# Expansion Tank Location



## Sid (Oct 28, 2015)

I'm not an expert nor a plumber/hydronics engineer but I do feel I understand the concepts relating to expansion tank location.

Ideally, it is to be right next to or connected to air separator, and on the suction (I call it before) side of a circulator.

My install is rather complex so I'd love a second set of opinions on this issue.

In the drawing you will see the tank is tied in right after the boiler output and right before the air separator.




In the following picture you will see the way I piped it, very similar, just put it right after the air separator and that first tee that goes into the Thermobloc.



It seems if the best location would actually have been right on the horizontal inlet of the Thermobloc (that connects Thermobloc to bottom of storage tank). I feel that would be the area of least pressure. Also, why would it have been drawn the other way? (I plan to call Tarm Biomass and run the question by them since they always are quite helpful and easy to talk to, and it is where the drawing originated).

Now, do I really need to cut and redo my new piping? This project is long over budget in regards to money/materials and time and would really love to just keep it the way it is if it's OK. On the other hand, if I do need to change it, now is the time and I do want the project done right.

Another thing to note is that I'm not even going up a full story (literally only about 5' to the baseboard convectors) to the first floor (there is no second floor).

Any advise helps, thanks.


----------



## ewdudley (Oct 28, 2015)

When you need to 'pump away', you should always pump away.  In this case you do not need to pump away.

There will be only a small amount of head generated by the pump when it is pumping through a short loop of fat pipes to and from storage, so all the dire warnings simply to not apply.

(The height of the system does not enter into it since the storage loop pump cannot 'see' the rest of the system, although the limited height of the system will allow you to run a higher-than-necessary static pressure, which would further guarantee that there will be no problem with cavitation anywhere in the system.)


----------



## maple1 (Oct 28, 2015)

Wondering why there are two feed setups & expansion tanks in the system diagram?

Or I'm not seeing anything that separates into multiple systems.

I would therefore be tempted to do away with the feed setup closest to the wood boiler, and tie the expansion tank into where the smaller one is shown.

EDIT: If I'm seeing things right.


----------



## maple1 (Oct 28, 2015)

Another from the 'if I'm seeing things right' angle.

Looks like there is a mixing valve in the circuit between the wood boiler/storage loop, and the load loop. But there isn't one between the oil boiler, and the load loop. So if heating only from storage, would the water hitting your zones be hot enough?

EDIT: Ok, nevermind that one, it's diverting not mixing. So chances are it won't be recirculating water unless the water is very hot.

Carry on...


----------



## Sid (Oct 28, 2015)

maple1 said:


> Another from the 'if I'm seeing things right' angle.
> 
> Looks like there is a mixing valve in the circuit between the wood boiler/storage loop, and the load loop. But there isn't one between the oil boiler, and the load loop. So if heating only from storage, would the water hitting your zones be hot enough?
> 
> ...


You got it Maple1, it's that expensive diverter valve that I wasn't originally going to install but last minute decided to. I figured I'd come all this way, let's not cheap out now, and I like the idea of letting the hot re-circ and only send cold ('water not hot enough to do work') to the bottom.


----------



## Sid (Oct 28, 2015)

maple1 said:


> Wondering why there are two feed setups & expansion tanks in the system diagram?
> 
> Or I'm not seeing anything that separates into multiple systems.
> 
> ...


The reason for the two feeds and expansions I feel is to preserve the ability to separate the systems (there's isolation valves for the diverter valve [impossible to see in picture since they are part of the union connection and don't have handles, I should probably note the ball valves on the drawing] and pump that would allow me to separate.)

I'm tieing into an existing setup and the more I can leave in place the better when it comes time for the big switch/ final tie in connection day. That is why I plan to leave the existing expansion and feed in. I also do not plan on separating systems so I do not plan on installing that second cold feed on the wood boiler.


----------



## Sid (Oct 28, 2015)

ewdudley said:


> When you need to 'pump away', you should always pump away.  In this case you do not need to pump away.
> 
> There will be only a small amount of head generated by the pump when it is pumping through a short loop of fat pipes to and from storage, so all the dire warnings simply to not apply.
> 
> (The height of the system does not enter into it since the storage loop pump cannot 'see' the rest of the system, although the limited height of the system will allow you to run a higher-than-necessary static pressure, which would further guarantee that there will be no problem with cavitation anywhere in the system.)



Ewdudley, your answer is exactly inline with what the guys (pros I assume) at TarmBiomass said. 

Thanks for your input, not just on my posts but I've read and follow much of your advise from other threads you've posted on...you always provide a great explanation for your reasoning and this forum is lucky to have you.

thanks again all!!


----------



## leon (Oct 28, 2015)

QUOTE="Sid, post: 1994093, member: 41272"]I'm not an expert nor a plumber/hydronics engineer but I do feel I understand the concepts relating to expansion tank location.

Ideally, it is to be right next to or connected to air separator, and on the suction (I call it before) side of a circulator.

My install is rather complex so I'd love a second set of opinions on this issue.

