expansion tank size

[NCFord]

I did a bit of searching here and did not find a good easy calc. for expansion tank size. I am just going to
bite the bullet and get a regular tank and not consider and open style. I am going to order from pex-supply.com, but their calc. does not consider water volume so it does not work. I currently have a extrol 60 with my system
without storage and it works fine and plan on leaving it in place. Total capacity right now is about 50 gallons.
I will be adding 550 gallons of storage for a total system capacity of about 600 gallons. I will be installing the
new expansion tank near the 550 gallons storage location.
Thanks

 

[NCFord]

It looks like the Extrol sx-110v 62 gallon tank will work, but I still want to make sure it not too small or big.

 

[maple1]

I forget now how I did it, but when I was doing my figuring I came to the conclusion that I should have 2 - 110's for my 660-700 gallons of system volume.

That might not have helped much...

 

[kopeck]

(broken link removed to http://www.amtrol.com/support/sizing.html)

That should do the trick for ya.

K

 

[NCFord]

Not sure what I am doing wrong but that calculator keeps coming up with ex-30?

 

[NCFord]

Also, Is there any problem with using say 3 extrol sx-40v 20 gallon in place of one 62 gal? I might be
easier for me to place 3 small ones than one bigger one. It's about the same cost.

 

[kopeck]

Just guessing at your figures this is what I came up with:



As far a multiple tanks vs one, I don't see why you couldn't do that UNLESS you plan on hanging all of them off the pipe, that could be pretty heavy.

K

 

[Floydian]

https://www.hearth.com/talk/threads/expansion-tank-volume.51241/#post-642119

Here is some great info that ewd posted a few years ago.

Noah

 

[NCFord]

yeah stupid me I keep clicking on the "residential" tab. I'm not planning on hanging any tanks but I have a spot that
I could fit 3 tanks that are less than 48 inches high.

 

[BoilerMan]

Remember that there is no negative system effect to too much expansion volume, just some wasted space and $$$. They can be piped with 1/2" copper, don't waste $$ on anything bigger than 1/2" and place the T somewhere before the circulator, this is called pumping away. Always pump away, WAY more efficient air elimination and circulator watt-to-water performance.

TS

 

[kopeck]

place the T somewhere before the circulator, this is called pumping away. Always pump away, WAY more efficient air elimination and circulator watt-to-water performance.

That seems to be the one obvious flaw in my system. The system circulatory is in front of both my scoop and my expansion tank. That what you get when you retrofit a system that's already in place.

I could have made it work but it would have ended up being a major piping change. I countered the scoop issue by putting a Spirovent over by my wood boiler in the proper location, that thing is so much better then the watts scoop anyway.

K

 

[Bob Rohr]

If the boiler is a cold start, the temperatures should be 60- 180F, not 140- 180F as in above example. It does make a size difference. And maybe 190F, even 200F if it has a chance of "running away" in a power outage condition

 

[91LMS]

Always pump away, WAY more efficient air elimination and circulator watt-to-water performance.

TS

got myself in trouble with this, tried it but couldnt make it work with my boiler protection valve. poor planning on my part but something to think about in planning stages

 

[maple1]

Depends on what you take it to mean - i.e. pump away from what? Usually that term means pump away from boiler, and expansion tank. But if using temp protection or Danfoss, you should pull through that. So you're pumping away from it, and usually towards the boiler (i.e. not away from boiler any more). Either way, you should pump away from expansion, i.e. your expansion tank should tie in on the inlet side of your boiler circ.

 

[BoilerMan]

Maple has it exactly right. Most think of the circulators having to be on the boiler's supply to "pump-a-way", but the expansion tank can be connected anywhere in the system. Pumping away simply means having the expansion tank connection before the pump's inlet.

FWIW: The expansion tank does not have to be connected to the 1/2" port on the air scoop or spirovent. It can simply be T'd in anywhere.

TS