Drainback vs. Closed Loop Circulators [RE-wrenches]

[Travis Creswell, Ozark Solar]

Good point, Todd.  That gives me an idea. Freezing could be solved by using
a $15 line voltage outlet timer (complete with built in battery backup) to
make sure the pump/controller doesn't get power at night.

To me it "boils" down to which problems you want to risk.  A drain back will
only freeze if controller or sensor fails and the storage tank is small and
if it fails during a freezing night.  The odds are pretty low, actually.
Even in most freezing climates it doesn't get below freezing that often.
The corrosion issue the Conrad has experienced is perplexing.  It shouldn't
be possible for water to corrode copper collectors and a non-ferrous pumps,
right?  There's got to be a million miles of copper plumbing in Boston
houses and it's not having problems, right?  Oversized pumps could erode
copper pipes and the Type M copper common to the collectors is the thinnest
wall so it would be the most prone to erosion.

I personally have never seen a drain back fail and freeze.  I have seen many
closed loop glycol systems stagnate when the pump fails or the power is out.
Bypass valves and dump loads won't solve this problem plus they add more
parts to break.  This usually has been a simple repair if any but I can
think of several occasions where the collector was damaged.  So the only
systems I've had to braze are closed loop glycol.

I'm here to listen and learn.  What a fun discussion!

Travis Creswell
Ozark Energy Services


-----Original Message-----
From: Todd Cory, Mt. Shasta Energy Services
[mailto:toddcory at finestplanet.com] 
Sent: Wednesday, June 07, 2006 9:31 AM
To: RE-wrenches at topica.com
Subject: Re: Drainback vs. Closed Loop Circulators [RE-wrenches]


The only caveat with drain backs is the possibility (albeit very small) 
of freezing. I agree with all the advantages mentioned about drainback 
systems versus glycol... but I do not think it wise to trust a snap 
switch and/ differential controller or its temp sensor to not accidently 
pump water through the system during times of freezing weather. Brazing 
leaks on a burst absorber panel is no fun.

Todd


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