Hi Terry, snip s > I don't understand much of what is in your post. Please explain. Comments > interspersed below: > > > Our weather conditions seem the same (humidity range) but right now we > have > > had a dry spell. I have been fitting Dampp-chasers for ten years now, > > started of with the humidistat's set at 42% and 25W rods to today's > > Humidistat set at 55% with 50W rods. > > So it sounds like we are installing the dehumidification portion of the > Damp-Chaser system? Keep in mind that you need to monitor inside RH to be > sure that is an appropriate installation. That is what I do here in Florida > (although I use a dry calibration humidistat). Yes, the dehumidity system. There are three types of humidistat DRY NORMAL WET. I am saying rough settings only of DRY 35% NORMAL 42% WET 55%. Switch on and switch of are a few Degrees either side of above %'s. > > > The 25 W / 42% system stays on all through the "wet" which means that the > > internal RH was most likely about 55% and then dries the piano out to 42% > > RH, then when the dry dry spell comes in, it all dries out too much. > > I disagree. If the 25W / 42% system stays on all through the "wet" season, > it means that the RH inside the piano is somewhere between 43% (if the > humidistat is performing as designed) and 99% - where do you get 55%? I mentioned a very rough "rule of thumb" before that I use as a guide for explanations. 'For every watt of heat you use ,you get rid of 1% of RH' On this basis if you are using a 25W rod and the humidity is 80% on average, the resultant difference is 55% RH on average. This is a guide only and is not to be taken as gospel. If the > system is on all the time, presumably it does NOT get the piano interior > down to the 42% (or wherever the device would turn off the power). Nit picking is a business for nit pickers. By the time that the RH has come down to 65% the humidistat will switch of because it has dryed the air out to show 38% RH then it will switch on again at 46% RH or so. Fortunately the RH does not go from 90% one day to 30% the next. Then when > the dry dry spell comes in it may indeed dry out too much (what does your > inside RH go down to during the dry period?) - but not from the heater rod - > if your humidistat is functioning properly, it turns the heat off when the > RH of the piano interior gets down to 42%. The Damp-Chaser system will NOT > lower the RH any more. The dry winds blew in at 20%RH. (at 29C.) Houses in the tropics are generally designed to capture every breeze possible with louvre windows and breezeways there is very few places that a piano can be put that is not affected by the weather. It is the dry breeze moveing past the piano that causes the problem. > > The dry > > spell only lasts for about 3 weeks but that's enough to dry the piano out > > too much. > > How dry is dry - in the home interior. Gotta take into account heating of > home. Why do you want to heat a home in the tropics. ??? We are talking dry humidity, not cold air. > > > The 50W / 55% system does switch off and on even when the RH is over 80% > but > > does not dry the piano out to the 42% mark, it stops at 55%. > > Have you measured that? The fact that the system switches on and off, means > that the system is properly sized to reach the RH at which the humidistat > turns the system on and off. The system will now keep the RH stable in the > piano interior when the room RH is at or above the RH at which the > humidistat turn on and off - presumably at 55% (you might be surprised if > you measure). Dampp-Chaser say that they are preset to switch on and off at set points. Sure, those points seem to vary a little but it is the stability we are after, not the exactness of 1 or 2 degrees. I do check them occasionally with my cheap Tandy humidity reader and they are approximately OK. > > > Now what > > happened when the dry snap came in was to dry the piano out to 40% which > is > > acceptable whereas with the other system, it dried out to say 30% which is > > of course, to dry in comparison to the upper limit. > > No way. Not if your humidistats were installed properly and functioning > properly. The 42% humidistat will not be part of a system that will dry the > piano out to less than 42%, and the 55% humidistat will not be part of a > system that will dry the piano out to less than 55%. That is what > humidistats do! So OK, I said it wrong. try this. Now what happened when the dry snap came in was to dry the piano out to 40% when using a 55% /50W rod system which is acceptable whereas with the other system (42% /25W rod), it dried out to say 30% RH which is of course, to dry in comparison to the upper limit. > > > > > I have always figured that if you can keep a piano to within a 20% > humidity > > swing, it will survive reasonably well. So go for a "wet" 55% humidistat > > with a 50W rod in your area. > > > > Tony Caught > > I do not agree. I say if the interior room RH does not dip significantly > below 40% (like here in Tampa), consider using a dehumidifier-only system. > Use a humidistat that will turn on-and-off as close to the 40% figure as > possible (the standard calibration SHOULD be proper - but you may wish to > measure them yourself - I have and I now use the dry calibration > humidistat). Use enough wattage in your rod(s) to make the system turn off > (at least for short periods) during times of high RH. If your average RH is in the higher levels you should be using a "WET" 55%RH humidistat in your area If you are using the "DRY" 35% one, my opinion is that you are over stressing the piano. Check with Dampp-Chaser. Terry, the last time I looked at a pile of Dampp-chaser warranty cards (should send them to Dampp-chaser I know) it was 5" high. Over the last 10 years I guess I have fitted 400 in regularly and not so regularly tuned pianos. I am talking about observations, not sientific facts. Its a practical world we live in. > > Terry Farrell Tony Caught
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