# Open vs Closed System



## Mass Heat (Mar 2, 2012)

Would you expect to pay more for the installation of a open or closed system? Either unit would be installed in a shed without storage at this point.


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## hobbyheater (Mar 2, 2012)

Mass Heat said:
			
		

> Would you expect to pay more for the installation of a open or closed system? Either unit would be installed in a shed without storage at this point.



Closed will cost more due to the extra cost for expansion tank or tanks .
I have run my system both ways , and found there was not much advantage to pressure unless you wanted to go over 212 F.  My  boiler is " H" stamped and my and storage is a X- Steam boiler with its tubes removed .

Corrosion is the main concern in a unpressurised system .


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## stee6043 (Mar 2, 2012)

Do a little reading before you beleive anyone that flatly claims that either one "will cost more".  Typcially pressurized storage tanks can be had for pennies on the dollar compared to non-pressurized tanks.  And again, typically, you will not need an HX coil in a pressurized setup.  But yes, pressurized systems do require you to deal with expansion and it can be expensive.  It can also be very, very low cost if you want to read a little more.

Do you own math but there is a reason that so many people hunt down used propane tanks and I suspect it's not because they want to spend more money.


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## tom in maine (Mar 2, 2012)

The big thing is to factor your labor.
Some folks consider sweat equity free, some have to pay for it.

Also, as some have done here, poking a hole in the side of your basement to get a big tank in is not a small cost.

I agree, it is wise to check costs, and add them up as needed.
Sometimes unpressurized works better for some folks.
I like the idea of an easy fix if something goes down on one of our tanks.
My 2 cents worth.


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## woodsmaster (Mar 2, 2012)

I agree with stee that it could go either way as far as cost. besides the things allready stated circulaters allso cost more for an open system. On a pressurized system you allso need an air scrubber that you wouldn't have on an open systen
I think of the old pressurized school house boilers that lasted well over 50 years everytime someone askes
what will last longer. With proper treatment an open system should last a long time though.


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## woodsmaster (Mar 2, 2012)

Are we talking open system or open storage ?

 EDIT : I reread OP. May want to decide if you are going to add storage later and plan from that.


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## EffectaBoilerUser (USA) (Mar 3, 2012)

I would agree that one has to evaluate their specific application to determine which system is best/most cost effective.

There are both pros and cons with a pressurized vs. non-pressurized system in the same way there are pros and cons with a boiler system located indoors vs. a boiler system located outdoors.

For my specific application, I had the following requirements and thus having a pressurized system indoors worked best:

1.) In addition to heating my house, DHW and Jacuzzi 365 hot tub I also wanted to heat my garage. However, I did not want to have to add dedicated heating devices (unit heater, baseboard etc.) or plumbing to do so. So, by having my effecta lambda 35 boiler with 1,000 gallons of propane tank storage in a lean to on the back of my garage I am able to keep my 28'x40' insulated garage at 60F when it is 10-20 F outside.
2.) I did not want to get bundled up/fully clothed when throwing wood in my boiler. By having it on the back of my garage I am able to put wood in the boiler while in my PJ's.
3.) I did not want to use a heat exchanger when hooking up my wood boiler system with my existing Burnham propane boiler. Once again, with a pressurized wood boiler I did not have to purchase or install a heat exchanger.
4.) I did not want to mess with water conditioner and monitoring of the boiler water on a regular basis. Once again, a pressurized boiler system met this requirement.
5.) I wanted to be able to make (1) ONE 5 hour per day to provide for 100% of my heat load and a pressurized boiler with 1,000 gallons of storage met this requirement.

So, as I said previously, the decission to go with a pressurized or non pressurized system depends mainly on the requirements one has in the beginning (usually these requirements are based on habbit, personal preference or performance related).

Hope this helps!

Brian


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## hobbyheater (Mar 3, 2012)

The  system that I have is very simple.
The boiler and storage share the same water with a vented expansion tank on the floor above.
There is a coil inside the storage tank for domestic supply.
There is also a second coil inside the storage tank to supply water to the baseboards.  This coil allows the water to the zones to be supplied at 2 1/2 to 3 lbs psi. We live in an area that has the potential for a serious earthquake.  With the water at this low of pressure, a cracked pipe or small leak will give you a soggy carpet; at 15 to 25 psi and water at 150 to 180 degrees, people in that room are at risk to serious burns.
The system only requires two circulators.
I have thought it would not be all that hard to put coils inside propane storage tanks.


