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re: drain-back or closed-loop
24 jul 2004
anthony matonak   wrote:

>vincent wrote:

>> for a solar water heating system, is a drain-back system better then a
>> non-drain-back pressurized system?
>
>both have advantages and disadvantages...

unpressurized drainback systems (are there pressurized versions?) need
heat exchangers. if a pressurized system circulates tap water up through
collectors to prevent freezing, what happens when power fails?

i'd vote for the drainback system, since it is simpler and more fail-safe
and doesn't require heat and electrical energy for freeze-protection.
drainback systems seem to need higher head pumps, unless the collectors
are vacuum-tolerant. then again, we might attach half of a uk shower pump
(2 pumps on a single shaft) to the downgoing pipe while using the other
half to pump water up, or find a way to make one pump with up- and down-
going valves and diaphragms.

nick




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