# Difference Between Open and closed systems



## 907plumber

whats the difference between an open boiler system and a closed? Or what is the definition of each?

I was looking at another thread that was talking about aqua pex being used for a closed system boiler (how that was a no-no) but would be okay for an open system


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## OldSchool

907plumber said:


> whats the difference between an open boiler system and a closed? Or what is the definition of each?
> 
> I was looking at another thread that was talking about aqua pex being used for a closed system boiler (how that was a no-no) but would be okay for an open system


An open system is open to the atmosphere. Like an out door wood boiler also a HWT is considered open sytem. 

A closed system is like an indoor boiler with a boiler feed that is pressurized to the pressure you need to rise the water to the given height you need ( top floor ) 

On a closed system you are able to use black pipe or cast Iron boiler or steel. Any oxgen getting in to the system ( usually by adding new water )
will corrode the pipe, pumps, boiler.

Hepex has an oxgen barrier which limits the amount of oxgen that can enter the pipe from the atmosphere. Aqua Pex has no barrier.

Hope that helped to answer your question


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## 907plumber

yeah that answered it thanks. I have never seen a open system.


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## OldSchool

907plumber said:


> yeah that answered it thanks. I have never seen a open system.


You must have seen an open system before because a HWT is considered open. 

Any time a system has new water going into it all of the time .... it is considered open.

Water has oxgen it in..... once that is boiled the oxgen comes out of the water.


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## gladerunner

I always thought an open system was a system relying only on the pressure of static head. we used to see alot of what we called open systems where there was an open overflow on the roof, usally with an expansion tank in attic. could only work as gravity system. no circulator


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## njoy plumbing

gladerunner said:


> I always thought an open system was a system relying only on the pressure of static head. we used to see alot of what we called open systems where there was an open overflow on the roof, usally with an expansion tank in attic. could only work as gravity system. no circulator


 That is one form of open system.:yes:


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## trick1

gladerunner said:


> I always thought an open system was a system relying only on the pressure of static head. we used to see alot of what we called open systems where there was an open overflow on the roof, usally with an expansion tank in attic. could only work as gravity system. no circulator


Was always fun to watch a new guy look for the expansion tank on one of those systems

Then you would open an attic door or third floor closet door and find it along with the pipe leading through the roof


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## jimclemmer

OldSchool said:


> An open system is open to the atmosphere. Like an out door wood boiler also a HWT is considered open sytem.
> 
> A closed system is like an indoor boiler with a boiler feed that is pressurized to the pressure you need to rise the water to the given height you need ( top floor )
> 
> On a closed system you are able to use black pipe or cast Iron boiler or steel. Any oxgen getting in to the system ( usually by adding new water )
> will corrode the pipe, pumps, boiler.
> 
> Hepex has an oxgen barrier which limits the amount of oxgen that can enter the pipe from the atmosphere. Aqua Pex has no barrier.
> 
> Hope that helped to answer your question



hey
Yeah i agree with your answer
Closed system normally operates above atmospheric pressure, this pressure is achieved by a filling loop connected from the mains water supply to the system.
open systems works at natural atmospheric pressure as the feed/expansion tank is open to the air.

Thanks

Regards
Ambani


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## Scott K

The common defintiion in the trade for an open system versus closed system is an open system is any system that receives constant or semi-constant introduction of oxygenated water. This means new, fresh water, potable or otherwise. ALL components must have superior corrosion resistance and are often made out of non-ferrous metals (i.e. brass, copper, bronze) or stainless steel, titanium, etc. These systems can be pressurized or not, but the most common system would be something along the lines of using a hot water tank through a heat exchanger to give off heat to a closed system or (not recommended) a hot water tank giving off heat to radiant loops. But if you let that water sit over the summer monthes and then pump it back into the tank you have a health hazard.

Closed systems depend on very slight to absolutely no incoming fresh water which can cause corrosion of any ferrous components (e.g. steel/cast iron). By using air removal devices, expansion tanks, piping with an oxygen barrier (i.e. metal piping or O2 barrier plastic pipe), and backflow preventers, most to all of the water in a closed system is often the same water it was filled up with when it was commissioned when new. The oxygen in initial fill is removed and subsequently no more corrossion can take place. This allows cheaper pumps, piping, & components to be utilized reducing costs of the equipment & installation. Any leaks or problems in the system can cause varying levels of corrosion through the introduction of fresh oxygenated water into the system. There are varying ways to mitigate in systems designed as closed systems to reduce this potential.


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