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Black Max engine dehumidifier in humid climate?

Majorpayne317641

Well Known Member
Hi all,

I’ve had my aircraft down for 3 months in moth ball status because I can’t fly it while out at work abroad. I have been using a Black Max dehumidifier, but I have been having a problem they state as “some reporting” that there is water in the tube at the base of the unit. I had this on one unit that I ran for 2 weeks prior to my departure and I adjusted the flow rate to be slower. I also placed an inline desiccant tube similar to ones you use for air tools to be sure it works. That unit failed in those short 2 weeks. The company has good customer service and quickly sent out a new unit. I had my wife plug in the new one and she checks on the aircraft regularly. I say this because now my wife is reporting the new unit also has water in the tube at the base. So I know it’s not because of a defective unit, maybe a design that’s not made for high humidity areas like coastal NC? The in-line desiccant was designed to check on if this thing works, she reports that after a week the desiccant is purple (should be blue if completely dry).

The engine is completely plugged up, I disconnected the breather and wired the machine directly to the breather inlet. The oil dipstick is snug. The engine only has 35 hours on it. I’m using the Phillips anti rust oil in it for storage. Cylinders have desiccant plugs in the spark plugs. She routinely swaps them when they change color and sprays fogging oil into the cylinders each time they are replaced. Exhaust and intake is plugged. What am I missing? Or is this machine the problem? There is no way my wife will be able to dissemble this thing to adjust the airflow like they suggest. When I adjusted it on the first unit it still produced water in the tube only less.

I don’t want to point fingers at anyone because the company is good with customer service but I’m also not wanting to damage my engine or make anything worse than it could be when sitting so long. Thanks!
 

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Install manual says

Water is not getting blown into engine,….
But
Air is flowing too fast through machine / engine, and,….


Check engine for tightness
And / or
Adjust flow rate of machine,…. See instructions


I used to have some issues,…and I would leave the oil dip stick not quite snug….

Seems to be ok now,..

I also decided to put it on a timer to have it shutdown for a bit every several hours
 
Once the unit has the engine crankcase purged of moisture then it will stay dry for days, maybe weeks or months. Running an hour per day should be good enough, as long as you know where the condensate goes. i.e. not back in the engine.

Since you both have the units, where does the condensed water go? and is the peltier device temperature controlled so ice doesn't form inside or is the volume adjustable to keep the temperature above freezing?


I know a few of the challenges from a prototype made with a thermal/electric cooler device but ran out of time before solving an internal icing issue. The solutions were more complicated than time to implement. It had 2-3 LPM flow and first water would condense in the cold side HX but then it would ice and block the flow. It always produced dry air until it stopped flowing. Defrosting and ensuring no water went in the engine was my issue. Can you set me straight?
 
Once the unit has the engine crankcase purged of moisture then it will stay dry for days, maybe weeks or months. Running an hour per day should be good enough, as long as you know where the condensate goes. i.e. not back in the engine.

Since you both have the units, where does the condensed water go? and is the peltier device temperature controlled so ice doesn't form inside or is the volume adjustable to keep the temperature above freezing?


I know a few of the challenges from a prototype made with a thermal/electric cooler device but ran out of time before solving an internal icing issue. The solutions were more complicated than time to implement. It had 2-3 LPM flow and first water would condense in the cold side HX but then it would ice and block the flow. It always produced dry air until it stopped flowing. Defrosting and ensuring no water went in the engine was my issue. Can you set me straight?

If you go to the black max website it explains how it works in detail better than I can explain it.

https://flyingsafer.com/2065#:~:text=The Black Max uses an,cooled by a thermoelectric device.
 
I run mine 24x7 and I am measuring the input and output humidity with an ESP32 and couple of temp/humidity sensors, sending the data to a google sheet, and plotting it with grafana.

It keeps the humidity below 40%. That said, I regularly have to replace parts in it - and the support I get from the company is good. I added the monitoring to both ensure that it's working (it can fail silently) and to investigate backup methods of drying the engine.

BlackMaxTempHumLogger.png
 
Where are you pulling the data point for graph?

I am surprised the humidity of output is not lower, if that is tubing going TO the engine. (Assuming input is local environment)

If that is output FROM the engine,… how is that area sealed ?

