Really Dumb Question on Pressurized/Non-Pressurized Water Tanks

[rickh1001]

After lurking for 2 years or more on this forum, and studying everything I could find on wood gasification boilers and hot water systems, just to demonstrate how little I was able to retain, I have the following questions. Can someone explain to me the advantages/disadvantages of an open tank storage system, such as the type that the Tarm literature advocates, vs. a pressurized system, such as an old LP gas tank?

I am taking the plunge this year, finally, and will install a (hopefully) well designed wood gasification boiler with adequate storage capacity, to replace our current oil/hot air furnaces. For now, I will use heat exchangers in the plenums, but eventually, want to plumb in baseboard radiators and radiant floor heat with various zones, and leave the oil burners strictly as backups.

Is the choice strictly one of size, in that it is easier to build an open atmosphere storage tank, vs. trying to get a large steel tank into the basement? It seems the open storage tank, with basically two separate heat exchanges going on (boiler to water, then water to heat loop) would be much less efficient.

So what is ideal heat storage setup, ignoring such minor details as figuring out how to get a 1,000 gallon tank into the basement?

Also, if I ever wanted to install some type of solar panel heating to augment the wood heat, would this impact the choice of systems?

 

[2.beans]

for me it was the cost.

 

[Rancherii]

Any decision should be based upon cost, that being total first and operational costs. Pressure system allows more heat to be stored theoretically. Should not affect addition of solar system later on if pressurized since will have a heat exchanger interface.

 

[Nofossil]

My analysis is that pressurized can obtain better performance (stratification,delta T) and requires one less heat exchanger. Downside is that pressurized tanks are heavy, bulky, and require a large expansion tank.

 

[jebatty]

Another upside of pressurized is less maintenance and less need to monitor water pH, total alkalinity and sulfite. Once up and running and in balance, so long as new water is not added, balance should continue indefinitely.

 

[Ron Lloyd]

How big of an expansion tank is required for a 1000 gal storage tank? I was looking at expansion tanks at Lowes yesterday. If I remember correctly they had an 86 gal, 52 gal, and a 36 gal. Of course they had many smaller ones. I was only looking at the larger ones because I remember reading here that a large expansion tank is required for pressurized storage but I don't remember how big. My Tarm 60 is supposed to be delivered the week of June 16th so I’m busy gathering other components for the install.

Ron

 

[verne]

I got a sxht 160, 81 gal I think ( $ 400 ) for my eko 40 w/ 1000 gal storage. You could also use two 100's. I think jebatty uses close to the same size

 

[Ron Lloyd]

If I added a second 1000 gal storage tank later would I then need a second expansion tank or can one expansion tank take care of two storage tanks? If just one expansion tank can be used for two storage tanks then I assume that it would have to be even larger. Would it have to be twice as big? I see online that Lowes has a 119 gal for $645.16. Would it be large enough for two 1000 gal storage tanks.

Ron

 

[verne]

from what I understand you would need twice as much regardless if you have two or one