Thanks for taking the time to read my post.
I built a rocket heater from a LPG gas tank with a proper firebox, insulated firebricks and all correct dimensions from research i did.
It was in my carport with 6" flue straight out from the bottom at 45 degrees for 1.8m then vertical for 1.8m and it runs extremely well. Have been able to hit 520 degrees Celsius on the top of tank.
I have recently installed it into my downstairs basement with the flue straight out the double brick wall and in the same orientation as i had under the carport.
First thing i noticed was that there was a constant draft inward through the rockets heater. Backwards!
Getting it lit is not too much trouble as i through a fire lighter in and blow gently to get the flow going.
It starts up fine with small sticks but as the heater warms up, I get back draft every so often and the flames are coming out the firebox! A quick blow and it goes the other way again.
Very dangerous as i cant walk away from it.
I believe its more than likely a flue length issue as i have tried to open doors to make sure its not a negative pressure issue but it did not solve it.
My vertical flue stops next to a brick wall outside with a cowl and i think its should be longer above the gutters of the house.
The flue doesn't bellow out the end it's actually pretty slow exit speed but it was the same when i had it setup outside running really well.
Is adding more flue going to help me with my problem?
I will attach a couple of pictures to show my setup.
I'm happy to answer any questions on design.
Thanks in advance