You have a chimney with a diameter of 150 mm. You’re looking for a wood-burning stove with a flue pipe of 150 mm. Perfect, everything fits! Can you order now?
That’s fast! The same diameter doesn’t mean that the oven and chimney will work together perfectly.
And since you’d rather deal with the chimney only after the oven has been delivered, we’ll explain what really matters.
The chimney needs to have the right draft. But what exactly does that mean?
The chimney draft helps to draw the exhaust gases from the stove to the outside. It is mainly caused by the density difference between the hot exhaust gases and the surrounding air.
If the draft is insufficient, the stove may burn poorly, be difficult to ignite, or, under unfavorable conditions, exhaust gases may flow back into the room.
Excessive airflow is also not ideal. It can lead to over-combustion and make proper regulation more difficult.
Each oven has its own requirements regarding operating conditions. The required chimney draft strength can be found in the manufacturer’s technical documentation.
Average 150 mm? That’s just the beginning!
Imagine two chimneys. Both have a diameter of 150 mm.
One oven is tall, well-insulated, and has a suitable connection. The other is short, cools down, and the flue pipe leads to it via several bends.
Although they have the same diameter, their operating characteristics can differ considerably.
The following factors are important when assessing a chimney:
- Effective chimney height – i.e., the height from the connection point of the device to the opening of the chimney.
- Ventilation diameter and design – A ventilation opening that is too large or too small may not be suitable.
- Temperature and quantity of the flue gas Different oven models have different parameters.
- Exhaust pipe construction – Length, bend and type of connection influence pressure losses.
- Combustion air supply Even a professionally constructed chimney is useless if the stove doesn’t get enough air.
Therefore, there is no universally valid rule that a chimney with the same diameter and a certain height is sufficient for every stove with an 150 mm pipe.
I have an old chimney. Can I connect a new stove to it?
Maybe. But just because an old stove has been used on a chimney for twenty years doesn’t mean it’s suitable for a new one.
Modern devices can have different exhaust gas temperatures, draft requirements, and other operating characteristics.
Sometimes the existing chimney can be reused without structural modifications. In other cases, it may be necessary to modify the flue or choose a different appliance.
It is definitely not a good idea to use the “connect and look” method.
Is a chimney inspection required for my oven?
When replacing a furnace, it must be checked whether a revision of the flue gas path is necessary.
Czech Regulation No. 34/2016 Coll. stipulates, among other things, an inspection before replacing a device. An exception applies to the replacement of a device of the same type, design, and performance, provided that the suitability of the flue system is confirmed by a cleaning and inspection report.
A routine chimney inspection and an exhaust gas inspection are not the same thing.
The inspection will be carried out by an authorized emissions tester. If you are unsure whether it is necessary, discuss this with a professional before installation.
What should you find out before ordering a stove?
You don’t need to become a chimney expert. Just have the basic information ready:
- What type of chimney is it, what condition is it in, and what are its dimensions?
- What is its effective height?
- Where is the exhaust connection located?
- What diameter is the flue pipe and what draft must the chosen stove have?
- Do you have current documentation for the exhaust system?
Based on this data, the chimney sweep or chimney builder can assess the suitability of the connection and, if necessary, carry out the required calculations.
Our final piece of advice
The oven and chimney must form a functioning pair.
You can have the most beautiful and highest quality stove, but if the chimney doesn’t fit, it won’t heat properly.
Therefore, check whether the chimney is suitable before purchasing.
This is much more convenient than waiting until after delivery of a 90 After discovering that there is nowhere to safely connect a heavy stove weighing several kilograms, there is nowhere to do so.