Hi Terry, Long before the instrument reached the temperature of the rod it would cycle to humidifying mode. At 11:28 AM 07/09/2001 -0400, you wrote: >> The energy >> "input" from a 50 watt rod is *only* 180 B.T.U's. Therefore a 50 rod can't >> increase the temperature of the whole piano much at all. > >Again, that all depends on the rate of heat energy loss from the piano >during rod operation. Under normal circumstances, yes, you are right. But if >the piano had some super-minimal rate of heat loss (sealed up, etc.) the >temperature could be raised quite a bit - in fact, theoretically, up to >approaching the temperature of the rod itself! I only raise issues such as >this because I believe it is important to understand how these things work >and what the range of possibilities is - not to nit-pick. > >> Where in >> the piano was your thermometer? > >About keybed height - just going for an average/mid-point-type reading. > >> Was it a min/max unit? > >Yes > >> Was it accurate? > >Reasonably so - within a couple degrees. I do check them against a high >quality lab thermometer I have. > >> Did >> you have more than one measuring device? > >Yes, three or four. > >> Was it an elcheapo from Radio >> Shack? > >Yes, that type. Two were from Dampp-Chaser, one was a little bit more >expensive Bonaire, and one something else. I realize these are not highly >accurate hygrometers. They are better than nothing - I will be buying a real >good one when I finally install my first soundboard. Three of them always >are very near to one another with their respective readings, and I have >checked them against the weather reports of stable-type days and they were >within 5% or so of the reported RH on numerous occasions. So I am pretty >sure they are within, let's say 10% RH, and maybe better. > >> What was the temperature outside the piano at the time? > >78 F (26 C). >> Please don't >> be so fuzzy Terry *grin*. > >Sorry, I didn't want to bore anyone with details. > >> And please don't be such a fussy reader! LOL > >I hope you are laughing. My humor is quite intact! Seriously though, I do >not mean for any of my zillion posts of subjects such as these to be >nit-picky. It's just that some things such as tuning a temperament, or >voicing a hammer, or applying a finish to a case do not lend themselves to >an analytical numbers game so well - or not at all. But other things about >pianos can be analyzed with measurements and calculations. The design and >operation of a dehumidifier can (and IMHO, should) be thoroughly analyzed >with numbers and calculations. Admittedly to be real accurate, we all seem >to be lacking a good hygrometer. But if an installation does not make sense >with the numbers, there should be an explanation, and a way to make it >right. That's all I'm really trying to point out. Piano dehumidification is >not like voicing: "I do this, that, poke a little here, steam a little >there, and the piano sounds more mellow to me and the notes have a more full >blossoming of partials.....", but rather you can measure the room RH and >temp, measure the temp inside the piano, calculate the resultant RH inside >the piano, calculate the moisture content of the wood at equilibrium >conditions, etc., etc. Even though most of us might not sit down with a DC >in one hand and a calculator in the other, I think it is important to >realize that there is a definitive relationship that can indeed be >determined with accuracy. > >> The 50 rod is going to cycle more often than a 25. I believe that rapid >> cycling leads to a more even moisture content in the wood, and less effect >> on the strings. I have no proof of this. I would love to have some. > >I agree absolutely. Sorry I can't provide a chart with numbers! However, >more rapid cycling will mean shorter periods of heat and cool, and because >the piano does take time to change its moisture content with changing RH, >the moisture content of the wood will vary less - as it has less time to >vary with the varying RH of the piano interior atmosphere. Now, the strings. >I don't know. I would actually think it might be about the same because >strings seem to react so very quickly. > >With Humor Intact, >Terry Farrell > >----- Original Message ----- >From: "Don" <drose@dlcwest.com> >To: <pianotech@ptg.org> >Sent: Monday, July 09, 2001 10:27 AM >Subject: Re: Damp Chaser in old upright > > >> Hi Terry, >> >> There is nothing