Best way to collect heat from outdoor storage?

Thanks to all for looking- I just signed up for this site after hours and hours of reading your great posts! However, I still just cannot make up my mind as to the best way to connect my 800 gal outdoor concrete storage tank. Everyone has a different way of how they did it, but I just could not find one that fits my "needs".

I have an E-Classic boiler and I just dug out a hole, 8' deep for the tank (I have absolutely no room in my house for it). I put the tank in ground, lined the entire outside w/ 6" of foam insulation (I figured the depth should help with insulation as well- inside will be lined w/ 2" of the heat resistant foam & EPDM when it arrives). My question is: what is the best way to run this storage tank to my current closed pressurized boiler system (which is exactly 90' away from tank)? I will be using a HX at the oil boiler inside my house no matter what because I obviously want to keep that system pressurized. The wood boiler will be an open system. An idea someone gave me was to run 100-150' of 1' pex from the return line from the house and right into the concrete tank. The supply line will be much shorter and run through the tank as well, but more heat will be going into the indoor oil boiler first. Our domestic hot water currently is heated from our boiler.

Will this 1" vapor barrier pex line be sufficient enough for heat transfer? If so, how much should I use (I have 300' roll left over). Or should I just use heat exchangers in the tank? The line I will be running is the 4" pipe fully insulated w/ foam w/ 1" supply & return inside it. I really need to get this done quick since my boiler has already been running for about 3-4 days now! Spent over 10k on boiler this spring and with the jobs we had this year, I just am getting to it. I would like to see a return on this investment so I got to do something quick.

Any advice offered will be much appreciated. Again, I learned more from this site in 6 hrs than I have in probably a year! Thanks again guys!

BTW, I'm not an expert in plumbing or hydronic heating so If I said something that makes no sense at all, please feel free to correct me

Nofossil,

Thanks for the first reply! I ran into a bunch of your posts in my previous searches, you sound like you know you "stuff".

The tank is much lower than the CB (I assume you mean Central Boiler?). At the top, it is almost 5' lower than where the boiler will be sitting. So do you recommend me running one loop- from the supply line of the wood boiler, into the tank via the PEX coil, then right to the plate heat exchanger by the indoor boiler? Or are you suggesting running 2 loops- I guess similar to 2 heat exchangers in the actual tank? One from the wood boiler to heat the storage tank & one from the indoor boiler to "absorb" the heat? I just want to be clear on this..

Again, thanks for any advice!

Yuri

North Border,

My current boiler has a built in coil (a Utica Boilers brand unit) for water heating. I took this coil out a few years ago because my dad designed the system using the coil in the hot water tank itself to heat the domestic water. Anyways, I plan on putting the coil back and using that coil to heat the indoor boiler from the wood boiler. I do not want to depressurize for several reasons. However, my only issue now is how to capture the heat from the storage tank; I know there are several possible ways, I guess I am just looking for the "best" way to do it.

Nofossil,

I just order a 60 mil liner for the in-ground storage tank so I have a little while till it arrives. Please let me know if you can get me a sketch, it would be much appreciated. As I mentioned, I don't know much about hydronic system design so anything help is better than none.

Thanks

Yuri Yanuk