Fridge Motor Air Pump

[Ca++]

Anyone tried this? I'm about done with typical air pumps, and the turbo fans used in cordless hoovers seem just as loud. I'm thinking a fridge motor could cut it. Perhaps a 12/24v one, as DC motors can be slowed, and don't have that AC noise. I think Samsung might be using EC motors by now, but DC seems like I might find a used one in an RV fridge.
I have been looking, and they seem to move some air. I know air compressors can use them, and 300 sheets could buy such a thing. I fancy the DC one though, to really slow that reciprocal mass down. Looking for actual silence.

I'm aware the motor runs in oil, and that the outlet pipe needs an oil separator. I would add a res anyway. Perhaps a 2L bottle, as I use anyway. I think it's likely the $10 part called a drier in most systems. I'm yet to look. It's just not an issue, but worth recording the fact for readers years from now, who might jump on the idea without realising. The youtube is full of such examples.



Has this been done? I have an idea regarding a number of buckets with a stone each, which means investing some effort anyway. I can silence the air flow to the stones from pulsing easy enough. That many pumps though... I hope just one fridge lump will do.

 

[Creeperpark]

I would just buy a couple of extra air pumps a year because they are not expensive. .

 

[Ca++]

I like that a fridge motor is a cheap option, but it's the noise why I don't want typical air pumps. I buy whisper one's that win awards, but they are only marginally better than cheap ones. Needing inline buffering so the tank doesn't shake, and hanging by elastic to reduce more direct vibration problems. The feet they come with being a joke. They are, in fact, a vibrator. A very reliable design, but very rough. I'm still getting spares for one I have used since time began. They just haven't moved on.

Even bargain brand garage compressors have fridge options. I feel sure I can do better with DC one's though. Or perhaps a vvvf drive, but that's still AC.

That's just a foot across (the size of your foot might vary) and is 43db. A Tetra AP150 tested at 42.3db doing a 5th of the air. Or for a similar air volume, you could use 3 AP300s making 54db.
I want 30db.

It's all a bit poorly measured though. What the sound meter says isn't my main focus. Vibration is the problem. Noise traveling through the building structure, and coupling to other surfaces like a loudspeaker driver.

I have been looking for years. Reliability holds back a lot of choices. Having a pair of pumps is the ultimate answer, but most of us compromise on that.

 

[Three Berries]

There are oil separators, filters and dryers that you put on the air out line. usually a porous stone type filter and then desiccant if needed for moisture. Oil separator is a baffle type thing usually.

 

[Ca++]

Thanks pal. That pretty much aligns with what I was thinking. Oil separators and catchers are common enough, and in this instance, they just let to drop back down the pipe it came from.

I had a dream, where I found not just a DC, but an EC compressor. With an external board to mod the speed. Without any pumping at all, but instead a rotary design. Then I didn't wake up.. I realised it was real.

Straight into the wank bank with that image

 

[Hiddenjems]

Why not just mount your pump/compressor in a baffled enclosure and run hard lines with valves to your rooms?

If you’re running a bunch of buckets with stones you don’t want one pump per bucket. I know if I have 20-30 of anything, at least one fails randomly, at exactly the wrong time.

 

[Hiddenjems]

Thanks pal. That pretty much aligns with what I was thinking. Oil separators and catchers are common enough, and in this instance, they just let to drop back down the pipe it came from.

I had a dream, where I found not just a DC, but an EC compressor. With an external board to mod the speed. Without any pumping at all, but instead a rotary design. Then I didn't wake up.. I realised it was real.

Straight into the wank bank with that image

The refrigeration pumps are quiet because they’re mounted to rubber mounts inside that tank. They do work forever if ran properly.

 

[Ca++]

I have never been happy with air pumps. In my grows you can hear things like the timer ticking, and the phone charger I have running fans over my cuttings. The air going in though a 600x150 carbon, but not going through the 4" fan a few feet of flex away, which is set at 40%. I selected my quietest 400 mag driver, which was the loudest mains hum by far. I like descent equipment.

Perhaps the fridge motor isn't the best idea, but I'm struggling to find a better one. I know with air pumps I will have to build quite a box and suspend it, but it's the pneumatic dampening to. It's will take up valued space, and isn't the nicely engineered solution I'm looking for. It's more of the same, and I don't even want one of them really.

The fridge pump is reciprocal, but that motor mass is a flywheel, that the air pump lacks. Then there is the frequency issue, where a 60hz air pump is abruptly changing direction 120 times a second. A fridge motor is likely to have 4 or more poles for torque reasons, and the piston change direction more smoothly. With an EC motor, that vibration situation effectively evaporates. Such that a pneumatic arrestor of some sort, is perhaps not even needed.


