Final questions before storage tank install

[Green Mtn Boy]

I've almost finished the modifications to my Three 250 gallon propane tanks and before I move them into the basement to start plumbing I have a few questions I was hoping to get answered :

These tanks will be installed vertically and as close to each other as possible. I plan on having them spay foamed with 2” of closed cell. Do you guys think this is adequate? The foam is R 7 /inch.

With the tanks vertical how should I connect the plumbing? Should I connect the supply to each tank together at the top of the tanks or should the supply go into the top of one tank, out the bottom and to the top of the next tank?

My Tarm and oil boiler are currently configured in a primary / secondary configuration with the system pump on the Tarm pushing supply water into the return of the oil boiler and then off to my radiant manifold via the injection pump. Since I have to break into the system for the storage tanks, should I reconfigure my plumbing to a parallel system? Will I see better response? Will it be worth the extra work? Will leaving the oil boiler “cold” lead to a shorter life span? The oil boiler usually never runs in the winter unless I'm gone some where. Perhaps with the storage, the response time of heating both boilers up before producing heat for the house will be non existent?

I currently have the 160° version of the Thermavor installed. To those of you that have changed it out to the 140° version.....was it worth the up grade?

Does anyone have anymore advise that I might incorporate into my system that might make it work better? All opinions are welcome! Thanks for advise. This site is a great resource because of its knowledgeable contributing members.

 

[Nofossil]

From your description of your current setup, it sounds like what is commonly called a 'serial' installation - the boilers are connected so that water flows through both, one after the other. Primary / Secondary is a whole different animal.

If your boilers are connected in serial, going to parallel will provide quicker response and higher efficiency. There are a lot of different approaches. There are two stickies at the top of this forum that describe different approaches - basic parallel and primary / secondary. Both allow the boilers to be connected so that either one can be heated while the other remains cold.

If it were me, I'd plumb the storage tanks in series, top of one to the bottom of the next in order to get maximum stratification. However, with vertical tanks you'll get lots of stratification anyway. You're probably OK just connecting all the tank tops and all the tank bottoms.

I'd do a LOT more insulation, though not necessarily all spray foam. I suspect that you'll lose enough heat through R-14 to make the floor above the tanks pretty hot. There's a lot of surface area and the water can be really hot.

 

[stee6043]

I'd also go with in-series plumbing if it's not too much of a hassel. And like Nofossil says - you need a lot more insulation than 2" of spray foam. I have, on average, two layers of R30 insulation around my tanks and closer to three layers on top, though the top layer is compressed a little.

The more heat you bleed from the tanks the shorter your period will be between fires. With my "box" setup, I would guess at an average of R50 insulation, I can usually get 16 hours between fires on an average winter day. This works out pretty well for me on most days. If I leave the tanks with no heat going in and no heat coming out I loose roughly 10 degrees every 24 hours (maybe 12-15, I forget exactly). That's roughly 84,000 btu's of stand by loss per 10 degrees...