Re;flat plate reliability--was thermax [RE-wrenches]

[Conrad Geyser]

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A distinction on drainbacks from my previous posting:
Ken and others have a large (500-4000 gallon) EPDM (or other) lined,
unpressurized tank system that warrants the drainback approach.  This is
because the primary storage is not compromised by heat exchanger temperature
differential losses.  The small (5-15 gallon) drainbacks have a poor track
record from what I've seen, and have no performance advantages.
Conrad Geyser
Cotuit Solar


----- Original Message ----- 
From: "Ken Schaal" <ken at commonwealthsolar.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, February 01, 2005 10:39 PM
Subject: Re;flat plate reliability--was thermax [RE-wrenches]

> Of the hundreds of SHW systems I have installed or serviced since 1976,
none
> have been taken out of service because the collectors just 'failed' or
'wore
> out'. Some of my large tank, corrosion free, drainback systems have gone
> more than 20 years with minimal  service needs since installation . The
> larger problem is with  anti-freeze systems--not changing fluid,
> over-temperature, failed vents and expansion tanks [ correlates with the
> first two ] , leaking storage tanks due to anode rod not being replaced,
> [also correlates with extreme temps].Simple measures to avoid
overheating--
> a durability as well as liability issue-- and regular  5 yr. maintenance,
> result in indefinite system life.
>
> More general problems,in my experience, are; 1--asphalt roofs needing
> replacement when collectors have not been installed with flashing under
the
> bottom mounts to allow for shingle replacement without moving the
> collectors, and 2-- 20 years of tree growth and shading of collectors [ I
> had one that was completely covered by a maple tree] and 3-- new owners
that
> didn't inquire about the system when they bought,didn't know or care about
> the value of the system, or just assumed that it was not an asset because
of
> the many shoddy systems installed with tax credits.
>
> I suspect these same problems will affect PV systems only more so because
of
> ;1-- larger roof area, 2--greater susceptibility to shading, and, 3-- 
well,
> maybe the industry has learned some lessons from the 70's. What do you all
> think in the high rebate states? I don't see many wrenches on this list
from
> NJ-- and what is the percentage from CA?
>
> As for Zev's comment re flat plates, he seems to not be aware of selective
> surfaces, and he took a cheap shot , and that is not how this industry
will
> prosper. Evacuated tubes may prove their durability as flat plates have,
but
> they will face the same problems cited above. Kelly, please tell Zev I
will
> address my concerns to Dr Mahjouri at Thermomax.
> Thanks to all for your collective wisdom---
>
> Ken Schaal  CommonWealth Solar, LLC

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