In this blog post we will look at the differences between wrap-around and fixed boilers when fitting a boiler stove, as well the differences between a closed system and an open system.
Whether a wrap-around boiler or a fixed boiler is best for your wood-burning boiler stove installation will depend on how much hot water is needed.
What is a wrap-around boiler?
A wrap-around boiler is just another name for a high output boiler (up to 30kW). It gets its name simply because it has more surface area to transfer heat to the water within. Most high output boilers are intended for use with radiators. These are steel or iron, so there will need to be rust inhibitor in the pumped water.
For this reason, wrap-around boilers tend to be made of steel instead of the much more expensive stainless steel. This is called a closed system because the water serving the boiler radiators and coil in the hot water tank never mix with the hot water in the tank.
What is a fixed boiler?
The small output clip-in or add-in boilers, like those for the Arada stoves (typically 1-4kW) are made from stainless steel. This allows them to be directly plumbed into your hot water tank, with no need for a coil in the tank.
In this case, the hot water from the tap will have been in the boiler at some point. This is called an open system.
Pressure
In terms of pressure, you can opt for either sealed and vented. This means there is either a header tank for the boiler in the attic or there is a pressure vessel near the main boiler. The likes of the Arada boiler stoves are high output and designed for used in a closed system. These can be vented or pressurised but, because there will be corrosion inhibitor in the water in the system, the cast iron pump should be fine.
This is only the briefest of introductions and boiler stove installations can get very complicated. We’d recommend contacting a HETAS installer capable of wet installations to get your system working as efficiently as possible.
