“I have a fireplace at home and a wood-burning stove in the living room. I would like to buy another one for the kitchen. Do I have to build a second chimney for this, or can I connect both stoves to the existing one?”
The answer depends primarily on how many ventilation openings the chimney has, which devices you want to connect, and whether the technical requirements are met.
A chimney does not necessarily mean a chimney flue. And that is the fundamental difference.
A chimney or a ventilation opening?
Imagine a brick chimney with two separate ventilation openings.
Each of these exhaust systems can, if suitable, also be used to remove exhaust gases from another device.
This differs from a situation where two ovens are connected to a common flue.
And the joint connection is technically far more complicated.
Can I connect two ovens to one extractor hood?
Not automatically.
The shared chimney flue must be expressly suitable for such a purpose and the entire solution must meet the relevant technical requirements.
This depends, for example, on the type of fuel, the design of both devices, their operating modes and the parameters of the exhaust gas path.
In some combinations, a joint connection may not be permissible at all.
It is not enough to drill a second hole in the chimney and connect another flue.
I have heating on one floor, but not on the other. Why should that matter?
“If I only use one oven, the others don’t bother me.”
That could be the problem.
Under certain conditions, a common exhaust duct can allow an unwanted flow of exhaust gases towards a device that is not in operation.
This can cause smoke or carbon monoxide to enter the room.
The situation is influenced by the chimney draft, the tightness of the devices, the air supply and the pressure conditions in the building.
The safety of a shared connection cannot therefore be assessed solely based on the question of whether you will use both ovens simultaneously.
How about a wood-burning stove and a wood-fired kitchen range?
“I have a wood-burning stove in the kitchen and would like to have one in the living room. Both burn the same fuel.”
The same fuel alone is not enough.
Each device may have different power consumption, required chimney draft, exhaust gas temperature, and other operating parameters.
Therefore, it cannot be automatically assumed that a joint connection will be possible.
The permissibility must be documented for a specific combination of devices and chimney constructions.
Can I connect a pellet stove and a fireplace to the same chimney?
Special care must be taken when using a shared vent valve.
Pellet stoves may use a fan to remove exhaust gases and have different requirements for the pressure tightness of the exhaust path than conventional wood stoves.
Therefore, such devices cannot be arbitrarily connected to a single ventilation opening.
The situation may be different if the chimney has two separate, suitable ventilation openings.
Is a larger chimney diameter sufficient?
NO.
“I have a chimney with a diameter of 200 mm, the exhaust gases from two ovens will definitely fit in there.”
The cross-section is only one of the parameters.
The effective height of the chimney, its thermal properties, the pressure conditions and the operation of connected devices are also important for proper exhaust gas removal.
Furthermore, a larger diameter does not automatically mean better traction.
In some systems, however, an inappropriately large vent opening can cause problems with exhaust gas cooling.
What if I already have two stoves connected to one chimney?
In older houses, there may be other, historically determined methods for connecting household appliances.
The fact that such a system has been in operation for several decades does not in itself prove its safety or its compliance with current requirements.
If you are unsure whether the connection is correct, you must have the exact exhaust path and the connected appliances checked.
In particular, if smoke enters the room, work must not be continued until the cause has been eliminated.
What should I consider before buying a second stove?
First, determine whether your chimney has one or more separate ventilation openings.
Furthermore, their condition and suitability for the intended purpose must be checked.
The assessment is based on the technical documentation of the furnace and chimney, the operating parameters and the relevant requirements for the exhaust gas paths.
If the existing chimney is not suitable, a separate new chimney vent or an additional external chimney may be the solution.
When connecting or modifying the exhaust pipe, the requirements for its testing before commissioning must also be met.
What can you take away from this?
Two stoves and one chimney may not pose a problem. However, two stoves and a shared chimney flue require special consideration.
If the chimney has two separate, suitable ventilation openings, each can operate a different device.
However, connecting two devices to a single ventilation opening is not automatically permissible and is not allowed in certain combinations.
Therefore, before buying a second oven, you should consider more than just the diameter of the flue pipe.
First, check whether your existing exhaust system allows for the safe connection of another device.