OK.



This thread is getting beyond the scope of what I originally intended. This is not a bad thing. Since I have discovered a valid, safe and air sealed method of providing air to an atmospheric boiler under conditions which it was not intended to operate (such as a well sealed house) any further speculation is in strict modder Territory.

Can one convert an atmospheric boiler to be a sealed combustion boiler? This is the question we are raising here. Aside from simply creating a sealed box around the unit there are certainly many, many, MANY more issues to take into consideration. If people are interested, let's hash them out.

Piwoslaw:

It is my personal opinion that your concerns about freezing are unwarranted due to the fact that there is a lot of heat present at all times. Either active or residual heat from the boiler itself or from the surrounding environment that will nullify this. Now if you keep you mechanicals in an unconditioned space (and if so you have better things to worry about than upgrading your functional boiler to a sealed combustion boiler) freezing might be an issue. From my point of view it is next to impossible to remove an entire basement from the thermal envelope of a house. It's more expensive, but, one should include it. You gain conditioned space and saves money on utilities.


Next:
Is it actually possible? Are the burners different in some way? I’m assuming the 97% efficient burners aren’t the same as the 80% efficient ones in a different box.
I know someone who. For the first decade of the operation of Buderus in the US was their troubleshooter. He did all of the Buderus training in the early 90’s. They flew him all over the place to troubleshoot new installations. He very well may be the most competent Buderus tech in North America. I’ll contact him ASAP about these issues.

OK, I searched for pictures of the insides of boilers to see the difference in hardware between open and closed combustion chambers. Here is a good comparison:
Notice the closed model on the right: The combustion chamber itself is not sealed, but instead is inside a sealed box, with the rest of the plumbing, motor, electronics outside the box. I think this is the way to go: seal the upper half of what is inside the boiler.

While searching I also noticed that all models had intake and exhaust in a concentric tube set-up (with the exhaust inside the intake), I didn't see any which would have the intake come in from a different side than the exhaust. Other than safety, maybe this to pre-warm the intake air?
This concentric intake/exhaust tube can either go vertically up a chimney, or horizontally out through a wall.

Also, all models had a fan for ventilating the combustion chamber. This fan could also act as a damper to hinder airflow when the burner is off, though with a totally sealed chamber this shouldn't be a problem.
I believe (though I am not sure) that a Rheem model has two fans: one for the intake and one for the exhaust:confused:

Now, once the combustion chamber is closed up it will be very temping to take the next step and convert the boiler to a condensering model increasing the efficiency by up to 15%. The problem for a DIY'er would be a good, acid resistant condensing heat exchanger. The commercial HXs are made of 409 stainless steel, from what I've read.
But 'condensifying' the boiler is worth its own thread.

S-F, I'm very interested in what your Buderus friend has to say.

Well, here's the reply from my friend:

Sounds like it's not possible. I'm not sure but judging by his statements it would seem as though it has something to do with air pressure.

Thanks S-F:)
I was starting to see potential problems with just boxing in the combustion chamber. For example, a fan would be needed to keep the fresh air flowing in, but it would have to compensate for different burner flame sizes (my boiler's burner adjusts the flame between 11-23kW) - too much air with a small flame could be wasteful and/or dangerous.

Replacing the innards with those from a closed chamber model probably wouldn't be cheaper than buying a new boiler.

So a pipe that ends right under the boiler it will be. But the damper which closes only when the flame is off should be OK?

How to provide fresh air to my boiler?
 

Hi,I don't know much but would suggest you to take the advice from the expert.