@Drake
I would be very interested in reasons why drainback systems are being abandoned in your reagion.
And yes mate, you are tackling some very important issues. "Green" and "eco friendly" are all very nice, but the whole thing should also be sustainable and financially benefiting.
So I do try to work everything into realistic payback calculation. That's why drain back systems look so tempting, they do seem cheaper both initially and from the perspective of the "cost of the ownership", maintenance and stuff like regular glycol changes (which drainback doesn't need, since it uses water).
I'm not sure how many sunny days you do get in Minnesota, but if this link is right - you do get quite a lot of sun (even if climate is quite cold, as I understand):
Sunshine & Daylight Hours in Minneapolis, Minnesota, Usa Sunlight, Cloud & Day length
Skopje, Macedonia also gets quite a lot of sun:
Total Annual Sunshine in European Cities - Current Results
In both our places this points to a conclusion that investing in solar technology,
should result in realistically achieved (and shorter) payback time for the investment made.
Quote:
Originally Posted by Drake
I would think that a heat "dump" might be more applicable to your overheating concerns than "drain-back" ability.
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Seems simpler to just downsize a bit the collector power, and live with somewhat lower temps of the heated water.
But even with dedicated "heat dump" in the system, my worries about overheating are really about overheating of the glycol, not the water (DHW). Overheating of the glycol, when public electric power grid goes down on a sunny day.
Dunno how good is the public power grid in Minneapolis, Minnesota - but power shortages are bound to happen at least few times yearly, here in Macedonia. Those power shortages can go on for longer than any reasonably sized backup UPS can cover up. PV panels and DC pumps are option, albeit seemingly more expensive one.
Can somebody recommend dependable and cost effective PV panels and DC pumps?
Also, if doing the standard closed loop glycol solar system, I was considering placing the collector lower then than water tank/boiler and thus benefiting from thermosiphon movement of the glycol, when power shortage occurs and the pump stops. This option would require some additional stuff (like additional piping with electro ventil) to circumvent the halted pump blockage (not sure how understandable is all this, english is not my native language).
Quote:
Originally Posted by jeff5may
There are lots of ifs to consider before ruling out a vacuum breaker or pressure relief mechanism up high. Whether or not you can tolerate the sound of your drain pipe gurgling slowly is one decision only you can make. Even if you design the system so it should never stagnate, it still might. If there is no pressure relief installed up high, any steam generated will clear your drain for you quickly and violently.
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Yes, in previous post I was concerned about the steam (after a stagnant phase). So as you say - a pressure relief valve wouldn't hurt anything. Gurgling sounds in the drain pipe, is something I can live with - since it will be only be heard in bathroom/attic.