All to say, don’t they claim output is very dry.
 
I run mine 24x7 and I am measuring the input and output humidity with an ESP32 and couple of temp/humidity sensors, sending the data to a google sheet, and plotting it with grafana.

It keeps the humidity below 40%. That said, I regularly have to replace parts in it - and the support I get from the company is good. I added the monitoring to both ensure that it's working (it can fail silently) and to investigate backup methods of drying the engine.

View attachment 42972

This is exactly what I was thinking of doing! I just simply ran out of time before I had to leave for work. What did you use to monitor this? It explains why my desiccant is turning colors. I must be drying it below whatever the RH is with the inline desiccant. I only see roughly a 20% drop in humidity with this device. It’s easily 90% RH in the hangar sometimes out here. Ideally 40% or less for metal but at least below 60% but if it only drops 20% that may explain my purple desiccant.

I saw another company that uses desiccant and a humidity sensor so when desiccant stops drying it heats it and vents it out of the unit instead of into the engine. Once dry it continues pump dry air into the engine.
 
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I am surprised the humidity of output is not lower, if that is tubing going TO the engine. (Assuming input is local environment)

If that is output FROM the engine,… how is that area sealed ?

All to say, don’t they claim output is very dry.

We don’t recycle the air with this device it uses only outside air and “dehumidifies” it according to the company website.
 
i am not familiar with this system but i am commenting on the previous post. if you are not using a closed system than you are wasting your time or are very busy changing dessicant. i am not gonna go thru it but dessicant can contain only a certain % of its weight, you can figure out the weight of water in air at a given humidity and use cubic feet per minute your unit pumps. i have done this and it becomes apparent you will quickly saturate your dessicant.
i have read that many do not recirculate the air. just do the math.
 
I have a simple, homemade dehydrator with an inline humidity sensor. After a flight, I pull air from the dipstick tube before completing the circuit with desiccated air. This is done in an attempt to extend the life of the desiccant. I do this for 5 minutes or so while I put the plane away for the day. During this time, the RH meter usually reads between 80-90% initially and drops to 50-60% by the time I hook up the dry air which enters thru the crankcase breather vent. Within another 5-10 minutes, the humidity level has dropped to 25-50% RH. I hook the system to a timing circuit that operates the system 15 minutes a day. When I return to the plane (a few days or a week later) the RH always is 10-15%. The meter is a very cheap unit from Amazon, so may not be very accurate, but seems show reasonable trends.

I've been running this system for a few months now and have not yet seen any change in desiccant color. (The system has about a gallon of the desiccant beads.)
 
i am not familiar with this system but i am commenting on the previous post. if you are not using a closed system than you are wasting your time or are very busy changing dessicant. i am not gonna go thru it but dessicant can contain only a certain % of its weight, you can figure out the weight of water in air at a given humidity and use cubic feet per minute your unit pumps. i have done this and it becomes apparent you will quickly saturate your dessicant.
i have read that many do not recirculate the air. just do the math.

This style is essentially similar to the way an HVAC heat pump removes humidity from a room, but it is very rudimentary when I took it apart to look inside. The other style is desiccant that is automatically dried and a more expensive set up by a competitor.
 
I have a simple, homemade dehydrator with an inline humidity sensor. After a flight, I pull air from the dipstick tube before completing the circuit with desiccated air. This is done in an attempt to extend the life of the desiccant. I do this for 5 minutes or so while I put the plane away for the day. During this time, the RH meter usually reads between 80-90% initially and drops to 50-60% by the time I hook up the dry air which enters thru the crankcase breather vent. Within another 5-10 minutes, the humidity level has dropped to 25-50% RH. I hook the system to a timing circuit that operates the system 15 minutes a day. When I return to the plane (a few days or a week later) the RH always is 10-15%. The meter is a very cheap unit from Amazon, so may not be very accurate, but seems show reasonable trends.

I've been running this system for a few months now and have not yet seen any change in desiccant color. (The system has about a gallon of the desiccant beads.)

After a regular recirculating system for several years, I made one to purge with 10 L/min for 5 min, then desiccant for 60 min. Both on mechanical timer switches. The purge does not flow through the desiccant, but both are filtered. Sure don't want silica in the oil. If longer than 2 weeks, then it gets another hour of running.

