Dampp-Chaser system in a grand

[Gayle Mair]

I thought the following question from Mike was such that the answer would
be of broad benefit, so I asked Mike if we could post the question and
answer to the entire list.  He said he didn't mind so here you have it.

Bob Mair

> From: Mike Imbler <MIKE-IMBLER@worldnet.att.net>
> To: damppchasr@brinet.com
> Subject: Re: Dampp-Chaser letter to Wm. Scherer
> Date: Monday, December 15, 1997 7:10 PM
> 
> Bob - would you mind answering a question I have or directing me to the
> proper source?
> I've replied privately to avoid clogging the piano list.  I've been
mildly
> curious about the benefit of your product on a grand where the lid is
always
> kept up.  I own a
> Steinway B, that is played too frequently to bother putting the lid up
and
> down.  I live in Wichita, Kansas; so would probably need only the
> humidifying part of the system.  With central air-conditioning, excess
> humidity is rare; normally 40 to 44% except in winter where heating
really
> dries the air beyond what you can replace with 
> an humidifier without damaging your house.
> 
> My precise question is: how does your system work without a closed in
space
> as you would find in an upright.  Do you install it under the soundboard,
> and then enclose it
> with a vapor barrier?
> 
> If you can answer my question, I would be grateful.  As an engineer, I am
> always curious about how systems work!
> 
>                                    Regards,   Mike        
Dear Mike:

	The heat produced by the humidifier creates rising moisture vapor.  This
hits the moisture distribution baffle and spreads out across the underside
of the soundboard.  There is no question that some of the moisture going
into the bottom of the soundboard is given off by the top of the board, but
on the whole the moisture content of the board goes up.  Eventually an
equilibrium is reached (assuming the ambient humidity doesn't change) where
the moisture going into the soundboard is the same as that going out of it.
 The moisture content at this point is significantly above what it would
have been had there been no humidity control system.

	When the humidistat turns the humidifier off and the dehumidifier(s) on,
the opposite takes place.  Warm, dryer air is generated.  It rises, hits
the soundboard, becomes cooler and heavier, and drops to the floor.

	Simple but effective.

	Yes, covers do provide benefit.

	We provide one for a vertical piano and will one day do the same for a
grand.  Moisture content testing on a vertical piano says you can cut the
swing from dry to wet from 5% to 21/4% with the old standard 5PS.  A cover,
more hardware & greater power, and you can get this swing to 3/16% moisture
content.

	I suggest that you consider a string cover and a complete Humidity Control
System for your B.  The string cover is available from:
				Edwards String Covers
				P.O. Box 646
				Brookdale, CA 95007

				Phone:	408-338-1828

	You may not need the dehumidifier, but it's the inexpensive part of the
system.  I'd get it for the additional control it provides.

Bob Mair