> 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 >
This PTG archive page provided courtesy of Moy Piano Service, LLC