Problems creating heat

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debtfarm

New Member
Oct 7, 2010
13
B.C., Canada
Bought a Bio Mass 80 gasification boiler. I have hooked it up as an open system to an 800 gallon stainless steel insulated tank. I've hooked the cold water from the bottom of the stainless steel tank to the cold inlet of the boiler and the hot water from the top of the boiler drops into the tank. I have a third line as a mixing line running through a Danfos mixing valve with a valve on it to restrict flow on the bypass. I am trying to heat this tank up without drawing any water out to the house or shop and I am not having any success getting this tank up to temperature. Any suggestions???

This boiler has a BTU output of 275,000, so with my calculations it should heat this 800 gallon 30 degrees of temperature rise per hour. Are my calculations correct?
 
If you are starting with a cold tank and boiler it is going to take a while to get the boiler cooking. My experience is starting with a cold boiler it takes along time to get the boiler up to temp so it can start to gasifiy properly. With a large boiler like you and I have you have a lot of mass and untill you get really gasifing you are just heating the mass with a flame that is like a OWB. Once you get the boiler temp up to 160* and above it will start to properly start to gasify and then you will put out the btu's. Even if you make gas at a lower temp it doesn't burn well as it cools down to much to burn efficient.
Also the boiler won't put out 275000btu's thru-out the burn, only in the hotest part of the burn and will then slowly drop off untill the wood is gone.
My experience has been that it takes about 1/3 load of wood to get the boiler really cooking. During the winter you don't have that problem as the boiler is hot so it can start gasifing quickly.
leaddog
 
800 * 8.3 gal/lb = 6640 lb of water, or 6640 btu's per degree 275000/6640 is 41.41 degrees per hour in a perfect world where your biomass actually does 275000 btu/hr. so 30 is probably realistic once you are up to speed
 
leaddog said:
If you are starting with a cold tank and boiler it is going to take a while to get the boiler cooking. My experience is starting with a cold boiler it takes along time to get the boiler up to temp so it can start to gasifiy properly. With a large boiler like you and I have you have a lot of mass and untill you get really gasifing you are just heating the mass with a flame that is like a OWB. Once you get the boiler temp up to 160* and above it will start to properly start to gasify and then you will put out the btu's. Even if you make gas at a lower temp it doesn't burn well as it cools down to much to burn efficient.
Also the boiler won't put out 275000btu's thru-out the burn, only in the hotest part of the burn and will then slowly drop off untill the wood is gone.
My experience has been that it takes about 1/3 load of wood to get the boiler really cooking. During the winter you don't have that problem as the boiler is hot so it can start gasifing quickly.
leaddog
Click to expand...

Also, if this is a brand new stove, it takes some time to get all of that ceramic to dry out. Good coals and it will gasify, but like said above, it takes awhile to really get rolling. This is partially why storage works really well especially with a large boiler. It takes some btu's to get them rolling like a giant fly wheel, but when they are rolling, they are also hard to slow down. The first few fires can be exciting and frustrating at the same time.
 
I'm not sure but could the problem not be that this is an 800 gal. open system and there is no heat exchanger in the tank? The boiler is trying to heat the entire 800 gals. of water and maintain 150 F. on return instead of the the 60 gals. it would be heating if it circulated a closed loop through a heat exchanger.
 
"instead of the the 60 gals. it would be heating if it circulated a closed loop through a heat exchanger."

Not really. The HX will be returning cold water also. My experience was abou the same the first few fires. If you look at it, to maintain 150F return temp starting with a 50F tank and a 165F boiler output, there will not be that much water drawn from storage. It is about a 6:1 ratio of 165:50. At 135F return temp it is a 1:1 ratio. At 150F temp is is all coming from storage. That's a good reason not to let your storage get too low. Most people will not let their storage get much below 100 to 130 so the ratios at firing are much better. And yes, the first few firing will take a lot of heat to dry out the mass and to bring the thermal mass up to temp. For me, it took about two weeks before I really understood the firing process and the burner really took off. Have patience.
 
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