With C15 in an old CLV each boiler gets its own PPs flexible liner ø60 or ø80 inside the old inner pipe, and the jacket stays the shared air supply. After the renovation there is no flue gas connection between dwellings.
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Enter the number of appliances and the height above to see which parts each boiler needs.
How C15 works in an old CLV
The old inner pipe carries no flue gas any more. It becomes the casing in which the liners run up side by side, each black and UV-resistant, from the boiler to above the roof. The jacket stays the air supply: air enters through the existing CLV mesh cap and flows down the jacket to the boilers.
The concentric connection of each boiler ends open in the jacket. Only the liner passes through the wall of the old inner pipe. Around that passage goes an ALU sealing collar (80/125 or 60/100), so the jacket stays airtight towards the inner pipe. At the top the liners leave together through the multikap, each with its own terminal.
The requirements for C15
| Requirement | What it means |
|---|---|
| Fan | Fan-assisted appliances only. Natural draught is not allowed. |
| Air section | The free ring in the jacket is at least 1.5 times the sum of the inner sections of the liners. |
| Terminal | Always vertical, through the multikap. |
| Shaft | Airtight: every passage sealed, hatches closed, no other pipes or cables. |
| Outside | Plastic that comes outside is UV-resistant. |
| Boiler | Approved as C(15) according to gas.be (NBN D 51-003 annex E). |
An old inner pipe of ø300 (jacket ø450) takes five ø80 liners comfortably and six tightly. A ø250 (jacket ø400) takes four. In both cases the jacket has enough air; the room in the inner pipe decides.
How to build your list, from top to bottom
- Multikap: stainless steel with 2 to 6 connections or ALU with 1 to 5. For a single boiler a mounting kit is enough.
- One black UV terminal per boiler.
- One 25 cm black UV pipe per boiler.
- One connection socket with flange per boiler.
- Flexible liner on a roll (12.5, 25 or 50 m). Choose the rolls so each boiler has one length without a joint.
- One bottom coupling per boiler.
- One support bend 87° per boiler.
- One ALU sealing collar per boiler, 80/125 or 60/100.
- Optionally per boiler a concentric pipe with finishing plate or rosette.
Frequently asked questions
Why do building managers choose C15 for an old CLV?
Because after the renovation there is no flue gas connection between two dwellings. Each dwelling has its own flue to above the roof.
How many liners fit in my CLV?
Measure the old inner pipe. A ø300 takes five ø80 comfortably, a ø250 takes four. More fit in ø60.
Does the existing CLV cap stay?
Yes. The mesh cap stays the air inlet. The liners pass through it with the multikap on top.
What diameter does the liner have?
ø60 or ø80. It follows from a calculation to EN 13384 with the boiler data, the height and the bends.
