Dampp-Chaser string

[Mark Bolsius]

G'day Jim,

I'm glad we agree on things. I wasn't just responding to your comments, but
adding some observations that your comments brought to mind. Sorry if I
hadn't quite grasped your exact words. (I just got back from a week
away.........419 emails awaited...... I confess now to skimming and deleting
many)

Another point that many techs may not be aware of now is that distributors
should no longer "knowingly" supply a rod without a humidistat. We in
Australia have been doing this for some four years or so, it's been a bit
harder to implement in the US. If the customer isn't aware that it is an
option.....they won't ask for it!
Or in other words, don't offer it to them!

I agree with all those that have already said that single rod installations
are positively irresponsible!

Obviously, we seem to be the converted that we are preaching to (ourselves).

...been a great thread though.

Mark Bolsius


----------
From: harvey <harvey@greenwood.net>
To: pianotech@ptg.org
Subject: Re: Dampp-Chaser string
Date: Thu, 8 Apr 1999 6:52 AM


Mark, you say potato; I say potato. Or is it the other way around? You say,
"the system is never actually off at any time"; I say, "since one or the
other would always be on", I think we're in agreement.

So, allowing for either set of words, my point in case #3 was simply that,
left to "human" rationale and external factors (cool, moist night air),
this human instinctively thought the DE-humidifying portion would have been
on at that moment. That's why I offered, in effect, that the Humidistat
knows what it's doing in its own little world, and that I shouldn't attempt
to second-guess what's going on in that world.

As to generalizing, years ago I purchased a large, battery-operated,
fan-driven psychrometer from Allen Foote. It was expensive, and not easily
carried and used. I was regularly taking and recording humidity readings
before such activities were in vogue. I later switched to a Sybron-Taylor
sling psych, which was much more portable. Now I'm happy with the little
LCD job, because it fits in my kit, and requires batteries! (It's a
personal thing).

Recently, in response to a "btrout" inquiry, I had 'puter spin off a list
of RH readings from my database. After looking at the results, I decided
not to post page after page of numbers that would mean absolutely nothing
when taken out of context.
 
So, in case it wasn't clear, I do take matters of humidity seriously. I'm
also one of DC's strong advocates, in spite of any appearances to the
contrary. That  combination attitude is what causes me to assess each
situation on its own merits, sometimes re-install or adjust an existing
system, and yes, sometimes disable or remove a rod-only installation.

Thanks for the 1-for-1 rule of thumb... that one escaped me, but will be
added to my arsenal as of now.



At 08:20 PM 4/7/99 +1000, you wrote:
>Hi JIm, Deb and list,
>I've been following the Dampp-Chaser thread with some interest (as the
>Australian Distributor). To answer your point about the system switching in
>at odd times......the system is never actually off at any time, it switches
>from humidifying (up to 50%) to dehumidifying (down to 38%) and back. This
>is more reliable, efficient and produces best test results. If it switched
>on and off it would be very prone to short cycling (on and off again in
very
>short bursts) electrically this is not good and doesn't make for good
>reliable mechanisms over the long term.
>In climatic conditions that are dry the dehumidifying cycle tends to be
very
>short with longer humidifying cycles and vice versa. Many techs make this
>mistake, particularly when the customer questions why the system is in the
>"wrong" cycle for the prevailing conditions  ie the rod is on and it's 90
>degrees F and 25%RH. It's just doing it's job getting the system back
>towards the _average_  42% the system is aiming for.
>
>A similar misunderstanding-type problem can develop when there is not
>sufficient dehumidifying power in the system. A system with a 25watt or
>worse a 15watt rod to keep the piano (vertical) under control in an
>environment that gets to over 80% RH is asking for trouble. The system
never
>switches over, and customers with a new system are constantly checking to
>see if it has switched over (notice that I never say it switches off?)
>The rule of thumb in an upright (vertical) is that you need 1 watt of power
>to reduce the RH by 1%. So if you want the system to cope with an
>environment that gets over 80% RH you need a rod that is more than 35
watts.
>
>
>The lesson here is .......Don't generalise! Take a Hygrometer and see what
>is actually happening in this customer's very specific and sometimes unique
>situation!
[cut]
>Mark Bolsius
>Canberra Australia


Jim Harvey, RPT
Greenwood, SC
harvey@greenwood.net
________________________
 -- someone who's been in the field too long.