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Hi Everyone,
I last wrote Nov 9. I had to leave town and got back yesterday. While I was gone I left my data loggers in place. My dampp-chaser was set up as shown on the first picture of this thread except that the controller was on the other side of the beam. There was no undercover in use while I was away. Here are the readings from Nov 7 to Nov 17:
COFFEETABLE



FRONT BEAM


As you can see from the coffee table measurement it was quite dry -- the RH was between 30 and 35% for the first 2.5 days, it was between 25 and 30% for the next 5 days, and for the final 2.5 days it was around 25% in the room.

The measurements on the front beam (actually the data logger is place on top of the belly rail) contain some good periods of fairly regular behavior in a reasonable humidity range, but there are also periods (e.g. the last few days) involving big humidity swings.

I think the prevailing view is that by having an undercover installed the behavior will become more stable (still oscillatory, but more reliably so). The undercover arrived while I was away and I installed it yesterday. Actually it is not fully installed, but I have it pinned up with the tacks provided. (The instructions say to tack it first, make sure everything is good, then use the velcro.) I used a large number of tacks and have a pretty decent seal. I watched my data logger for a couple of hours on-and-off and it did not look promising. I saw an excursion from 30-50% at first. But, I suppose that the microclimate needs to stabilize, so I have left everything in place over night and will post the latest results in a few hours.

It's also possible that I will need to move the reservoirs now that the undercover is on to get the nearest reservoir 12-14 inches from the controller. BTW that seems like it will not be an easy task given that there are two reservoirs. At any rate, the next measurements will give a sense of the difference with/without an undercover and with everything else in the setup unchanged.

I gave my humidistat 5 days, then opened up the piano. It read 33%, and didn't change at all after I opened the piano for several hours. Finished installing a humidifier today, so I suspect further experiments won't be as useful.
Todd

I have to take back what I said at the end of my last post:
"At any rate, the next measurements will give a sense of the difference with/without an undercover and with everything else in the setup unchanged."

I was watching my data logger with the undercover on, and I did not like what I was seeing: the RH was varying between around 30-50%. It just seemed like it was getting too dry, and that the heater rods were on too much of the time. I have been struggling with this for a long time and am coming to the conclusion that, in a dual reservoir system in a dry climate (like mine), the 36" heater bar is a problem because the reservoir gets in the way of positioning the heater bar in relation to the controller.

I finally moved the front reservoir in such a way that it is nearly parallel to the front of the piano. Then, I positioned the heater bar *behind* the reservoir, closer to the conroller. The difference is huge, and it makes sense. The controller now senses the dry air sooner, and the minimim humidity is now around 40% instead of 30% as it was previously.

I will post the latest measurements soon.

Another observation: when the humidifier comes on, the humidity climbs quickly to around 46%, then very, very slowly rises to 50-52%, and lingers there for a very long time, before the heater rods finally kick in and the humidifier turns off. (Remember, the data logger is on the belly rail, with no obstruction between it and the reservoir; the controller is in the triangular opening between the beams that contains nothing, i.e. no reservoir in that triangular space). I am guessing that this means that humid air is filling the underbelly of the piano, but the conroller is not sensing it until there is sufficient buildup? My controller is just a bit higher than the top of the beams, I don't think I can get it higher because the ribs get in the way. If I could angle the controller between the ribs I could probably raise it another 1/4 inch, maybe a bit more, closer to the soundboard. Has anyone else tried angling the controller to get the top closer to the soundboard?

You're trading off one thing for another.

The humidistat needs to be near the center of the soundboard (horizontally). This is more important than its distance vertically to the s/b. Another 1/4" won't make a difference.

The long heater rod needs to be near the belly rail, to be near the center of the piano overall, and to provide minimal protection to the action.

Additionally, to protect your five-year Dampp-Chaser warranty, you need to go with the installation position that your installer selected. I'm just trying to protect you.

Different humidistats are available with slightly drier or wetter set points, if you need to make adjustments.

How long did you measure with the undercover on before moving it?

How are you getting the controller to stay on the belly rail?

--Cy--

It sounds as though the humidistat is at an appropriate height given the beam/rib construction of this piano. (those installing the new H-5 humidistat will note that you need a little space above one side of the humidistat in particular)

The recommended location of the components for the system have to do with creating a stable average moisture content of the wood, particularly the soundboard.

Prior to determining that there needs to be a change in the setup of the system, it would be most beneficial to verify whether or not the system is accomplishing this goal. There are devices available for measuring this, although the simplest way to tell, is if the pitch of the piano remains stable.

Cy,
In answer to your questions:
-The undercover was only on for ~12 hrs before I changed the setup. Probably not long enough, but I did not like the low humidity swings (regularly down to 30%).
-The controller is not on the belly rail; it is my data logger that is on the belly rail. The controller is in the general area that it should be for a standard installation.

Regarding the front heater rod: I am just saying that if, for example, you had 2 18" rods with a small space (few inches) between, you would have more flexibility to move a rod a couple of inches away from the front without the front reservoir getting in the way.

Rich:
Regarding pitch stability, this is what got me started monitoring the RH again after a several month break. During my last tuning, which I think was in October, my tech said he was surprised: there had been a lot of wet weather in the area previously, and he had found the other pianos that he had serviced to have high pitch, but mine was actually low. He knew that I had at times monitored the RH inside my piano, and suggested I do it again to see what was happening.

I will now upload my measurements from a couple of days ago. Will post within the hour...

