Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Need help troubleshooting my Dampp Chaser system

Dcd:

The difference between the reading you get with the humidifier plugged in directly and the using the humidistat may be due to the automatic cycling of the dehumidifier bar that the humidistat calls for. This is to cause an air current within the piano in order to distribute the humidified air. It makes sense to me. After more humidity is absorbed by your piano I expect that the humidity will rise. It can take weeks especially when starting off as dry as you are.

The reason for a higher reading without the humidistat is obvious, isn't it? Without anything regulating it, it's running constantly.

The only thing that I don't understand is that the dehumiifier bar is only supposed to go on when the RH% hits 46% (based on DC info). So, theoretically, the dehumifier bar should never go on below 46%.

My temperature readings support this becuase the temperature has been dead steady with no max/min variation.

I'll give it some more time...if the piano is still soaking up the moisture, maybe teh wood is soaking up the moisture faster than the humifier can add water to the air...then once the wood is moister the air RH may rise. Makes sense. We'll see if I see it over time. Someone who knows more than I do could probably calculate how long that would take, but I don't know the calculations.

Hi Loren. The reason for the higher reading isn't obvious. It's interesting...I thought it was obvious how a humidistat worked, but maybe it's not so let me review. Note that the high and low set point percentages were given to me by DC.

-humidifier on until RH% = 46%
-then the dehumifier turns on to pull the RH% down to 38%
-then the humidifer turns on to bring the RH% back up to 46%
-cycle continues

So my confusion was that technically, the dehumidifier bar should not turn on until it reaches 46%. My system never got past 44% so even when the humidifer was on its own...it never reached a point where the dehumidifier turned on.

My temperature reading is constant so it doesn't indicate that the 50W heater bar ever turned on so my conclusion is that my humidifier is working as hard as it can but never reaches the point where it gets "too high" and triggers the dehumidifier.

So I still can't explain why I could get up to 44% with the humidifier plugged in directly. It might have been a fluke and maybe I should repeat the test.

dcb:

I think it may only be mentioned in the installation instructions about the dehumidifier bar coming on occasionally even when the unit calls for moisture in order to circulate the humidity.

So if you got up to 44, and the rods shouldn't come on before 46, and the rod didn't come on, what exactly is the problem? Now you're confusing me.

As to achieving higher humidity with uncontrolled humidification vs. controlled humidification, sorry, that's what should be expected!

dcb, (Dampp-Chaser buyer? Dampp-Chaser buster? Doubting credible beliefs?)

I too am slightly confused by what you have just written, but then again I could use some more coffee.

This was mentioned previously, and Jeff just alluded to it, but again...the humidistat will sometimes work in a counterintuitive way, because the system is regulating itself. And Jeff is right - The DC takes at least 3 weeks of running properly to maximize its effect. But really, why get worried about a measurement being "off" by 2% ? Even expensive hygrometers usually have an error window of +-3%.

Another anecdote...

Yesterday I tuned four pianos, all in Manhattan: a Steinway 45, a Steingraeber 138, a Bluthner Model 6, and a Steingraeber 205. All four apartments had RH levels between 24-27% (according to my mid-priced hygrometer which I believe to be fairly accurate.)

All had Dampp-Chasers installed except the Steingraeber 138, which was 15 cents flat of 440. The other three w/ DCs were within 2 cents of A440. Both Steingraebers are about one year old, and, according to the owners, yesterday was the third tuning for each since delivery.

Re: further research...It would be interesting to see more studies on wood and how the humidification of just one side affects it. But isn't it true that cut wood absorbs and desorbs mostly along the end grain anyway? I would also think that - at least in a grand - the water vapor can pass through the nose bolt holes in the soundboard as well, which would put some of the vapor on top of the soundboard.

Again, for me anyway, the alternative of not using a Dampp-Chaser based on "insufficient data" or unknowns is a much less appealing proposition than having one installed in a piano environment that goes from 24% to 60% relative humidity each year. That kind of humidity swing puts a lot of stress on glue joints and the wood itself, does it not? Plus we know that humidity changes can affect regulation, and even the tone of hammers. I also believe that the German pianomakers know more about wood than just about anyone, so if they recommend the use of the DC they must have a very strong belief in its benefits - and little concern about any potential destructiveness. And I would think that any negative side effects of DC use would have appeared by now, but that is just my opinion.

