confused about burn times on gassers

[maplewoodshelby]

After reading the posts I am a bit confused. To simplify can folks please answer this question

I will be installing a gassification boiler somewhere n the neighborhood of 150,000 btu to heat my home. This is the size of the output of my now in use propane boiler so I am assuming the wood boiler should be about the same.

I am currently looking at either a Attack DP, Biomass, or Econoburn. How long will this stove keep a fire and heat in the house with no storage if fully loaded. I have hydronic baseboard heat.

What if I added storage with a 500 pound propane tank which i ahve on hand

 

[jebatty]

A simple question but so many variables -- what's your heat load, what temperature outside, what wind conditions, what kind of wood, how dry is the wood, how warm do you want to keep your house, do you have low heat floor radiant, baseboard or something else, and the list goes on, and the list changes from day to day in the winter. Do the heat load calc, don't assume you should get a wood boiler with the same btuh as the propane unit. I'm not familiar with a 500 lb propane tank, how many gal? but that said, any storage is better than no storage.

 

[Piker]

A simple question but so many variables

Couldn't agree with this statement more. Until you have some hard numbers it's difficult to tell where you will be with burn times. I can tell you that most of my customers, whose boilers I have sized for systems without storage, tend to run 7 to 8 hours on the really cold nights when it's below zero. Folks whose wood boilers are a little on the small side might even be around 6 hours. A load of wood in most of these boilers will only last 4.5 to 5 hours at maximum output. This of course depends greatly on what you feed your boiler. As I have said in the past... it's wise to save a stash of really high quality firewood for those couple weeks in the dead of winter when it gets bitter cold. When the weather gets more moderate, in the 20's... most of my customers can get around 10 hours with good firewood. Some a little more, some less... and obviously as the temperature climbs, the burn times get much longer. Upwards to 12, 14, or even 16 hours. This is when Thermal storage really shines. No idling means no creosote buildup in your boiler during the shoulder seasons.

I do not recommend that anyone ever fill their firebox full to the point where they are getting such long burn times unless they absolutely have to. It's always best to put only enough wood in the boiler to get you through until the next time you are able to load up. This keeps the efficiency as high as possible by reducing the heat load that is satisfied by the pyrolysis reaction in the upper chamber alone, thereby forcing the boiler to gasify more, and reducing overall creosote deposits in the combustion chamber and and heat exchanger.

If you don't want to install thermal storage, there are ways to shut the boiler down safely before the coal bed dissappears, and at the same time turn on your oil or propane boiler so that it takes over until you can load more wood in the wood boiler. Yes, you will have to use a little fossil fuel when it gets really cold out, but ease of use is also important for most people. Even if you are supplementing your wood heat with some fossil fuel when it gets very cold, you will be able to save a significant amount on your energy bill.

cheers

 

[Duetech]

As stated there are many variables with wood heat. The higher btu rating for the wood will make a lot of difference no matter what season it is and you will use dry wood or complicate your efforts with a gasifier. The load capacity of the boiler will obviously make a difference with fire duration as well. Air adjustments for "tuning" the gasifier will also make a difference. Fossil fuel furnaces used to be tuned by the installing technician and a gasification boiler is no exception and is actually easy to tune once you understand the principles and have one with adjustable settings. Tuning and leaving a fossil fuel unit is primarily what you can do with a gasifier if you only burn one type of wood and keep the moisture at a consistent level but different wood types may require tweaking for best results. Un-tuned my EKO40 would get 14 hour burns with dry red oak in cool weather now it can do 16 hours + and that is without storage. Bear in mind my unit is slightly over sized for my current usage but expansion is in the planning for future usage. The "40" has about 6.5 cu. ft. in the loading chamber. Some of the threads in this forum suggest that the rating for the biomass gasifiers and wood boilers is overstated and to figure on about 85% of the stated value in comparison to fossil fuel/electric boilers. With a side arm dhw heater I can recoup any perceived $ losses by having a little larger than "needed" gasifier. Going to storage will change the way I use wood but from all accounts it will be for the better. Without storage I heat my dhw in the summer with daily short fires for peak hot water usage times to reduce boiler idling time and save wood.

 

[Piker]

Some of the threads in this forum suggest that the rating for the biomass gasifiers and wood boilers is overstated and to figure on about 85% of the stated value in comparison to fossil fuel/electric boilers.

I cannot speak for all brands of boilers, but according to last years Intertek test data on the Econoburn EBW-150, output capability was measured at a little over 162,000 Btu's per hour under ideal test conditions. From a marketing standpoint, it seems like they would be better off calling the boiler an EBW162... but from a practical customer satisfaction standpoint, it's better to be underrated than overrated, especially considering the fluctuating output of solid fuel burners.

cheers