The chimney systems for condensation boilers are manufactured in the single-wall version (MKKS system), in the double-wallair-flue gas version (MKPS system). They are special chimneys designed for extraction of flue gas from boilers which use the phenomenon of condensation of steam produced in course of combustion process, which produces flue gas of negative impact upon traditional ceramic chimneys and chimneys made from standard steel sheet. version with insulation (MKKD system) and in the

The MKK chimney systems are a perfect protection against such impact.

The more and more commonly used modern and efficient appliances which employ the phenomenon of steam condensation in the process of combustion. They produce flue gas of lower temperature and mass as compared to the appliances used thus far. The high potential of steam thermal energy has been thus far absorbed together with the flue gas. Nowadays, new condensation appliances and new chimney installations allow recovering some heat from the flue gas via cooling and condensation of steam from the combustion products.

In consequence, the application of the condensation technique in combustion process provides for reduction of the outlet temperature below the dew point.

However, the use of the heat recovered from the condensed steam brought about a few technical problems related to the technique of flue gas extraction:

· the refluxed condensate shall not fall freely as that would cause certain disturbances of appliance’s performance,

· appropriate means must be provided in order to absorb the condensate easily from the flue gas extraction installation,

· all the parts in contact with the refluxing condensate must be resistant to humidity and corrosion,

· since the flue gas which leave the appliance are cooled so intensively that their natural uplift pressure is insufficient, which calls for application of flue gas fans or air blowers and, thus, the flue gas extraction system operates at overpressure.

The result of the above phenomena is that traditional ceramic chimneys that extract flue gas from new-generation appliances have too low temperature. As such chimneys have very high mass, they do not reach the temperature above the dew point in course of flue gas extraction process. This phenomenon results in depositing the condensed flue gas on the walls of the traditional ceramic chimneys, which forms aggressive condensate that damages the chimney walls. The phenomenon is inversely proportional to the temperature outside the chimney that affects the temperature of the chimney walls, particularly at its upper outside part.

For the purposes of extraction of flue gas from condensation appliances, a chimney system of thin, stainless steel walls must meet new requirements:

· due to the falling condensate, and due to the overpressure in the flue gas extraction conduit, the system must be tight and resistant to capillary aspiration of the condensate at the joints of the long parts of the system,

· the condensate extraction system must be made and, particularly, located so that it prevents the condensate from passing from the flue-gas conduit and from the connection duct to the appliance in the event when the appliance is not adapted to condensate collection.

The system of elements made from stainless steel used in chimneys and flue-gas conduits includes a set of pipes and profiles of circular cross-section with sockets at one end which provide insert connection of the elements where appropriate tightness is provided with a gasket in the form of a profiled ring.

The parts to be applied in flue gas extraction systems from condensation appliances may be divided into three groups:

· Single wall parts, i.e. a set of pipes and profiles of round cross-section, with pipe sockets at one end which provide insert connections of pipes. The tightness of connections is provided by profiled ring that serves as a gasket. The parts are designed for existing ceramic chimneys. They are marked MKKS;

· Double wall parts which are a set of pipes or profiles of round cross-section. They have an inside jacket that contacts the flue gas, and outside jacket which contacts the outside environment, and thermal insulation placed between these pipes. The pipes have sockets at one end for insert connections of pipes. Appropriate tightness of connections is provided. The double wall parts are used as outside chimneys or as non-encased inside flue-gas conduits. Double wall insulated parts are marked MKKD.

· Double wall parts which are a set of pipes or profiles of round cross-section with inside and outside jackets each of which has a pipe socket at one end for tight insert connections. The core of the system provides a tight condensation flue-gas conduit. The space between the core and the jackets (ring intersection) provides a tight conduit which supplies air for combustion purposes. This is the air-flue gas system marked MKPS.

The pipes and profiles of single wall and double wall systems (the latter for inside and outside jacket) have pipe socket at one end whose extreme part is bent outside. The other end of the pipe has an outside lapping at the distance slightly smaller than the length of the socket. The socket and the lapping provide for tight connections of pipes.

The longitudinal seams of the length parts and profiles are welded with plasma-arc technique, which provides for gas-tightness of the flue-gas conduit in compliance with the conditions specified in Item 5, Section 6.2.6. (p. 92) of the “Technical terms of construction and acceptance of appliance room for gas and oil fuels” – ed. Polska Korporacja Techniki Sanitarnej, Grzewczej, Gazowej i Klimatyzacji [Polish Corporation of Sanitary, Heating, Gas and Air-Conditioning Technologies].