Recirculating contaminated my beads in 6 months. The 2.0 beads last 6 months, and don't stink up the kitchen for regeneration.

I have read all the Black Max material, and it still leaves questions. The operational data is helpful and appears it may be just turned on and off to defrost. I was concerned with my similar Peltier prototype that it was not completely allowing the water to drain out and just sat as beads on the internal walls until it pumped the remainder in the engine. This is why I asked where the water goes.

If a a purge were used, then recirculation of a Peltier device might be the best of all, if the condensation issue is addressed satisfactorily. My engine breather discharge is over the 4-into-1 header and not easily accessible.

The complication of valving and sequencing in my prototype of the flow to blow out the condensate was too big of a hurtle and I returned to the desiccant design with purge.
 
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After a regular recirculating system for several years, I made one to purge with 10 L/min for 5 min, then desiccant for 60 min. Both on mechanical timer switches. The purge does not flow through the desiccant, but both are filtered. Sure don't want silica in the oil. If longer than 2 weeks, then it gets another hour of running.

Recirculating contaminated my beads in 6 months. The 2.0 beads last 6 months, and don't stink up the kitchen for regeneration.

I have read all the Black Max material, and it still leaves questions. The operational data is helpful and appears it may be just turned on and off to defrost. I was concerned with my similar Peltier prototype that it was not completely allowing the water to drain out and just sat as beads on the internal walls until it pumped the remainder in the engine. This is why I asked where the water goes.

If a a purge were used, then recirculation of a Peltier device might be the best of all, if the condensation issue is addressed satisfactorily. My engine breather discharge is over the 4-into-1 header and not easily accessible.

The complication of valving and sequencing in my prototype of the flow to blow out the condensate was too big of a hurtle and I returned to the desiccant design with purge.

Can I see a pic of your device? It sounds like a better mouse trap.
 
After a regular recirculating system for several years, I made one to purge with 10 L/min for 5 min, then desiccant for 60 min. Both on mechanical timer switches. The purge does not flow through the desiccant, but both are filtered. Sure don't want silica in the oil. If longer than 2 weeks, then it gets another hour of running.

I, too, share the silica concern. I have a HEPA filter on the output side of the desiccant.

I've asked one of my son's to make a humidity controller with an Arduino board. It may be a while, but I would like to have a set up that comes on when the RH increases beyond some set point and turns off when it drops below some other point. I'm hoping that, coupled with an intial "open loop" purge, provides maximum desiccant life.
 
i am not familiar with this system but i am commenting on the previous post. if you are not using a closed system than you are wasting your time or are very busy changing dessicant.

I haven't found that to be the case, depending on what you consider to be "very busy". I have a home-made unit using an airtight food container, an aquarium pump, and 15lbs of color-changing desiccant. I used to run it closed-loop (return line attached to the oil separator) but found that it had no effect on the measured humidity in the desiccant chamber (about 15-18%), so I stopped doing that, thus avoiding the necessity of laying on my back after a flight to attach the return line. I expected that the only penalty would be cooking the desiccant more frequently based on how pink the stuff has turned an a rise in the chamber humidity. In this moderately-humid (summer) climate, I find I have to do that about every 6 weeks. Much less in the winter. I haven't found a significant advantage to a closed loop system and am satisfied with the desiccant change vs plug-and-play convenience.

Disclaimer: Climates vary, so my experience may not be universal. Just an anecdote, not actual evidence.
 
I am surprised the humidity of output is not lower, if that is tubing going TO the engine. (Assuming input is local environment)

If that is output FROM the engine,… how is that area sealed ?

All to say, don’t they claim output is very dry.

My understanding from Google is that if the humidity is less than about 40% you won't get much rust, if any. My two measuring points are ambient air, and air just before going into the engine. It is not a closed loop system.

No idea if this thing "works" or not, but seems like keeping humidity less than 40% over a range of ambient temperatures and humidities is a good idea. There might be better ways to do it, but I have not yet found any.

