Oxygen diffusion in closed and open hydronic systems

[RZ1]

Hi Folks,

I am considering getting a wood fired boiler to help with root zone heating and other hydronic heating needs. I have been reading up on units like Econoburn and Garn and trying to best deal with minimizing oxygen corrosion in theses systems.

The basic problem is that I can use pex barrier pipe or something similar that minimizes oxygen diffusion for most of the supply and return but where we enter the root zone I will have to use more UV type resistance material (some applications heating will be on or near soil surface) and something that can hold up to getting a bit roughed in the soil, not necessarily pex.

I was wondering if anyone has considered or dealt with this type of situation. One thought was to use a plate type heat exchanger prior to root zone heating.

Thanks

 

[E Yoder]

An open system would typically use some type of water treatment to prevent corrosion.
We treat and then test yearly.
What piping would be more durable than pex? Just curious.

 

[RZ1]

An open system would typically use some type of water treatment to prevent corrosion.
We treat and then test yearly.
What piping would be more durable than pex? Just curious.

Thank you for the reply E Yoder and good question. What I was trying to figure out is that is seems the PEX and diffusion barrier coating does not hold up to UV well and if you scratch it ect (such as maybe in direct soil burial) the oxygen barrier can get compromised. As a result in root zone application or bench top heating it seems people tend to use various types of plastic or rubber pipe (e.g. EPDM pipe, drip tube).

It seems that in hydronic heating this type of piping is not recommended and since I have not done this before I was unsure if water treatment alone would be adequate or if I need to build in a heat exchanger to isolate the boiler system from the plastic pipe. There are a lot of great examples of people using boilers for rootzone/bench top heating but hard to find information on best practices for corrosion protection. In my financial situation I am hoping to optimize my boiler lifespan.

 

[salecker]

Use copper tubing,or pipe

 

[Fred61]

Install 500 gallons of storage, charge it with one zone and draw heat from tank with a second zone. The system I just removed would have been perfect. Unpressurized, heated the bath with boiler through HX and distributed to zones through submerged copper coil. You should have storage anyhow.

 

[tom in maine]

Stay away from EPDM tubing, it is quite permeable to oxygen and breaks down with higher temps. Anyone who is old enough to
remember Solaroll or ONIX 1, 2 and 3 knows what I mean.