<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"><meta name="Generator" content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Hi Carl,</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I'm glad you're making some progress. I've always had good luck following the Schuco table for setting the expansion tank pressure. I would expect the pressure in the expansion tank to be higher than the glycol charge pressure under most fully charged circumstances. For example, if you started with an expansion tank pressure of 26 psi with the glycol loop dry and then charged the system the expansion tank pressure would certainly increase as you added pressure to the glycol loop. The pressure in the expansion tank will vary depending on the glycol temperature. </span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I would follow the Schuco expansion tank pressure recommendations rather than the Caleffi tables if you have a Schuco kit. Each manufacturer tends to have its own recommended pressures depending on the type of system - ie steamback, pressure stagnation, etc. Setting the correct pressure and really thoroughly bleeding all air out of the system has been the key to long term reliability in my experience. I've seen Schuco systems not operate properly if the expansion tank pressure is too low.<br>
<br></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Lastly, you might consider draining the glycol/relieving pressure through a ball valve rather than the pressure relief valve in the future. There should be a couple of fill ports on the pump station. My experience has been that opening pressure relief (and T&P) valves tends to make them more likely to fail and start leaking. Just my experience.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Best,</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">August</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Luminalt Energy Corporation</span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a> [mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of </b>Carl Adams<br>
<b>Sent:</b> Monday, July 01, 2013 4:52 AM<br><b>To:</b> RE-wrenches<br><b>Subject:</b> Re: [RE-wrenches] SHW expansion tank pressure</span></p><p class="MsoNormal"> </p><div><p class="MsoNormal">Andrew, Daniel, August,</p>
<div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">Thanks for your suggestions. </p></div><div><p class="MsoNormal">Andrew, the PR valve had gone off only twice that I could tell. When I checked it again on Saturday the pressure was again at zero but I used the PR valve to vent some residual pressure/fluid from the system. It seems sound.</p>
</div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">Daniel,</p></div><div><p class="MsoNormal">On my previous visit I had also assumed a system leak and so checked connections at the collectors, at the line set transition, and there was no evidence of a leak. The pressure tank was clearly marked with the set pressure, commissioning date, and initials of my lead installer, so I "assumed that was good". After all the system had been in service without issue for approximately 1 year. Wrong! After relieving the fluid in the system I checked the expansion tank pressure, and it was at zero. My thought was either the bladder had ruptured or the Schrader valve had a slow leak. When I pulled the valve out there was no fluid (thanks for the suggestion to check this August ), so I assumed a leaking valve. I lubed and re-seated the valve and re-pressurized the tank. I then recharged the system, bled the air,and 4 days later the pressure is rock solid after a couple of good solar days.</p>
</div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">I had never had an expansion tank lose pressure before, so my take away was to add "Verify the expansion tank pressure", to the troubleshooting/service checklist.</p>
</div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">Daniel,</p></div><div><p class="MsoNormal">I was unaware that the corrugated line set had capacity for expansion , but witnessed this on the recharge cycle. As I pressurized the system, closing the drain valve, to allow pressure to build, I noted the insulation on the return line set slide up the pipe 2 inches or so and then slide back as pressure was released. It makes sense that the line set can expand along the length of the pipe. Good to know.</p>
</div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">So in reviewing things last Friday evening before my service call Saturday, I went back and verified the pipe, collector, heat exchanger, and expansion tank volume. I was sure the exp tank was adequate but still wasn't thinking empty expansion tank. In doing this I pulled out the Calefi idronics 3 manual and did some reading. The appendix there offers some calcs for determining expansion tank volume (attached). Tha calcs showed the 18 liter expansion tank to be oversized for the system (so good to go on this front). The appendix also offers calcs for expansion tank charging pressure. These calcs suggest a system charging pressure of 18 PSI (rather than the 26 psi suggested by the Schuco table I posted previously. The Calefi calcs also seem to be independent of the charging pressure, where as the Schuco table clearly correlates the two. If anyone has any insights on this please share.</p>
</div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">I rechecked the expansion tank pressure after filling the system. What I found was that the expansion tank pressure had increased from 26 psi to 35 psi, with the system pressurized to 30 psi. My expectaion was that the expansion tank pressure would have increased to match the glycol charging pressure. I thought at first this was a gauge offset, but on second thought I considered it might be the glycol is an incompressible fluid whereas the air is a compressible fluid. Again, If anyone has any insights on this please share.</p>
</div><div><p class="MsoNormal"> </p></div><div><p class="MsoNormal">Thanks again for your replies,</p></div><div><p class="MsoNormal">Carl Adams</p></div><div><p class="MsoNormal">SunRock Solar</p></div><div><p class="MsoNormal">
</p></div></div></div></body></html>