I have a build coming, and the schedule is now saying this won't happen. F&D pebbles is looking like soil drip again, and tbh, cleaning pebbles is going to be too noisy. I may have to stick with drip, that has no use for air pumps at each site. Though I keep looking... It's another a life long mission.


Edit: With two pumps, I would feed each into a common manifold, through non-return valves. A pump dropping out would loose capacity still, but unload the remaining pump to work a little better than it did in the pair. The real gain is running just one common set of pipes and stones though. Not two entirely separate systems.

 

[Hiddenjems]

Sounds like what you need is a small roots air pump driven by a dc motor with a controller.


I’m not sure, but I think there are some high end airbrush pumps made that way.

 

[growshopfrank]

There may be a issue with duty cycle for the fridge motor.
Seen small styrafoam coolers with some small holes punched in them used as quiet boxes for loud air pumps.
With reservoir based systems a smaller submersible pump running in the res can be used to increase aeration with the possible downsides of temperature gain or fertilizer element precipitates.

 

[Ca++]

It's a roots I often search for. I end up looking at hoover parts.

A pump in the tank could be alright, with some sort of venturi to draw in air through a tube. Aiming for nanobubbles. That would be a worthy sacrifice. I have found 3 very quiet pumps in a res can make the mains water pressure that some nanobubble venturi's want. It seems perfect... but I can't find a supplier. A ready made box has little interest in hobby level noise control, or pricing. I don't even see them in commercial use by green growers. Which suggests it's not as a good a tech as it's touted to be. It seems like a must have item, when you spend some time on the subject. With projects in open river mouth's turning sludge to life. h2o2 starts to look uninteresting.

Dead company email with sea water capable nozzle https://oknozzle.com/products-2/standard-nozzle/#h02

It seems carbon nanotubes are the ideal way of blowing nana sized bubbles. Again.. I have failed. Though perhaps I could stop looking for something ready made, and just look at nano tubes.

The fridge motor can make some real pressure for airstones with tiny pores. Though I'm aware it could fire one through my window also

Edit: I hit a snag. A nanotube based nozzle, wouldn't pass a lot of impurities. My searches took me to water filtering applications, based on movement through osmosis.

No.. I won't be sending my RO filter through my window, but the idea has some merit

 

[Hiddenjems]

This looks like a good design to copy.

​

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[Ca++]

I was just looking at that motor set somewhere. It's remarkable that a 750w AC motor can make so little airborne noise. It also shows how much better we can do, using something like the DC screw designs you spoke of.

This is my room

I will break in down, for those unfamiliar with such analysis. Top half first. We see yellow trace, as our typical spectrum analiser. The red is the peak hold. Making the red a better gauge. My mains frequency is 50hz, and 50hz is almost absent. 60hz-2khz is my noise bandwidth. So my room isn't humming away with the monotonous noise of AC powered items.

The bottom half is a waterfall. The db scale down the side is a red herring. Though it does tell us the -70db noise is painted with pink. While -120db is black.
What the waterfall shows is is the history. Lets say it's a 100x100 bitmap image. The top row of 100 dots, are right now. The second row down, were a moment ago. The third row of dots, just before that. The bottom row of 100 dots is about 15 seconds ago.
Look at the 855hz peak in the top graph, then look at it's prevalence in the waterfall below. I have a constant 855hz whine as one of my main concerns, stood where I was. However, in fact, it is only stood right there, and is a function of the 2khz noise my extractor produces. Stood where I was, the 2khz was nulled by standing waves in the room, and this 855 created. We know tones shift, like the bass amplified down corridors. This is why I have the 855hz not the 2khz. If I go to the fan, the story changes. The 60hz is a pair of 12cm PC fans (arctic p12) running at 10v. Fans knowing for being very quite. The 176hz peak doesn't show in the history, as it was not always there. It was me touching the screen to pause the recording. These are the noise levels in my room.


I need something quite a bit smaller than 750w. A typical under counter fridge is about 250w. Which is still a few big fish tank pumps in output. These designs are really about small parts running very fast to make pressure though. I'm trying to slow it all down. I perhaps should of said, but I have a couple of little air pumps for smaller tanks. I fancied 8 outlets though, with big stones. The 750w compressors 40db is very impressive. It makes me more determined to do better.

I saw a youtube where someone opened an AC compressor and actually swapped the motor for a DC one. Lots of cutting and welding though. I don't weld. I'm hopeful a big fridge with good noise and energy figures will provide a motor. I can't keep stopping to look at scrap white goods though. I look like a hobo.


I know they are out there now, and want it

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[Three Berries]

Why not just mount your pump/compressor in a baffled enclosure and run hard lines with valves to your rooms?

