<!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 content="MSHTML 5.00.2314.1000" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV>Hi List</DIV> <DIV> </DIV> <DIV>After reading more mail on the subject I decided to post this = answer to further questions that John asked.</DIV> <DIV>I am not a master on the subject, I am not an engineer, these are = just my thoughts and observations. OK</DIV> <DIV> </DIV> <DIV>Tony Caught ICPTG Australia<BR><A href="mailto:caute@accessnt.com.au">caute@accessnt.com.au</A></DIV> <DIV> </DIV> <DIV style="FONT: 10pt arial">----- Original Message ----- <DIV style="BACKGROUND: #e4e4e4; font-color: black"><B>From:</B> <A href="mailto:caute@accessnt.com.au" title=caute@accessnt.com.au>Tony = Caught</A> </DIV> <DIV><B>To:</B> <A href="mailto:John.Woodrow@pil.com.au" title=John.Woodrow@pil.com.au>John.Woodrow@pil.com.au</A> </DIV> <DIV><B>Sent:</B> Wednesday, 2 February 2000 11:33</DIV> <DIV><B>Subject:</B> Dampp Chasers</DIV></DIV> <DIV><BR></DIV> <DIV>Hi John</DIV> <DIV> </DIV> <DIV>Not sure if you wanted me to post this on the list or send = privately. If you wish it post it that's OK.  Your e-mail was addressed to the = pianoteck list not me.</DIV> <DIV> </DIV> <DIV>How does one define the 'tropics'.  For six months of the = year, coastal<BR>Sydney has humidity levels of 70+% and temperatures of mid = 20's to mid 30<BR>degrees Celsius.  This is not much different to the = coastal Queensland towns<BR>for all but maybe the 3 months of summer when the = humidity goes a bit higher<BR>and its slightly hotter for longer during the = day.  <BR></DIV> <DIV>I wish I new all the answers or could explain myself better but = here goes.</DIV> <DIV> </DIV> <DIV>I just checked the weather today in Sydney, Darwin and Alice = Springs. This is 3 totally different weather conditions.</DIV> <DIV> </DIV> <DIV>Sydney temp 22 C 75% H 18 C dew point</DIV> <DIV>Darwin temp 29 C 77% H  25 C dew point</DIV> <DIV>Alice    temp  33 C 16% = H    4 C dew point</DIV> <DIV> </DIV> <DIV>I just sent a post back to the list on this subject. I don't know = the formula.</DIV> <DIV> </DIV> <DIV>With a temp of 29 C in Darwin and a H level of 77% the dew point is = 25 C.  This means that if the temperature suddenly dropped to 25 C = then the RH would be 100%.  Dew point is the temp that moisture forms out of = the air.</DIV> <DIV> </DIV> <DIV>Now in Sydney you notice that the RH is 75%, about the same as Darwin,  but the dew point is 18 C.  This is a 7 degree = difference in temp to achieve 100% H.</DIV> <DIV>Alice is just too dry.</DIV> <DIV> </DIV> <DIV>To me, the correct measure is or should be moisture content of the = timber. As you can see from the above that the same H levels at different = temperatures shows different levels of moisture content in the air. That is using the = dew point as a guide as to how much moisture is in the air. If you bring = Alice Springs into the same system you will see (hopefully) why there are 3 = D-C systems.</DIV> <DIV> </DIV> <DIV>Timber that is cooler will accept more moisture that warmer timber, = so the heat of the timber is another factor to be taken into = consideration.  Remember, what we are trying to achieve is a stable tuning.  to me = this is a stable moisture content of the timber.</DIV> <DIV> </DIV> <DIV>Remember that I wrote about the moisture content of the timber in = different places ? OK Sydney is 16% Darwin is 19% (average)  Alice Springs is = 8%.  Apparently Dampp-Chaser worked their figures out to produce 3 = systems, wet, average and dry so as to not have to use more heat than necessary = to reduce the moisture level to an accepted level.</DIV> <DIV> </DIV> <DIV>I always used the average one (42%H) with a 25 watt heater before = they introduced the wet model and upped the wattage to 50 in the = heater.  To me both worked fine but, the wet one with the 50 watt heater did dry the = piano out more than the other one.  The 25 watt heater stayed on all the time = until the humidity level dropped back to 65% whereas the wet one with 50 watts = of heat still switches of and on at 80%.</DIV> <DIV> </DIV> <DIV>I guess that the right idea is to try to keep the piano within a = 20% swing.  If the lowest H level you get is 20%H (in the winter with = heaters on inside the house) then you use a 42% humidistat. At 55%H the heater = will be off more than it is on.  Remember, the H sensor is in the = humidistat, just below the rod where the variation will be the greatest.</DIV> <DIV> </DIV> <DIV>I know, clear as mud.  Best I can do.  Will explain more = in Sydney at the Convention. I plan to be there.</DIV> <DIV> </DIV> <DIV>Regards</DIV> <DIV> </DIV> <DIV>Tony Caught ICPTG Australia<BR><A href="mailto:caute@accessnt.com.au">caute@accessnt.com.au</A></DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV> </DIV> <DIV>My logic for considering the 'wet' DC is simple. If the DC is = trying to<BR>create an environment under the soundboard of 42%, and the external<BR>environment never gets below 55%, then the DC will be = permanently on and<BR>flat out trying to dry the board down to a level that this piano = has not<BR>experienced since it left the Kawai factory 15 years ago.  = Isn't this asking<BR>for the same problems as transferring an old piano from = one environment to a<BR>greatly different one.  This is exactly the = issue that you stated when you<BR>said that "the issue of a tropical or wet = humidistat of 55% RH was developed<BR>to ensure that the heater was not on all the = time and that the piano<BR>moisture content was not reduced too much more than = the lowest level of<BR>moisture content.<BR><BR>As the lowest RH recorded over the = past several months was around 55% for a<BR>period of only a couple of days, = a 42% humidistat must be on all the time,<BR>and the piano moisture content = will be reduced too much lower than the<BR>lowest level of moisture = content.  Surely the 55% RH humidistat is closer to<BR>the mark if I go ahead = given the feedback from guys like Roger Jolly who<BR>said 'let it be'.<BR><BR></DIV></BODY></HTML>