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## kopeck (Mar 4, 2012)

I think there is some confusion here.

You can have a pressurized system with unpressurized storage.  Tom's tanks use a exchanger coil that sits in an unpressurized tank.  This is getting mixed in with "open system" where nothing is under pressure.

I think a lot of people lump the two together but they're really not the same.  I like my setup (Tom's 820 gallon bank), it was easy to install and I didn't have to add a huge expansion tank.  When you figure the cost of a decent size LP tank, then have someone weld it up so you can pipe it the way you want it and then insulate the whole thing and add expansion I just didn't see that there was that much savings there.  That and I carried the whole tank to the place where it sits by hand.

A lot of guys here are very quick to suggest pressurized storage but there are other options that not only work but are more flexible as well.  Not saying pressurized is bad, it seems to work really well for a lot of folks.

K


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## Onfoot (Mar 4, 2012)

kopeck said:
			
		

> I think there is some confusion here.
> 
> You can have a pressurized system with unpressurized storage.  Tom's tanks use a exchanger coil that sits in an unpressurized tank.  This is getting mixed in with "open system" where nothing is under pressure.
> 
> ...



Thanks for making the point, K.  I was noting the same confusion.  I also have a pressurized system and use an unpressurized heat sink for precisely the reasons you note.


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## tom in maine (Mar 4, 2012)

So, then, there is a third option,  which is a completely unpressurized storage system.

Dick Hill and I always did this when we were making boilers. We were too cheap(?) to use a hx.
I am doing this now with a stainless steel boiler. 
The boiler and distribution loops run with bronze pumps and there is no noise.
I have run test systems up to boiling (always fun) without cavitating the pump.
Not that I recommend that.

Dick and I mostly did steel boilers so we treated the water when using ferrous materials. Never had a corrosion issue.
I cannot in good conscience recommend spending $5-15k on a steel boiler and then using a corrosion inhibitor and
asking you to hope everything will be okay although I have done it. You need to have the boiler manufacturer tell you this
for warranty purposes!!

Garn does it and they have a lot more metal than a lined tank would. And it works well as long as you monitor
the system.

One should do what makes sense to them.


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## huffdawg (Mar 4, 2012)

If I hadn't made the mistake of welding cast fittings on my tanks  I would have spent under $600  for 2- 500 gal tanks  and 1- 150 gal tank ready to pipe .  The expansion tanks cost more than the storage.

Huff


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## heaterman (Mar 5, 2012)

EffectaBoilerUser (USA) said:
			
		

> I would agree that one has to evaluate their specific application to determine which system is best/most cost effective.
> 
> There are both pros and cons with a pressurized vs. non-pressurized system in the same way there are pros and cons with a boiler system located indoors vs. a boiler system located outdoors.
> 
> ...



Brian, I'll call you out on number 4. You're saying no attention has to be paid to water chemistry in a closed system?


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## hobbyheater (Aug 21, 2012)

stee6043 said:


> Do a little reading before you beleive anyone that flatly claims that either one "will cost more". Typcially pressurized storage tanks can be had for pennies on the dollar compared to non-pressurized tanks.


 
Propane tanks can also be used in a unpressurized system . Why would they cost only pennies when used in a pressurized  and more when used non- pressurized?


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## velvetfoot (Aug 22, 2012)

So, if you had a pressurized wood boiler hooked up with an oil boiler for backup, you could run a pressurized loop with a coil heat exchanger into an unpressurized tank?  Is that done?  Building an unpressurized tank in the basement has its appeal.


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## tom in maine (Aug 22, 2012)

velvetfoot said:


> So, if you had a pressurized wood boiler hooked up with an oil boiler for backup, you could run a pressurized loop with a coil heat exchanger into an unpressurized tank? Is that done? Building an unpressurized tank in the basement has its appeal.


There are a couple companies I know of who do this.


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## hobbyheater (Aug 22, 2012)

velvetfoot said:


> So, if you had a pressurized wood boiler hooked up with an oil boiler for backup, you could run a pressurized loop with a coil heat exchanger into an unpressurized tank? Is that done? Building an unpressurized tank in the basement has its appeal.


