"Tony Caught" <caute@accessnt.com.au>

[Farrell]

I wish we had some experts from DC willing to provide input to the points
being talked about.

> "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..."<

What are the systems designed to do. I read their brochure and I conclude
that even if room RH is @ 95%, the dehumidifying system should lower the RH
in the area of the soundboard to 42% and turn off periodically. Is this
true? How many watts are required typically for a given type/size piano?

> "As the lowest RH recorded over the past several months was around 55% for
a
> perior 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."<

This basically raises the same point. What do others think? What do folks
that KNOW know? It seems to me that a properly designed, sized (wattage),
and installed system will lower the RH in the area of the soundboard and
then TURN OFF.

BTW, it seems logical to me that if the RH IN THE HOME (or wherever the
piano is) - outdoor RH means nothing - does not go below 55%, and the piano
sounds good, has reasonable soundboard crown, etc. at 55% RH, then the
humidistat that shuts off around 55% would be a good choice.

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com

----- Original Message -----
From: "Woodrow, John (Parramatta)" <John.Woodrow@pil.com.au>
To: "'Pianotech List'" <pianotech@ptg.org>
Sent: Wednesday, February 02, 2000 2:06 AM
Subject: "Tony Caught" <caute@accessnt.com.au>


> Tony,
> Thanks for the feedback.  I would like to expand on some of the points you
> raise and would appreciate your comments.
>
> 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.
>
> 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
> perior 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'.
>
> Appreciate your comments.
>
> Regards,
> John
>
> Date: Tue, 1 Feb 2000 22:50:18 +0930
> From: "Tony Caught" <caute@accessnt.com.au>
> Subject: Re: Dampp Chaser or not, that is that question!
>
> John
>
> If you were in the tropics, yes I would go for the 55% humidity bar, but
you
> are not.
> What you have to remember is that their are two factors that control the
> moisture content of the timber in the soundboard (piano), humidity and
> temperature.
>
> I have a copy of the moisture content of various timbers as registered
with
> the CSIRO that cover most of Australia.
>
> You will find that in Newcastle the moisture content for Radiata Pine is
> very stable, varying 1 degree only from 15% to 16% with the average of
16%.
> Sydney, for the same timber in the same thickness (1/4") varies between
13%
> and 16% with the average of 14%.
> Melbourne goes from 12% to 17% with an average of 14%.
>
> Parramatta being further inland (not much but further) than Sydney, a
little
> less humid, thus you could expect the moisture content to be lower.
>
> Pianos in general are made with a moisture content in the soundboard of
8%.
> This 8% is expected to increase to say 12 or 13% to increase crown etc.
but
> that is another story. My point is that with your lower average
> temperatures, you require a lower humidity level in the soundboard.  Go
for
> the standard 42% humidity Dampp-chaser system, it will give you a better
> sound.
>
> Here in Darwin, today the temp was 33 Celsius and 90% humidity.  Now if I
> was to install a D-C with 50 watts of heat it would bring the RH in the
> piano down to 40% (rule of thumb 'for every watt of heat you remove 1% of
> humidity') but that would mean that the heat would remain on constantly
and
> that in turn may cause considerable damage to the piano.
> However the moisture content of the same timber in the tropics for Cape
York
> are 17% to 21% with a mean of 19%, thus a tropical or wet humidistat of
55%
> H 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.
>
> Stick with the standard 42% is ideal around that area.
>
> Tony Caught IC PTG Australia
> caute@accessnt.com.au
>
> - ----- Original Message -----
> From: Woodrow, John (Parramatta) <John.Woodrow@pil.com.au>
> To: 'Pianotech List' <pianotech@ptg.org>
> Sent: Tuesday, 1 February 2000 10:10
> Subject: Dampp Chaser or not, that is that question!
>
>
> > List,
> > Piano is a Kawai GS-30 grand that I am guessing is about 14 years old.
> The
> > piano is an ex-institution piano currently being restored.  It has lived
> all
> > its life in a mild coastal environment (60-90 F) where one can be pretty
> > certain the relative humidity of its environment was greater than 50%.
> The
> > soundboard has a few noticeable pressure ridges but nothing extreme.
Board
> > has minimal crown (although much the same as every other GS-30/40
> measured),
> > pins are TIGHT!  The to be restrung strings are rusty.
> >
> > The piano is now located in a room that the humidity swings from 60% to
> 80%.
> > On occasions it dips briefly to 50% on very 'dry' days.
> >
> > So my question to the list is do I:
> > (a) install a DC de-humidifier (tropical version which is set at 55% or
so
> I
> > believe), or
> > (b) because the piano has lived in a high humidity environment all its
> life
> > and settled into that groove just leave it alone.
> >
> > I am concerned that the pressure ridges may open up if the DC is
> constantly
> > trying to pull the humidity down from the 70% to 55%.
> >
> > Appreciate the wisdom of the list on this one.
> >
> > Regards,
> > John Woodrow
> > Sydney, Australia ICPTG.
>
>