All the length parts and profiles have a special socket at one end in order to provide the required gas-tightness. A special gasket is placed in the socket, between the inside and outside surfaces of the connected parts. Connection of MKKS system parts is presented in Figure No. 1.

In case of double wall parts (MKKD), the gasket is put only at the place of connection of the surfaces of the inside jacket of the connected parts (see Fig. No. 2). The parts of the outside jacket shall be fixed with clamps only.

In case of double wall parts (MKPS), the gasket is put only at the place of connection of the surfaces of the inside jacket of the connected parts (see Fig. No. 3).

MKKS and MKKD systems are manufactured for the range of diameters shown in Table 1:

Ø60 is not offered for the MKKD system.

The MKPS system is manufactured for the range of associated diameters shown in Table 2:

The manufacturer reserves the right to apply versions of particular variants of flue gas extraction for the parts of MKKS, MMKD and MKPS systems in compliance with the actual needs.

The parts of the MKKS, MMKD and MKPS systems are applied together, and the basic variants are as follows:

• WKW and WKN variants – placing of the flue-gas conduit inside the existing ceramic chimney,

• WKZ variant – construction of the flue-gas conduit as an outside chimney based upon a firm outside support, the connection duct penetrates the side wall of the boiler room – the flue-gas conduit of single wall parts,

• WSC variant – construction of the flue-gas conduit as an external chimney fixed to the outside wall of the building; the connection duct penetrates the side wall of the boiler room,

• WST variant – the flue-gas conduit in the form of a straight double wall distance that penetrates the ceiling of the boiler room.

The MMKS pipes and profiles may be used solely as flue gas extraction conduits encased in the existing ceramic chimneys whose cross-section allows such designs.

Chimneys with flue-gas conduits made of acid-resistant steel may be connected to appliances that employ steam condensation phenomenon in the process of oil or gas combustion.

The construction of the flue-gas conduit should be made by trained personel and it should follow the current counstruction regulations, investor"s recommendations and the recommendations of the manufacturer of the system.

Terms of use

The choice of the variant of the flue-gas conduit is the sole option of the designer of the flue gas extraction installation.

WKW variant

The following factors are decisive for the WKW variant:

• the existing ceramic chimney which allows the flue-gas conduit parts to run outside of the building in which the boiler room is situated,

• no possibilities for the flue-gas conduit to run outside the boiler room through the outside wall.

The parts of the flue-gas conduit to extract the flue gas from condensation appliance in the WKW variant as per Figure 4 are shown in Table 3:

A version of the same variant where the MKPS parts are applied between the appliance and chimney is shown in Table 4 and Figure No. 5.

Prior to constructing of the flue-gas conduit in the ceramic chimney, the latter should be cleaned of loose ceramic parts inside the chimney and of the excess of the combustion products remaining in the flue-gas conduit. For the purpose of inserting the lengths and profiles, openings of appropriate size must be made in the bottom part of the ceramic chimney (in the area of the connection to the boiler), in the places where additional inspection profiles will be installed and at any curves and chokes of the flue-gas conduit.

The flue-gas conduits shall be installed centrally and firmly in the chimney. The lengths and profiles are inserted into one another. Prior to inserting one part into another, a gasket must be put on the part with the socket. The assembly must be very careful so that the gasket fits exactly the surfaces to be sealed and that it is not damaged in course of the assembly. For details of the insert connection, see Figures 1, 2 and 3.

Between the elbow 930 with support and the top edge of the chimney, the RPK length parts are installed. The parts are inserted into one another with the use of gaskets. The number of the parts depends on the chimney height.

The elbow 930 with support should be installed firmly in the chimney, and the elbow support should be used as a point to set the vertical distance of the flue-gas conduit. The SKR-H support may be used to mount the elbow. The support length should be selected appropriately.

The outlet of the flue-gas conduit shall be fitted with a roof connection to close the chimney conduit. The end of the flue-gas conduit should allow free extension due to the thermal expansion of steel. The value assumed for the compensation of the thermal expansion of the lengths depends on the entire height of the chimney and the temperature parameters of the flue for a given boiler. For the purpose of a correct outflow of flue gas, the flue gas outlet should project beyond the closing plate of the ceramic chimney by at least one diameter of the flue-gas conduit.

For the sake of cleaning and control of the flue-gas conduit, the ŁRK (see Fig. 4) or GBRM PS (see Fig. 5) elbow 930 with inspection door must be mounted at the bottom part of the chimney. The opening of the inspection door shall be easily accessible.

WKN variant

The WKN variant is similar to the WKW variant. The only differences consist in the application of Tee-pipe, inspection length and condensate collector.

