Thermosiphon Advice

[Hunderliggur]

Well, everything is in (except 1-wire montioring), tank is insulated, etc. I can now confirm that my system thermosiphons when the boiler is NOT producing heat. I thought that 80' of in ceiling basement pipe, 5' drop to get underground, 80' undeground, 4' rise to the shed, and 5' to the top of the boiler, plus all the fittings, would be enough resistance to keep the reverse flow from not happening. Good news is that I don't have that much pressure drop!

To solve this, I am contemplating putting a swing check valve in the return line near the storage tank. Comments, suggestions, concurrence?

[Corrected diagram]

 

[jebatty]

You might try, if you have insulation on your boiler supply/return lines, to remove the insulation from the boiler to part way down the 4' drop on both lines. You need the hot water to rise to a thermal break. Your diagram also shows return to the top of your boiler and supply from the bottom, which would be opposite of what normally is done. Mistake or reason for this?

 

[in hot water]

A weighted flow check or a spring check would be the best protection. Swing checks can tend to rattle and also thermosiphon under some conditions.

hr

 

[Donl]

I had the same problem. I used a spring loaded check valve and that solved the problem of thermo siphoning.

 

[Hunderliggur]

Mistake on the drawing, return is on the bottom.

Interesting suggestion on the insulation. I'll give it a try while I wait to get some time to put a flow check in the return line.

Thanks