Читать книгу Solar Water Heating--Revised & Expanded Edition - Bob Ramlow - Страница 45

Pipe insulation comes in a wide variety of materials and specifications. Most kinds will not withstand the temperatures experienced in a solar loop; most plastic or rubber pipe insulation will melt right off. Only a few kinds of pipe insulation will work, and these are made specifically for high-temperature situations. We recommend that insulation should have a minimum continuous temperature rating of at least 250°F on the hot pipe coming off the collector to the heat exchanger, and a rating of at least 180°F on any other pipes on the solar loop. The material it is made of is not critical as long as the temperature rating meets the minimum standards. This will ensure that it retains its insulating value.

Fiberglass pipe insulation is great for all interior pipe runs but is unacceptable for exterior runs or buried runs because it will soak up moisture, become saturated and lose its insulation value. Some lower-temperature rubber and EPDM types will work, but unless intended for high temperature and exterior applications, they will eventually become hard and brittle and can wear away, especially when exposed to the elements.

It is always best to place a jacketing material on exterior insulated pipes. It is a tough world out there, and exterior insulation is subjected to UV radiation, rain, freezing conditions, insects and birds. Installing a jacket on all exterior pipe runs will greatly prolong the life of the insulation. Aluminum jacketing has proven to last the longest, but there are some new vinyl types that appear to be promising. PVC jacketing is also commonly used, but we have seen several issues with longevity in exterior applications, especially on the joints and fittings.