----- Original Message ----- > My opinion is equally firm and 100% opposite to yours. Hmmm. The statement above appear to me to be about the only one we really disagree on. Most everything else you state regarding my last post, I agree with. > Household level > equipment requires far too much of the owner to be useful. Proper Hivac > installations are probably going to cost more than anyone other than the > "ultra rich" are able to afford, and certainly more than the cost of many > "home size" grand pianos. I agree. That is why my home does not have WRHC and my grand piano is equipped with a DC dehumidification system. BUT, that is not to say that a DC system is more effective that a proper WRHC. > As I said, it is possible to maintain within 5% but not easy and not cheap. > DC units properly installed (and serviced) are magnificent. Absolutely on both counts. >>From a home use point of view a quilted cover may not to be useful as it > need to be opened and/or removed when the instrument is used. String covers > and bottom covers do stay in place 24/7. Right on. > I had "state of the art" controls in two music studios in 1980. Each studio > had independent heating, air conditioning, dehumidifier (drain hose in > place), and humidifier (self filling, fed from a reverse osmosis unit). The > humidity controllers were the most expensive part of the system and had > human hair activators, which operated a relay so that the contacts did not > have to deal with the relatively large "start up" surge from the dehumidifier. > > As this is a lifetime ago I'm sure controllers are more sophisticated and > have narrower limits, but what I found was that I could not set the "swing" > from dehumidifier cut in and humidifier cut out to a very narrow range, or > both would operate at the same time--with the humidifier winning "hands down". > > It was not possible to use the studios with the dehumidifiers on nor with > the air conditioning. Fortunately the climate where I did this has many > more heating months than cooling ones, and more dry months than wet ones. Well, I wrote my post this morning. Last I looked it was the year 2008 this morning. I guess I am guilty of implying that I was talking about current technology. ;-) > In another post you mentioned how heat may transfer through the sound board > panel. The same thing is true of humidity. Yes, BUT....... I'm just guessing, based on experience, but not proper experimentation, that with moderate insulation on the top side of the piano (a good string cover and a closed lid, let's say) that if the humid room was 70 degrees (F), you turn on the DC dehumidifier, the air below the soundboard warms to 90 degrees (just an estimate) and operates intermittently to keep the temperature at 90, I would expect the string area of the piano to equilibrate with the heat source maybe at 80 or 85 degrees (really just depending on how good the insulation was on top) within a few hours. However, if the room is dry and the humidifier kicks on (let's stuff something in the nose bolt holes to seal those areas off, and let's not have a Fandrich or Nossaman design with a loose foot), boy, I don't know exactly how long it would take, but it would be some many days before water molecules actually migrate through the soundboard from below to the string area. Many days. Maybe more like weeks or longer. You'd have to have a heckuva seal on the string environement to trap the slow trickle of water molecules migrating through that soundboard panel. In realistic situations, you can expect heat from below a soundboard panel to affect the string environment, but a higher humidity environment below the soundboard will not have any easily measureable effect on the string environment. So I disagree with you on that one, but we didn't address that in my last post - so I still agree with what you say above as it relates to my last post! > That is why upright pianos with > DC systems installed that have back covers (I recommend 5 mil poly > installed by the client) are about 4 times more stable than those that > don't have a cover. Here also, we didn't address this topic, so I gonna feel free to disagree with you - but I'll also agree with some of it. If I read this correctly, you are saying that and upright back cover will improve DC system performance because humidity (water vapor) migrates through the soundboard panel? An upright back cover will help quite a bit with DC dehumidifier performance, but less so with humidifier performance (assuming the DC system is installed inside the piano - string side). An upright back cover improves DC system performance by isolating the environment of the soundboard rear from the room. If the dehumidifier goes on, it simply helps to reduce air movement out from that environment - because hot air rises, the warmed air would tend to escape quickly. If I'm not mistaken, DC does not sell or promote "poly" back covers (I assume "poly" refers to some sort of plastic). The covers I've seen from them are a fabric - much like speaker cloth. Yes I agree that if you actually seal the rear of an upright with plastic, you will indeed trap the water vapor in there. Some limited amount will indeed migrate through the wood, althoughI suspect the majority of water molecules back there would have migrated through the nose bolt holes. Consider that with the back sealed up, you will have the necessary weeks, months and years for the water vapor to get back there. So yeah, I'll buy that. I wonder if there is any danger of trapping too much water vapor in the rear of the piano with plastic covering the back? Hasn't DC experimented with that previously? To the best of my knowledge, DC does not recommend use of plastic as a back cover. Terry Farrell > At 09:54 AM 2/18/2008 -0500, you wrote: >> I have a very firm opinion that whole room/house/institution humidity >>control is superior to a standard DC installation, or even a DC >>installation with bottom and string covers. The better the instrument >>is isolated from the room, the better the DC can perform (undercover, >>string cover, and better yet, a nice quilted cover with long sides for the >>entire piano - that is used whenever the piano is not being played). >>is regulated, likely is humidity OUT OF CONTROL. A room with a Sears >>dehumidifier with a tank that is not emptied or does not have a >>functioning drain for water discharge or a room with some crude humidity >>source and likely an even more crude regulatory device (if any such device >>at all) is humidity OUT OF CONTROL. > Regards, > Don Rose, -------------- next part -------------- An HTML attachment was scrubbed... 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