[RE-wrenches] Thermal storage water stabilizer

[Will White]

Nathan,

We've done a couple of systems with large unpressurized tanks (STSS).  They work well but there are a couple of things you need to pay attention to.  We use tap water to fill the tank which works fine but you have to make sure the PH of the water is in the correct range.  I can't remember what that is off hand but the STSS manual has a whole section on correct PH and want to add (I think it's baking soda) to correct the PH.  The second tip is make sure all the ports and the lid are properly sealed with calk.  The STSS tanks come with the calk, I'm not sure if other brands include it.  If you don't seal all the openings well when the tank heats up and produces condensation that water will leak out the ports and create a mess and reduce the efficiency of the insulation.

We used to make our own heat exchangers with K soft copper and trex to hold it all together.  That worked well on most systems but we had one where the copper eroded where it was in contact with the trex.   We think it was due to improper PH of the water in the tank. I'd recommend buying the heat exchangers from the manufacture.

Good luck,
Will

__________________________________________________________________________________________
Will White
Regional Field Operations Manager - New England

Real Goods Solar
64 Main St.
Montpelier, VT 05602
Tel: (802) 223-7804
Cell: (802) 234-3167
www.realgoodssolar.com<http://www.realgoodssolar.com/>

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From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Nathan Stumpff
Sent: Friday, August 10, 2012 3:03 PM
To: re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Thermal storage water stabilizer

Thermal wrenches,

I have a series of upcoming projects involving large (up to 10,000 gallon) water storage. They are closed (air-tight) but unpressurized (oversized expansion capability) systems, basically just a mass of water. We move heat in (solar, masonry heater) and out (DHW, space heating) exclusively via heat exchangers, so once we seal up the lid there is no introduction of any new material, including air, until bladder replacement or other maintenance, hopefully a long time off.

Obviously de-ionized water would be the best choice for initial fill, but it is not going to happen. My thought is that with no new source of oxygen, minerals, etc., the small amounts that will be present on fill up can't pose a big problem.

Anyone with experience here? Any ideas or leads for a stabilizer to add on initial fill? What problems am I not seeing?

Many thanks,
-Nathan

--
Nathan J. Stumpff - Arctic Sun, LLC
NABCEP Certified PV Installer #091209-175
NABCEP Certified Solar Heating Installer #032412-14
nathan at arcticsun-llc.com<mailto:nathan at arcticsun-llc.com>
Office: 907/457-1297
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