I like the idea of having a replaceable core, and the flexibility you mention, but there are a couple things I'd wonder about...
1. How much heat leakage do you get between the pipes inside - not just the supply and returns, but also any other lines - say if you were trying to run a cold water feed for a sink / bathroom in the heater shed, or how much would your low voltage control lines get cooked? (I know my CAT5e cable is only rated for about 150*)
2. What is "PAP"?
3. I can see how you could get foam around the length of the pipe, but it would seem like there would have to be a gap at the joints - do you fill that gap with some sort of spray foam as well as tape sealing it, or what?
4. How do you deal with less than full lengths of pipe?
5. Are there elbows and other such fittings available for the ends of the run? I know I would not want to make below grade penetrations through my basement wall, and would far rather come up high enough to go through the sill plate area - wood is easier to drill than concrete.
Gooserider
Plenty of wire available with a 90 C (194F) temperature rating both low voltage t-stat wire and basic THHN stranded wire.
The joints glue together, and the outer jacket is long enough to cover the seam. I suppose you could silicone the foam to foam connection.
Yes the additional lines will get warm from the heated lines, somewhat. It would flush out in a matter of seconds.
PAP is Pex al Pex. it is a pex tubing with aluminum inside. It handles much like soft copper tube. when you uncoil it stays straight. Much easier to push inside a tube. I tape the whole gob together to shove it in. Connect a rope to pull if you need to go more than 100 feet of have fittings along the way.
They have long sweep ells and 45 ells if you need. Also insulated and wrapped.
You can cut it anywhers. One end of every stick has a belled end for coupling together, as do the fittings.
More details at
www.insulseal.com
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master of sparks said:
My favorite product/ method is the InsulSeal product. It is PVC pipe with a foam sprayed around it and a water proof liner. The 10 foot sections glue together, and you tape the seams. It is available in various r-values.
This provides 3 nice features. First a consistent r- value, unlike the pipe in coiled drain tube. It provides a 100% water proofed condiut, unlike the easily punctured black slinky drain products.
It also allows you to install, and remove if needed, the tube inside.
I install a PAP supply and return, and a few extra pex tubes for water and or pulling low voltage lines for control circuits. The 4" InsulSeal easily handles 6 tubes or more.
Mine has 4- 1" pex lines and 4- 1/2" pex lines inside.
Also run some tube inside to add solar to the roof of your outdoor boiler building. One 4X8 panel will go a long ways to supplying DHW for a typical family.
hr