Insulated flue is all the rage in the market now. Installers love how easy it is to assemble and put together which gives them the opportunity to install more heaters in a day.
Sales people enjoy simplified sales tools such as our Flue Sales Guide making it easier to navigate the process of this new shiny product as well.
Even the average consumer is quickly adopting it due to clever marketing and buzz words like 'Room Sealed' and the problems it solves such as reducing external wind noises, rattling sounds from loose casings, helping the room the fireplace is in be more efficient leading to less heat loss, having the ability to bring in air for combustion via a single point of penetration using our AFS+ system. There's many pluses to this new type of flue system but if we're not careful, we may get a bit excited and sell an insulated flue system to someone for a fireplace that doesn't meet the requirements for this type of flue.
Approvals and testing
All insulated flue systems that are now approved within the Australian market have had to undergo quite extensive testing. Some of this testing is to ensure that in the event of a flue fire, the fire and heat doesn't escape the system leading to a catastrophic event whereby the house burns to the ground. This test is referred to in the standards AS/NZS 2918:2018 as Appendix F.
When a fireplace appliance is tested to determine clearances to combustible materials, referred to as Appendix B, the fireplace is generally tested with a default (air cooled) flue system with either a single or double shield.
In order to get approval to use an insulated flue on a unit tested with an air cooled default flue, the laboratory will test many different fireplaces and then once testing is complete, compare the clearance results with the original clearances determined with the tested flue system. It is then that an 'Opinion letter' will be provided to the manufacturer that determines the limits in which the flue system can be installed.
Limits of use
To understand some of these limits, we need to understand that when fireplaces are tested they will end up with a power rating. This is then documented on the compliance plate found on the rear of the appliance expressed as 'Maximum Average Heat Output when using Hardwood' and a KW figure is at the end. This is not to be confused with 'Peak' output which is for a short time at any point during a burn cycle. Maximum Average is a factor worked out over several burn cycles at this high setting for the duration until the next load is added.
Both AFS+ and IFS flue systems have opinion letters that determine how the flue system can be used and you can download both here;
Fireplaces outside the KW limit
For fireplaces that are above the general 15KW (max avg) limit listed on an opinion letter, the only way to install it with what would be considered in this case to be a non-compliant installation, would be if it was installed in a situation where clearances are not an issue, such as within a brick chimney. This obviously has it's limitations.
The alternative to this would be to have the fireplace in question tested specifically with the intended flue system to determine what the clearances would be. We're in talks with one Australian manufacturer in particular to have individual tests done on some of their higher KW output units to increase the scope for insulated flue and will provide updates as things change.
The IFS installation manual version 1 is pending upload to our website but for the moment you can download a version from this link.