[Greenbuilding] single flat plate collector for household with 29gpd total indoor water use (faucets)
Frank Tettemer
frank at livingsol.com
Mon Jul 8 12:39:28 CDT 2013
Hi Reuben,
Since you are considering thermosyphon (gravity powered) circ. system,
and Autumn drainage, here's a couple more details to toss around.
1,) Consider plumbing the circulation loop with 3/4" piping. The larger
diameter will facilitate thermosyphoning. You will have an increased
flow rate that way.
2.) To stretch the solar hot water heating season, consider plumbing the
drain valve at the lowest point in the system, which should be at the
bottom of the circ. loop. This should also be a few inches lower than
the lowest part of the flat plate collector. Be sure that the flat plate
is tilted in two directions, not just one. The obvious angle is to match
the summer angle in your area. (Our area calls for about 30 degrees off
the horizontal.)
But be sure to tilt the thermal panel slightly East or West, as well, to
facilitate the complete removal of all water droplets. Nothing more
disheartening than a burst absorber unit, within the flat plate, caused
by just a tablespoon or two of un-drained water.
Now consider the activity that you may be involved in during September.
Supposing a frost warning is out for your area, but the next week is
forecast to be warmer and sunny. In this case, make it easy to drain the
absorber in your flat plate, without draining the tank. This means a
couple of ball valves inside the house to close in that evening, before
going out to open the drain valve. Only a few litres of water will come
from the absorber to contend with. Next day, close the drainvalve to
almost closed, open one of the ball valves, to allow water into the
absorber, and watch the air hiss out of the almost closed drain valve.
When water starts to come out, it's time to finish closing the drain
valve. Now you can open both ball valves, and your back in business.
(The process i just described is akin to bleeding air out of a hydraulic
brake system in your car). Air introduced into the system can be
annoying to someone at the kitchen sink, who is filling a glass with
water to drink.
3.) Consider spending about $60 on a Conbraco Frost Protection Valve.
These are valves that are typically used in the Florida orange grove
irrigation systems, to prevent bursting pipes. If you place this valve
in a tee near the drainage valve, i.e., at the lowest point in the
system, then this allows a small flow of water to trickle out when frost
threatens. The Conbraco unit has a bi-valve spring loaded closure
system. As the night temperature drops, and dips towards freezing, at a
few degrees above freezing this valve begins to open, thus allowing a
small flow of water to exit from the warm water tank. This tiny flow of
warm water can protect the absorber from frost heave, down to four or
five degrees below freezing. You can rely on your own intentions to
watch the weather like a hawk, and you may not need this Conbraco unit.
Until that one day you are away from home overnight in May or September.
Or that one night that you are celebrating (something) and forget to
drain your absorber.
All the Best,
--
Frank Tettemer
Living Sol ~ Building and Design
www.livingsol.com
613 756 3884
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