Here are my measurements from after installing the undercover. I had let the system operate over night and observed low (down to 30%) humidity swings when I looked at the data in the morning. It seemed like the controller was not sensing the dry air soon enough, and I wanted to get the heater rod a bit closer to the controller. So I adjusted the front reservoir and moved the heater bar behind it. Here is the new setup:





In the 2nd figure you can see my data logger. Just the corner of it is visible, it's white with a red dot on it.

Here are the results. There are 4 red dots on the right hand portion of the plot. Ignore the 4th from the end. The data overnight are between the 3rd dot from the end and the 2nd from the end. The data for the next 12 hours with the new setup (in the above pics) are between the last two dots.

First, here are the room (coffee table) data:




Here are the data from the data logger on the belly rail as seen in the photo:



In the original setup the data are varying between roughly 30-40%, although near the end of that period the RH appears to be climbing higher. The data for the new setup vary between 43-54%. Here is a zoomed in view of the data with the new setup:



As you can see from the steep drop in the curves at the end of each cycle, the heater rods are now on for only a very short time. If I could just bring the RH range down to 35-45% I would be satisfied.

How flat was the piano? Did it require a pitch raise?

How new is the piano and the system?


A couple tips with respect to the installation as pictured:

1) The heater rod should not be directly beneath the humidistat. The system is tested to work best with the components within certain distances of each other.

2) Watch that those wires aren't directly resting on top of the heater rods. Over time, this has the potential to cause the rubber to dry up and crack off, leaving the wire exposed.

3) Try to make certain that the moisture baffles above the humidifier tanks are clicked onto the hanger rods at all four points, and are in general sitting level. To do otherwise can cause the moisture to distribute much less evenly. In one extreme case, I saw where this caused there to be a large mold/mildew stain on the underside of the soundboard. Ugly.

Best

If the heater rod were farther from the humidistat would that not lower the overall humidity as you wish to do?

Roy:
Since a tech has not yet responded to your question I will give you my thoughts. Hopefully a tech will respond if this is wrong or incomplete.

If the heater rod was moved further from the controller, then, after the heater rod started to operate, it would pump more dry air into the system before it was detected by the controller, eventually shutting down the heater rod and turning on the humidifier. (This assumes the controller is in a sensible location and will eventually detect the changes.) During that time dry air would diffuse through the system. Thus, moving the heater rod further away from the controller would generally lower the minimum RH in the humidification/dehumidification cycle underneath the piano. I don’t know what it would do at the location of the controller itself; if the controller responded instantly, it would make no difference, but, if controller response is an issue (which I think it is), then it could also change the minimum RH at the controller too. Moving the heater rod further away doesn’t seem as though it should change the maximum humidity in the cycle anywhere underneath the piano; that would be controlled by the location of the reservoir with respect to the controller.


Rich:
1) Yes, I can see that, by having the heater rod too close, the controller would almost immediately sense the dry air coming off the heater rods and shut down too soon.
2) I’ll watch out for this.
3) Thanks for pointing this out. It was something I had not heard of before.

Regarding your other questions: My piano and DC system are about a year old. Regarding the last tuning, I need to ask my tech how flat it was. He did not do a pitch raise. He thought it better that I first monitor the RH and find out what was happening.

I left my piano undisturbed over most of the Thanksgiving holiday. During that time the undercover was installed with (many) tacks. One thing that is different from my previous measurements is that I unplugged the front reservoir’s humidifying bar. It still has water in it, and it provides some humidity, but the humidifying bar that the pads rest on is not being warmed. I did this because I had previously made some measurements that made me think the front reservoir was providing too much humidity to the front of the piano.

The data begin at 9pm on 11/19 and end at 4:30pm on 11/26.

Here is the measurement from the data logger on the coffee table:



The spikes in the above data correspond to me carrying the data logger to a bedroom where we had a room humidifier running.


Below are the logger data underneath the piano. There are several red dots on the graph (these denote me connecting the USB cable to the logger), with a period of about 4 days in the middle when it was not disturbed. NOTE WELL: this time, the logger is not on the front beam as in my previous measurements; instead, it is actually sitting adjacent to the controller. It was at that location for all but the final 24 hours. At that point, I moved the logger to the front beam to see the difference between the front beam RH and the RH at the location of the controller. The data corresponding to the front beam measurement are between the last two red dots.



I am satisfied with the readings at the location of the controller. It is a bit on the dry side, but I am fine with that in my dry climate. There is one thing that I do not understand: The dampp-chaser has long nearly stable periods of slowly dropping humidity punctuated by the oscillatory behavior typical of dampp-chasers. My question is, what is happening during the nearly stable periods? I was under the impression that the system was never “off,” that it was either humidifying or de-humidifying. During the nearly stable periods the heater rods are cool. So, its as though the microenvironment is slowly drying out (toward the ambient RH) during these periods. How is this possible if the humidifier is on?

Near the controller the RH measurements range from 35-45%. During the final 24 hours, the RH at the front beam reads 36-55%, and most of that time it is in the range of 50-55%. Should I be concerned that this is too wet given my dry background environment?

One way to keep track of what the system is doing is to install "cube taps"--those little things that have one male plug and typically 3 female sockets that allow you to plug in more than one device into a wall socket.

Put them on the outlets for both the dehumidifier rods and humidifier rods. Then, in addition to the rods, use the cube taps to plug in some low wattage devices, like 5 watt night lights. This will give you a clear indication of when the various rods are getting power. The indication may help illuminate what's going on during those quiet periods. I did this to my own piano.

All this makes me want to buy a room humidifier instead.

See my very different results with my Dampp Chaser in the "My Dampp Chaser" thread.

Todd - how did this turn out?