NVS Limited

Single Wall (Single Skin) Stainless Steel Flue

Here's what Schiedel have to say about the Prima Plus and Prima Plus 1mm stainless steel single wall (single skin) wall flue system:

System Design

"Restrictions on use of Single Wall (Single Skin) Flue Prima Plus range is principally intended for internal use and to reline existing chimneys. Its siting is governed by the requirements of CE, BS7566 and the Building Regulations. When single wall (single skin) flue is used to connect an appliance in domestic situations, eg stove, BS 7566 Pt2 states that the connection onward from the appliance into the twin wall flue or brick chimney must be made within the same room as the appliance and not closer than 150mm to the ceiling/wall. A continuous run of Prima Plus is permitted when using it as a liner entering an existing chimney in the same room as the appliance.

When connected to an appliance operating below 160°C eg a condensing boiler, Prima Plus may be run through floors or in an enclosed shaft provided that a minimum distance to combustibles of 200mm is maintained (400mm for diameters above 200mm). For external or exposed installations where there is a risk of condensate freezing, a twin wall insulated chimney such as ICS, ICID or KVent should be used. A twin wall insulated chimney additionally will keep the flue warmer and assist flue efficiency. To this end, Building Regulations Document J now requires all domestic external flue runs over 3m to be made in twin wall stainless steel lined insulated chimney".

Flue Routing

"The chimney should remain as straight as possible through its vertical run to assist flow. Horizontal runs should be avoided or kept as short as possible. Should it be necessary to offset a chimney run the following guidelines should be adhered to:

Gas - An offset no greater than 45° to the vertical, with a run between the bends not exceeding half the overall height of the chimney should be maintained.

Oil - Solid Fuel: An offset no greater than 30° to the vertical, with a run between the bends not exceeding 20% of the overall height of the chimney should be maintained. In both instances a maximum of two bends in any one chimney run should be used. A vertical rise of 600mm should be allowed immediately above the appliance before any offsets. Reference for both guidelines can be found in the Building Regulations Doc J and relevant British Standards on installations".

Single wall (single skin) stainless steel flue, system design Single wall (single skin) stainless steel flue, system design Single wall (single skin) stainless steel flue, system design

Terminal Types

"For solid fuel appliances, BS7566 Parts 1, 2, 3 and 4 recommends use of an open terminal for chimneys up to 200mm diameter. Rain ingress should not be significant, but drain components can be fitted. Above 200mm a covered terminal can be used, and for all oil and gas installations. Mesh carries the risk of sooting and requires regular cleaning to avoid blockage particularly with oil and solid fuel".

Provision for sweeping, cleaning and maintenance

"Provision should be made for inspecting and cleaning the chimney. This is particularly important on solid fuel applications. It is recommended that chimneys serving solid fuel appliances be swept as frequently as necessary but at least twice a year. Choose an access component suitable for your installation unless cleaning/inspection can be done through the appliance. It is essential that the flue way be kept clear at all times in the interest of good practise and health, safety and appliance performance. The system should be checked regularly during the appliance maintenance. (Refer appliance manufacturer's instructions). All as per HETAS Guide".

Room Ventilation

"The room carrying the appliance should have an air vent either direct to an external air source or vented into a room that has an external vent direct to an air source. This is required to provide adequate air supply to allow the appliance and flue to operate efficiently. These requirements are specified in the Building Regulations (Document J) also by CIBSE and BS5440".

Commercial Installations

"The Prima range is appropriate for use in a variety of commercial applications. Schiedel RiteVent can provide a full design and flue sizing advice service".

Provision for condensate disposal (subject to appliance manufacturer recommendations)

"Normally solid fuel and atmospheric gas and oil appliances will not need a drain unless rain ingress is significant. Most condensing appliances however need provision for drainage. As a rule of thumb a condensing boiler produces 1 to 1.5 litres of condensate per hour per 10kW of input. This is a significant amount of acidic liquid which must be drained from the system. Choose appropriate flue drainage components, normally fitted at the base of the stack and close to the appliance outlet. A 5° slope on horizontal runs is advised, using the appropriate 85° or 40° bend and 95° tee".

Return to previous page