Damp Chaser in old upright

[Farrell]

Comments below:

----- Original Message -----
From: "Tony Caught" <caute@optusnet.com.au>
To: <pianotech@ptg.org>
Sent: Saturday, July 07, 2001 9:50 PM
Subject: Re: Damp Chaser in old upright


snip
> >
> > > 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.

OK, fair enough, an educated guess.

> 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.

I don't mean to nit pick. I was simply trying to point out that if the unit
does not cycle on and off, you really don't know what is going on inside the
piano, other than the system is undersized for the application.

> 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.

> 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.

It will do this in Florida at times.

> 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.

Right, the atmospheric conditions lower the RH in the piano below 38% (or
whatever), not the DC system.

> > > 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. ???

I don't heat mine, but some of my clients do. If it drop below 80 degrees in
the home, on goes the heat! - And down goes the RH.

> We are talking dry
> humidity, not cold air.

Hmmm. OK.

> > > 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 find them to be about 10% to 15% higher than indicated (using several
cheapy gauges). But you are right, stability is the objective. However if
you are only using a partial system, i.e., the dehumidifier portion, you are
then relying on the dry season RH to be near your targeted wet season RH in
the piano.

> 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 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%. 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.

> > > 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.

Only on a full DC system installation. Not, IMHO in a partial installation.

> 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 scientific facts. Its a
> practical world we live in.
> >
> > Terry Farrell
>
> Tony Caught

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