Damp Chaser in old upright

[Farrell]

> Darwin, average temprature during the wet season is da
> ily MIN 25 Celcius Maximum 33 Celcius.  A 50W rod is HOT, if it stays on
all
> the time (which it would if it was with the "DRY" humidistat), how hot
would
> it make the piano ?. And what damage would it do ?.  Would this mean that
> the piano is capable of being at a temp of say, 50 C for half the year
then
> 28 C for the other half ?

You have a legitimate concern there. This has crossed my mind also -
especially because I advocate placing enough wattage in the piano to make it
cycle during periods of high humidity. I don't know that I have seen any
hard data on the effects of temperature. Since we are talking about tuning
stability, obviously large temperature differentials will affect metal
components - plate size and string tension - but maybe they would cancel
each other out - with rising temp, the plate would grow, pulling the strings
tighter, but the strings would relax because they would grow also, maybe
being about the same in the end. My understanding of heat effects on wood is
that it is minimal in the range we are talking. The only significant effect
elevated heat will have on wood (and lets just pull a high number out of the
air - so to speak - let's say up to 60 C) is that it will dry it out - but
keep in mind that with a properly functioning, designed, and installed DC
system, the heat will turn off when the RH reaches the target level, and
therefore the wood will not dry out too much, but rather will be held at a
relatively constant moisture content.

So, to answer your question, IMHO, yes, it would be much better to have a
piano interior oscillate during the year between a high temp of 50 C (122 F)
and a low temp of 28 C (82 F) and have constant RH, rather than have the
temp vary less and RH more.

Wow, it sure is hot in Darwin! I've spent the last half hour or so looking
at maps, etc. about northern Australia. Pretty far out place you live in.
Have you been there a long time? Do you get out on the ocean? I found an
interesting site that gives all sorts of climatological data for Australia
http://www.bom.gov.au/climate/ .

I have enjoyed this exchange. If you care to tell me a bit of off-topic
stuff about your neck of the woods there, send me private. I would be very
interested. Take care.

Terry Farrell

----- Original Message -----
From: "Tony Caught" <caute@optusnet.com.au>
To: <pianotech@ptg.org>
Sent: Sunday, July 08, 2001 9:28 PM
Subject: Re: Damp Chaser in old upright


> Hi Terry,
>
> >
> > > 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
> >
> > Is there a typo here? I do not understand what this statement is. Please
> > clarify.
>
> Try it this way: By the time that the RH  has come down to 65% (actual
> humidity prior to the air being heated by the rod which by my simplified
> rule of thumb reduces thr RH to approx 40%) the humidistat will switch of
> because it has dryed the air out to show 38% RH
> >
> > I guess I have to say the same thing. Assuming proper appliance
function,
> > the 55% humidistat will not lower the RH more than a couple % below its
> > rated %. So, the 55% humidistat will turn a rod off at 52% (or so), and
> the
> > 42% humidistat will turn a rod off at 39% (or so). Neither will be part
of
> > an operating system that lowers RH to 30%.
>
> Right.
>
> How could the 55% humidistat
> > lower RH to 40%? How could the 42% humidistat lower RH to 30%. How are
you
> > getting your measurements? If these reflect actual measurement, I would
> > suggest that one dry snap was simply more dry than the other dry snap,
but
> > neither has anything to do with the Dampp-Chaser system installed on the
> > piano.
>
> Timber does not react immediately to the drop in RH, it take a little
time.
> What I mean is that if one system has dried the Piano to say 55%RH and the
> other system to say 42%RH, then when both pianos (with different sysyems
> installed) are subjected to the same drop in RH to 30%, then the first
will
> drop down to approx 40% in the same time span as the second drops down to
> 30%.
>
> > > 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.
> >
> > Only on a full DC system installation. Not, IMHO in a partial
> installation.
>
> I remember in one of your earlier posts that you mentioned that the
majority
> of homes with pianos were air conditioned.  In Darwin it is the reverse.
> Sure, lots of air cons, but only turned on in extreems.
> If the rooms where the pianos are installed are subjected to air
> conditioning, then the RH%'s we have been talking about do not apply as
the
> piano is not in the RH enviroment directly.
>
> > Again, the objective is maintaining a consistent RH in the piano all
year
> > long. If you use a "WET" calibration humidistat (55% - assuming it is
> > accurate) on a partial system installation, you will get humidity swings
> > from 58% during the wet season, to let's say a low of 35% RH during the
> dry
> > season (35% seems consistent with the low RH numbers for both our
areas).
> > So, with the wet calibration humidistat, you have a 23% RH swing AND the
> > piano does get dried out to the 35% RH level. If you use the "DRY"
> > calibration humidistat (I think they advertise that it is 38%) in a
> partial
> > DC installation (dehumidifier only) you will minimize your RH swing over
> the
> > year from about 41% RH max (again, assuming product funtion as
> advertised),
> > to 35% RH min. In this case you would have only a 6% RH change over the
> > year. How does that stress the piano more than the other way? (It does
> > indeed stress the capacity of the DC system (that is why they have to be
> > sized properly), but I want it to work for me - I am seeking consistent
RH
> > values for my piano environment.) I would suggest that the dry
calibration
> > humidistat is a better choice for a partial DC system installation,
where
> > the RH dips to 40% or less during the dry season. Such a system will
help
> > minimize shrinking and swelling of wood and be much less stressful to
the
> > piano than using a wet calibration humidistat.
> >
> > Terry Farrell
>
> Terry what works works, maybe you are right but I am not game enough to
try
> and find out. It terrified me when I started installing 50W rods in
general.
> In my mind I agreed with my self to use these rods only with the "WET"
> humidistats.
>
> My reasoning is this. Darwin, average temprature during the wet season is
da
> ily MIN 25 Celcius Maximum 33 Celcius.  A 50W rod is HOT, if it stays on
all
> the time (which it would if it was with the "DRY" humidistat), how hot
would
> it make the piano ?. And what damage would it do ?.  Would this mean that
> the piano is capable of being at a temp of say, 50 C for half the year
then
> 28 C for the other half ?
>
> Regards
>
> Tony Caught
>
> >
>