Rotary vane compressor

[HenryC]

My new pond will be 8' deep so the concern comes into play about the performance of most diaphram aerators ability to supply air at that depth. It has been recommended that I consider a small rotary vane compressor versus several diaphram aerators. The rotary vane compressors handle the back pressure much better. I looked in the AES catalog and the smallest they have is a 1/3HP model which would provide more than enough air for all the diffusers at the 8' depth. The initial cost would be far less than separate 80lpm or 120lpm aerators, but the power consumption may eat up that savings. For example, an Airtech 80lpm diaphram aerator is rated at 62 watts (not sure if it will draw more power when under load). That times 3 would be 186 watts. The Sweetwater 1/3PH rotary vane compressor is rated at 550 watts when operating at 8psi. 8' depth is roughly 3.5psi so I would think it may draw less in my situation. The cost of 3 Airtech 80's would be roughly $1200 while the Sweetwater rotary vane compressor would be only $400. At the cost of power in my area, I would have to run the Airtechs for 5 years before regaining the initial expense.

The question is, does anybody have any experience with rotary vane compressors? Pro's & Con's?

[dick benbow]

Henry,
I think most pumps warranties clearly state your out of their protected range, maybe think about the rotary....

[Ryan S.]

Thats not an ideal range for a rotary vane, they are great if you need deeper. I don't have the numbers in front of me, but I think its the Airtech's that do so great at roughly that pressure.

[Ryan S.]

Another thought is how much air do you need to the drains, I don't know of any that carry "ratings" or suggestions, but the diaphram itself on some of the popular drains appears by the manufactor to be rated for around 1cfm (roughly 28LPM), over that backpressure really kicks in. An Airtech 40 will give you 30LPM at 9ft, Airtech 80 60LPM at 9ft. You could possibly get by with 3 Airtech 40s. In any case, you would probably want the 80 over the 120 at depth, since it can pump to greater pressure it would better suited in this application.

[mynamy1]

Based on the performance curve of Alita air pumps at fancykoi .... website, three AL80 would produce about 210 LPM @ 8ft deep and cost you $945 plus shipping. However, one AL200 produces about 180 LPM (same depth) at a cost of $700. Not bad of a choice! Furthermore the AL80 has the pressure rating of only 2.18 psi, using them constantly at 3.5 psi would cut down on reliability and durability. The AL200 has the pressure rating at 2.9 psi, not ideal but would last longer. Your ideal air pump would have a pressure rating of 3.5 or larger. So search around .....

Henry, I would prefer two AL120 for your application best. This combo would produce 240 LPM @ 8 ft, 248W, consumption and still has the 2.9 psi pressure rating. The negative side is cost, a whooping $900. Search around for sale and competetiveness!

Rotary vane compressors' biggest problem is noise and make sure you get the oil-less version. MA Le

ps. Your showa (with traces of sumi on her face) is so nice. You can send her to my pond any time!

[mynamy1]

Doing a Google search, I found the HiBlow HP series that has pressure rating of 3.5 psi or larger. Good luck Henry! MA Le

[HenryC]

Thanks for the replies. I may end up going with the new Sweetwater line of linear air pumps. First, since AES is right here in town, I can get spare parts quickly and they have always been great about warranty issues. The SL94 has a maximum warrantied depth of 180" (15 feet) and will pump 70lpm at the depth of 8 feet. AES gives a discount for quantity so if I use them for the 2 Nexus units as well, I should be able to get a pretty good discount.

[bekko]

A very minor consideration could be the carbon soot produced by oil-less rotary vane compressors. The vanes are made of sacrificial carbon and are designed to wear down over time. This keeps them seated properly (no air leaks) without the need for oil. As they wear down, the carbon is blown into the air lines and sort of makes a mess of things. It would take a very long time before enough carbon is worn down to actually clog a diffuser or something. The soot is mainly an aesthetic issue.

A larger consideration is that rotary vane compressors can be a little loud. The ones I'm familiar with had a high-pitched whine. You might check to see if the specs provide an operating decibel level. The diaphram units have a lower-pitch hum.

I would opt for the lower operating cost and the safety factor provided by having multiple units (in case one goes kaput).

-steve hopkins

[mynamy1]

Steve, good contribution and great science and common sense as usual. The rotory vane compressor has a shriking loud metalic noise that drive the neighbors and the wifes off the wall! I suspect this noise can suppress, or, even cancel out all the advantages of FIR!

Henry, AES re-labels somebody else products and charge premium price. However, good warrantee is AES's add-on value. A diaphram air pump is a simple electro mechanical device that is so reliable that I just wonder if the money is well spent? MA Le

[jwhite]

Henry, when I was rebuilding my pond about 8 years ago I put all the koi in the swimming pool which was 8 feet deep at one end. I am pretty sure that I ran two of the larger 9 inch diffusers off one of the smaller outdoor linear type pumps. Sorry, I can not remember the tech info, but I know they worked fine at that depth.

Joe