Using casette fireplace to add hot air heating
Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

Posts: 1
Joined: Mon Jan 17, 2022 3:09 pm

Using casette fireplace to add hot air heating

by steve94034 » Mon Jan 17, 2022 3:35 pm


My apologies in advance if there is key information that I need to include. Please let me know if you have any quesitons.

We are slowly reforming an old house in the mountains to the north of Madrid and we want to maximise the heat that we get from our casette fireplace. It's a standard metal casette with fans pulling air in at the bottom and blowing it out of the top of the unit and into the living room.

I addition, there is a 100mm flexible metal tube running alongside the chimney. The lower opening to this is directly above the casette inside the fireplace itself (but separated from the smoke). The tube passively draws air in from the living room, warming it against the chimney and the air then exits into the bedrooms. This works but I would like to make it more efficient.

I am thinking of rather than having it draw air from the living room (robbing the living room of hot air) I would continue the metal tube down snaking around the casette, it would then continue through the fireplace floor and into the basement below. Here it would be connected to the outside to draw in air. I would then connect a small 100mm inline unit to blow air in and up to the bedrooms. I like this idea since it means we are not drawing warm air out of the living room and it means we are adding air to the house so there will be a tendency for draughts to leave the house and not enter. I appreciate that the air will start off cooler and so may not reach the same temperature as before when it enters the bedroom.

However, I have some questions;
1) What distance of 100mm tubing will I need around the casette to give it time to adequately warm up?
2) What would be a sensible volume of air to pass through the piping? The fan I am looking at ( ... _SHEET.pdf) has a setting of 145 m3/h. Does this seem reasonable?
3) What sort of flexible metal tubing should I use? The area around the casette gets very hot.

I'd appreciate anyone's thoughts on this.

Thanks in advance,