FWD: Is complete 5-Part Dampp-chaser unit always necessary?

[larudee@pacbell.net]

Farrell wrote:

> I agree completely. As someone else pointed out however, you need to be
> aware that even if it is not real dry outside, if it is cool and indoor heat
> is used, you really need to monitor the indoor relative humidity (RH) levels
> to be sure that it is not getting real dry inside.

Terry,

The 40% to 75% refers to humidity measured at the pianos of my clients.

> Have you monitored your systems to see what RHs are achieved? Have
> you measured the duration of the ON cycles?

When the humidity is high (65% or more), I rarely find my customers'
systems in
the "off" mode.  When it is lower it is sometimes off, sometimes on. 
Obviously
more off the lower the humidity.

> > Lower wattage also reduces the risk of
> > heat
> > expanding parts of the plate or the strings in some uprights.
>
> Again, maybe. If the rod is located close to the plate, and it is on most of
> the time, might it not heat the plate (is this a problem?). Perhaps it would
> be better for more rods and less duration.

There was a thread on this subject some time ago (2 months?).  One
customer of
mine had a large upright moved from Fresno to Berkeley.  It had a full
D-C
system with a 50W rod.  It was one of the few times I encountered the
problems
discussed on the thread having to do with heat.  Not a lot of proof, but
indicative.

> >  Here in
> > the San
> > Francisco Bay area, where the humidity is usually between 40% and 75%, I
> > find
> > that 25W is usually enough for spinets and consoles, 35W for larger
> > uprights,
> > 50W for small grands, 75W-88W for larger grands and 113W-126W for
> > concert
> > grands.
>
> Again, have you monitored RHS achieved or duration of ON cycles? Or are you
> relying only on how the tuning seems the once or twice a year you see the
> piano? (Obviously, a stable piano is what we are after, but only infrequent
> visits to the piano to subjectively render an opinion on its tuning, may be
> misleading - for me anyway, reams of data make me more comfortable.) I
> usually recommend 50W for a console and 100W for a large upright. I have 220
> Watts under my 5' 10" Boston grand. I find that during the winter, I rarely
> find the system on. During the humid summer, it will run between 50% of the
> time and when it gets really humid, perhaps 80% of the time. (The pitch and
> tuning on my Boston is absolutely, rock solid - it just does not budge) I
> found that with fewer rods, the sytem would stay on all the time and not
> reduce the RH to targeted levels. I also use a dry calibration humidistat. I
> use the dry because my own personal observations have been that the dry
> calibration will cycle on and off at right around 48% to 50% RH. (I put the
> hygrometers on top of the case beams - almost touching the soundboard - in a
> variety of locations - and it never dries it out to less than about 45% RH.)
> The normal calibration humidistats cycle on and off around 60%. Again, these
> are observations that I have made in my own shop with the cheap hygrometers.
> But what else can I do - until I buy a good hygrometer?

I do not mean to recommend my figures to everyone.  I am only saying
what seems
to work here, where we don't encounter extremes in either direction. 
When I
worked in Saudi Arabia (in seaside locations where the humidity ranged
from 30%
to 100% almost every day), I installed much more robust systems. 
However, Ryan
was asking about a particular situation.

> I talked to Bill Spurlock at the KC convention and he has a similar
> philosophy to put in lots of power - that is what you have the humidistat
> for. Lots of power means more rapid cycling, which in turn means more
> consistent RH environment for the piano.

In either case the RH bounces back and forth between the trigger points
of the
humidification and dehumidification systems.  I don't see that bouncing
back an
forth faster makes the environment more consistent.

Paul Larudee