SIZE OF STORAGE TANK FOR GASIFICATION

[keith]

I am planning 3000sqft new construction with a condensing boiler to run a low temperature radiant system.
I plan to connect this main condensing boiler to an indirect storage tank 100-150 gallon, and then use the Tarm/Eko gasification boiler to supplement. Wouldn't it be more efficient to store the extra hot water in a 400 gallon custom tank instead of an 800 tank. Isn't it harder to keep 800 gallons at a set temperature. What am I missing?

Also, the Tarm website offers 3 illustrated setups "parallel";"primary-secondary""auto-mix" Any preferences for my situation described above.....

 

[Eric Johnson]

Welcome to the Boiler Room, PARTTIMEPYRO. I'm a full-timer, but everyone's welcome here. Sounds like you appreciate quality equipment.

The mantra on hot water storage is that more is almost always better. I think, without the benefit of any actual experience--yet, that hot water storage is like battery power in that the more you have, the longer you can run on it. It's a momentum thing. It may take half a day to get a 2,000 gallon tank up to 180, but once you get it there, it will stay in a usable range with relative ease and give you a lot of cushion and flexibility in your firing. You fire the boiler at your convenience, in other words, and you can fire it hard for maximum efficiency.

And you don't have to keep the tank at a set temp. With infloor radiant, you can pull water out of there all the way from 190 down to probably 90 degrees. That's a huge amount of storage when you consider the btus. So you charge the tank up when it suits your schedule, not when you need the heat, because you've already got storage to draw from. And a big bank account is almost always better than a small one, if you want another tortured metaphor.

Probably somebody else can explain it better than me. And someone with more expertise in system piping can surely give you a good recommendation on the best way to pipe yours. But it sounds like a great project, and I look forward to seeing it progress. We have a whole mess of EKO and Tarm owners here, plus some guys with Econburns, BioMaxes, Garns, Greenwoods and a bunch of other gasifiers that escape me at the moment. We like to answer questions and share ideas. So again, welcome.

 

[Nofossil]

When it comes to storage, more is definitely better. The more you have, the longer you can go between fires.

However, I made a mistake that I would urge others to avoid. There is a distinct advantage in having two heat storage tanks - a high temp and a low temp. The high temp tank can be smaller, and it's purpose is to heat and/pr preheat domestic hot water. It's useless below about 120 degrees. The bigger tank is for space heating, and if you have radiant you can run it down to 90.

I've been playing with this for a while. I've got a writeup of sorts on my site - link is in my signature below.

 

[Reggie Dunlap]

With new construction you have a lot of options. I just did what you are planning to do on my new house. As Eric said these systems are perfect for radiant heat because you can run much cooler water. Hot water baseboard is not really effective below 150-160 degrees. I have 750 gals of storage but I wish I had 1000. The more storage you have the longer you can go between fires. It takes longer to get 1000 gals to temp, but in a properly insulated tank it will hold the heat indefinitly.

I put my wood boiler in the attached garage so I can drive the firewood right to it. I don't know if this passes code in CT, we don't have any code in VT so I just did it. Good luck with it.

Reggie

 

[keith]

Thanks Eric,Nofossil,&Reggie;. Based on your replies it appears the larger storage tank offers flexibility while the smaller indirect tank would better suit instantaneous high temp. needed for domestic hot water demands. Nofossil thanks for the diagram on coordinating the indirect tank with the larger storage tank.