ᐅ Flush-mounted boxes (for switches, thermostats) installed in chimney structure
Created on: 30 Mar 2026 10:58
M
Martin..Hello,
We renovated a single-family house built in 1954 and during the renovation, we rebuilt a previously unused chimney in the attic and connected a 5kW wood stove to it on the ground floor. Unfortunately, neither we nor the various contractors involved (site manager, electrician) noticed that some electrical installations were made on the chimney: on the ground floor, there is a power outlet (below the stove connection), a light switch (approximately at the height of the stove connection), and two thermostats for the underfloor heating (30cm (12 inches) above the stove connection); on the upper floor, there is another light switch and a thermostat.
The external dimensions of the flue are approximately 42cm by 48cm (17 by 19 inches); the internal dimensions, as far as I can measure through the two access panels, are about 15cm by 18cm (6 by 7 inches). The masonry and plaster are therefore about 13.5 to 15cm (5 to 6 inches) thick. The installed devices are Gira E2 for flush mounting, with device boxes about 6cm (2.5 inches) deep, which raises concerns that there may be only about 7 to 9cm (3 to 4 inches) of masonry between the cables and the flue.
At least the electrical installation is not positioned exactly in the center of the chimney; the center of the switch on the ground floor is approximately 16cm (6 inches) to the right of the masonry, roughly where the internal flue begins.
This is probably not permissible, which makes me wonder why this went unnoticed by our site manager and the craftsmen, and why the chimney sweep, who inspected the house both during construction and recently during the official flue inspection, raised no objections.
What surprised me and gave me a bit of cautious optimism was that the temperature shown by the thermostats installed in the chimney (Gira System 3000) was only 28 degrees Celsius (82°F) after two hours of stove operation, with a room temperature of 24 degrees Celsius (75°F). Considering the proximity to the flue, I would have expected significantly higher temperatures. Do you have any explanation for this?
The practical question is: We will only use the stove occasionally, perhaps 10 to 30 times a year. From your point of view, is this acceptable, and what are the risks?
Thank you very much!
We renovated a single-family house built in 1954 and during the renovation, we rebuilt a previously unused chimney in the attic and connected a 5kW wood stove to it on the ground floor. Unfortunately, neither we nor the various contractors involved (site manager, electrician) noticed that some electrical installations were made on the chimney: on the ground floor, there is a power outlet (below the stove connection), a light switch (approximately at the height of the stove connection), and two thermostats for the underfloor heating (30cm (12 inches) above the stove connection); on the upper floor, there is another light switch and a thermostat.
The external dimensions of the flue are approximately 42cm by 48cm (17 by 19 inches); the internal dimensions, as far as I can measure through the two access panels, are about 15cm by 18cm (6 by 7 inches). The masonry and plaster are therefore about 13.5 to 15cm (5 to 6 inches) thick. The installed devices are Gira E2 for flush mounting, with device boxes about 6cm (2.5 inches) deep, which raises concerns that there may be only about 7 to 9cm (3 to 4 inches) of masonry between the cables and the flue.
At least the electrical installation is not positioned exactly in the center of the chimney; the center of the switch on the ground floor is approximately 16cm (6 inches) to the right of the masonry, roughly where the internal flue begins.
This is probably not permissible, which makes me wonder why this went unnoticed by our site manager and the craftsmen, and why the chimney sweep, who inspected the house both during construction and recently during the official flue inspection, raised no objections.
What surprised me and gave me a bit of cautious optimism was that the temperature shown by the thermostats installed in the chimney (Gira System 3000) was only 28 degrees Celsius (82°F) after two hours of stove operation, with a room temperature of 24 degrees Celsius (75°F). Considering the proximity to the flue, I would have expected significantly higher temperatures. Do you have any explanation for this?
The practical question is: We will only use the stove occasionally, perhaps 10 to 30 times a year. From your point of view, is this acceptable, and what are the risks?
Thank you very much!
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