In the drawing you will see the tank is tied in right after the boiler output and right before the air separator.
View attachment 165437


In the following picture you will see the way I piped it, very similar, just put it right after the air separator and that first tee that goes into the Thermobloc.
View attachment 165439


It seems if the best location would actually have been right on the horizontal inlet of the Thermobloc (that connects Thermobloc to bottom of storage tank). I feel that would be the area of least pressure. Also, why would it have been drawn the other way? (I plan to call Tarm Biomass and run the question by them since they always are quite helpful and easy to talk to, and it is where the drawing originated).

Now, do I really need to cut and redo my new piping? This project is long over budget in regards to money/materials and time and would really love to just keep it the way it is if it's OK. On the other hand, if I do need to change it, now is the time and I do want the project done right.

Another thing to note is that I'm not even going up a full story (literally only about 5' to the baseboard convectors) to the first floor (there is no second floor).

Any advise helps, thanks.[/QUOTE]



=====================================================================

Where is your point of NO PRESSSURE CHANGE?, Your circulators may be confused with having 2 bladder tanks in the system.


You need to put a tee at the suction side of your circulators and a tee on the pressure side to install a set of vacuum gauges(suction HG) and pressure(PSIG) on the discharge side of the circulators to see what the HG and PSIG pressures are(I would)/ (I AM).
=======================================================================
If it were me I would have a have a common steel expansion tank for both boilers in the basement ceiling. There are no moving parts and it can be connected to both boilers with a common 3/4 inch header pipe you do not want or need an air scoop or automatic air bleeders and as long as its plumbed correctly no bleeding radiators.

I am reinstalling a 15 gallon steel expansion tank for my dual fuel coal stoker replacement heating system after 33 years of air bubbles and leaking automatic air vents.
=======================================================================
Me-
I would move the larger bladder tank near the air scoop(remove the air scoop)
(not needed with the spirovents)and reconnect it to your piping after removing the scoop and snaller bladder tank. I would also move the feed valve and back flow preventer to the suction side of C1 but away from the inlet about 2 feet.

Were your bladder tanks properly adjusted for thier air pressure as it relates to the pressure created by the circulators(18 PSI+-) and your altitude with no water in the system??

Is your water feed valve at the point of no pressure change? You only need one feed valve BTW.

If you move the larger bladder tank and eliminate the air scoop you should move the feeder valve and the backflow preventer on the suction side of C1 at the same time.

My thoughts anyway.

You should invest in two of Dan Holohans books "Pumping Away" and "Classic hydronics" from Barnes and Noble or Amazon.


----------



## Sid (Oct 30, 2015)

leon said:


> QUOTE="Sid, post: 1994093, member: 41272"]I'm not an expert nor a plumber/hydronics engineer but I do feel I understand the concepts relating to expansion tank location.
> 
> Ideally, it is to be right next to or connected to air separator, and on the suction (I call it before) side of a circulator.
> 
> ...





=====================================================================

Where is your point of NO PRESSSURE CHANGE?, Your circulators may be confused with having 2 bladder tanks in the system.


You need to put a tee at the suction side of your circulators and a tee on the pressure side to install a set of vacuum gauges(suction HG) and pressure(PSIG) on the discharge side of the circulators to see what the HG and PSIG pressures are(I would)/ (I AM).
=======================================================================
If it were me I would have a have a common steel expansion tank for both boilers in the basement ceiling. There are no moving parts and it can be connected to both boilers with a common 3/4 inch header pipe you do not want or need an air scoop or automatic air bleeders and as long as its plumbed correctly no bleeding radiators.

I am reinstalling a 15 gallon steel expansion tank for my dual fuel coal stoker replacement heating system after 33 years of air bubbles and leaking automatic air vents.
=======================================================================
Me-
I would move the larger bladder tank near the air scoop(remove the air scoop)
(not needed with the spirovents)and reconnect it to your piping after removing the scoop and snaller bladder tank. I would also move the feed valve and back flow preventer to the suction side of C1 but away from the inlet about 2 feet.

Were your bladder tanks properly adjusted for thier air pressure as it relates to the pressure created by the circulators(18 PSI+-) and your altitude with no water in the system??

Is your water feed valve at the point of no pressure change? You only need one feed valve BTW.

If you move the larger bladder tank and eliminate the air scoop you should move the feeder valve and the backflow preventer on the suction side of C1 at the same time.

My thoughts anyway.

You should invest in two of Dan Holohans books "Pumping Away" and "Classic hydronics" from Barnes and Noble or Amazon.[/QUOTE]

Wow, that's a lot of different things to consider. It's funny you mention using a steel compression style expansion tank vs bladder. I actually bought on craigslist an old propane tank someone converted to a large expansion tank, all setup with a gauge and stand to be mounted correctly. My original plan was to use this since those large Amtrol's are super expensive, but after enough research and advise from people I decided it wasn't worth the risk of long term oxidation in my system with two expensive boilers and two steel 500 gallon tanks from dissolved O2 from the compression tank (basically the consensus was that the compression would work, but the bladder would be better [hence the reason why you don't see compression style installed on new/and-or commercial systems]). 

