Posted by Chickenwang on January 7, 2006, 2:23 pm
Hello nice people.
I am in the research phase of converting over to solar hot water
(this is for a customer of mine)
so I need a panel. I was thinking it would be cheaper to build
a box (permanent material) and pack it full of copper tubing
and nail it to the roof.
anyway, anyone feeling brave enough to gimmie roughout of
what I am approaching, would be appreciated.
Say I make the panel, and run the lines.
My neighbor claims his solar panel heats a liquid like
anti-freeze. if this is true, how exactly does the heat
get transfered to the water. it makes me think
there is a seperate exchange unit along side the HW tank.
Posted by Robert Scott on January 7, 2006, 4:06 pm
Think what would happen at night if you ran regular water through the
pipes in the collector. They get cold and freeze and pipes break.
That is why anti-freeze is used. But anti-freeze is poisonous, so it
must be kept separate from the water that you use. Most building
codes require that a heat exchanger have a double wall so that no
single failure can allow poisonous anti-freeze to contaminate your hot
Of course you could prevent freeze-ups by circulating regular water at
night, but that wastes lots of energy because the collector is
actually loosing heat at night. And if you happen to get a power
failure at night, your pump stops and you still get a freeze-up and
pipes will break.
Another solution is to use regular water in the collector, but design
the system so that when the pump stops, air enters the pipes and the
water drains down into a tank in the house. That way there is no
water left in the pipes to freeze. That method has its own particular
set of design problems, such as the accumulation of corrosion at the
None of these solutions is simple. All require some serious thought.
Don't just "build a box and pack it full of copper tubing and nail it
to the roof."
Posted by Levon on January 9, 2006, 3:59 am
Robert Scott wrote:
Thanks Robert and SJC...
this is good starting point for big dumb american
yeeeaah! i was fixing to nail a copper tube storage box to roof
cold in, hot out... :)
someone else suggested building box from aluminum (extruded)
seems if everything is covered, I see no reason why cost of install and
upkeep cannot pay for itself.
You've given us plenty to consider.
Posted by Levon on January 9, 2006, 8:56 pm
Posted by SJC on January 7, 2006, 5:13 pm
You need to study a bit on the basics first I think.
Here is a simple diagram of a closed loop system.
The quadrod they talk about is an external heat exchanger.
If you use the antifreeze that they use for RV systems, it is
less toxic. If you use a drainback system, you may not need
any at all.
If you are set on making your own collectors,
you might consider buying the finned tubes.