Because there is always a convection current happening. With a full system either the dehumidifier is on, or the humidifier is on. There is never a period when both are off. At least there shouldn't be if the system is working properly. <div> <br></div><div>Ryan Sowers<br><br><div class="gmail_quote">On Fri, Sep 7, 2012 at 7:39 AM, Terry Farrell <span dir="ltr"><<a href="mailto:mfarrel2@tampabay.rr.com" target="_blank">mfarrel2@tampabay.rr.com</a>></span> wrote:<br> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">Ryan - why do you say that with a "...full system......the air beneath the piano is constantly moving..."?<span class="HOEnZb"><font color="#888888"><div> <br></div><div>Terry Farrell</div></font></span><div><div class="h5"><div><br><div><div>On Sep 7, 2012, at 1:00 AM, Ryan Sowers wrote:</div><br><blockquote type="cite">I have experience installing both types of systems. I have a number of clients in Tacoma. Years ago I used to only recommend the partial system, however, my experience the past few years is that pitch is more effectively maintained with a full system. Many forced air heating systems create a fairly dry environment during the winter. <div> <br></div><div>One theory I have as to why the full system is more effective is that the air beneath the piano is constantly moving with a full system. </div><div><br></div><div>One important caveat however, is to make sure the client understands the need to keep the full system properly serviced. I now recommend distilled water if possible with a minimal amount of humidifier treatment. I find the build up of minerals on the heating bar and pads is greatly reduced. If the client is not that keen on keeping the system maintained, I recommend the partial system, since it is basically care free.</div> <div><br></div><div>It is true that we have a wonderful climate for pianos, and many 100 year old instruments are working surprisingly well. But we still get significant swings: I tuned my son's piano teachers Steinway "M" in may. When I last checked it a couple of weeks ago, it was at 444 - and the octaves across the break sound pretty nasty. With a full system, you can almost keep the piano in good tune throughout the entire year around here. More time for voicing and regulating!</div> <div><br></div><div>Ryan Sowers<br><br><div class="gmail_quote">On Thu, Sep 6, 2012 at 7:42 PM, William Monroe <span dir="ltr"><<a href="mailto:pianotech@a440piano.net" target="_blank">pianotech@a440piano.net</a>></span> wrote:<br> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi folks,<div><br></div><div>I've got a piano moving to Tacoma in the future, and am wondering about installing a Piano Life Saver - either full or half system. Any techs out there want to give your two cents as to what would be best in that environment?</div> <div><br></div><div>Many thanks,</div><div>William R. Monroe<br> </div> </blockquote></div><br><br clear="all"><div><br></div>-- <br>Ryan Sowers, RPT<br>Puget Sound Chapter<br>Olympia, WA<br><a href="http://www.pianova.net/" target="_blank">www.pianova.net</a><br> </div> </blockquote></div><br></div></div></div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br>Ryan Sowers, RPT<br>Puget Sound Chapter<br>Olympia, WA<br><a href="http://www.pianova.net">www.pianova.net</a><br> </div>