of the flue gases and therefore the higher the probability of condensate formation. For traditional boilers, this process usually takes place on the walls of the chimney, and for condensing boilers under the ideal mode of operation. on the walls of the condensate heat exchanger. where the heat released during the phase transition of water vapor into liquid is utilized as a useful.
Aggressiveness of the condensate
Water (in the form of vapor) contained in the exhaust gases is formed during fuel combustion from hydrogen of organic compounds and air oxygen, and it can also be water vapor already contained in the air supplied for combustion, or formed during the evaporation of water from the fuel composition. For example, wood fuel almost always contains some amount of water. Pellets, for instance, are allowed to have 6 to 12 % moisture, depending on their quality, and even hard coal contains 2 to 4 % water.
Water, as it is known, is not chemically aggressive on its own, and removal of its vapor condensate from the place of accumulation is usually not a serious problem. Thus, condensate formed by split air conditioner systems from water vapor in the air is simply drained through a pipe to the outside. However, this approach is inadmissible for removal of condensate formed during cooling of flue gases after combustion.
The exhaust gases, apart from water vapor, also contain products of fuel combustion, which dissolve in the condensate and react with water to form acids.
The combustion reaction products of gas-fired boilers should ideally contain only carbon monoxide IV (CO2) and water (H2O). But in reality there are also nitrogen oxides (NOx), which are obtained as a side product of the reaction of nitrogen and oxygen in the air. The higher the temperature in the combustion zone, the higher in the combustion products NOx. It is generally believed that there should be no sulfur in gas fuel, but in reality sulfur is present in natural gas in the form of hydrogen sulfide (H2S). Thus, depending on natural gas deposits, hydrogen sulfide usually ranges from fractions of percent to 12 %, but there are also deposits with high m H2S.Thus, in gas from the Orenburg field hydrogen sulfide reaches 5%, from Karachaganak. up to 710%, from Astrakhan. up to 25%. When burning such gas in the boiler combustion chamber, in addition to carbon and nitrogen oxides, sulfur oxides are also formed. When dissolved in condensate and interacting with water, the carbon and nitrogen oxides turn into carbonic, nitrous and nitric acids, and the sulfur oxides turn into sulfuric and sulfuric acids, making the condensate chemically aggressive. The area of its pH value for gas fuel is 2.84.9.
In liquid fuel boilers, sulfur compounds contained in diesel fuel contribute even more to lowering the condensate pH value to 1.83.7. Low pH values indicate that the medium in question is acidic, and high values indicate that it is alkaline. The normal pH values are in the range of 77.4.
Due to its high level of acidity, the condensate resulting from flue gases leaving the combustion process is chemically aggressive. If it falls out on the wall of a draining stack, it can cause corrosion of the stack material, up to its rupture, destruction and damage to the structure around the stack. Normal for condensing boilers condensate formation on the heat exchanger will also lead to undesirable consequences if the condensate will simply flow down unchecked somewhere by gravity.
Devices for the collection and subsequent removal of generated condensate is necessary when it appears or can appear in volumes that adversely affect the operation of boilers and (or) reduce the service life of chimneys.
To avoid such consequences condensate traps and condensate pots are used. For small capacities of heat generators, it is possible to avoid using only condensate collectors, but in this case, the long-term operation of the boiler in automatic mode becomes impossible, because the condensate must also be removed from the condensate collectors.
Condensate traps for condensate discharge from the chimney to the outside, to prevent its penetration into the boiler, are made of stainless steel AISI 321, equipped with nozzles and plugs.
In addition, in accordance with EN 13384 and DIN 18160, combustion gases must be conveyed via a flue gas venting system into the atmosphere and prevented from cooling in such a way that vapour components in the chimney are not creating a dangerous situation. If the gas outlet system is equipped with a condensate trap, a trap must be installed.
Aggressive condensate can not always drain into the sewer, so in some cases, in addition to drainage, there is the problem of neutralization of condensate.
The need for neutralization
To transform condensate into a product that is safe for sewage systems and the environment, it is required to reduce its acidity to permissible limits. This can be achieved by adding appropriate reagents and/or by increasing the volume of discharged liquid. by diluting it with conditionally neutral sewage.
According to regulatory documents, acids (present in the condensate) that can form explosive, toxic and flammable gases in sewage networks and facilities are prohibited for discharge into sewers. normative values of general properties of waste water taken into the sewerage system of settlements are established uniform for waste water of all categories, based on the requirements to protect networks and facilities of sewerage systems: temperature. not higher than 40 C, pH. in the range of 6.58,5. From this point of view it is inadmissible to discharge condensate into the sewer without its preliminary neutralization. However, when operating condensing boilers of household series up to 100 kW, users drain not only condensate, but along with it other domestic sewage, diluting it and reducing acidity. According to the European regulations (VDI Directive 2067) condensate can be discharged into the sewerage system by diluting it with water in the ratio of 1:25, but this rule only applies to boilers with a capacity of no more than 260 kW.
The European working regulations ATV A 251 can be used to determine whether condensate can be discharged into the sewer system and whether the flue gases can be drained. Domestic normative documents do not provide such methods. For boilers with a capacity of up to 25 kW, neutralization of condensate is usually not required; with a capacity of 25-200 kW, the neutralization system can be dispensed with if a large amount of waste water is discharged together with the condensate into the sewer. Their average annual volume must be 25 times the condensate volume. European regulations for draining condensate are also laid down in DIN 4702-6.