I like the idea of a purge and then a closed-loop desiccant system. I might experiment with that. Also, i'm testing using silicon kitty litter to see if it will dry air. So far I'm only seeing about 10% reduction in humidity. The good thing about kitty litter is it's very cheap, so you would not have to stink up the house drying it.
 
well, i just don't understand how these things work if they dont recirculate . maybe someone can explain. at 70 deg and 100% humidity a pump that circulates only 1cfm moves 18 ounces of water thru the system per day.
 
well, i just don't understand how these things work if they dont recirculate . maybe someone can explain. at 70 deg and 100% humidity a pump that circulates only 1cfm moves 18 ounces of water thru the system per day.

The ambient air is pushed through the desiccant and dried to maybe 25% RH then pushed into the engine. The engine crankcase for a 320/360 is about 8 liters or quarts if you will. At 2 liters/min, the dry air will displace the crankcase air in about 20 min. 60 min is good enough to be sure. For this length of time less water is absorbed from the outside air than is/was present in the crankcase.

If the single pass runs all the time, then yes, the desiccant must mass must higher and/or it will saturate and need to be regenerated.

There are more contaminants in the crankcase (blow-by) than just water, the fuel sulfur creates sulfates that will form some acids, mostly neutralized by the oil additives.
 
Stalled development cause: Ignorance

If you go to the black max website it explains how it works in detail better than I can explain it.

https://flyingsafer.com/2065#:~:text=The Black Max uses an,cooled by a thermoelectric device.

I did look at several of the published descriptions of the MAX. My real question is based on how they collect and expel the water from the airflow to the engine. The collection would certainly be by condensation on the internal walls. But the properties of water to bead and stick on vertical surfaces leave me puzzled. It would seem that the chilled walls would have to be vertical and of such diameter to allow the water beads to grow and then fall by gravity down the walls to a collection point. All of this still allows the water to be within the stream of air flowing to the engine. That is OK as long as the dew point is maintained so it does not evaporate an get into the engine.

This is the basic lack of understanding on my part. It is like cleaning the inside of a tall glass. When it is rinsed there are beads left inside, like in a graduated cylinder. I have trouble cleaning and drying mine and it is more than an inch in diameter. Now, add the challenge of frost and the same phenomena. My ignorance of how to design around this is why my Peltier prototype development stalled.

If anyone has some good pictures of the B Max it might be educational as to how it really works and to address the issues presented.

My prototype thermo electric dryer produced 15% RH @70F stream of air from 90% RH @70F air. Until it froze at an hour + into operation, so it certainly has the ability to reduce the DP.
 
Give Ben a call - he'll explain how his device works. Here is what it looks like inside.

IMG_8039.jpg
 
well, i just don't understand how these things work if they dont recirculate . maybe someone can explain. at 70 deg and 100% humidity a pump that circulates only 1cfm moves 18 ounces of water thru the system per day.

The air pump pumps ambient air through the bottom of a container of silica gel. As the air passes toward the top of the canister through the silica, some amount of water from that pumped ambient air is absorbed, leaving only dried air to go out through the top of the canister in through the engine dipstick. I keep an RH meter on top of the gel and another small container inline in the output tubing before it hits the engine. Those two meters assure me that the air that it being pumped into my engine at about 250 GPH is somewhere between 15% -- 18%. As the silica gel beads absorb water, they turn increasingly pink. That color change along with a rise in the desiccant chamber humidity tells me that it's time to cook the beads which will turn them back to blue.

I used to run second tube from the other end of my engine (breather/separator) to return crankcase air to the pump, so that the pump would only be pumping already-desiccated air. My reasoning for doing that was to increase the bead-changing interval. As it turns out, it didn't help that much and laying down under the plane to put the return tubing on the separator output was more of a hassle than I wanted. I abandoned the closed-loop concept.

Someone here mentioned that that cooking was a smelly process. I haven't found that to be the case at all. I cook 15 lbs in a large roasting pan about every 6 weeks in the summer and I am certain that my wife would mention that if there were noticeable odors involved.
 
Give Ben a call - he'll explain how his device works. Here is what it looks like inside.

Thanks!! I talked to Ben, super nice guy. The cooling cavity for the air will pre-cool and freeze any water in the cavity. In the operating cycle in when the unit is turned off, the theory is ice will melt and collect the condensate in a wool pad at the bottom. A hole there allows liquid to drain out, but everything refreezes before air to the engine restarts keeping the water from evaporating - - -and therefore the DP is low. This part seems pretty well thought out.

