Open circuit hydronic system

geo_23

(sorry about cross posting as I did not know how to post a new subject.)

I need some plumbing information about a hydronic heating system which has a solar panel plus a sun-spool (h-g spool) drain down valve.

What exactly is the flow pattern through the drain down valve when it is in the operating position and when it is in the drain down position.

Which of the five ports (to panel, from panel, to storage tank, from storage tank, and drain down outlet) are connoted together in each position?

In addition, since the valve is about two feet below the top of the storage tank, does the drain down valve drain the tank when in the drain don position?

ALH_4

Draindown

Why not go to drainback instead of draindown? It's simpler, less to malfunction, and less chance of freezing collectors if you are in a freezing climate.

geo_23

drainback?

What is it and how does it work.

I am about 50 miles north of San Francisco,CA. (some freezing.)

Any comments on my original question?

ALH_4

Drainback Tank

With drainback solar systems you have a drainback tank that contains enough water to fill the collectors. You don't drain the water, and there is no spool valve to fail and leave your collectors full of water with the danger of freezing. In a quick search of the web, I have not come across a good drawing of a drainback tank. It is simply a tank with the pumps pulling out of the bottom with the return pipe extending through the top down into the tank far enough that the end of the pipe remains in water. A few holes are drilled in that pipe near the top of the tank to let air back into the collectors when the pump is shut off.

A drawing is worth a thousand words. Maybe someone has one.