This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Hi List After reading more mail on the subject I decided to post this answer to = further questions that John asked. I am not a master on the subject, I am not an engineer, these are just = my thoughts and observations. OK Tony Caught ICPTG Australia caute@accessnt.com.au ----- Original Message -----=20 From: Tony Caught=20 To: John.Woodrow@pil.com.au=20 Sent: Wednesday, 2 February 2000 11:33 Subject: Dampp Chasers Hi John 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. How does one define the 'tropics'. For six months of the year, coastal Sydney has humidity levels of 70+% and temperatures of mid 20's to mid = 30 degrees Celsius. This is not much different to the coastal Queensland = towns for all but maybe the 3 months of summer when the humidity goes a bit = higher and its slightly hotter for longer during the day. =20 I wish I new all the answers or could explain myself better but here = goes. I just checked the weather today in Sydney, Darwin and Alice Springs. = This is 3 totally different weather conditions. Sydney temp 22 C 75% H 18 C dew point Darwin temp 29 C 77% H 25 C dew point Alice temp 33 C 16% H 4 C dew point I just sent a post back to the list on this subject. I don't know the = formula. 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. 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. Alice is just too dry. 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. 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. 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. 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%. 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. I know, clear as mud. Best I can do. Will explain more in Sydney at = the Convention. I plan to be there. Regards Tony Caught ICPTG Australia caute@accessnt.com.au My logic for considering the 'wet' DC is simple. If the DC is trying to create an environment under the soundboard of 42%, and the external environment never gets below 55%, then the DC will be permanently on and flat out trying to dry the board down to a level that this piano has not experienced since it left the Kawai factory 15 years ago. Isn't this = asking for the same problems as transferring an old piano from one environment = to a greatly different one. This is exactly the issue that you stated when = you said that "the issue of a tropical or wet humidistat of 55% RH was = developed to ensure that the heater was not on all the time and that the piano moisture content was not reduced too much more than the lowest level of moisture content. As the lowest RH recorded over the past several months was around 55% = for a period of only a couple of days, a 42% humidistat must be on all the = time, and the piano moisture content will be reduced too much lower than the lowest level of moisture content. Surely the 55% RH humidistat is = closer to the mark if I go ahead given the feedback from guys like Roger Jolly who said 'let it be'. ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/6f/1c/6d/ff/attachment.htm ---------------------- multipart/alternative attachment--
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