Thus, it can be assumed that neutralization of condensate is necessary for boilers or cascades of several boilers with capacities over 200 kW. But in some cases, it may also be required for capacities under 25 kW (condensate volume up to 3.5 l/h). For example, if the drainage takes place into the house sewer system and small sewage treatment plants according to DIN 4261-1; for buildings and land plots where the sewer lines do not meet the requirements of ATV A 251 for the materials used. Condensate neutralization is also required for boilers and boiler cascades from 25 to 200 kW in buildings where the conditions for sufficient mixing with the domestic sewage are determined by the ratio 1:25.
DO BOILER CONDENSATE PIPES NEED INSULATING look into BS 6798; 2014 and building regs H1 to find out
Neutralization plants
If it is not possible to discharge condensate into the sewer system without neutralisation, condensate neutralisation units are installed (Fig.3). They are tanks which are filled with an acid neutralizing agent. The neutralisation unit can be enough for the whole boiler room, and its lifetime will be several years.
The simplest and most effective device for neutralization is a tank with marble chips, in which acids react and form chemically inactive salts. The consumable reagent in this case is marble chips, which are added as they are produced. Other reagents are also used: granulated chalk combined with activated carbon, magnesium dioxide (MgO), special granules.
Some manufacturers of chimneys, such as Jeremias, offer a line of neutralizer models designed for use with boilers of different capacities.
General principles
Proper design of the whole heating system is a guarantee of proper installation of boiler and its further normal operation. It is the fact that, for example, a significant efficiency and comfort of the equipment can not be achieved without the installation of thermoregulators. Modern technology allows you to create zonal heating systems. In this case each heating zone maintains its own microclimate under the control of a room temperature sensor.
The temperature of the condensation heat exchanger must be below the dew point of the flue gases, and the formation of chemically active liquid condensate on its surface is not only normal but necessary. It must be somehow removed to the outside and neutralized. Flue gas discharge systems must be made of corrosion-resistant materials.
When installing systems with condensing boilers is important to accurately calculate the heat loss of the building and heating design with regard to the use of such equipment.
To reduce the required temperature of the coolant, it is important additional measures to reduce heat loss insulation of building envelopes, installation of windows with laminated glazing.
Condensing boilers can be used in any water heating system. But the proportion of operation in the mode of condensation
will depend on the calculated parameters of the heating system, the temperature of supply and return lines. The lower the return water temperature of the heating system, the greater the specific weight of the condensing mode. Low-temperature heating systems (return line below 40 ° C) provides it practically during the entire period of operation.
In the case of reconstruction of old systems, it is important to consider that the hydraulic schemes for condensing units are also different from traditional. For example, all devices for increasing the return temperature must be excluded. It is important to pay attention to correct selection of heating devices.
Condensation in condensing boilers
Currently, energy efficient appliances are becoming increasingly popular and widespread in our country. With regard to gas boilers, this trend is reflected in an increasing number of installed condensing boilers for both domestic and municipal purposes.
The high efficiency of condensing technology is due to the use of the heat which the water vapour contained in the flue gases transfers during condensation. Thanks to technological and design solutions, the heat from steam condensation is used to heat the coolant. The condensing boiler efficiency in condensing operation is conditionally greater than 100 % and is determined by the fact that in this case the calorific value is given. This index is calculated as the sum of the lower heat of combustion (heat received from the combustion of fuel) and the heat received from the condensation of water vapor.
Condensing boilers have a number of advantages over their traditional counterparts: significant savings in fuel; low temperature of flue gases and, consequently, cost savings for the organization of the chimney system (chimneys for condensing boilers in most cases are made of plastic, which greatly simplifies and reduces their installation costs); easy design, installation and operation of low-temperature heating systems, which are more preferable in terms of microclimate for installation in residential areas. However, there is a downside of condensing boilers, their higher cost compared with traditional heating equipment and the need to utilize the condensate produced during operation of the boiler.
According to the manufacturers of condensing equipment, depending on the design and settings of condensing boilers, the amount of condensate produced is about 0.10,15 liters per 1 kW⋅h of energy produced. Thus, the amount of condensate generated during operation of a 30 kW condensing boiler will be approximately 34 l/h, and during operation of a 500 kW boiler 5075 l/h. It should be noted that the pH (hydrogen index) of condensate is in the range of 3 to 5, indicating its high acidity. These data are confirmed by the results of long-term experimental studies, conducted by specialists of ZAO Tsentrgazservis at municipal boilers in Belgorod, Saransk and Tambov. Acid-proof materials should be used for condensate drainage.
Most internal drainage systems are made of polypropylene, which are highly acid-resistant and provide a leak-proof system at a pH range of 2 to 12. The discharge of condensate from municipal boiler plants (which are production facilities) into centralized sewerage systems is regulated by the Rules of Industrial Wastewater Intake into the sewerage systems of settlements, which state that the discharge of wastewater whose flow and composition may lead to exceeding the amount of pollutants allowed by the established rules into the water body; industrial wastewater with a temperature above 40 C, pH below 6 is prohibited into centralized sewerage systems. Thus, under current Russian law, condensate from municipal boiler plants cannot be discharged directly into the municipal sewer system without pre-treatment.
In the leading countries of the European Union, where domestic condensing appliances are widespread and increased requirements are made to environmental safety, there are also various standards that regulate the need for condensate neutralization, depending on the capacity of the heat generator and the fuel used.
In Germany, there is a regulatory document, according to which for boilers with a rated heat output of up to 200 kW, condensate is generally allowed to be discharged directly into the public sewer system. In the case of a larger boiler plant (or boiler house), it must be pre-treated in a condensate neutralization unit, where its pH will increase to 6.59.0.
