Dampp-Chaser Humidistat Placement

[jpiesik@arinc.com]

    Dear Bob,

    A wonderful response - exactly what I needed!  I just wish I knew this
    earlier, but that's why I asked, so that I can be sure to provide the
    best possible D-C installations for my clients.

    Thank you, Bob, for responding!

    John Piesik

    P.S.  I will be calling for the "Fine Tuning" reprint!

We recommend and urge that the humidistat be located where it will NOT
recieve feedback from the dehumidifiers.  The sketch on the humidistat
instruction sheet showing the underside of a grand piano with a humidity
control system installed does only a fair job.  It shows the humidistat 6 to
8 inches from the humidifier tank and just slightly more than this from the
primary dehumidifier.  This is not exactly the positioning I would chose and
I'll be sure to correct that the next time we revise this instruction sheet.


In any case, the humidistat should be located 4 to 5 inches from the
humidifier and not closer than 15 to 18 inches from any dehumidifier.

Now just for a bit of history, years ago, Dampp-Chaser instructed technicians
to place the humidistat equidistant from the humidifier and the dehumidifier,
the thinking being that it would receive equal feedback from each unit and
would essentially call for equal operation.  This assumed that the
dehumidifier and humidifier had equal capability.  In fact they don't.  The
humidifier has a great deal more capability than the dehumidifier and thus
the dehumidifier needs to be favored.  You do this by placing the humidistat
to get as much feedback from the humidifier as possible.  If you have ever
read the article "Fine Tuning a Piano Climate Control System"  from the
November 1990 Piano Technicians Journal which deals with tests on an upright
 piano, you will note the principle is the same.  If the humidistat is so
close to a dehumidifier that it gets most of its feedback from the
dehumidifier then the dehumidifier will be controlled to turn off before it
should (probably WAY before it should) and the general level of moisture will
be higher than you want, probably higher than you think it should be and
you're scatching your head as to why.

The distances provided above are pretty  good.  I suggest that  if push comes
to shove and you can't  install all the dehumidifiers that you want because
of this limitation, then leave one out.  Remember that shorter, higher
powered  dehumidifiers are available (24-25, 36-38) now compared to 5 years
ago.  I would use these without exception.

Don Rose,  I'm glad to hear your comment about dehumidifier placement under
the beams rather than under the soundboard.  A 7F (36" and 25 watt) is
normally used to keep the keybed from warping which in turn puts the keys in
a bind.  It further contributes a little to keeping the moisture content of
all action parts down.

I hope this helps.  We have reprints of the " Fine Tuning" article if you are
interested.


Bob Mair
Dampp-Chaser Electronics
1-800-438-1524