Silicone hose to connect boiler/ FlatPlate HX to unpressurized storage-

[pybyr]

Passing along an idea here in case it may help others-

It's time for me to get back in gear on completing my storage- my Econoburn 150 worked well intially without it, but I am looking forward to the increased convenience and flexibility (plus DHW) that storage will offer.

One of the things that slowed me down on finishing the storage and connecting it to the boiler was finding some non-ultra-pricey large diameter piping material (and connectors) to span the 18+/- feet from my boiler to storage-- but that would handle any foreseen temperatures without any risk of failing (either the tube or at any joints/ fittings. The thought of hundreds of gallons of near boiling water spilling around my basement for hours (if something failed) really was uninviting. I decided to plan to place the FlatPlate HX near the boiler, so that at least the main length of piping to and from the unpressurized storage would not need to include oxygen barrier, or be subjected to potential moderate/ high pressures- but that still left the temperature issue.

Even then, I was coming up stumped on what to use that would be about 1.25 net inside diameter, could handle 200 F with near zero risk of failure, and would not cost an arm and a leg (especially after figuring in end connectors and several turns' worth of fittings needed to get around obstacles)

Then... after looking into many things that weren't quite right (mill hose, CPVC schedule 80... solar-rated hoses), thought of silicone vehicle heater hose-- but... too expensive. Then-- onto eBay, where, at last, I found 75 feet of unused 7/8 inside diameter/ 1.25 outside diameter reinforced silicone food grade tubing -- rated at up to 400F, and 100+ PSI, for less $$ than I'd pay for two 10 FT lengths of 1.25 copper pipe.... I'll run two parallel sets of the 7/8 silicone in each direction (to and from) the tank to achieve approx the same flow as 1.25-- and the 7/8 inside diameter will allow use of the outside diameter of 3/4 copper as fittings (with outside clamps, doubled) at the tubing ends. Tubing has arrived- looks bomb-proof. Onward to ordering some other parts and moving forward...!

 

[deerefanatic]

Dang! Why didn't I think of silicone.........

 

[jebatty]

Deleted.

 

[jebatty]

Good idea. I used regular auto heater hose, 1" ID, for the "flexible" connections between hard plumbing both at the tank and the boiler, with hose barb connections. It runs about $2/foot at the auto parts store. If I remember correctly, it is rated to 250F.

 

[Sting]

I think of silicone all the time!

 

[in hot water]

If your system is a closed loop, be sure the hose you chose has an oxygen barrier. The early SolarRoll and Heatway Entran caused a lot of systems to fail, and the lawsuits to fly! Goodyear is paying a steep price for that failed rubber/ hydronic hose.

O2 actually gets through the wall of the tube and allows rust and corrosion to attack all the ferrous components. The higher the operating temperature, the faster the O2 ingress.

MPH (multi purpose hose) or radiator hose may not be O2 proof? Silicone probably is.

hr

 

[pybyr]

If your system is a closed loop, be sure the hose you chose has an oxygen barrier. The early SolarRoll and Heatway Entran caused a lot of systems to fail, and the lawsuits to fly! Goodyear is paying a steep price for that failed rubber/ hydronic hose.

O2 actually gets through the wall of the tube and allows rust and corrosion to attack all the ferrous components. The higher the operating temperature, the faster the O2 ingress.

MPH (multi purpose hose) or radiator hose may not be O2 proof? Silicone probably is.

hr

Thanks, HotRod-- agreed that this is an important consideration. In my case, since I cannot be certain whether even the silicone tubing will be impervious to oxygen, I am going to keep the 'boiler side' of my plate HX plumbing all 1.25 copper (with the HX in close proximity to the boiler)-- and use the silicone tubing only between the other side of the plate HX and the storage tank. Since pressure on that side will be minimal, my hope/ expectation is that the silicone tubing should last indefinitely.