BS8303 standard update

BS8303 standard update

In the latest HETAS Technical Bulletin we updated our registrants on the imminent changes to BS8303. In this article we highlight some of the key changes to the standard that will impact upon registered installers.

Over recent years, the industry through the UK BSI standards committee RHE/28 have been working hard in reviewing and updating the requirements contained in the solid fuel recognised standard BS 8303: 1994 Installation of domestics heating and cooking appliances burning solid mineral fuels. With the new standard due for publication and release in the coming days, it is important for registered installers and other industry personnel to be aware of the relevant changes, which include more up-to-date installation practices that better reflect the products and materials available on today’s market.

HETAS will continue to publish ongoing information to its registrants on the new alternative approaches contained within the BS 8303 standard through its technical bulletin publications, as well as an update to the current HETAS H003 and H003 refresher training courses to include the relevant requirements.

Application of the Standard

HETAS continue to receive queries relating to the appropriate application of any provisions contained within recognised BSI standards, and how they can be applied with continued re-assurance in meeting the UK Building Regulation requirements. For solid fuel installations, page 40 of Approved Document J gives clear guidance on this issue by means of stating the following;

Alternative Approach

The requirements may also be met by adopting the relevant recommendation in the publications listed below to achieve a level of performance equivalent to that obtained by following the guidance in this Approved Document:

  1. BS EN 15287-1 Design, Installation & Commissioning of chimneys for non-room-sealed heating appliances
  2. BS 8303 Installation of domestic heating and cooking appliances burning solid mineral fuels

The important part of this statement is the word “equivalence”, which ensures that by way of adopting the approaches given in these two recognised standards that the installation is no less safe than what would occur by following the technical guidelines given within the Approved Document.

So what will change?

With the original standards last publication coming in 1994, the new standard will look more closely at covering the basic requirements surrounding more highly efficient closed appliances, and base less emphasis on new installation of inefficient opened fire appliances (covered in more detail in BS 1251:2015). This will include provisions for the hearth, recess construction, closure/register plate, air supply and maintenance.

There are two principle additions to the upcoming standard amongst the other covered that were not previously contained within the 1994 version, mainly constituting requirements for

  • The appropriate heat shielding of a freestanding appliance (not situated in a builder’s recess) up to 7kW nominal output in scenarios of lightweight timber construction properties
  • Information on the design, installation and assessment procedures relating to the installation of dedicated external air supply appliances.

The annex will also include updated commissioning guidance relating to the methods for commissioning flues and installations of varying types, using the industry recognised smoke and spillage test procedures.

Shielding of Combustibles

The standard will contain caveats for the appropriate protection of combustible materials when using a shield in a freestanding configuration, and state the required clearance and air gaps distances. In particular;

  • Use of a 1.5mm galvanized steel metal shield, affixed with non-combustible fixings to maintain an air gap of 25mm between the shield and the wall
  • Shield protrudes at least 300mm above the top surface of the appliance and extend to the edge of the hearth horizontally
  • The shield shall be open top and bottom to allow the flow of cool air between the shield and the wall
  • Distance from the appliance rear to the outer surface of the shield of at least 95mm and at least 90mm from the side of the appliance to the outer surface of the shield (if near to an adjacent wall)

Dedicated External Air Supply

The annex to the new BS 8303 will contain information to the appropriate design, assessment and commissioning of appliances with a dedicated external air supply, in line with HETAS technical guidance document HETAS_TN_0020. These include;

  • Ensuring installation of a dedicated external air supply kit is completed in line with manufacturer’s instructions, including consideration for the duct diameter, total length, air inlet terminal position and duct material specification
  • Appropriate risk assessment and commissioning procedures are undertaken to understand the properties current ventilation and air tightness, appliance roomsealed properties and again ensuring manufacturer instructions are available and met.
  • Appropriate smoke tests are completed, including with any extract running, and spillage test when the door is opened for refuel.

Further details and assessment/commissioning forms are available within the current version of HETAS_TN_0020, which is available on the technical area of the HETAS website at

If you have a technical question you can contact the team on 01684 278194 or email


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