Neutralization of condensate formed during liquid fuel combustion is mandatory without reference to power. Thus, as part of the equipment of a condensing boiler plant, it is necessary to include condensate neutralization units, which are offered by most manufacturers of condensing technology: Ariston, Baxi, De Dietrich, Vaillant, Viessmann. Some of them have units with an intermediate tank where neutralized condensate is collected and forced to be pumped by a built-in pump into the sewage system (as it is done at De Dietrich, Vaillant, Viessmann, for example).
Neutralization units should be selected according to the maximum capacity of the amount of generated condensate neutralized per unit time. When discharging condensate into a local sewer system (e.g. a septic tank) there are no restrictive discharge regulations due to the closed nature of the system. However, if the acidic condensate is not diluted with other effluents (e.g. alkaline solutions formed during washing, etc.) then the sulfuric acids will be removed.п.) The high acidity of the medium can lead to the death of the microorganisms responsible for the processes of intensification of domestic wastewater treatment in the septic tank. In this case it is therefore necessary to provide equipment for neutralization of condensate.
Most units for the neutralization of condensate is a container filled with marble chips or limestone crumb. As acidic condensate passes through the filler, it dissolves and the pH value of the filtrate rises to neutral and is discharged into the sewage system. As the neutralizing material dissolves, its volume must be replenished.
We are not afraid of condensation
In this case, the condensate is a weak mixture of acids and water formed during the combustion of fuel. In conventional boilers, these combustion products literally fly down the drain, as their temperature is quite high and they remain in a gaseous state. And in condensing boilers the products of combustion are cooled, releasing additional energy. due to which, in fact, a higher efficiency of equipment is achieved.
A small amount of condensation is not a big problem. Its acidity corresponds approximately to the acidity of many fizzy drinks. However, so much condensate is formed that it must be somewhere to dispose of.
Depending on the capacity, condensing boilers are available for floor and wall mounting
If there is a public sewer connected to the house, it is possible to negotiate with local authorities to drain the domestic sewage to completely neutralize the entire volume of condensate from the boiler. This possibility is provided for in our building standards and therefore does not raise objections from local services. However, you have to pay for the drainage of a large volume of waste water, which at current is more expensive than installing a condensate neutralizer, the cost of which is about 5-10 thousand. For boilers up to 100 kW.
Example of calculating the service life of the backfill
The specifications of all models of neutralizers specifies the volume of condensate that can neutralize one filling (e.g. 520 m³. the dosage depends on the amount and pH level of the condensate). In the instructions on the boiler is always specified the maximum volume of the condensate formed per hour of work (say, a model Buderus GB162-100 can produce up to 10.8 liters per hour). To find out how much condensate is formed per year, you need to specify the duration of heated period (for Moscow region, for example, it is 3200 hours per year). That is for a year boiler GB162-100 in the Moscow region will develop approximately 10.8 × 3200 = 34,560 liters = 34.56 m ³ of condensate. It remains to divide the capacity of filling (520 m ³) to the annual volume of condensate (34,56 m ³), and we see how long will not need to call the service to replace the neutralizer. 520 : 34,56 = 15 years. After this period, the neutralization deposit must be completely renewed.
Neutralizer is also needed if the house has its own sewage system. Usually, it represents a system of tanks, where special bacteria live, for which even a very small concentration of acid is destructive. This is why acidic condensate must not be poured directly into the tanks. It is also unacceptable to pour condensate directly into the garden.
Condensing boilers, like other types of boilers, require annual inspection by a service technician
The simplest neutraliser is a vessel with grains of neutralising agent. complicated models have a pump, an acidity indicator, their own control system and much more. All these details are important for the installer, not the consumer. The latter needs to know how long the backfill will serve, and find out the frequency of its replacement. It is not difficult to calculate the lifetime of a single pellet.
Bosch neutralizers to neutralize condensate from natural gas combustion
When installing condensing boilers do not forget that the chimneys for them must be made of materials that are resistant to condensate, such as stainless steel or special types of plastic
Maintenance of the simple neutralizer involves replacing the fill and checking the pH of the neutralized condensate (pH of 5.5 or more is acceptable) twice a year. The charge can be changed independently if the neutralizer is simple and easy to open for maintenance. It is very important to find a neutralizing agent from the manufacturer of your particular neutralizer, and it may not always be commercially available (be sure to check the availability of the fill before purchasing an appliance). If the neutralizer is equipped with additional functions and devices, such as a pump or an acidity indicator, maintenance is more complicated and must be performed by a specialized service organization.
Service features of condensing boilers
Economical heating condensing boilers are considered to be the most promising. Perhaps their most significant disadvantage is the condensation that forms during operation. What is this condensate and how dangerous it is?
In this case, condensate is a weak mixture of acids and water from the combustion of fuel. In traditional boilers these combustion products literally go down the drain, as their temperature is quite high and they remain in a gaseous state. And in condensing boilers, the combustion products are cooled, releasing additional energy. due to which, in fact, a higher efficiency of the equipment is achieved.
A small amount of condensate is not particularly dangerous. Its acidity is about the same as that of many fizzy drinks. But there is so much condensate forming that we have to dispose of it somewhere.
If the house is connected to the city sewer, you can arrange with local services for the drainage of domestic sewage to completely neutralize the entire volume of condensate from the boiler. This possibility is provided for in our construction standards and therefore does not raise objections of local services. However, for the drainage of a large volume of waste water will have to pay, which at current will cost more than the installation of a condensate neutralizer, the cost of which is about 5-10 thousand. For a boiler with a capacity of up to 100 kW.
