Replacing old style expansion tank.

Glenn Harrison_2

Here's a link to Hot Water Heating Expansion Tanks made by Flexcon Industries, the main tank manufacturer I have used. Under downloads to the right, they have a Spec sheet, Sizing sheet, Installation sheets, and a cross reference sheet to go from Flexcon numbers to your favorite Brand of tank. Do keep in mind the sizing sheet is for a system operating at 12 psi.

<a href="http://www.flexconind.com/html/htx.html" target="_blank">Flexcon Industries Hydronic Expansion Tanks </a>

CPyne

Replacing old style expansion tank

Hi,

I have a 1 story ranch with a forced hot water boiler with an old ceiling mounted expansion tank. I'd like to replace this with a new bladder style tank due to a few pitted spots that look like they're about to spring a leak.

Based on this article, I was planning to replace the copper pipe that goes up to the tank with about a 1 foot steel pipe threaded into the existing elbow. I'd then have a T with an autovent on one side, a nipple that goes sideways roughly the width of the tank, and then an elbow down to the tank.

http://www.contractormag.com/articles/column.cfm?columnid=60

A few questions...

What tank size is appropriate for a system like this?

Does the tank need to be supported or can the pipe just carry the weight of the tank? (I'm guessing a steel pipe could probably handle this and copper would probably bend)

Any other advice anyone can offer?

Thanks
Charlie

CPyne

Picture #2

Picture #2

CPyne

Here's another picture

Here's another picture

Big Ed

tank

A average size ranch with fin & tube radiation ? Use a # 30 tank and support the tank.If the tank loses its charge it would get heavy and swing down with that piping configuation.

CPyne

Yeah, its an average sized ranch. What do you typically support these with?

Thanks
Charlie

Big Ed

Support

Screws and band iron would do just fine.Kendal track ,rod & clamps if you want fancy-better.....

John Di Lauro

I have a similar problem

except that my house has cast iron radiation. My current expansion tank is 12 inches in diameter by 30 inches long, which works out to about 15 gallons if I did the math right.

Would a 30-size bladder tank be an adequate replacement?
Thanks for any help.

Big Ed

Tank Size

In thory and in the paper work if anyone reads it , a #15 is equal to a 15 gallon tank.....Out in the field we find a #30 works better...........


Try a # 30 ............if the system pressure increases 10 pounds or better in a heating cycle, then use a #60 or twin in a second #30 at the same location... This is our trial and error approch... You can also measure the amount of system water and calulate the size needed.

P.S. The tanks air charge should be adjusted to match the systems working water pressure..

Joe Mattiello

No air vents with plain steel tank

I happen to notice a Taco Hy-vent installed on your system when using a plain steel convention type expansion tank. There are three types of systems available for handling thermal expansion of your heated water. Your system is what we call air control, and there should not be any air vents installed on this type system. You must constantly drain some of the water out of the tank. I guess if you are changing over to a diaphragm type tank then you can leave it there, because that will be an air elimination type with air vents to purge the air out.

Taco, Inc.
Joe Mattiello
Technical Service Technician
joemat@taco-hvac.com
401-942-8000 X 484
www.taco-hvac.com

John Di Lauro

Thanks

Thanks for the information. I have checked literature from B&G and Amtrol but have not found anything about sizing.
Can you point me in the right direction to find the stuff you mentioned?

CPyne

THANKS!!!

Wow... Thanks for the info. I wasn't aware of that.

There was an old vent there that was rusted and clogged up, so I replaced it with the new Taco one that you see. While I was at it, I added another one that you can see in the background. I guess this would have made my problems worse this winter. Now I'll make sure I follow through with this and not try to keep using the old tank! Thanks!!

By the way, how would you refill one of these old style tanks if you fully drained it and it was 100% full of air? I'm assuming it's supposed to be 1/2 full when not pressurized, but I can't see how you'd vent some of the air in order to fill it to this level.


Thanks again
Charlie

John Di Lauro

Thanks for the info

on sizing. That website indicates I would need a 60 size (my system is about 75k BTU output).

However, I also looked at Amtrol's site and they suggest a 30 size for the same scenario.

I don't know the water volume of my system, but my guess is that it is fairly small (I suppose I could estimate). Thoughts on whether on not the 30 size will work? Thanks.

Glenn Harrison_2

Based on my personal experience,

and knowing that your cast iron rads will hold a lot more water than a baseboard system, if the chart calls for a #60 tank, I would go with a #60. I have had a couple of cases where the chart said 30, but it was border line 30 or 60, and we had to go back and put in the 60 to keep from popping the relief. Plus the #60 will give you a little extra room for error as the air side slowly looses pressure from year to year.