As another tech pointed out earlier, an incorrect installation is probably the biggest risk of using a DC system, or continuing to use the old systems from 50 years ago that had no humidistat or humidification capabilities. Oh yeah, another important variable beyond our control: piano owners with DCs who ignore the flashing yellow light...

What isn't working correctly is that after the system achieved 44% without the humidistat plugged in, it dropped to 36% once I plugged the humidistat in again. If the dehumidifier bar only goes on at 46%, I should have been able to get to the 44% with the humidistat plugged in. (Note that my hygrometer is certified to be accurate +/-2% and measures min/max so it is not the case where it got higher than 44% then dropped to 36% when I took the reading.)

I'll be honest, if I were reading my post I would doubt everything I said based on the conventional wisdom of how effective Dampp Chasers are.

I'm hoping that this conversation might spark enough people to be curious enough to do their own testing. If 10 people test their systems and only get an average 26%...maybe there's something to it. If 10 people get measurements close to the 42% claim DC makes...I would conclude perhaps that thre is something ineteresting or different about my conditions.

Or...like so many gray areas in life...maybe the results would be mixed. Some systems would work as claimed and others wouldn't. This could continue the research as to why certain ones work and why certain ones don't work up to the company claims.

Another note is that I don't, and never did, believe that DC harms your piano in any way. Also, I've never questioned the need to control humidity to as close to 42%...those benefits have been scientifically proven. My only question was do the DC systems perform up to my expectations which are equal to but not above the claims made by Dampp Chaser....1)pitch stability of 2-3 cents per year, 2)my piano will last twice as long as it would without a DC, and 3)the humidty will be controlled to a constant range between 38-46% RH.

Maybe I'll call DC and see if I can talk to someone higher up in the company. It might be an interesting conversation. Maybe the company would be interested in some free customer insight. If anyone knows anyone at the company who I could talk to...an introduction would be very cool.

Yes, I can give you the name of the head of the complaint department. It is Helen Waite. So, if you have a complaint, go to Helen Waite!

(Oh, I crack myself up...)

I think most of us probably see the dramatic difference in tuning and regulating stability and are content to leave it at that without stressing about whether it's stable because the humidity level is at 42, 44, or 46. At some point you're going to have to leave the system alone and see if your piano is better off because of it.

Good luck!

Hmmm...

Loren, I couldn't agree with you more. 42, 44, or 46% humidity makes no difference. When I get to those numbers I will consider my DC working perfectly.

In the beginning, if I didn't alter the installation to a non-recommended way, I would have still been at 26%. I think that is too low.

Your point is well taken...once you get to an acceptable range small fluctuations aren't significant.

However, I'm going to be really upset if my piano doesn't last 200 years. (Two times the expected 100 year lifespan) (Of course I'm just kidding.)

Also, I've been on the phone with DC for over an hour. I asked to speak to Helen Waite and still haven't been connected.

One thing some people in here need to remember is that placement of a Dampp Chaser system is just that.... Placement... A starting point. It is not set in stone that x piano will have the Chaser system placed in x position every single time. If the humidifier just as an example, is turning off to quickly, not humidifying enough, we might have to place the humidisat in a different location to compensate. In a way, that's sort of like tuning. No two pianos tune alike. While we may use the same system to tune, we must compensate with every single piano to one degree or another in order accommodate for its quirks, needs and/or failures.

As for proof? Who cares? If it works, we recommend it. If it doesn't work, we do not recommend it. Most of us have installed many of these units and endorse them upon our own findings and the changes we see within the piano itself over the course of many years. I have systems that have had Dampp Chasers on them for over 30 years. The piano is in marvelous condition because of it. Otherwise, many of these pianos would likely have cracked sounding boards like their neighbor's do, or some other problem due to our very major humidity fluctuations here in Michigan. Personally, I've installed hundreds and hundreds of these units over the past 40 years and I highly endorse them because of how I have seen them perform from my own personal experience which is all that matters to me.

95% of the time I find a Dampp Chaser system not working or not working properly? I find it to be the fault of the owner, mostly through neglect of some sort intentional or not ---- not the fault of the system... The other 5 % I find is an improperly installed unit or failure of a system part which is fairly rare.

They work extremely well IF and only IF they are properly installed. And, IF, the client faithfully fills the unit when it is required, changes the humidifier pads and stops playing around with it themselves and listens to the advice given.