The neutralizer is also needed if your home has its own sewage system. Usually it is a system of tanks, where special bacteria live, for which even a very small concentration of acid is destructive. Therefore, you must not pour acidic condensate directly into the tanks. It is also unacceptable to pour condensate directly into the garden.
The simplest neutralizer is a vessel with a granulate of neutralizing agent. The more complex models have a pump, an acidity indicator, their own control system, and more. All these details are important for the installer, not the consumer. The latter needs to know how long the backfill will last, and find out the frequency of its replacement. It is not difficult to calculate the life span of one cartridge.
Maintenance of the simple neutralizer involves replacing the fuel charge and checking the pH of the neutralized condensate (pH 5.5 or more is allowed) twice a year. The charge can be changed by yourself if the neutralizer is simple and easy to open for maintenance. It is very important to find the neutralizing agent from the manufacturer of your neutralizer, and it may not always be available on the market (be sure to check the availability of the fill before purchasing the unit). If the Neutralizer is equipped with additional features and units, such as a pump or an acidity indicator, service becomes more difficult and must be performed by a specialized service organization.
Characteristics of all catalyst models contain information on condensate volume that can be neutralized by one charging (e.g., 520 m³. dosage depends on quantity and pH of condensate). In the instructions on the boiler is always specified the maximum volume of condensate produced per hour (say, a model Buderus GB162-100 can produce up to 10.8 liters per hour). To find out how much condensate is formed per year, we need to specify the duration of the heating period (for the Moscow region, for example, it is 3200 hours per year). That is in one year boiler GB162-100 in the Moscow suburbs will make about 10,8 X 3200 = 34,560 l = 34,56 m³ of condensate. It remains to divide the capacity of the filling (520 m ³) to the annual volume of condensate (34,56 m ³), and we will see how long will not need to call the service for replacement of the neutralizer. 520 : 34,56 = 15 years. After this period, the neutralizing backfill must be completely renewed.
Hidden reserves of comfort
The range of wall hung boilers available in the sales network is wide and varied, so the consumer can easily choose a technically perfect unit. Among the most effective and environmentally friendly are wall hung condensing boilers that run on mains gas. methane.
Unlike wall hung gas boilers of traditional design, the efficiency of which is about 80-85%, wall hung condensing boilers allow to use fuel more efficiently. their efficiency reaches 93-96%. That’s why thrifty Europeans legally encourage the use of condensing units. And in the UK, since recently only condensing heat generators are allowed to be installed in residential buildings. This is due to stringent requirements of British legislation defining the permissible standards for harmful emissions, and rising commodity for gas. Yes, and in our country in the foreseeable future consumers may abandon the conventional wall hung gas boilers in favor of condensing, especially in the most developed regions.
Higher calorific value of the fuel. is all the heat which can be utilized during the fuel combustion, including its share in the water vapour of the flue gases. Lower calorific value. amount of heat without considering the energy latent in the vapor of flue gases. To show their products in a favorable light, sellers of heating equipment almost always indicate the efficiency of heat generator, calculated using the method with the lowest calorific value of fuel. However, the buyer is not informed about it. As a result, instead of efficiency of 80-85%, the real one for a traditional heat generator, the indicator is 92-95%, and the efficiency of condensing units instead of 93-96% turns out to be 107-109%, which is contrary to the law of conservation of energy. This fact arouses certain skepticism among consumers unfamiliar with the basics of heat engineering. But do not be afraid of the extra-high efficiency of condensing boilers. This is the cost of the existing calculation methodology.
Advantages of design
Conventional wall hung boilers utilize the heat released during gas combustion by means of a convection heat exchanger (essentially a tube on which numerous copper plates are attached). The combustion products of methane heat this unit, and it transfers the resulting heat to the heating system heat carrier. The draught necessary for maintaining combustion in conventional wall hung boilers is provided by the vacuum produced in the gravity chimney; the average temperature of the flue gases discharged into the atmosphere at the boiler outlet is 120 C. To cool the exhaust gases to a lower temperature traditional boilers are not able to due to their design. Of course, it is possible to install a more efficient heat exchanger in a wall mounted boiler. But if the exhaust temperature drops, condensation will appear on its plates and in the chimney, containing acid, which will cause the elements of the boiler to deteriorate. That’s why we have to use the energy to “heat the street”. it is better than replacing condensate-damaged heat generators one after the other.
Where does the condensate come from?? Combustion of natural gas (as well as any other hydrocarbon fuel) causes a chemical reaction, resulting in the formation of water, which immediately turns into steam in the fire. Steam represents up to 11 percent of the energy in the methane mix. Purpose of condensing boiler. use this energy by reducing the temperature of the flue gases to the dew point (for the products of gas combustion. approximately 57 C), at which the steam starts to condense, the thermal energy for the steam production (water evaporation) is released and the heat, which was “going down the pipe”, can be used, for example, for heating the heat carrier.
| Photo 1 De Dietrich | Photo 2 De Dietrich | Photo 3 Vaillant | Photo 4 Viessmann |
Condensing wall hung boilers Innovens (De Dietrich) will provide an optimal level of comfort for heating and hot water preparation. 2. MCR boilers of 6,3-39 kW output operate on natural gas or propane. For hot water supply boilers are equipped with flow-through heat exchangers, allowing to obtain hot water immediately after ignition of gas, or are connected to boilers. The 80-litre capacity is installed next to the boiler, the 130-litre capacity. underneath. 3. The ecoTEC plus condensing boilers (Vaillant) are very economical and do not pollute the environment. 4. Wall mounted Vitodens 200-W (Viessmann) condensing boiler installed in a row with wall mounted kitchen cupboards.
