Liner for a gas boiler

Why a brick flue does not suit a gas boiler without a liner

A condensing boiler also uses the heat of the water vapour in the flue gases. So the flue gases leave it cool and very moist, and they keep condensing in the flue. The condensate is acidic. Brick and mortar soak it up, the moisture freezes in winter, and the masonry begins to crumble from the inside. The first signs are usually visible in the attic and above the roof: dark patches, crumbled mortar from the joints, salt deposits.

Older open-flue gas boilers also produce much cooler flue gases than a masonry stove, and in a wide brick flue channel they have time to cool down. On top of that, condensing boilers often work with a fan and positive pressure in the flue, so they need airtight joints that brick masonry cannot provide. If a new flue has to be built through a wall or outside: gas boiler flue.

Which liner suits a gas boiler

• Material: acid-resistant stainless steel intended for wet operation (for example AISI 316L).
• Joints: with sealing rings if the boiler works with positive pressure in the flue, as the manufacturer requires.
• Diameter: according to the boiler's installation instructions and the length of the flue, not the width of the old flue channel.
• Bottom section: a T-piece with a cleaning door and a condensate collector, from which the condensate is drained to the sewer through a siphon.
• Combustion air: for room-sealed boilers air can be supplied through a separate pipe or through the gap between the liner and the flue channel walls, if the boiler manufacturer allows it.
• Top section: a closure on the crown slab and a terminal that the boiler manufacturer allows.

Thin gas boiler liners are not intended for solid fuel. If you plan to connect a fireplace or wood stove to the same chimney in future, it will need a separate flue channel with its own liner. A comparison of materials: ceramic or stainless steel liner.

What the regulations require when a gas boiler is replaced

When a heating appliance is replaced, before the new appliance is used the flue is inspected and a technical condition inspection certificate is drawn up stating whether the new appliance may be connected to the flue. For a gas user with flue-connected appliances, the condition and connection of the flue must be confirmed by such a certificate. In Gaso's simplified boiler replacement procedure, one of the conditions is a certificate on the technical condition of the flue channel and ventilation ducts. More on the inspection itself: chimney check for a gas boiler.

In use, a gas appliance is cleaned, serviced and checked at least once a year. A lined brick flue for a gas appliance is inspected and cleaned at least once every two years. If the boiler has been disconnected for more than six months, an extraordinary check of the flue and ventilation ducts with a certificate is needed before use.

How we fit a liner for a gas boiler

1. Boiler data From the boiler instructions we find out the flue outlet diameter and the requirements for the flue and the air supply.
2. Cleaning and camera An old flue often holds soot and fallen bricks from the days of the stove. We clean it and inspect the whole length with a camera.
3. Fitting the liner We lower the liner from the roof, install a T-piece with a cleaning door and a condensate collector at the bottom, and fix and close off the liner at the top.
4. Connection The boiler and the flue pipe up to the liner are connected by the gas appliance installer. We prepare the flue and agree the connection point.
5. Certificate We check the draught and draw up a technical condition inspection certificate with photos or video. The work is done by a qualified chimney sweep, and the certificate states their qualification document.

How much does a liner for a gas boiler cost?

We name the price based on the boiler data and an inspection of the flue. It depends on the length and diameter of the flue, the type of liner joints (with or without seals), whether an air supply is needed and whether the old flue channel must be widened. The height of the chimney, access to the roof and whether we do the cleaning, camera inspection and certificate on the same visit also matter. Materials are priced separately from the labour. The specialist will name the price after you submit the form and after the inspection. Other prices: prices.