An example of the flue gas extraction installation for condensation appliance in the WKN variant is shown in Fig. 6, Table 5, Fig. 7 and Table 6:

WKZ variant

The following factors shall be taken into account while considering application of the WKZ variant:

  • absence of the ceramic chimney into which the flue-gas conduit parts could be inserted;

  • possibility to lead the flue-gas conduit out slightly above the ground at the outside wall of the boiler room;

  • possibility to construct the outside flue-gas conduit on the existing wall of the boiler room.

The parts of the flue-gas conduit to extract the flue gas from condensation appliance in the WKW variant as per Figure 8 are shown in Table 7:

Table 8 shows the parts of the air-flue-gas conduit in WKZ variant constructed as per Fig. 9:

The following shall be taken into account while building the WKZ variant of the flue-gas conduit:

  • make the pass through the outside wall of the boiler room, and insulate thermally the part that penetrates through the wall; the acid-resistant material shall not come into contact with the mortar;

  • select the SFT support height so that it carries the weight of the vertical distance of the flue-gas conduit;

  • mount the vertical distance of the flue-gas conduit to the building wall so that the WHT clamps are placed not further from one another than 2 meters along the flue-gas conduit. Choose appropriate version (1, 2 or 3) to provide for vertical position of the chimney;

  • the height of the flue-gas conduit shall comply with the “Technical conditions of construction and acceptance of oil and gas boiler rooms”, pp. 88, 89;

  • optionally, WBK condensation cover and WBT wall-end may be used for the wall-penetrating assembly.

3.3.4. WSC variant

The following factors are decisive for the WSC variant:

  • absence of the ceramic chimney into which the flue-gas conduit parts could be inserted;

  • possibility to construct the outlet of the flue-gas conduit close to the roof (ceiling) of the building near the outside wall of the boiler room;

  • possibility to mount the outside flue-gas conduit to the existing outside wall of the boiler room.

The parts of the flue-gas conduit to extract the flue gas from condensation appliance in the WSC variant as per Figure 10 are shown in Table 9:

The chimney is mounted to the building wall with the construction clamp (SBK) supported upon WKT supports, and with WHT clamps.

The parts of the air-flue-gas conduit to extract the flue gas from condensation appliance in the WSC variant as per Figure 11 are shown in Table 10:

The chimney is mounted to the building wall with the construction clamp (SBK) supported upon WKT supports, and with WHT clamps. From the heating appliance to the intermediate elbow, it is the conduit of the air-flue gases MKPS system that is further led in the MKKD system.

Still another version is presented in Figure 12 and Table 11.

Here, directly beyond the wall of the building, flue gases are exhausted horizontally and the air for combustion is taken concentrically.

The following shall be taken into account while building the WSC variant of the flue-gas conduit:

  • make the pass through the outside wall of the boiler room, and insulate thermally the part that penetrates through the wall; the acid-resistant material shall not come into contact with the mortar;

  • the vertical section of the flue-gas conduit shall be mounted to the wall of the building so that the distance between supports along the flue-gas conduit are not smaller than 2 meters;

  • optionally, WBK condensation cover and WBT wall-end may be used for the wall-penetrating assembly.

WST variant

The following factors are decisive for the WST variant:

  • absence of the ceramic chimney into which the flue-gas conduit parts could be inserted;

possibility of penetration of the flue-gas conduit through the ceiling of the heating boiler room directly to the outside of the building.

The parts of the flue-gas conduit to extract the flue gas from condensation appliance in the WST variant as per Figure 13 are shown in Table 12.

The parts of the air-flue-gas conduit to extract the flue gas from condensation appliance in the WST variant as per Figure 14 are shown in Table 13.

The following shall be taken into account while building the WST variant of the flue-gas conduit:

  • make the pass through the outside wall of the boiler room, and insulate thermally the part that penetrates through the wall; the acid-resistant material shall not come into contact with the mortar;
  • selection of the vertical section of the flue-gas conduit so that it projects beyond the building structure elements as specified in the “Technical conditions of construction and acceptance of oil and gas boiler rooms”, pp. 88, 89;
  • sealing of the section that penetrates the boiler room ceiling with the use of appropriate flashings and rain flanges.

LAS variant

The LAS variant is designed mainly for installation in multi-story buildings. The variant is based upon the complete independent appliance operation (closed combustion chamber) of the air in the room in which the appliance is installed. Figure 15 and Table 14 show an example of the system assembly.

The installation comprises two concentric sealed conduits: the external one (which in this case is a ceramic conduit), and the internal flue-gas conduit mounted inside it. The conduits are closed at the top with DHK roof plate that provides air for combustion, and the bottom parts are connected with TRR regulation Tee-pipe.

