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Outdoor Wood Boilers....using more than one together...

Started by Captain, April 15, 2007, 09:13:23 AM

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Captain

We really want to get an outdoor boiler here for the property.  We have been holding off, because we anticipate a new building for shop space and want to buy one to heat that too.  However, the price tag of $10,000 is holding us back at this time.

I was considering the purchase of a smaller unit for the house, and another one later for the new building.  Does anybody have any experience in running them in a series or parallel setup sharing the same water??  I was thinking that one could be used in times of lower demand, and the second one fired when necessary.  Just a question to ponder.

Thanks in advance.

Captain

farmerdoug

Captain,
I have been pondering the same question since the bioburner was anounced.???
I do not see why you could not connect them together.  But since most outdoor boilers are open systems ie. no pressure, I am sure you would have the close one boiler system tight and pump from the open boiler through the closed boiler treating it just like a line or storage tank.  Then the water would flow back to the open one on the return line as usually. :)

Clear as mud?  Let me know if you need a better explaination. ::)

Farmerdoug
Doug
Truck Farmer/Greenhouse grower
2001 LT40HDD42 Super with Command Control and AccuSet, 42 hp Kubota diesel
Fargo, MI

Daren

You can tie 2 systems together (or 10). I have put in "boiler packs" that do just what you are talking about. 4 small boilers that fire as needed, that was in big office buildings and such. It just takes a check valve (a valve that only lets water go one way) to stop one boiler from backfeeding the other. I have designed and installed many systems that use the same piping for a boiler and a chiller. They feed the same units (air handling units) That is a little more complicated with control valves and such. Hot water runs through the pipes in cold weather and vice versa.
I am sure your boiler suplier could make you a quick sketch for the best installation and would have the parts you need.
Experience is something you don't get until just after you need it.

farmerdoug

Daren,

I assume those boiler paks are pressurized sytems?

Most outdoor boilers are open to the atmosphere.  How would you interconnect those boilers without all of the water pumping out of the top of the first boiler?  I think you would have to close one boiler tight and circulate through it.  I am open to better ideas though.

Farmerdoug
Doug
Truck Farmer/Greenhouse grower
2001 LT40HDD42 Super with Command Control and AccuSet, 42 hp Kubota diesel
Fargo, MI

mur

Hi Captain:

Don't know if this helps or not.  I don't know your physical site and heating needs.  My outdoor boiler - Global Hydronics 3000 - made in Canada, has two sets of infeed/outfeeds on it at the back.  Therefore, this large boiler can run two separate systems with one common tank of water.  I only run one system into my kiln and moulding room and blocked off the second infeed/outfeed.  Each system needs its own pump and piping of course.
Don't dream it, be it.

Daren

Quote from: farmerdoug on April 15, 2007, 07:04:33 PM
Daren,
How would you interconnect those boilers without all of the water pumping out of the top of the first boiler? 

I will admit I am no outdoor boiler expert (I am a 3rd generation steam fitter/licensed plumber though) Unless I am misunderstanding the question...a check valve on each boiler is still my answer. One on the outlet side of the boiler will only let the water go one way, out into the system. It will not let one boiler pump into another, they are 2 separate units using the same pipe  ???. What you are talking about is another answer too. One boiler is a primary on low demand and preheater on high demand. The second boiler is storage on low demand and "more power" when needed it will fire.
I see about the same amount of controls with either set up. I just think installation would be easier if the were to be put in at different times like Captain is talking about if they were set up separate and isolated with a check valve from each other.
I may be on the wrong track here because of the return piping, but in my mind the boiler that is pumping water will be the one the water returns to. So if only one is running the other is idle/no flow. If they both are running 2x the flow and heat exchange. Without knowing the piping arrangement in this specific case (distances, flows...) I cannot give a better explanation, but worst case scenario maybe a solenoid control valve on the returns that is tied to the circ pump totally isolating the second boiler when not in use? 
Experience is something you don't get until just after you need it.

Furby

Well I see a couple problems here.
You would need some heat in the idle unit to keep it from freezing.
But if you were to run only one and pump it through the other keeping it up to temp, you would have a high rate of heat loss at the idle unit.

I'm thinking the two units may be tied together with a large manifold and be able to almost totally close off one unit.
That way there would be a trickle charge so to speak to keep the idle unit warm enough, yet not have a large heat loss by trying to keep that much mass up to temp.

But I really don't know much about these units so this is just talk from me. :)

Daren

Yea you got me there Furby ::). How much water do they hold? If it is a bunch, you do have a thermal mass problem with an idle boiler. If it is totally isolated when there is a call for extra heat (if there is a large amount of water in the "cold" boiler) there will be a slug of cold water to deal with. And the freeze up I had given no thought to. farmerdougs storage tank second boiler would fix that little problem. If you are only talking a few gallons in the boiler, there is much more water in the system and even the return is not cold just not hot. Good thinking about a small return through the idle boiler, it would not take but a trickle.
Good thing you have all summer to stew on it Captain  :D, surely with enough heads together something will work.
Experience is something you don't get until just after you need it.

Furby

They can hold a 75 to a couple hundred gallons I belive.

Mooseherder

Wouldn't 1 Boiler take care of 2 buildings?  How far apart will the buildings be?
Maybe have a backup oil furnace for the house but not the shop.

farmerdoug

My CB is plated at 794 gallons of water.

This is a very interesting topic.  I am really open to ideas.  I just stated the one that I had centered on first.


Farmerdoug
Doug
Truck Farmer/Greenhouse grower
2001 LT40HDD42 Super with Command Control and AccuSet, 42 hp Kubota diesel
Fargo, MI

Captain

Certainly one unit can heat both buildings, but the second building does not exist yet,  :-[ and I can't justify the $10,000 +/- price tag right now when heating for free with an indoor supplemental force hot air unit.

I would love to move to outdoor heating, but I don't want to throw $6000 into a boiler that will meet my needs now, but not in the future  :)

thecfarm

What kind do you plan on getting?The heatmor that I have bought have blowers on it and it just sits there waiting for the next heat cycle.Why couldn't you set them up independant of each other?One small one like a 2 footer for the house and than another one for the shop.You didn't say how many square feet each building is.I would go to a dealer and run all your ideas by them and see what they have to say.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

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