fuzzy about 50w and 180 btu. Do the math yourself. >> >> I believe a 48" upright weighs in at around 400 lbs. If I am wrong please >> tell me. But certainly it weighs atleast 200 lbs. >> >> I mentioned water to define what a btu is and how *little* energy input we >> are dealing with. If you can make an "ice" piano let me know ok? (grin no >> need for humidity control there!) >> >> Woods make up a piano are considerably denser than water, therefore it >> would take longer to raise their temperature. Metal allows heat to >transfer >> very quickly, and the plate is a pretty massive (or usually is), so it >> would take more to heat a plate than a similar amount of water. The energy >> "input" from a 50 watt rod is *only* 180 B.T.U's. Therefore a 50 rod can't >> increase the temperature of the whole piano much at all. It can and does >> affect the strings however. >> >> It's nice that you have measured the inside of the piano at 35 C. Where in >> the piano was your thermometer? Was it a min/max unit? Was it accurate? >Did >> you have more than one measuring device? Was it an elcheapo from Radio >> Shack? What was the temperature outside the piano at the time? Please >don't >> be so fuzzy Terry *grin*. And please don't be such a fussy reader! LOL >> >> The 50 rod is going to cycle more often than a 25. I believe that rapid >> cycling leads to a more even moisture content in the wood, and less effect >> on the strings. I have no proof of this. I would love to have some. >> >> At 09:21 AM 07/09/2001 -0400, you wrote: >> >What's with all this "fuzzy math"? I thought only American Presidents >knew >> >how to use that? A piano is made of wood (admittedly with a small >percentage >> >of water) and metal, and felt and glue, etc. It isn't made of water. So >how >> >do you come to your conclusion based on a 400 lb. weight of a typical >piano? >> > >> >I have measured temperatures inside a studio piano up to about 95 F (35 >C), >> >when equipped with a 50 W rod and a standard calibration humidistat. The >> >temperature that the piano achieves will be dependant on two things: 1) >the >> >maximum rod temperature - let's just assume it gets way hotter than we >want >> >any piano, and 2) the rate at which heat energy escapes the interior of >the >> >piano - either through direct transfer of air between the piano interior >and >> >the room atmosphere (I would guess this is the primary route) and/or >thermal >> >transmission through the case/soundboard/etc. It will not depend much on >the >> >weight of the piano. The weight (wood weight, that is) will only affect >the >> >total time required for the piano to come into equilibrium with the DC >> >system and room atmospheric conditions, when you have a properly sized DC >> >system. The weight of the piano could however affect the ultimate >> >temperature only in the case where you have an improperly sized DC >system. >> > >> >I think. :-) >> > >> >Terry Farrell >> > >> >----- Original Message ----- >> >From: "Don" <drose@dlcwest.com> >> >To: <pianotech@ptg.org> >> >Sent: Sunday, July 08, 2001 11:16 PM >> >Subject: Re: Damp Chaser in old upright >> > >> > >> >> Hi Tony, >> >> >> >> A little point 50 watts is about 180 btu's. A British Thermal Unit is >> >> defined as the energy it takes to raise one pound of water one degree >f. >> >> Assuming an upright piano weighs 400 lbs 180 btu's is *never* going to >get >> >> the piano to 50 degrees C. (unless the room is 48 C already *grin*) >> >> >> >> Use the 50 watt rod with a humidistat. Things will be just fine. >> >> >> >> Regards, >> >> Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T. >> >> >> >> Tuner for the Saskatchewan Centre of the Arts >> >> >> >> mailto:drose@dlcwest.com >> >> http://donrose.xoasis.com/ >> >> >> >> 3004 Grant Rd. >> >> REGINA, SK >> >> S4S 5G7 >> >> 306-352-3620 or 1-888-29t-uner >> > >> > >> > >> >> Regards, >> Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T. >> >> Tuner for the Saskatchewan Centre of the Arts >> >> mailto:drose@dlcwest.com >> http://donrose.xoasis.com/ >> >> 3004 Grant Rd. >> REGINA, SK >> S4S 5G7 >> 306-352-3620 or 1-888-29t-uner >> > > > Regards, Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T. Tuner for the Saskatchewan Centre of the Arts mailto:drose@dlcwest.com http://donrose.xoasis.com/ 3004 Grant Rd. REGINA, SK S4S 5G7 306-352-3620 or 1-888-29t-uner
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