Chimney Connector on a B-3 Series Unit
The necessary size of this connector (and the chimney system connected to it) depends on quite a number of things. Our units NORMALLY have a flue sized for a chimney that is average height, 16 feet. For most normal applications, that means an 8" flue (chimney) for a B-3B, B-3A, B-3N. A 6" flue is normally on the B-3J, B-3JN, K-3. A 10" flue is normal on the B-3D, B-3C, C-3, and other three-glass-sided units, and on the F-9A Built-In Fireplace models.
On free-standing JUCAs, the OUTSIDE diameter of the connector is EXTREMELY accurately that diameter. The tolerance is generally about 0.003". This accuracy is so the first piece of smoke pipe goes over the OUTSIDE of it, and is so tight that no leakage of gases or liquid creosote could occur.
There are some circumstances where a different sized flue is called for. For example, if the chimney is a lot taller, it draws better. Sometimes, a 25 foot tall 6" chimney will draw as well as a 15 foot tall 8" one. In such cases, sometimes customers choose to use an existing 6" chimney system rather than an 8" system, often to save money.
If this possibility is being considered for a B-3B, for example, please consider also having us make another change in the unit. Since we custom build each unit, it would not be any problem for us to build a B-3B unit with a (smaller) B-3J door. We call that unit a B-3B-6. Let me explain the thinking.
In reducing the chimney to a 6", (28 sq.in.) with the normal-sized B-3B door opening, you might be increasing the chance of some smoke back-puffing out when you open the door. To reduce the chance of this, making the door opening also smaller (to 204 sq.in) matches the reduction in the chimney area. Voile! A B-3B-6. Similarly, we could make a B-3A-6, a B-3D-8, or an F-9A-8, IF you are sure that the chimney is extremely tall.
Our Technical Series includes a very technical discussion of chimney design.
The JUCA Home Page is at: http://mb-soft.com/juca/index.html
E-mail to: JUCA1@mb-soft.com