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Old 02-10-13, 02:18 PM   #6
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A little clarification on pipe insulation:

The less expensive type sold at the big-box stores (frost king O/E) is polyethylene plastic foam. This stuff is ok for insulating water pipes. At higher temps than about 140 degF, it tends to shrink (up to 25%, quickly), then melt at higher temps. Since dhw rarely gets above 140 degF, it is by far the most widely used in homes. It isn't used much in commercial applications, due to the lack of industrial ratings. When exposed to the elements, it lasts up to 10 years.

The more expensive type sold at the same stores is (armaflex AP) is rubber foam. This stuff is the go-to material in industry for insulating anything where moisture is a factor. It is rated to 220 degF (105 degC), and has very minimal shrinkage properties. Long-tem durability is 15 years or more. At high temps or when exposed to the elements, it tends to harden. However, it costs about twice as much as the plastic equvalent.

Both types have close to the same r-value (about r-4 per inch thickness), so the main considerations when deciding which type to use are temperature range and exposure to the elements.

For insulating solar and steam heating systems, contractors use armaflex HT or an equivalent. It is rated for temps up to 150 degC and has UV protection built in. It is not readily available at your local home improvement warehouse. It also costs 3X as much as polyethylene.

Lots of DIY'ers stick a rubber layer inside a poly layer when superinsulating solar or boiler lines. The armaflex takes the heat, the frost king provides added r-value for less money.

Here's an article comparing the two common types:


The new rig looks and sounds as if it should perform much better than your previous setup. I anxiously await your progress. That unit is much more massive than anything I would ever need. But with heat pump tech, bigger is definitely better.

The variable-speed compressor is the icing on the cake with your rig. It should be able to allow you to do whatever you want to with the new unit. At start-up, you can save power. Then you can ramp up to whatever capacity you need, then slow down to maintain a high COP near your target temp. It should save you a lot of energy and pay itself off quickly.
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