If you’re running a bunch of buckets with stones you don’t want one pump per bucket. I know if I have 20-30 of anything, at least one fails randomly, at exactly the wrong time.

Where I worked they had a huge double pump set up for back up. Big pumps that if they failed everything flooded. Worked great as they were programed to cycled between the two over time to 'share the wear'.

Well when one goes the other isn't far behind so you better stay on top of it.

 

[Ca++]

These pumps are so close now (keeping in mind my wait) and are 150 sheet items found in washer/driers of even budget brands. Used for heat recovery, in a market where people are aware of energy efficiency when buying products.
I'm really looking forward to there use in dehumidifiers. The variable power of them, will stop machines cycling so much, and if well sized to the application, they will just find the right running speed and keep going. Without the 'brrrrrrr' noise, and with less heat generated, and electric used. They are just holding out on us really. It's there.

These pumps have that can shape. Even in larger sizes.
Short clip of pumping arrangement, and electronic motor drives effect.


It's still designed for pressure though, not volume. The volume is there, but the motor won't need to make any effort to spin up.

 

[Ca++]

Poking around this topic again, I see a typical aerator is 0.35psi to deliver bubbles at 10" deep. Typically less than 100L per hour.
I have seen the little blower fans around $50, smashing this.

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At that 3Kpa, this pump will supply 40,000L
It's not what I want though. It's just more of the same.


We are using medium pore diffusers, giving 1-3mm bubbles.
Fine pore diffusers make 0.5 - 2mm bubbles. This takes a little over 0.5psi, so we likely use them, and the above fans ability is barely impacted (3Kpa was 0.45psi anyway)
Ultra Fine make 0.1 - 0.5mm bubbles. This can take 25-50psi

Suddenly I find something a bit more interesting. These are usually run from bottled gas, such as oxygen. We know we can get an oxygen generator that's not astronomically priced. 50psi is back to the fridge motor though. Which tbh is available and quiet. 250psi is nothing for one though, so unless you are very handy, it's going to be better to buy the fridge motored compressor, that you can dial for the right pressure, and has a safety valve fitted to a vessel that can take silly pressure. Not just a rubber hose, you hope pops off

The micron-sized bubbles produced by the ultra-fine bubble diffuser ensure a very high gas transfer efficiency. Typical Applications Aquaculture: For supplemental oxygen to boost fish densities and for emergency backup. For fish transport by truck, barge, boat or plane

Pic of what they sell, and setup info: https://pentairaes.com/media/docs/DYPFP4-DYPFP24_flat_diffuser_plastic_base_0213.pdf

The price list ($45 - 200)

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I'm not quite ready to move on this, but I do see some of this kit being useful in larger opps. Larger, where a compressor isn't ridiculous

Plus that oxygen generator needs looking at, as it's little more than a post I once read (before I looked at ozone as a more likely option)

This $300 New device, makes 1-5L of oxygen per minute. 300L per hour, of nearly pure oxygen is useful, when a 4 stone air pump is about 300L.

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The air around us is about 20%, so about 90% through any airstone is good, but microbubbles really make it happen.

We can't ignore the power bill for all this. We might be near 500w, flat out.

 

[Drop That Sound]

They make much smaller battery powered portable oxygen concentration devices for medical purposes now too. Super compact compared to the bigger units most people use.

I'm guessing you already looked into the "o2 grow" emitters, using a cell with SS or titanium plates to split the water back into pure hydrogen and oxygen via electrolysis.. Get all the DO you need with virtually no noise at all. Here's how to make your own for pennies on the dollar!

 

[Drop That Sound]

Have you checked out vortex tube chillers, that use compressed air with no moving parts, and a little bit of black magic to separate hot and cold air streams?

I see they can be replicated using regular PVC and some fittings, or even 3d printed now days. Practically free if you can make your own.

If you were to use one large centralized air compressor with extra storage tanks for a large commercial sized grow, not only could you power all the pumps for air or water re-circulation (or just about any mechanical device!), but you could chill your hydroponic solution by blowing the cold air from the vortex tube right into it. Get your DO and chill your system at the same time!


The larger you scale up, the more efficient the vortex chiller idea seems..

 

[Drop That Sound]

As soon as I finish rounding up my copper tubes for my water cooled SIL fixture, maybe I'll try printing\fabricating a vortex tube, and create the first vortex chilled LED grow light by pumping the chilled air through the pipes and blocks instead of coolant. Just for fun

 

[Drop That Sound]

Perhaps you could use the fridge compressors to power your own mini homemade o2 concentrator, that only puts out enough that you won't turn the grow room into a bomb.