What are the differences between condensing boilers and conventional boilers? The former have a special heat exchanger made of acid-resistant materials (stainless steel, silumin etc.). п.). It has a large surface area in contact with flue gases, which, by the way, can clean itself with fluctuations in the temperature of the coolant, as in the ComfortLine model (Wolf, Germany). Such a heat exchanger is able to operate both in low-temperature mode (temperature of water returned to boiler) and in low-temperature mode (temperature of water returned to boiler). about 30 C, and exiting. The boiler can operate in the low-temperature (40-50 C) and high-temperature (70-90 C) modes of operation. True, in the latter case, condensation in the heat exchanger will not start, and the boiler efficiency will be almost the same as in traditional wall mounted gas. In addition, condensing boilers use a special modulating fan burner. It can produce from 8-20 to 100% of the rated heat output (depending on the model), adapting the heat output of the boiler to the needs of the house. And the problems with gas supply, typical for the Russian countryside, condensing burners are not afraid of. They also work when the gas pressure at the inlet to the house is reduced to 5 mbar, not significantly losing power. The condensate does not destroy the burner.
Modern wall mounted condensing boiler (both single and double circuit) is functionally superior to almost any wall-mounted gas appliance of traditional design. Power wall condensing boilers range from 5-125 kW. This means that with just one unit it is possible to heat quite a large house. If the home’s heat requirements exceed 120 kW, condensing boilers can be combined into a cascade, which can satisfy the appetite of any private country house. For example, condensing boilers Rendamax (Netherlands) can be equipped with a cascade control device, which includes up to eight units.
The condensing boiler produces a significant amount of hot water. Thus, a single-circuit condensing boiler can always be connected to an external boiler. For example, ProCon (MHG, Germany) is able to work with an external boiler volume up to 500 liters. With low water consumption (eg, a mixer in the kitchen and shower in the bathroom) is a good idea to buy a two-circuit condensing boiler, which heats water using a built-in plate heat exchanger. It could be, for example, a two-circuit ComfortLine (Wolf). Very compact and efficient models with integrated miniboilers. In boilers Vitodens 333-F (type WS3C, Viessmann, Germany) a built-in tank-water heater of 86 l capacity is provided for HWS.
| Photo 5 Viessmann | Photo 6 Wolf | Photo 7 Vaillant | Photo 8 Biasi |
The Vitodens 200-W (Viessmann) high-efficiency wall-mounted condensing boiler in the kitchen of a country house. The apparatus heats the coolant for heating and water for DHW. 6-7. CGB-K-24 Comfort-Line condensing boiler (Wolf) with integrated control panel (6) and calorMATIC 330 remote controller (Vaillant) (7). 8. Biasi wall hung condensing boilers can be combined into Cascade to increase the output. Assembling the equipment greatly simplifies the special metal cabinets-cells.
Is the game worth the candle?
On average, because of the difference in efficiency, a good condensing boiler spends to produce 1 kW of heat for heating needs gas by 15% less than a wall boiler of traditional design. For example, to heat a house with area of 200 sq. m., a traditional 24 KW boiler during the heating season would consume 6 thou. m3 of gas, and the condensing boiler of the same capacity. a total of 5100 m 3. Then, if the price of 1000 m3 of gas is 3690 (which is how much mains natural gas now costs to owners of summer houses near Moscow), the owner of condensing technology will save about 3321 In 10 years, this amount will increase to 33 210 thousand m3 and even more, since natural gas for the population are growing, and recently at quite a fast pace.
Chimney flue options from condensing boilers
De Dietrich The diagrams show: a horizontal coaxial flue through the roof (a) or outside wall (b); a flue in a vertical shaft of air intake for combustion from the atmosphere (c) or from the room (d); a vertical coaxial flue with passage through an inclined (e, f) roof; a coaxial flue in the shaft (g); a flexible flue in the shaft of non-linear shape (h).
However, if we assume that gas in Russia will remain unchanged (which is unlikely), the economic feasibility of buying a condensing boiler can be questioned. After all, for example, a 24 kW condensing boiler is more expensive than a traditional heat generator of the same capacity, just the same 30-35 thousand which will be saved on fuel and will fully return to the boiler owner only after 10 years of operation. Besides, though this equipment has an increased resource (which, by the way, partially compensates a high cost of condensing boilers), it still requires regular and expensive technical service.
| Photo 9 De Dietrich | Photo 10 Viessmann | Photo 11Foto B. Balashova | Photo 12Photo C. Balashova |
Modern condensing boilers are usually quite compact in size, small weight, delivered in assembled form. All this makes their installation much easier and allows fitting them into any interior. Works quality condensation technique with a fairly low noise level, even in maximum output mode. 10. The Vitodens 300-W (Viessmann) condensing boiler is equipped with Smart (Self Monitoring And Reporting Technology), which detects malfunctions and informs the user in good time. 11-12. Condensing boilers BWC 42 (Bosch) (11) and Logamax plus GB 162 (Buderus) (12) are equipped with multifunctional control systems, extremely easy to set up and easy to maintain.
