Posted by Greg Campbell on November 5, 2005, 2:26 am
Christian Kaiser wrote:
The drainback reservoir tank holds the collector fluid. It
can be installed at any height above the solar storage
tank, but must be within a conditioned or freeze-free
environment. The reservoir tank is typically mounted on
a strong shelf above the storage tank. It may also be
placed on the second floor of a two-story home to
reduce static head by decreasing the distance the pump
must lift the fluid to the collector."
So much for my 'claim' of originality. :)
Posted by Greg Campbell on November 5, 2005, 2:20 am
Iain McClatchie wrote:
It need to have sufficient capacity to accomodate the water in the
panels, when they drain, and to allow for the thermal expansion you
<Sound of rusty grinding gears....>
It would be simple to add a float switch to the E.R. If the water level
falls too low, a small auxiliary pump/tank adds water to the system. At
the other extreme, a simple overflow drain, leading back to that aux
tank, would catch any thermaly induced spillover. Compensating for the
thermal issues should allow a much smaller E.R. (The few dozen feet of
plumbing in and around the panels can't hold too much.)
OK, if you say so. :)
I hadn't done any math along those lines. I was simply looking for a
way to reduce pumping effort, while still allowing a full draining of
the panels. The system I'm contemplating is for my mom's mobile home,
and will be rather small. Thermal expansion was barely on my radar.
I'm a bit surprised that it seems to be an 'original' idea. I've not
yet seen a similar idea described on line. And here I went and blabbed
it to the internet.... There goes 'another' (LOL) opportunity to make
Posted by Solar Flare on November 5, 2005, 1:00 pm
LOL. It appears to be a well established method, published in many, many
websites but many have gotten into this and confused the issue badly.
Now we are talking about adding water to a closed system. I wonder when it will
In the supplied link system the pump has to ***not*** have a checkvalve so that
the drainback is accomplished back through the pump to the E.R. tank. The whole
thing is quite genius but not the previous way I was shown elsewhere with the
air intake valve etc..
Posted by nicksanspam on November 4, 2005, 9:24 am
So... if the main tank is say, 16' below the ER, it is slightly pressurized
by about 0.433x16 = 7 psi, ie 1000 psf, so the top of a 4'x8' main tank
would need to resist 16 tons of uplifting force? :-)
The main tank might have a big coil of PE pipe on the bottom, with no ER...
Posted by Iain McClatchie on November 4, 2005, 9:44 pm
NIck> So... if the main tank is say, 16' below the ER, it is slightly
Nick> by about 0.433x16 = 7 psi, ie 1000 psf, so the top of a 4'x8'
Nick> would need to resist 16 tons of uplifting force? :-)
Ouch. If the dirt/rock over the main tank is density==2 kg/litre, then
the height to the aux tank has to be filled in.