Replacement of steel expansion tank with diaphragm tank

eRock

I've removed my old steel expansion tank from the ceiling in order to make room for an A/C return and would like to replace the tank with a modern diaphragm. The furnace is a Buderus GA124X, which I had installed a few years ago. I've done a lot of my own plumbing over the years and I'm comfortable with the work but hydronics is rather new and I'm unsure of the expansion tank details and air removal components which go with it. I've attached a few pictures of the plumbing and any suggestions, guidance or help would be greatly appreciated on the following questions.

- Is there a reasonably accurate way to calculate the size of the expansion tank needed based upon the old steel tank (1' x 2'.6") rather than the capacity of the system?

- What are the better brands of diaphragm tanks?

- Where should the new diaphragm tank be plumbed into the system?

- I've read that converting to a diaphragm tank 'closes' the system and therefor requires an air separator / air vent / air scoop / spirovent....  What is actually needed and what's the difference between all of these? 

- Where should the air eliminating device be plumbed into the system? 

Mark Eatherton

Response ...

Your existing tank is rather small, at just around 10 gallons. THe model number of most diaphragmatic tanks is the non captive tanks equivilant. THe smallest diaphragm tank I've seen is 15 gallons. If it were me, I'd go for the #30.



- What are the better brands of diaphragm tanks?

Amtrol invented the diaphragm tank. I think they are the oldest, hence most experienced manufacturer. I've had "issues" with ALL diaphragm tank manufacturers.







- Where should the new diaphragm tank be plumbed into the system?



The expansion tank, air eliminator and make up connections should all be located right before the main boiler circulator. This is where oxygen will come out of suspension. It will also insure that the pump works in a good way.





- I've read that converting to a diaphragm tank 'closes' the system and therefor requires an air separator / air vent / air scoop / spirovent.... What is actually needed and what's the difference between all of these?



The way your system is installed indicates to me that it is connected to upright cast iron radiators. Personally, in these situations I don't bother with an air separator unless the boiler is also providing DHW. The radiators will work quite efficiently at eliminating air by trapping it in the upper portions of the radiator. Once you manually bleed the air from the system, it will no longer be an issue. If you must us a separator, the microbubble resorbers are faster at air elimination, and there is one or two that are intended for vertical installations, which would be conducive to your system.





- Where should the air eliminating device be plumbed into the system?



After the heat source,because this is where air and oxygen will easily come out of suspension. It also creates what we refer to as the Point of No Pressure Change, which is critical to pump performance, hence the reason you want to install it BEFORE the circulator(s).



HTH



ME

eRock

Thank you

Thanks Mark -

I appreciate your response and time; this is very helpful. The system is a baseboard aluminum fin type system vs radiators and does not supply DHW. After countless purging's, air always re-enter the system after 2-7 days so I appreciate the additional advice on the location of the air separator.

Eric

Mark Eatherton

Oy....

If you paid for this installation, I would call the installer back and ask them why they didn't follow the manufacturers basic installation standards.



You are going to have to re-pipe the system to incorporate an air separator/expansion tank into the system. The scenario that I explained where I wouldn't use a separator is NOT the same as yours. Your system MUST have an air elimination system, or you WILL have bubbles in the system.



Where are you located? Might be able to find a good contractor to help you out.



ME

eRock

That explains it....

I was going crazy last winter purging air from the system.  I'm in Richmond, VA.

Ironman

Location

I'm near Staunton. Not sure that I've have time to go to Richmond any time soon, but I'd be glad to check with my Buderus rep to see if he has someone he'd recommend.



If you're interested let me know by emailing me through "the wall". Just click on the "contact user" tab under my user name. Please include your contact info.



I also have a former employee who's in business in Spottsylvania who might do it.



Let me know if I can help.



P.S. You could save alot of fuel and have better comfort by adding the 2107 Logamatic control to your boiler.

eRock

Second chance

The installation was done by a local and well established company here in Richmond.  I'm going to give them a call and provide them the opportunity to respond or correct the oversight prior to doing anything else.

Many thanks for your feedback and advice -

Eric

Mark Eatherton

If that fails...

Contact Dan Foley with Foley Mechanical Inc. He's one of the best.



http://www.heatinghelp.com/find-a-contractor/VA/Lorton



My recommendation would be to go to the manufacturers web site, and arm yourself (if your I&O manual is missing) with the installation and operations manual so you can point the obvious deficiencies out to the sales person.



If that fails, then you've already begun the formal legal due diligence process in that you've given them a chance to make good before pursuing legal avenues.



Hopefully they will see the error of their ways and make good the installation at no additional costs to you.



Let us know how it works out.



ME

Mark Eatherton

An exercise in futility...

I just went on line to the Buderus web site and pulled up an I&O manual, and guess what, they don't give piping installation diagrams. That might pose a problem.



Your fall back would be to state the fact that the installation does not follow a "Standard of Care" as it pertains to a typical closed loop baseboard hot water heating system installation, which should include an air elimination/capture system.



Buderus needs to get their act together... and finish their I&O manuals. It may be accepted that the only people in Germany that will be installing their boilers are "certified" and qualified, but here in the US, you never know WHO is going to be installing the equipment and what their abilities and qualifications are.



http://www.buderus.us/files/201001221904130.63040308_Buderus_G124xII-SP042005.pdf



ME