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[sixmenn]

Hello all! 

In a few days I hope to connect a 2 year old Nature's Comfort NCB250 to my house and end the onslaught of high heating bills.  I have some questions for you veterans of wood boiler use.

I have a 3600 square foot 2 story house with an unfinished basement which, if finished, would add another 1500 square feet.  I have two forced air furnaces: the upstairs one is a propane furnace, and the furnace that services the main and basement floors is an open-loop geothermal unit.  We never use the propane furnace (too $$$), so the geothermal unit does the whole job, but costs us in the neighborhood of $400 in electricity per month during the winter. 

My questions:

I want to plumb the hot water to both furnaces and a sidearm for DHW.  The distance between the two furnaces is approx 15-18 feet, one directly two floors above the other. The water heater (with extra buffer tank) is located in the same room as the lower furnace. 

1. What would the path be for the water to and from the OWB? 
2. Would I need to add a pump somewhere in order to move the water to the upper floor? 
3. I have 2@ 120 gallon propane tanks that I hope to use for extra storage.  How would the plumbing work in this mix as well? 

Any other advice/suggestions are welcome!  Thanks everyone!

Sixmenn

[Scott7m]

I see no reason you'd need extra storage, that doesn't necessarily make it more efficient. 

You would go to the hot water tank first, then first coil, then second floor.  Your also gonna need a high flow pump to keep the return temps up, I think it will be rare when all 3 are on together as the upstairs ones don't run much. 

The pump is gonna be an important part of this...

[sixmenn]

I see no reason you'd need extra storage, that doesn't necessarily make it more efficient. 

You would go to the hot water tank first, then first coil, then second floor.  Your also gonna need a high flow pump to keep the return temps up, I think it will be rare when all 3 are on together as the upstairs ones don't run much. 

The pump is gonna be an important part of this...

Thanks, Scott. 

How would I figure out which pump to get?  Is there a formula, or can anyone advise me about what specifications to look for?


Also, everything I've read seems to suggest that extra storage really increases efficiency.  Does that only apply to gasification boilers?  Am I wasting my time trying to tie these two storage tanks into the mix?

Thanks again!

[Scott7m]

Well...  To me water capacity is just like the mild steel vs stainless debate, different companies do it different ways and both work

Some of the most efficient stoves on the market hold the least gallons of water.  Look at the stove I'm running, it's holding maybe 55-60 gallons of water, uses less wood than stoves I ran that held 200 gallons.  It's a gassifier as well so that kinda debunks the "you need mass storage" debate for me.  The Emyre pro 100 only hold 30 gallons of water, I've seen folks heating some nice sizes houses on those. 

The whole mass storage think comes from the European models, but what most people don't realize is that all of those folks "batch burn" there stoves.  They build a fire daily, and often times twice daily and let the fire roar for a couple hours and store the heat in tanks. 

With that being said, the ncb 250 isn't designed to operate in that fashion. In milder times if you take a conventional stove and then give it 3 times more water than it was designed for, the idle times will be longer and it will be more likely for the fire to go out, the firebox will be much nastier because the stove will be idling for much longer than it was supposed to, and dirty creosote caked firebox walls suck at transferring heat.  Which is the name of the game

With that being said, system design and sizing accordingly is what will give you the best burns, the cleanest firebox, the best efficiency, and ultimately, the least amount of hassle if your future.  But system design is just as important as the stove, speaking with someone who understands what a system needs to function properly and getting you pumps, line, heat exchangers, to match your job at hand is critical.  But to take a stove that is designed to function in this matter, and then try to force it to do something it wasn't designed to do, usually don't work to well.

Your home is gonna require the same number of btu regardless of the storage, but when factoring in a couple positives that mass storage brings in, and then all the negatives, it's not a good thing to do IMO

I hope this helps you and if you would like to call me to discuss the details of what pump you should be running according to your situation feel free to call, my number is in my signature.   Leave a MSG if I'm not available.

Hope this helps!!!