The basic dimensions are shown in Table 15.

Notes pertaining all the variants

While assembling the lengths and profiles of MKKS group, the following shall be observed:

  • the gasket shall be placed on one of the parts prior to the assembly;
  • the sections are assembled via their insertion so that a bell-connection is obtained as in Figure No. 1.

While assembling the lengths and profiles of MKKD group, the following shall be observed:

  • the gasket shall be placed on one of the parts prior to the assembly;
  • the external and internal jacket of the sections are assembled via their simultaneous insertion so that a bell-connection is obtained as in Figure No. 2.

While assembling the lengths and profiles of MKPS group, the following shall be observed:

  • the gasket shall be placed on both jackets of one of the parts prior to the assembly;
  • the external and internal jacket of the sections are assembled via their simultaneous insertion so that a bell-connection is obtained as in Figure No. 3.

For the purposes of disposal of the condensate and the excess of rain water that may penetrate the flue-gas conduit, a connection with condensate collector shall be applied, which should be installed on the horizontal section of the conduit that connects the vertical flue-gas conduit with the heating appliance, near the appliance. The condensate may be also drained by the condensate collector.

In case of using the space between the flue-gas conduit and the ceramic chimney lined with this very flue-gas conduit for the purposes of the boiler room ventilation, the outlet of the flue-gas conduit shall be fitted with a roof plate with ventilation opening marked as DHKK.

The recommended assembly dimensions are shown in Fig. 16:

A – The height of the intermediary support for the chimney founded on a concrete slab.

B - The height of the intermediary support for the chimney installed on the WKT support.

C – Location of WHT clamps.

D – Maximum height of the chimney protruding above the last WHT clamp.

Figure 17 shows a typical application of profiles as a transition from MKKS system to MKKD system. This is the case when the system of flue gas extraction has been made partly as a chimney liner in a traditional brick chimney, and partly as an external chimney of the MKD system. Here, the basic element is the straight anchor plate KFKP or bent anchor plate KFKZ. Below the anchor plate, MKKS-system parts are mounted, e.g. RPK pipe, and above the plate – MKKD-system parts, e.g. ATK pipe.

In case of flue-gas extraction system mounted on the outside wall of a building, as in variant WKZ, the chimney base is placed upon a firm foundation or on a support.

A typical set of connection pipes for the bottom part of the flue-gas conduit mounted on a support is presented in Fig. 18. In such a case, the following connection pipes are provided for the bottom part of the flue-gas conduit:

  • WKT support,
  • bent anchor plate with condensate collector KFZ,
  • inspection length POK,
  • 870 Tee-pipe AFK 87 or
  • 450 Tee-pipe AFK 45.

A typical set of connection pipes for the bottom part of the flue-gas conduit mounted on a support is presented in Fig. 19. In such a case, the following profiles are provided for the bottom part of the flue-gas conduit:

  • straight anchor plate with KFKS condensate collector,
  • inspection length POK,

870 Tee-pipe AFK 87 or 450 Tee-pipe AFK 45.

For ceilings or hipped roof ends penetrations, flashings (DDT 0, DDT 15, DDT 30, DDT 45) may be used together with rain caps (RKT). For tile roofs, parts with lead jacket are useful. Figure 20 presents examples of application of parts DDT 0, DDT 15, DDT 30, DDT 45 depending on the inclination of the hipped roof end. Above the flashing, the RKT rain flange should be mounted in order to prevent excess of atmospheric precipitations from penetrating the flue-gas conduit.

In case of the flue-gas extraction system installed on its own structure, the parts of the system provide installing a few flue-gas conduits on one structure. Fig. 21 presents examples of the versions of the flue-gas extraction system on its own structure.

After the installation of flue gas extraction has been completed, it is subject to approval which consists in the following checks:

  • permeability of the flue-gas conduit
  • tightness of connections,
  • correctness of the connections and compliance of the flue gas extraction parts with the design,
  • standard outlet above the roof,
  • compliance with the atmosphere protection standards.
  • Four fumes conduits assembled to one supporting structure.
  • Three flue-gas conduits assembled to one supporting structure.
  • Two flue-gas conduits assembled to one supporting structure.
  • A single flue-gas conduit assembled to a supporting structure.

The formal approval consists in the following:

  • checking of the compliance of the installation with the design and documentation made after the installation has been completed,
  • checking of the validity of the conformity certificates of the construction, insulation and assembly materials used in course of installation.

The acceptance of the flue gas extraction system should be attended by a licensed chimney sweep and a protocol should acknowledge the acceptance.