As for the rest of the things you mentioned, I just don't have the expertise to comment on those. I'm hoping that the engineer/s who developed that drawing considered those issues and accounted for them. I have another thread that has the entire install detailed and covers some of the planning parts of it. It can be found here: https://www.hearth.com/talk/threads...iler-with-1000-gallon-thermal-storage.138501/

Maybe some more people here on the forums who know more about those issues will chime in as well.


.


----------



## leon (Oct 30, 2015)

Where did you get the idea that steel expansion tanks are no
longer used in large boiler installations????

They are still made and sold and installed and for that matter they are still hanging
above the boilers to this day because they have no moving parts and a new boiler will
still work with them AS they have no moving parts.

There are tanks that are 50 plus years old still hanging in ceiling joists.
The problem is that a lot of plumbers do not understand how they work
and they get rid of them and replace them with bladder tanks WHEN THEY
DONT HAVE TO.


The tank that I had hanging in the ceiling of the laundry room was over
30 year old and was working fine and if they had not ripped it out it would
be over 60 years old

You would and should use boiler treatment for any boiler to manage
the PH of the feed water.

Buying the replacement  15 gallon tank, airtrol valve and gauge glass valve was a little over $385.00 for the new coal stoker I am installing or having installed if I can find a plumber to help after I do the preliminary work

Steel expansion tanks are ment to separate the air in the hydronic or gravity system with a water cushion  with 1/3 of the volume of a steel tank begin the air cushion and the other 2/3's being the water that absorbs the microbubbles that rise from the boiler tapping or the Inline air separator(IAS)depending on how its properly plumbed.  

in many cases where space is an issue a battery of steel expansion tanks equivalent to the volume needed for a hydronic system can be hung in ceiling joists and piped in parallel with a common header sloping upward from the boiler or boilers and they cost much less than one larger bladder tank.


----------



## Sid (Oct 31, 2015)

Yeah, I'm aware of these practices an the physics behind them and that's why I said in my summery of research that both would work but I personally feel bladder is better. 

"Systems using Bladder/Diaphragm tanks are called air elimination or air removal systems. Systems using compression tanks are considered air management systems."

I like the thought of being able to get all of the air out and keep it out vs air constantly going into and out of solution.


----------



## Bob Rohr (Oct 31, 2015)

Sid said:


> Yeah, I'm aware of these practices an the physics behind them and that's why I said in my summery of research that both would work but I personally feel bladder is better.
> 
> "Systems using Bladder/Diaphragm tanks are called air elimination or air removal systems. Systems using compression tanks are considered air management systems."
> 
> I like the thought of being able to get all of the air out and keep it out vs air constantly going into and out of solution.




Agree on the bladder or diaphragm style tank.

With a plain steel compression tank you would need about twice the capacity in the tank, it should have the proper fitting to direct and keep air at the top and limit thermosiphoning.  You may need to replenish the air bubble from time to time, and add the heat loss from the larger tank surface area.

The Wessel site has a nice sizer program to show the comparison.


----------



## leon (Oct 31, 2015)

Sid said:


> Yeah, I'm aware of these practices an the physics behind them and that's why I said in my summery of research that both would work but I personally feel bladder is better.
> 
> "Systems using Bladder/Diaphragm tanks are called air elimination or air removal systems. Systems using compression tanks are considered air management systems."
> 
> I like the thought of being able to get all of the air out and keep it out vs air constantly going into and out of solution.


===============================================================================================

A bladder tank is nothing more than fluid accumuator/energy storage device with a gas charge being "air" which stores energy to put fluid pressure into a system to do work.

A steel expansion tank with the airtrol valve has 2 major benefits for the consumer or commercial heating or cooling.
1. It does not waterlog and it works by simple gravity.
a. The air charge always stays in the tank because the airtrol valve keeps it there.
b. The airtrol valve has two passages to allow the cooler water to drop past the hotter water that is rising in the tank line that has air bubbles to enter the steel expansion tank.

The air in the steel expansion tank keeps it all at the same level 1/3 air -2/3 water.
The airtrol valve is designed to allow the air bubbles in the hot water to rise in to the steel expansion tank to be absorbed while gravity lets the cooler water pass it on the way back in to the boiler.

As long as the feed line from the boiler or IAS  is installed properly the system always works, its when automatic air vents are  installed and or the systems are not bled properly to begin with or you have a leak somewhere is when problems occur and a steel expansion tank waterlogs.


----------



## TS Beniot (Nov 1, 2015)

Sid,  Been reading your posts and would like to hear how the system is running now.


----------



## Sid (Nov 2, 2015)

TS Beniot said:


> Sid,  Been reading your posts and would like to hear how the system is running now.


Still working on it, pretty much done with all the piping until the final connect to existing system. Working on wiring and controls this week, possible be ready to fire in a couple weeks I hope.


----------

