<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=iso-8859-1" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 8.00.6001.19328">
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT size=2 face=Arial>9/23/2012</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Wrenches:</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>We did some maintenance on a 29 year old solar
thermal system in South Dakota last week -- 468 sq feet of water heating
collectors and 300 gallons storage. This is a drainback system and the entire
300 gallon tank works as the drainback tank. The system owner pays
very close attention to the system and it has been running every day since 1983.
The area's record low the past 50 years is in the neighborhood of -25
F.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>The propylene glycol mix (not ethanal) is 29 years
old and measures -8F freeze/slush protection with the refractometer. The PH
measures 7.8. He still has an unlabeled container with a couple of gallons of
the original stuff (manufacturer unknown)--it also measures -8F freeze
protection but a with 8.4 PH (or higher, 8.4 is the top of the litmus
paper scale we had).</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>We would normally insist that it's time to clean
out and replenish the solar fluid but for a 300 gallon drainback tank we're
talking $3000 for just for the glycol!</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>What are the risks of continuing to use the
existing mix? Since it is a drainback system, should be little chance
of burst pipes. The PH is a little low although we don't really know what it
started at since the old unused glycol may have changed some having sat for
29 years. Should we insist that the mix must be changed out immediately or
can he continue to watch it carefully and keep going? If he does keep going,
what is the indicator to watch for that will tell him he absolutely must change
it out?</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Thanks in advance for your opinions!</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Charlie Pickard<BR>NABCEP Certified Solar PV
Installer ®<BR>Aladdin Solar<BR>952-401-7073<BR><A
href="mailto:cpickard@AladdinSolar.com">cpickard@AladdinSolar.com</A><BR><A
href="http://www.AladdinSolar.com">www.AladdinSolar.com</A></FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV><BR>
<BR>
__________ Information from ESET NOD32 Antivirus, version of virus signature database 7508 (20120923) __________<BR>
<BR>
The message was checked by ESET NOD32 Antivirus.<BR>
<BR>
<A HREF="http://www.eset.com">http://www.eset.com</A><BR>
</BODY></HTML>