They have an improved version where the Peltier reverses, heats and air purges that cavity to reduce the residual water. This is a more active elimination of the condensate and will include a discharge humidistat to ensure the DP is always low and as a failsafe.
 
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Thanks!! I talked to Ben, super nice guy. The cooling cavity for the air will pre-cool and freeze any water in the cavity. In the operating cycle in when the unit is turned off, the theory is ice will melt and collect the condensate in a wool pad at the bottom. A hole there allows liquid to drain out, but everything refreezes before air to the engine restarts keeping the water from evaporating - - -and therefore the DP is low. This part seems pretty well thought out.

They have an improved version where the Peltier reverses, heats and air purges that cavity to reduce the residual water. This is a more active elimination of the condensate and will include a discharge humidistat to ensure the DP is always low and as a failsafe.


Bill, did they say when they expect the new BlackMax version? I have one for my Dakota, but will want one for my RV14A.

Thanks
 
To give everyone an update, the in line desiccant is now turning purple within 3 days. The wife reported it changing color weekly before this while running continuously. Water is still in the tube at the base. Indicator lights on the device all show normal. I’m going to ask her to shut it down and cap off the tube. I have contacted the company, we will see what they say. I have a new device on order called DryBot. When it comes in I’ll report what the inline desiccant will look like while it is continuously used for the remainder of storage time (about 30 days). I’d rather not be pumping any air into the engine if the black max can’t pump dry air into it.

https://www.rpxtech.com/drybot.html
 

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To give everyone an update, the in line desiccant is now turning purple within 3 days. The wife reported it changing color weekly before this while running continuously. Water is still in the tube at the base. Indicator lights on the device all show normal. I’m going to ask her to shut it down and cap off the tube. I have contacted the company, we will see what they say. I have a new device on order called DryBot. When it comes in I’ll report what the inline desiccant will look like while it is continuously used for the remainder of storage time (about 30 days). I’d rather not be pumping any air into the engine if the black max can’t pump dry air into it.

https://www.rpxtech.com/drybot.html

Let us know how the DryBot works out. I have been considering one.
 
I got the drybot in and it’s so easy the wife hooked it up. After 3 days the in-line desiccant test tube has stayed solid blue. We will see what it looks like in a week and 2 weeks but it seems to already preform better than the black max in real world Carolina heat conditions.
 

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I got the drybot in and it’s so easy the wife hooked it up. After 3 days the in-line desiccant test tube has stayed solid blue. We will see what it looks like in a week and 2 weeks but it seems to already preform better than the black max in real world Carolina heat conditions.

Thanks for the pirep. Looking forward to further results!
 
I have the Black Max and I am in NC as well. I had a similar problem with water forming in the tube. I talked to Ben about this and he said the air is flowing too quickly. (I sent him a video of it blowing bubbles in water....) He sent me a 1/4 turn adjustable valve to slow the air output down to make bubbles at a "string of pearls frequency". So far that seems to have solved the issue.
 

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I have the Black Max and I am in NC as well. I had a similar problem with water forming in the tube. I talked to Ben about this and he said the air is flowing too quickly. (I sent him a video of it blowing bubbles in water....) He sent me a 1/4 turn adjustable valve to slow the air output down to make bubbles at a "string of pearls frequency". So far that seems to have solved the issue.

I had the same result when I asked Ben about this and he sent out this kit to me. My issue with this is if I buy a product and it says it’s supposed to do xyz, why should I be the one that has to retrofit or repair said product if it doesn’t do xyz? I would be asking a lot from my wife to do it, and why? It should work out of the box regardless of the flow rate your engine requires. So far the drybot is working as advertised. The blackmax was not plug and play in my case. If I’m going to pay $600 plus for a product it better work. Sorry Ben is a nice guy but business is business.
 
It’s been 7 days and my in-line desiccant is still solid blue while being plugged into the drybot. I should have bought it right as my first option but I guess you learn the hard way. Attached is the picture of the desiccant after 7 days. The black max was turning purple after 3 short days of running.
 

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