Damp Chaser in old upright

[Tony Caught]

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