I know you already know this, but I'm going to mention it anyway because you may not have considered the implication.

The DC has no dead band. It is not like your house furnace. Your furnace turns on when the room gets cold. When it gets to the setpoint, it stops and does nothing. It doesn't immediately turn on an airconditioner. When your room temperature drops below the setpoint, it doesn't turn on right away. It waits to drop below the dead band, usually two degrees.

The DC has no mode when it is not doing something. Even if your humidity is in the perfect range, it will be trying to change it up or down. It humidifies (runs power to the humidifier bar) until it reaches whatever RH is set on the humidistat, then it immediately starts dehumidifying (running power to the heater bars). It is ON or ON, there is no OFF.

As a mechanical engineer who works on HVAC and control systems, I find that frankly horrifying. It works, kind of sort of, but it doesn't control humidity to a point or even a range. It averages humidity by swinging back and forth past that point.

However, in your situation, the heater bar never comes on. The most obvious diagnosis would be that the humidistat never got to the desired RH, so it never "satisfied" and never turned off. Why you got any higher RH bypassing the humidistat is kind of a mystery, and I suspect a measurement error.

I want to commend you for actually doing measurements. That is so rare as to be almost nonexistent. However, if you search this forum, you may find a previous thread where someone did very careful measurements and posted the results. They were in some other language, French maybe (I disremember) but the graphs were very instructive. In that example, the wood of the piano obviously serves as a slow time constant mass, smoothing out the rapid humidity swings produced by the DC.

The fact that blocking your slit with insulation produced better results shows your unit was undersized for your local conditions. This would never have been detected without actual measurement - you could not have known that your DC was not working.

Would your installation technician have known? Sure, if he measured. But as far as is known, the number of technicians who actually do this measurement is zero, and the DC firm does not seem to recommend it.

Am I missing something? If the humidifier was plugged directly into a wall outlet, making it constant on, and allowed to run in that state, it's going to produce a higher reading than if it's plugged into a humidistat that is cycling it on and off.

As for being undersized, there is only one size humidifier and it has an 8-watt bar. Two humidifiers are used on concert grands, but it would definitely be overkill for a vertical.

Technicians may not measure, but they do return three weeks later for a follow up and tuning; the state of the piano at that point speaks volumes of what is happening as far as humidity within. If the piano is not as it's expected to be, then troubleshooting starts. Again, my concern is that the piano become stable, and I don't worry about if it's stable at 42% or at 46%. If the pitch stabilizes and it goes from season to season with only a few cent change in pitch, I'm happy. So is the customer.

I tuned a Bell upright today that has an open under the key frame. I installed a Dampp-Chaser system in this piano about 2 or 3 years ago. Even with the extra open area under the keys the piano was within 2-3 cents of pitch. When I see results like this I don't worry about sealing the cabinet up because it is not necessary. I know the system work, so I don't try to find fault with them.

You are missing something, Loren...here is what you are missing.

Your statement would be true if the directly plugged in humidifier got above 46% but it didn't.

If it never got above 46%, the results should be the same as with the humidistat enabled. This is because theoretically, the dehumidifier only turns on once it reaches 46% so never turned on.

This is what the system should do (more or less)
38,39,40,41,42,43,44,45,46,Dehumidifier kicks on 45,44,43,42,41,40,39,38, Humidifier kicks on again 39...

Another way to say it is that the dehumidifier stops the environment from rising above 46%. So if you are talking about conditions below 46%, the dehumidifier is out of the picture.

Not to confuse things, but I think I figured it out. I observed my system today when it was reading 33% I looked at it and found out the dehumidifier bar was turned on and hot. So this makes me believe that both parts are working but the humidistat is set a bit too low from the factory. It also explains why the RH is lower with the humidistat enabled vs. not enabled. (even below the 46% threshold.)

But you're never turning the humidifier off. When the humidistat turns the dehumidifier on, it simultaneously turns the humidifier off.

Run the furnace in your house for an hour without it being connected to the thermostat. Then run it the next day for an hour with the thermostat set at 70 degrees. Which scenario is going to produce the highest temperature?

When I tested the humidifier directly plugged in, correct, the humidifier was on all the time. But...it peaked at 44% and wouldn't go any higher.

Under different conditions, you are right, it is obvious that a directly plugged in humidifier may reach 50,60 or more percent RH which would be higher than the system with the humidistat enabled.