Flue gas non-return valve PPS cascade and CLV Ø60 Ø80 Ø110

PPS non-return valve for cascade and CLV under positive pressure: it stops flue gas from flowing back into an idle boiler. For PZ and PW series, Ø60, Ø80, Ø110. The valve belongs to the LD Flue PPS flue system; the flue gas flow pushes the flap open and it closes by itself as soon as the flow stops. Only use it if the boiler manufacturer allows a non-return valve for the appliance; otherwise design the installation under negative pressure, without a non-return valve.

Application. Several condensing boilers on one common header (cascade) or on a shared air supply and flue system (CLV) working under positive pressure: a boiler that is not firing must not receive flue gas from the other appliances. The valve then closes the connection of that boiler. If the boiler already has a built-in non-return valve, follow the boiler manufacturer's instructions. The valve can also be retrofitted in an existing installation.

Operation. The valve works by gravity and has a built-in siphon function with a back pressure of 320 Pa, so no water stays standing in the flue. It is tested to DVGW worksheet G 635 (positive pressure) and must be approved together with the appliance.

Installation. Vertical only, never horizontal or inclined. Push the valve with its O-ring all the way in, up to the stop. The arrows on the flap point in the flue gas direction. Fill the siphon with water after installation and before first use, and mark the valve with a sticker. Have its operation checked at least once a year during boiler maintenance.

Which code do I order? It is the same valve in flame-retardant polypropylene (PP, T120, up to 120 °C). PZTK belongs to the black UV-resistant PZ series, PWTK to the white PW series. Dimensions L1 (high side), L2 (low side) and D1 (outside diameter) are in the table and on the dimension drawing per diameter.

Do I need a non-return valve? Only for a cascade or CLV under positive pressure, and only if the boiler manufacturer allows the valve for the appliance. If the installation works under negative pressure, no non-return valve is fitted.

Can the valve be fitted in a horizontal flue? No. The valve works by gravity and may only be installed vertically.

Why does the valve need water? Because of the built-in siphon function: filled with water it holds a back pressure of 320 Pa and no water stays standing in the flue.

Ventichim supplies this non-return valve together with the complete PZ and PW series to installers throughout Belgium.