Expansion tank(s) question.

We are in the process of installing My New E-100 Wood gun with an approximately 375-400 gallon storage tank. Boiler guys did half of the job on this past Saturday and hope to finish this coming Saturday. A quick question for you. The E-100 holds 60 gallons. Let's call the storage tank 400 gallons. The oil boiler holds 30 gallons. Let's throw in 20 gallons for the piping thoughout the house. For a total of 510 gallons. Can I use three smaller tanks for expansion to save money on buying a large, very expensive tank?

For example. We have an Amtrol 60, which is rated at 14 gallons for the E-100. That is greater than 10% for that. The oil boiler already has it's expansion tank that has been with it for 7 years now. No problems there. For the storage tank. Could I use three Amtrol Extrol 90s? They are rated at 14 gallons each. That would be a total of 42 gallons between the three expansion tanks. Just over the 10% mark of 40 gallons for the storage tank. Thanks for your time.

It took some looking, but I found a Danfoss 1-1/2" bypass valve. 140Deg. temp setting for $180.00.

Thanks for the responses.

Mine is the E100 S.S. as well. I bought it last spring and am now just getting it hooked up. I and my boiler guys have been swamped with projects.

Have your plumbers installed these types of units before? And if so would they be willing to come to Long Island?
They have not installed one of the Wood Guns. But they have installed several boiler systems. To include some larger ones for a small school and several small commercial buildings. We are about 8 hours from Long Island. My boiler guys barely had enough time to install my project and I live about 8 miles from them. So they are not willing to come to Long Island.

My suggestion would be to find a respected boiler guy/company and use one of the diagrams from the Sticky for him to review. Most importantly, I also made sure they were on the same page as I was and understood the "theory of operation" in the posted sticky Simplest Pressurized Storage System Design by Nofossil. Thanks Nofossil. Now I just hope the guys can get their electrical components to work right and make the system work like that theory of operation. They said no problem.


As far as I know, there’s no functional difference between multiple small expansion tanks vs. one large expansion tank.
I could not believe the cost of the expansion tank that would be the appropriate size for the 400 gallon tank! $2000-$3000! What the ______? :gulp:
Is there any special location I should put the expansion tanks? For instance. Should they be as high up in the system as I can get them? Thanks for your time guys.

I’m guessing somebody’s got their signals crossed:

I hope you are right! I went to the Amtrol sight and followed there product sizing for the 400 gallon tank. Used the hydronic expansion tank sizing. Put in my number of gallons (400), my temperature difference 50-200 deg, and pressure of 10-20 and it recommended an AX Series: AX-100(V), L Series: 200-L , LBC Series: 200-LBC , all very expensive. What did I do wrong?

As far as location goes, I was wondering if I should place the expansion tank up towards the ceiling in the boiler room, at top of my vertical storage tank, or if that would even make any difference.

Thanks for your time.