PEX Coils

January 31, 2014 • Radiant Heating • Views: 729

How to make your choice?
PEX Tubing ismade from HDPE (High Density PolyEthylene). The manufacturing process of pipes uses HDPE granules melted inside the extruder and forced through a die under pressure.

Three types of PEX
The manufacturing of PEX tubes are divided into 3 main types: A, B and C. These categories are used to identify the manufacturing process.

All three types of PEX have to meet the ASTM F876 and ASTM F877 standards in order to be sold in North America. ASTM imprint must be present legibly on the pipe.

PEX-A type is produced using Peroxide method (also known as “Engel”), named after the inventor Tomas Engel. During the manufacturing process, free radicals are created when HDPE polymer is melted and cross-links between molecules occur at temperatures that exceed the decomposition temperature of the polymer. Most common manufacturers producing PEX-A type are Uponor, Rehau and Mr. PEX.

PEX-B type is produced using a Silane method (also known as “Moisture Cure”) of cross-linking. Links between the molecules of the HDPE are form after the extrusion process using a catalyst and exposing PEX tubing to water. This is the most frequent type of PEX found in North America and the most common manufacturers include: Viega, Watts, Bow, GTGlobe, Zurn and many others.

PEX-C type is manufactured using an Electronic Irradiation method of cross-linking. Cross-linking of the molecules is achieved after the process of extrusion by exposing the pipe to an electron radiation beam. The radiation emitted allows breaking the existing links between molecules of the polymer and initiate cross-linking process. Some of the manufacturers are: Nibco, Roth, Cash-Acme.

Which type of PEX should I chose?
All three types meet the ASTM requirements and it is often a matter of budget and personal preference which will determine the choice of PEX.

PEX-A is the most expensive of all 3 types. Manufacturers typically require using their own proprietary connection system. Because of that, tools and fittings can also be more costly. This PEX is slightly more flexible than the other types at temperature above 60oF. However, below this temperature, PEX-B tends to be more flexible and offer an advantage during installation in colder climates.

PEX-B is the most commonly use PEX in North America. It is readily available to consumers, as it offers a distinctive pricing advantage while maintaining quality.

PEX-C is priced similar to PEX-B. However, the cross-linking process for this type creates the least amount of bonds, which makes it closer to a regular PolyEthylene plastic pipe as opposed to true PEX tubing PEX A and B).


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