Drainback vs. Closed Loop Circulators [RE-wrenches]

[Ken Schaal]

Geoff
some thoughts to follow up on your questions below---

From: "Geoff Greenfield" <Geoff at Third-Sun.Com>
To: <RE-wrenches at topica.com>
Sent: Wednesday, June 07, 2006 10:35 AM
Subject: Re: Drainback vs. Closed Loop Circulators [RE-wrenches]


>
Here are two possible wrench wives tails I am looking
> for feedback on:

We'd better leave the ' wrench wives tails ' out of this discussion ?



> #1 - plain old water is still a freeze liability IF the controller or
> thermistor fails and circulates at night.  Has this EVER happened? is this
a
> real issue?


Sure ! control failure or installer mistake. Always consider how idiot proof
your system needs to be. Any mechanical system that gets no attention is
prone to some type of failure.


> #2 - a glycol mix in an open system leads to corrosion as the glycol
drains,
> leaves residue and then (either the acid from bad glycol or the alkaline
> inhibitors from fresh glycol???) corrode the collectors and plumbing.

Isn't glycol only likely to become acidic under stagnation conditions ? If
the system is appropriately sized, usually around 2g/sq ft.,then the
collectors would rarely be stagnant, ie drained during the day.
I do know well, but not my design or install, a large 2400 sq ft array w/
about 1000gal storage and inadequate HX on the collector side , on a hot,
non AC, prison workcamp that used a couple hundred gallons of AF [ethylene
glycol] in an unsealed container in the basement. The fumes were horrendous
!

> And for good measure, a third question about experience (or the stupidity
of
> even thinking of) locating a reservoir/HE tank in an unconditioned attic,
> wrapped in an insulated "hot box" with insulation removed from the ceiling
> and or knee wall separating it from conditioned space.

Why go to all that hassle and liability when there are pumps that can push
50 ' head on 25W.?

By God , I think we're actually learning from the past ! Just think what we
have to look forward to from the PV world !?

good night all
Ken Schaal


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