Temperature Change affecting pitch

[Farrell]

> I do take RH readings each visit.  The indoor air in our dry summer is
> always higher than the outside RH.  I presume because the AH remains the
> same, cool air has a higher RH.

I usually leave my AC unit off when I am not in the shop. My
DC-humidistat-controlled dehumidifier keeps the RH from exceeding about 62%.
When I am in the shop, I turn on the AC unit and within 15 minutes watch as
the RH DECREASES to around 50%. I use a regular-type AC unit with cooling
coils, etc. Even in the dry winter the un-AC shop will hover around 40% RH,
and when I turn the AC on it will drop to near 30% RH.

I have one thought regarding the performance of the same type AC unit in a
very dry climate. Could it be that the AH on the air passing through the
coils (whether it be from an outside source or recirculated indoor air) is
so low that it never gets to the dew point and hence water is not removed.
In such a case one would see a RH increase as the indoor air temp decreases.
Perhaps this is what is happening.  :-)

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

----- Original Message -----
From: "Larry J. Messerly" <prescottpiano@juno.com>
To: <pianotech@ptg.org>
Sent: Thursday, March 30, 2000 4:45 PM
Subject: Re: Temperature Change affecting pitch


> I do take RH readings each visit.  The indoor air in our dry summer is
> always higher than the outside RH.  I presume because the AH remains the
> same, cool air has a higher RH.
> Larry
> ps we do have many evaporative units (swamp coolers) in Arizona.  They
> really pump up the moisture where I can measure 20% RH outside the house
> and 80% inside.  I've seen strings go rusty (in Arizona) in less than a
> year because the client would not move the grand piano, close the lid, or
> close off the air vent.
>
> On Thu, 30 Mar 2000 12:40:38 -0600 Don <drose@dlcwest.com> writes:
> > Hi Larry,
> >
> > Have you taken empircal readings of RH in a home with AC? I have and
> > believe me they *are* lower where I live.
> >
> > At 09:15 AM 3/30/00 -0700, you wrote:
> > >" You are sitting in your house and get to feeling to  warm so you
> > turn
> > >on the airconditioner which takes the outside air as it is...
> > humdity
> > >and all and cools it down while pumping it around inside your
> > house."
> > >
> > >Dear List, I disagree,
> > >
> > >Air Conditioners do NOT remove moisture from the air.
> > >
> > >Pray tell, unless you have an air handler system as is used in
> > large
> > >structures to keep the air fresh, HOW are you getting that air into
> > your
> > >house to cool.  Most air conditioners I know just cool and
> > recirculate
> > >the air already in the structure.  Absolute Humidity remains the
> > same,
> > >relative humidity rises.  That's why in Phoenix (and I presume
> > elsewhere)
> > >air conditioned air is good for pianos.
> > >
> > >Larry Messerly, RPT
> > >Prescott/Phoenix
> > >
> > >
> > >
> > >
> > 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
> > drose@dlcwest.com
> > http://donrose.htmlplanet.com/
> >
> > 3004 Grant Rd.
> > REGINA, SK
> > S4S 5G7
> > 306-352-3620 or 1-888-29t-uner
> >
>