Rocket mass heater issues

Hi
Ive been using my RMH over the winter in NZ
Not sure why this is happening?

Mine did that.
It's condensation; the exit chimney temps are not hot enough, or your wood is not dry.

Tricky Smith wrote:Hi
Ive been using my RMH over the winter in NZ
Not sure why this is happening?

My wood is dry so how do I increase the exit temp?

Even dry wood gives off lots of water vapour when it burns. Most of what comes out of an RMH is steam, and if it cools down in the flue you get condensation. Mine does this and it eventually rusted out the thin duct that I used in the cob bench in my original build, so over the winter I tore it down and refashioned it as a stratification chamber. I've still got a relatively cool stack, barely over 40 degrees where it leaves the bench, so I probably have a lot of water in the chimney but I don't see it because the joints funnel it to the inner surface.

Some designs that exit via a wall put a tee at the transition to vertical so that this water can run down and out of the system instead of getting trapped. I'm thinking about doing this on mine before next winter.

Tricky Smith wrote:

Tricky Smith wrote:Hi
Ive been using my RMH over the winter in NZ
Not sure why this is happening?

My wood is dry so how do I increase the exit temp?

Would it help to put another flue liner on the chimney?
It currently only has an inner and outer flue above the roof.

Do you have a way to check the outlet chimney gas temperature?
It should be 60 C or higher.
We need more info on your system (sizes).

thomas rubino wrote:Do you have a way to check the outlet chimney gas temperature?
It should be 60 C or higher.
We need more info on your system (sizes).

6" system 22 foot cob covered ducting.
Based on Erica and Ernie Wisners The RMH Builders guide.
No im not able check exit temperature.
Best i could do is temp of inside flue just before it goes through the ceiling.

Are there any 90-degree bends in your pipes?
Each one adds 5' to the total length, you are allowed 30' with a 6" J-Tube

Maybe you mounted the stove pipes with the crimp ends up? Change this to crimp ends down and your problem is gone.