Pond Boss Forums AERATION Systems questions Moisture issue in lines

OK - didn't take long to move the pump to bank and run directly into the manifold - everything is heading down into the water now. With the heat of the pump, I expect all to be OK as far as freezing now. I put a plastic cover over it and left one side open for the manifold. I figure I can change it back in the summer - just one more prepping job when winter comes each year.

Now for the new problem - I think it is anyway.

I am currently running 3 diffusers and plan to use just the shallowest one thru the winter. I just closed off the other two for a quick check and hear my pump clearly go from an "idle" to definitely building back pressure with only one diffuser in use.

Is this an issue? Should I do something to vent some pressure when I go to one diffuser? If so, what is the best method? I can just pull a line off and use the manifold valve to bleed it if that is acceptable?

10x, higher pump pressure means much more pump wear. You can use your pressure gauge and simply dump some air to reduce flow/pressure to the single diffuser.

I am sure you accounted for this but, just in case, does your plastic cover provide for good ventilation to the compressor? They can over heat, even in winter, without good ventilation.

Thanks for the info - yes, the side that is open is plenty large for ventilation but thanks for the heads up - I will monitor closely for a while.

I will just open one of the other valves with the line removed to dump air when I change to using one diffuser this winter. Just wanted to know if that was an acceptable way of relieving the pressure.

That's how I did it last year and it worked fine. Just make sure you cover the end of the airline you disconnect to keep stuff from getting in there.

It works fine, but the constant hiss of escaping air is maddening. To a mechanic, anyway.

Accumulating back pressure when using just one diffuser indicates the diffuser does not have enough holes to allow all the air to escape. Enlarge the diffuser for next winter's operation. Why waste the air when it could be creating a larger ice free area in the pond?

It's even more maddening to a dimwit like myself that these compressor companies keep churning out canned electric motors that you can't do a darn thing with to vary the output to meet conditions. Oh, I could rant on this for hours!!

Could you possibly use a medium to coarse bubble diffuser for winter? That could possibly let more air out to clear ice, and just open a winter valve?

Awesome thought! Had not occurred to me. If my well pump can run at whatever speed it takes to maintain pressure, why can't my aerator pump. Let me know when you start looking for investors man. I'm in!

I would imagine those off the shelf motors are relatively cheap, but I do like the idea of variable control. Wonder if the compressor efficiency (from an air-producing standpoint) would decline as rpm dropped? ( more time for leakage as rpm decreases)Seems like it might be more of an issue for rotary compressors vs. piston, but then again as the cups and valves wore I would expect a loss there also.

Sometimes higher rpm can compensate for worn components. For a time, anyway.

Affinity Laws.
I recently bought a little 1/3hp Marathon 3 phase motor to adapt to one of my pumps. This sucker will hold zero speed with full torque from one of my PowerFlex 525 drives, and zing to whatever you want it to do within it's threshold. I don't think I can truly explain how awesome some of this stuff is.

I agree. The variable speed would definitely require a fixed displacement pump to make sense. Theoretically, when subjected to a constant load (back pressure), pump life for a fixed displacement pump is determined primarily by number of cycles. When parts start to wear, the motor would need to run faster to compensate for the loss in efficiency. The speed control input would either need to be pressure or flow.

This is one of the few speed controls that will work with some of the single phase compressors: Dart 55AC

I was going to order one last spring for my 75R compressor, but never got around to it.

There are some VFD's available, but price is outrageous, and you'll fry these PSC motors from Gast.

Not necessarily. Rotary vane compressors are quite popular in factories for supplying required air flow at a constant pressure.

Look at the graphs for the Gast rotary vane and you'll see what happens when you change the speed.

Sorry. Poor choice of words on my part. I should have said positive displacement not fixed displacement. A variable or fixed should work as long as it is a positive displacement type of pump.

JKB,

I agree a vane pump would work. They are also a positive displacement pump. Pumps that I think would not work as well are centrifugal pumps for example.

Rotary vane compressors are kinda sorta like a positive displacement compressor, but not true in nature as a piston compressor would be.

The affinity laws would not apply to either of these, but they would on a centrifugal water pump and air moving devices like fans and blowers. Ring compressors (Regenerative Blowers) are a different animal as well.

Nice thing if you get a decent VFD to run your pumps and compressors with, you don't need sensors for pressure or flow. SVC (Sensorless Vector Control) has made some pretty impressive improvements over the years.

What I mean by a canned motor is one specifically made for each of these compressors and will not fit much else. Privy and exclusive to the manufacturer.

Now, what I would like to see is these people adapting NEMA (off the shelf) motors so we all have options.

I think I mentioned the small motor rule that took effect this spring, but these guy's squeaked by that so you'll all have to live with it. It was actually a screw up on the gub part, but think private dollars to the right people played a major role

If a person uses a moisture separator, it would be important to remember the separator itself would need to be protected from freezing somehow.

If a person could add a relatively large air tank after the compressor and before the air line with the air running through the top of the tank (so the air has a chance to cool and condense before entering the air line) with a drain on the bottom (that could be drained in above freezing temperature times) it might help. Another form of moisture separator but would not hurt to freeze in the bottom of a rounded bottom tank (horizontal type tank like a tire air bomb) as long as the water level was not over half full. Some alcohol could be added to the tank to prevent freezing. That is what truckers do to the air brake lines and air tanks in freezing weather to prevent their air brake type brakes from freezing up.