However, condensing boilers should be preferred primarily because they are environmentally friendly. As the emissions of condensing units are more environmentally friendly (in comparison with the combustion products of traditional units), this equipment can be placed in residential buildings without building high chimneys. By pre-mixing the fuel and air, and lowering the temperature of exhaust gases can suppress the formation of nitrogen oxides NOx and CO (carbon monoxide), because the latter is oxidized to less dangerous CO dioxide CO2 (carbon dioxide). In addition, the condensate captures a significant portion of harmful substances, so the amount of harmful emissions into the atmosphere is sharply reduced. For example, nitrogen oxides and carbon monoxide in condensing boilers Baxi (Italy) compared to conventional wall mounted gas boilers is reduced by 80% and 90% respectively.
There is another important advantage of condensing boilers over conventional. The first is adapted to low-temperature heating systems (more comfortable than conventional, high-temperature). In such systems heating devices of large size are used. Their set will cost the homeowner 20-50% more than for a high-temperature heating system (for a dwelling of 150 m 2. for 10-20 thousand euros more than it would cost to build a high-temperature heating system. ). But the radiators of low-temperature systems are heated only to 40-45 C, so even touching them for a long time, you will not get burns. Longwave infrared radiation from the surfaces of radiators, pipes and other components of low-temperature heating system is most beneficial for humans. And there are almost no draughts in the rooms, because large, moderately warm radiators under windows are more efficient in fighting the downward flow of cold air than small, but high-temperature radiators in traditional heating systems. Condensing units are also perfectly suited for underfloor heating.
| Photo 13Photo V. Balashova | Photo 14Foto B. Balashova | Photo 15Photo B. Balashova | Photo 16 |
Boiler Logamax plus GB 162 (Buderus) is equipped with a heat exchanger with capacity up to 100 kW, whose high efficiency is due to its large surface heat exchange. 14. The ceramic burner of boiler GB 162 allows to change its output from 18 up to 100 %. 15. The GiegaStar (Giersch) series wall mounted gas condensing boilers use a cylindrical stainless steel burner installed in the upper zone of the corrosion resistant heat exchanger made of aluminum alloy with high silicon content (11%). 16. Operating diagram of an MCR boiler (De Dietrich).
Process costs
Unfortunately, a condensing boiler “gives out” a significant amount of condensate. Of course, even with an ordinary boiler in the chimney is sometimes quite a lot of this liquid, especially in cold weather, but the “productivity” of condensing boiler these volumes are incomparable. For example, a 25 kW condensing boiler produces up to 3.5 liters of condensate per hour, almost two buckets of it in a day, and in a year (with continuous operation). up to 7 thousand. л. Essentially, condensate. is a weak solution of carbonic and sulfuric acids in water. Its pH value depends on the fuel, heat exchanger design, excess air ratio, final condensate temperature and when using main gas is 4-6.
This raises the question of where to dump the condensate? After all, you can not take it in the stream flowing next to the house, on the ground or in the gutter on the border of the site (thus you worsen the ecological situation on your territory and the neighbors). If the basis of sewage in the building. Biological treatment plant, to run into the pipes acidic solution is undesirable or even unacceptable (as a result the colony of bacteria that provide wastewater treatment can die). Thus, for many high-tech models of sewage treatment plants designed for a country house, the required pH value of the effluent. at least 6.5.
However, there is quite effective and inexpensive equipment that allows preparing condensate for disposal by traditional methods. So, before being discharged into the house sewer, the condensate must be deacidified in the neutralizer. The latter is generally installed in the vicinity of the wall mounted condensing boiler (on the floor or wall). Neutralizer. is usually a small container, at the inlet of which a filter is installed that cleans condensate from solid particles. Once in the neutralizer, condensate gradually percolates through the filling of alkaline granules or marble chips, and the output is quite safe for any septic tank liquid with a pH of 6.5-9.
The pH value of the deacidified condensate must be systematically monitored (at least once a month). You can use an indicator strip from the Neutralizer delivery set or a pH meter for this purpose. You have to add granules to the neutralizer on a regular basis or (if the User’s Manual requires) completely change the top-up every 6-12 months. Examples of neutralizers. Neutrabox GENO I-25 (Grunbeck, Germany), HC 33 (De Dietrich, France). The price of the neutralizer for a 25 kW condensing boiler (the package usually includes deoxidizing pellets for one filling) is about 10-19 thousand. Additional package with pellets (5 kg) costs about 1-1.5 thousand.
Condensate can be poured into the village sewer (if dozens of houses are connected to it) without neutralization if the boiler output does not exceed 200 kW. After all, domestic wastewater, including from washing machines and dishwashers, often have a low alkaline composition (pH 7.2-7.8). Therefore, the condensate is neutralized directly in the sewer, due to the contact of alkaline and acidic media. However, in this case you may also need to install a deoxidizing device. e.g. if the pipes and seals in the sewage system are made of material which cannot withstand prolonged contact with a weak acid solution, or if the condensate is not mixed in sufficient proportion with the domestic sewage water (at least 1 : 25).
| Photo 17 Viessmann | Photo 18 Biasi | Photo 19 Biasi | Photo 20 Wolf |
“The heart of the Vitodens 200-W wall mounted condensing boiler is the stainless steel Matrix burner, which significantly reduces pollutant emissions into the atmosphere. 18-19. The heat exchanger (18) and cylindrical burner (19) of Biasi wall hung condensing boilers are made of long-life acid-proof materials. 20. Condensing wall hung gas boilers CGB-K-24 (Wolf) are equipped with a stainless steel DHW heat exchanger. These heat generators are designed for heating and hot water preparation in the flow mode. If in the course of time the needs of the country house for warm water increase, the boiler can be connected to a boiler, for example CSW-120.
