cold wood

[leaddog]

This kind of goes with the cold air thread but I thought it deserved a seperate thread. I have found that putting cold wood into the boiler has a big effect on the time to get the temp up on the boiler. It makes me understand the effect having water surrounding the fire box has as far as cooling down the flame. I have a BIG boiler so the effect is larger but I was having a hard time trying to understand why when I loaded it up and had good gasification going my water temp would go down. I totally isolated the boiler and just circlated the water in the boiler and it still went down. it took quite a while and the temp would go down sometimes several degrees and just slowly went up. then when it got up in the 160 range it would heat fast. What is happening is the cold load of wood is pulling heat from the water in the upper chamber and it takes alot of heat to heat that wood up. From a cold start this can take quite a long time to get the water up to that magic temp of 160 plus to make gasification work the best and was one of the problems I was having in the fall when I was starting from a cold start. Now that I understand it I make sure I don't fill it all the way up on a cold start even if gasification is going. I can then go back and finish filling it when the water is up there.

Another thought I have is on a cold start you could start your fire and get coals started, then take a propane rosebud or weed burner on a wand and aim it from under at the nozzels and heat the nozzels up which should get things going faster. Has any one done this and your thoughts!!
leaddog

 

[Eric Johnson]

Somebody more comfortable than me with the math ought to be able to figure out how many btus it takes to get 100 pounds of wood from 0 to 150 (more?) and be able to calculate what it's costing you.

Along the lines of your refractory pre-heat idea, I have noticed that the optimum time to reload my boiler, from a gasification point of view, is (not surprisingly) when I have several inches of coals covering the nozzles. Let it burn down much farther than that, and it can take a few minutes to get back up to speed with a fresh load of wood, and it will smoke until it does. Maybe your cold wood theory has something to do with that.

 

[ISeeDeadBTUs]

Amen on the cold wood theory.

My un-scientific observation of this phenom has led me to store my bestest wood in the shed, right next to the GW (Obvious no-no form an inadvertent incendiary point of view).

I'va also tried the semi-load till it heats up, then finish the load, but I think mis-timing it and the hassle factor and the introduction of large volumns of cold air defeat the purpose.

 

[barnartist]

Ive been trying smaller loads the last few days to see what kind of effect it has on overall consumption. I think there is a fine line. As soon as the door is opened, heat comes out, and cold goes in. So more smaller loads just might make it have to fight off the cold wood temps. I had one good 1/4 load trial with good results, but the following loads not as well. But who knows it could be many factors.
With this last cold snap, it's been like putting a freezer inside the boiler with all that bone cold wood. Part of the restart has to fight moisture, cold, and cold air inlet temps (for outside boilers). Its a wonder it even gets going at all really.

 

[Eric Johnson]

I think that's right about the losses when you open the door and toss in cold wood. Lots of smaller fires is probably much less efficient than fewer, larger ones. Plus, with a bigger load, the sweet spot, when you reach peak efficiency, is extended.

 

[barnartist]

Eric, you have 1000 gallons of storage. How cold do you let your water get before you reload with your setup? Do you have a sort of point of no return?
Returning to the post, It might be a good experiment to get enough wood for a load and put it in the house for a couple of days to warm it. Try that and compare. Best to do it on a really cold day-same outside temps with one load cold, one load warm. Then since none of us are really busy, monitor the results.

 

[Eric Johnson]

Storage "pending." The boiler has been working so well without it, that I've been goofing off and not getting it done.

 

[barnartist]

I have the ability to by-pass my storage. If I do, its really hard for me to run it. Oh well.

 

[eekster]

I" ve noticed that when the wood is cold it does take longer to bring boiler up to temp. My wood is in the garage( around 55 degrees ) I did bring in some cold stuff for more moisture content from outside, and did notice a difference.
Keith