flue temps

[Scotty2]

With the GARN 2000 I've been advised to keep the flue temp between 300 and 400 degrees.
What's happening if it's higher or lower?
Does lower mean either I'm burning wood with too much moisture, thus increasing the chance of Creosote, or the fire is too small?
Can the temps get much higher? I'm (usually) burning very dry wood (inside shed 5 years)...even then the flue temp is usually in the high 300's with a good fire going.

 

[Sodbuster]

Scotty, I'm not familiar with the Garn, but generally lower flue temps mean sluggish combustion and higher flue temps mean you are wasting energy out of the stack.

 

[BoiledOver]

As long as your flue is evacuating the water vapors before they condensate, a low temperatures are acceptable. On the other hand, if running over say 450F, a lot of btus are leaving before the storage can take them in. My Eko25 does pretty well between 380F and 420F. Unlike the Garn, it is a 20 gallon boiler.

 

[TCaldwell]

During highburn your temps are well within a safe operating range. Remember due to the large tank flue temps are influenced by the tank water temp. If you fire with a water temp of 120 you will have much lower flue temps than if the tank temp is 170 with a same size fire. This creates a wide safe flue temp range that could appear confusing.

 

[Highbeam]

Are these surface temperatures of single wall flue or internal flue gas temperatures as measured with a probe?

 

[BoiledOver]

Mine are measured inside with a probe, 10 inches up from the tee of the horizontal exit.

 

[Scotty2]

I believe the GARN measures the flue temp sensor that's installed about 1/2 way along the convoluted exhaust pipe...maybe 10' from the burn?