And one more thing. If the boiler is located in the basement or ground floor of the house, below the entrance to the sewer, condensate does not flow by gravity into the sewer. You will have to install a neutralizer tank with float valve, which in the process of filling the vessel will include a pump, or a special sewage system, such as Conlift (Grundfos, Denmark, about 6.2 thousand, approx. ) to automatically remove the condensate into the drain.
It is very important to choose the right chimney for a condensing boiler. The design of the latter is such that combustion gases are forced to be drained. This makes it possible to connect the boiler to the coaxial chimney and also to a pipe for air intake from the street or from the room and removal of products of combustion through the chimney. Temperature load on the chimney condensing boiler is small (at the time of receipt in the chimney exhaust gases cool to 40-60 C). But condensation often continues in the chimney, so it must be sealed and resistant to acids. The brick channel is definitely not suitable. acid will destroy it in a few months of operation. But the chimneys, for example Vaillant, Raab (both of which are. Germany), made of polymeric materials, will last longer. As a rule, chimneys are made of PP-, PPS- or PVDF- plastic. To assemble the chimney use straight sections of pipes 0.5-2 m long (80 mm diameter PP-pipe costs approximately 800-2500 per 1 pg. m) and a variety of shaped pieces. There are, however, chimneys based on flexible corrugated PP-polymer pipe, which can easily be “stretched” inside old brick chimneys, including with uneven internal surface. They are offered, say, by Immergas (Italy). Are “friendly” with condensing boilers and traditional chimneys made of stainless steel (brand AISI 304, AISI 409, AISI 430).
| Photo 21 | Photo 22Photo B. Balashova | Picture 23Photo B. Balashova | Picture 24Foto B. Balashova |
Removal of condensate into the town sewer. When removing condensate from a wall mounted condensing boiler into a city or large town sewer, a neutralization device may not be used. The pH normalization will occur as a result of mixing the condensate with sewage. 22. Granules in the condensate neutralizer. 23. Neutrabox I-25 neutralizer. 24. Conlift (Grundfos) with integrated non-return valve for automatic condensate removal (pressure. 5,3 м).
What the market offers?
At present, condensing boilers are produced by almost all leading boiler manufacturers. We can note the products ACV (Belgium): Prestige series; Ariston: Genus Premium; Beretta: Exclusive Green and Power Plus (both. Italy); Baxi: Prime HT, Luna HT, Luna HT Residential and Nuvola HT. Very good products are manufactured by De Dietrich: Innovenc, MCR. Names and Immergas: Victrix; Ferroli: Energy Top, Econcept; Sime: Format Dewy.zip and Planet Dewy (all. Italy); Protherm (Slovakia): “Lion” series; Thermona (Czech Republic): KD, KDC, KDZ of 28 kW nominal output and Therm 45 KD condensing boiler of 45 kW nominal output with the combustion chamber of heat-resistant plastic. One of the trendsetters of condensing technology is the company Rendamax (in Russia, for example, boilers R30 series are popular). Finally, superior in quality performance and thermal characteristics condensing boilers are supplied by German boiler builders. Companies Buderus (Logamax plus of three types: GB022, GB112, GB162), Junkers (Cerapur), MHG (ProCon Streamline), Vaillant (ecoTEC plus), Viessmann (Vitodens 200-W, 300-W and 333-F), Wolf (ComfortLine). Approximate cost of a domestic wall mounted condensing boiler can be determined by multiplying the value of its rated capacity by 3 thousand.
The editorial thanks Biasi, Buderus, De Dietrich, Vaillant, Viessmann for their assistance in preparing the material.
Article “Condensing boilers” from C.О.К.
Ever-increasing energy costs, rising environmental standards and the demands of the times to improve heating technology have led to the creation of a new type of heat generators condensing boilers. Different manufacturers produce such boilers in wall mounted or floor standing version. Subject to compliance with all conditions of installation, temperature schedule, settings and installation in low-temperature heating system, the boiler can show the efficiency of 98-106% in operation. In addition, the low smoke temperature and removal of combustion products together with the condensate, reduces the amount of harmful substances emitted into the atmosphere by up to 70%. The main design difference between condensing boilers and conventional boilers is the ability to remove heat from the condensate produced during the combustion of gas and release it back into the heating system. Thus, returns up to 11% of the heat that in classic boilers goes with the flue gases. Maximum energy return is obtained when the combustion products are cooled in such a way that the water vapor contained in the smoke condenses. Condensation occurs at a heating water temperature below the dew point of about 57 C. The special heat exchanger (usually made of stainless steel) and the boiler components made of acid-resistant materials allow the boiler to work with condensate.
Because of the technical features of the condensing boiler there are a number of requirements for its correct use. The most important thing is to provide the necessary operating temperature. Feed from the boiler to the heating system 50C, return 30C. This mode is achieved in the warm floors, or in the heating system of radiators, with an increase in their effective area by 2.5 3 times, compared with the classical calculation. If you do not comply with these standards when installing the boiler, it makes no sense to expect a return of 11% of the heat in the system, as there will be no condensate and all benefits will be reduced to zero. As practice shows, a country house is built 2, 3-storey with a system of underfloor heating on the first floor and classical radiators on the upper floors. Radiators are installed according to the rules for the conventional heating system and to heat the room, turn on the condensing boiler at a temperature of 60-80C. In this mode, there will be no condensate and the boiler will not show the benefits of high efficiency.
