Frequently Asked Questions

What is PEX?

PEX is a kind of tubing made from crosslinked HDPE or high density polyethylene. The “PE” stands for polyethylene and the “X” for cross-linked, hence the acronym PEX. There are three different methods of making PEX:

PEX-A is produced by the peroxide (Engel) method. This method performs “hot” cross-linking, above the crystal melting point. However, the process takes slightly longer than the other two methods as the polymer has to be kept at high temperature and pressure for long periods during the extrusion process. The cross-linked bonds are between carbon atoms

PEX-B (PE-Xb, PEXb). The silane method, also called the “moisture cure” method, results in PEX-B. In this method, cross-linking is performed in a secondary post-extrusion process, producing cross-links between a cross-linking agent. The process is accelerated with heat and moisture.

PEX-C (PE-Xc, PEXc). PEX-C is produced through electron beam processing, in a “cold” cross-linking process (below the crystal melting point). It is the cleanest, most environmentally friendly method of the three, since it does not involve other chemicals and uses only high-energy electrons to split the carbon-hydrogen bonds and facilitate cross-linking

What is the difference between oxygen-barrier PEX and non-barrier PEX?

Oxygen Barrier PEX, often abbreviated as O2B or referred to as O2 Barrier, has a coating applied to the outside to prevent oxygen (O2) from entering the system (The O2 molecules are smaller than those of PE.)

Oxygen Barrier PEX is used when installing in a closed or pressurized system. It is NOT necessary with an ‘open” type system.

Need help deciding which type of PerformaFlex XT you need?

Do I need oxygen-barrier PEX for my outdoor wood boiler or hydronic system?

Only if it is a CLOSED system which would also likely be pressurized. Typically, a closed system would not require require filling of the vessel, nor a rust inhibitor water treatment. Only about 5% of outdoor wood boilers are closed / pressurized systems.

OPEN systems do not require O2 Barrier for their insulated PEX pipe.

Need help deciding which type of PerformaFlex XT you need, just call?

How do I know if my outdoor wood boiler is an open system?

Of course your manufacture would be the first resource. But if it requires intermittent filling due to water evaporating from the vessel, or if there is a vent on top of the outdoor wood boiler, these are very strong indications. 

About 95% of all outdoor wood boilers are in fact open systems.

This would include: Central Boiler, HeatMaster, Hawken, Natures Comfort, Earth Outdoor, Hardy, Polar, Portage & Main, WoodMaster, Crown Royal, Ridgewood, Tenessee, and many others.

Have more questions about outdoor wood boilers?

Contact Matt Stairs at Z Supply, he would love to discuss your situation and help you with your wood boiler and PEX needs.

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