 
Hope this helps.


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## hobbyheater (Aug 22, 2012)

velvetfoot said:


> So, if you had a pressurized wood boiler hooked up with an oil boiler for backup, you could run a pressurized loop with a coil heat exchanger into an unpressurized tank? Is that done? Building an unpressurized tank in the basement has its appeal.


 
This is the section from the Jetstream manual on building your own storage tank.
It has been suggested on a similar thread to use pressure treated lumber.
http://www.americansolartechnics.com/products.html  This company sells tank liners that are much superior to the EPDM liner that are talked about in these instructions.


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## velvetfoot (Aug 23, 2012)

Thanks.


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## velvetfoot (Aug 23, 2012)

And those Heat Banks look pretty spiffy as well.


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## stee6043 (Aug 23, 2012)

hobbyheater said:


> Propane tanks can also be used in a unpressurized system . Why would they cost only pennies when used in a pressurized and more when used non- pressurized?


 
I was referencing the cost difference between propane tanks and the pre-packaged tanks sold by many dealers for use in open systems.  Obviously, there is no cost difference between propane tanks used in open and closed systems, boss.


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## BoilerMan (Aug 23, 2012)

The cost is mostly for the copper HX in the open tanks, used in a pressureized system. 

TS


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## velvetfoot (Aug 24, 2012)

In an unpressurized storage application, can the tank be used to supply domestic hot water directly, i.e., no heat exchanger?  That way, eventually, depending on the size of the tank, the water will get changed out periodically.  Otherwise, since it's "open", wouldn't you have to treat the water like a hot tub, to prevent stuff from growing?  Even with pressurized storage, does anyone put a coil in the tank, so that the heater is separate from storage, and the tank is like a huge indirect water heater?


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## jebatty (Aug 25, 2012)

> Brian, I'll call you out on number 4. You're saying no attention has to be paid to water chemistry in a closed system?


 
I'm not answering for Brian, only for myself. My answer is yes and no, which means 'yes' - attention should be paid to water chemistry in a closed system. The 'no' part is that in a low volume closed system with black iron plumbing, and using tap or well water, the odds are pretty good that pH is about 7.0 and that there is sufficient iron to handle any initial corrosion so as not to cause any long term problem for the system, and so long as new water is not being added. If a high volume system, meaning substantial storage, and even with iron plumbing, but especially with a non-ferrous storage tank and copper or pex plumbing, I could anticipate a potential corrosion problem with thin steel parts, particularly expansion tanks, and possibly with the boiler vessel itself or any area that may be "thin," like an elbow bend, weld defect, etc. The large volume of water may yield sufficient corrosion before stabilizing which could result in failure/leak.

But playing the odds is not a good idea. I believe water should always be tested for a closed system, especially for pH and total alkalinity. Low pH (below 7.0) and low alkalinity can result in substantial corrosion. I experienced this in my first setup, although it was an open system, when after noticing very rusty water, I tested the well water and found pH to be about 6.5, OK for drinking water but very acidic and corrosive for a boiler system. This setup was used for one season, and then I switched to a closed system with a 1000 gal propane storage tank.

After the switch and filling the system I acted as my own chemist and added sodium hydroxide, an oxygen scavenger, and other chemicals designed for pools to raise pH and buffer the system, all to my own amateur specs. This resulted in 'clear' water, i.e., no evidence of rust corrosion, even when again the water source was well water at pH of 6.5. This setup was used for two seasons and the water remained clear.

Then I built a new shop and moved the entire system. A different well was the water source which tested at pH of 7.0. I then did what I now would recommend to anyone with a closed system with or without storage. I had the water professionally analyzed and then treated the entire system with a commercial boiler chemical treatment, including a pre-wash treatment and emptying before the final fill and final treatment. This setup now has been in operation for two seasons, I had the water again analyzed after the first season, with a report of little change following the initial operational fill and very acceptable chemistry. Since I don't add any water to my system, I probably won't have the system checked again, other than my own visual check and then using test paper to check pH and total alkalinity.

The investment in professional analysis and commercial treatment is small, considering the cost of the entire system, and I believe the investment is well placed. Final thought: pay attention to water chemistry, whether the system is open or closed.


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## BoilerMan (Aug 25, 2012)

GOOD CALL! 

Where were you able to have the boiler water tested?

TS


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