Condensing boilers can be single-circuit (only for heating or for heating and hot water preparation in a boiler of indirect heating) or double circuit. In the case of hot water preparation, the boiler is heated to maximum temperatures, and in this mode the efficiency is reduced. The boiler features a special stainless steel heat exchanger and acid resistant components. Heat exchanger is technically complicated and expensive component. The cost of the heat exchanger along with the replacement works is approximately equal to the cost of a similar new classic wall mounted boiler of the same power. Therefore, care for the safety of this part is reduced to the use of prepared, softened coolant, without rust, iron salts, foreign particles. To flush a clogged heat exchanger is extremely difficult. In the case of malfunction the owner expects an expensive replacement. Installing a condensing boiler, it is necessary to revise the entire heating system, flush it thoroughly. It should not have rusty pipes and radiators.
Using condensate as a heat source, involves its utilization. Condensate is an acid solution. Volume of condensate formation 1 liter per 1 m. cube., burned gas. Boiler with 28 kW output consumes at maximum output 2,85 m.cubic. gas per hour, so during this hour there will be about 3 liters of condensate. Under the European norms, boilers up to 28 kW, condensate disposal is not required. This is because users at home dilute condensate with household water and as a result, damage to sewage pipes is not expected. But if we assume that the condensing boiler will be installed in a private house with any type of autonomous sewerage (septic, aerobic, etc.).), the condensate cannot be discharged into the sewer system. Useful and expensive bacteria will die. It must not be discharged onto the ground. The irreversible salinization of the soil will occur and nothing will grow there. In a day from the 28 kW boiler can be up to 70 liters of condensate, so the removal and disposal of condensate outside the area is likely to be extremely difficult. And the owners of apartments and houses with public sewer systems still need to be more careful with public property, because cast iron and concrete pipes do not tolerate acid.
When deciding on the installation of condensing boilers in your climate zone, it is better to ask the manufacturer’s representative for clarification of the possibility of operating the boiler in this range of local temperatures. An important detail of the boiler functioning combustion products removal and access to air for combustion. Coaxial pipe from the boiler must be installed with a slope towards the boiler, to drain the condensate into the boiler. As practice shows, at low temperature of flue gases and air inlet through the coaxial pipe, the air inlet can freeze, which reduces the access of oxygen for combustion, reducing efficiency, up to complete emergency shutdown of the boiler. At relatively high winter outside temperatures (above 0C), there are no problems with freezing of the chimney and the equipment works properly. But if you choose the boiler for the low design winter temperatures, it is necessary to think carefully about access for combustion air at the time of icing pipes.
The most important part of a long trouble-free and proper operation of the boiler is a qualified service organization. Start-up and adjustment of condensing boilers is performed by a certified service engineer using a gas analyzer. This is an expensive device that requires annual inspections and careful maintenance. The device helps to adjust the required amount of air for combustion depending on the capacity. Without special equipment and a complete list of works to be carried out, the required boiler efficiency cannot be achieved. Maintenance is carried out using the same devices. That is why the price for start-up and maintenance is much more expensive than similar work with classic boilers.
Choosing a condensing boiler is not common to save money. Well-proven manufacturers use high quality acid-resistant materials, expensive components and guarantee the operation of the boiler with aggressive environment. The price of a good household condensing boiler from a well-known manufacturer will be quite high. Compared with a classic boiler of the same capacity condensing boiler costs 2-3 times more. Of course, properly installed and used as intended condensing boiler will ensure gas savings in operation. For a house with the area of 250.kv., which has a 28 kW condensing boiler with a maximum gas flow rate of 2.85 m.cu./hour (a classic boiler with the same capacity of 3.25 m.cube./The cord duct can be located on either the left or right side of the needle hole.00. in the current of natural gas for the Russian consumer. Probably can not call such savings significant, especially since it does not even cover the difference in the cost of annual maintenance. If we look at this saving from the perspective of an average European consumer, where the price of natural gas is 4-5 times higher, the amount will be about 300 euros, and this is another result.
The above-mentioned savings can only be achieved when the boiler is installed in a low-temperature heating system, the heating system is filled with a pre-prepared coolant, the boiler is protected from sludge and dirt and is operated by trained and competent professionals. And what happens if there is a failure or carelessness at any of these steps. In the best case you can forget about the additional return of 11% of thermal energy into the system. In the worst case would require costly replacement of the heat exchanger, or even the boiler. If you do not pay attention to the chimney-air exhaust for combustion, you may have to periodically warm the pipes from the ice.
How to take full advantage of the condensing boiler. The need for this type of equipment should be understood at the design stage of the house. Assess your financial capabilities to purchase a condensing boiler and heating system elements, followed by installation and commissioning. The heating system must necessarily consist of a warm floor or large area heating radiators (using a coolant temperature up to 50C) or both together. Radiators are designed in front of the windows to create thermal comfort. For the utilization of the condensate, special equipment with a replaceable reagent is used. Annual maintenance is mandatory.
In European countries, often the condensing boiler is part of the whole system of economic complex use of all possible types of energy. So in the house is set the heat accumulator of 1000 1500 liters and it is brought to the heated coolant from a heat pump, solar panels, condensing or classic boiler, where each element works in the most optimal time for him. The use of heat accumulators in our country is not yet widespread. Climatic conditions make it difficult to use solar panels with heat pumps as well. Condensing boilers are also used as independent heat sources, but the owners are trying to organize their proper use.
Condensing boiler is an achievement of modern heating technology, which must be used for its intended purpose, in the operating conditions for which it is designed. Only then will it bring cost savings and the joy of using the latest science and heating technology.
