How big and why?

[Martin Strand III]

Don't be confused with "efficiency" claims by dealers or Mfgs. This term is widely misunderstood and a bit complicated.

The amount of the heat that is actually transferred into the room from your stove depends on a number of factors:

1. Combustion efficiency. In all new Phase II stoves this percentage is near 90% with dry cordwood.

2. Heat transfer efficiency (thermal efficiency). How much of the heat generated in the firebox escapes through the chimney into the atmosphere (stack loss) depends on the firing strategy and the thermal mass of the heater. Newer metal stoves and fireplace inserts with firebrick lining are designed to be clean burning but still have poor thermal efficiency because they lack a thermal mass that functions as a heat exchanger. The combustion efficiency multiplied by the heat transfer efficiency, is the overall efficiency, but this term still does not fully characterize the true efficiency of a heater.

3. Linearity of output. For clean combustion, wood requires a brisk, hot fire which results in short burn times. If the heater has no storage capacity the fire must be damped, otherwise all the heat is transferred into the room during the burn time. As a result, the room becomes overheated and/or the stove over fired while the fire is burning and under heated after the fire has died down. An overheated room loses more heat to the environment because of the higher temperature differential between the room air and the outdoor air.

4. Partial charge efficiency. See above post.

So, there's more to it than "burn efficiency". If you can digest the above, you'll be ahead of the pack.

Aye,
Marty

 

[Hakusan]

Marty, ideally I would be getting a masonry heater for the points you have made--it is about the only heat system I know of that works efficiently and simply. Unfortunately, my understanding of economics, specifically what is in the bank account, is preventing me from taking that option. A TERM wood boiler with a hydronic is also in that list.

The wood stove is harder to understand for exactly the reasons you point out. I think what I am having a hard time with is unlike the masonry heater which transfers the energy to a thermal mass which then releases the heat slowly into a space, the wood stove is dumping the energy directly into the environment. Burning hot and fast is the most efficient, but can be uncomfortable. Dampening does control output, but by making the burn less efficient. How do I find the point where those two meet for the best burn for the situation? I am starting to think there is no answer until I start to try to heat my house. Pity there are no rental stoves...

I want to thank everyone for chipping in.

 

[lexybird]

get a NC-30 and dont look back , you can always add some firebrick to reduce the firebox size

 

[Martin Strand III]

Marty, ideally I would be getting a masonry heater for the points you have made--it is about the only heat system I know of that works efficiently and simply. Unfortunately, my understanding of economics, specifically what is in the bank account, is preventing me from taking that option. A TERM wood boiler with a hydronic is also in that list.

The wood stove is harder to understand for exactly the reasons you point out. I think what I am having a hard time with is unlike the masonry heater which transfers the energy to a thermal mass which then releases the heat slowly into a space, the wood stove is dumping the energy directly into the environment. Burning hot and fast is the most efficient, but can be uncomfortable. Dampening does control output, but by making the burn less efficient. How do I find the point where those two meet for the best burn for the situation? I am starting to think there is no answer until I start to try to heat my house. Pity there are no rental stoves...

I want to thank everyone for chipping in.

The answer you seek, which also helps in life, is "compromise".

Look at as many newer model wood stoves that you can which appeal to you.
Talk to dealers and talk to their customers. Ask questions.
Select your choice realizing "heavier is better" (as opposed to bigger).
Place it centrally in your home in the primary area you want the additional heat (have realistic expectations).
Construct a first class chimney.
Wait for cooler weather as your wood dries.
Burn appropriately sized dry fuel loads hot .
Sit back, relax, read a good book and enjoy.

Aye,
Marty
Grandma used to say, "Do your best, then relax. It's not up to you anymore."

 

[begreen]

If I lived in an 1800 sq ft. house in Maine, you can be pretty sure that a heavy, 3cu ft stove would be in my house unless is was an igloo. One thing we really like about the Alderlea is its flexibility. It's not a masonry heater, but the T6 has a lot of mass. This allows us to burn shorter, hot fires, stove top up to about 550-600 in the shoulder seasons and not drive ourselves out of the house. The mass of the stove takes time to heat up and then gently radiates the heat. Normally, after 3-5 logs, we let the fire die out. In the winter, we load the stove full up, and burn full hot fires taking the stove top up to 750. And keep it above 400 all day long.

 

[Wet1]

I guess this is why I really like the cat stoves, and the BK stoves in particular. With a cat you can burn a small fire in a larger stove. While the small fire might not be the most efficient, the cat will utilize the unburnt pollution from the otherwise inefficient fire. And with the BK, you get the thermostatic damper and the super long burn times so there's less fussing with the stove.