Sicce pumps

[Bax]

<a href=showthread.php?s=&postid=10717009#post10717009 target=_blank>Originally posted</a> by hahnmeister
60-70 lph per square inch of neck diameter is the ideal. So 8" neck is good to about 3500lph. 6" is good just up to 2000lph. If you go higher (like 100lph/sq. in.) then you can have more frequent overflow problems because bubbles will get shot up the neck too fast.

ostrow

I've been planning this based upon information like this quote above. Given the 8+" diameter body, 30" overall hieght and that my two siccis will not be over 3000 lph, I have been thinking it should work well. I have tested one meshed sicci on it and it can definitly handle more than the one sicci. I figure if it's too much, I'll run on as a recirc and one as a feed.

Any thoughts?

 

[ostrow]

The BODY on the G4 is 8". The neck is 4".

 

[ostrow]

The BODY on the G4 is 8". The neck is 4".

That quote ... I wouldn't go much by that. Sorry Hahn but it just doesn't hold true.

That said, a G4 can't handle 2 Sicces.

 

[hahnmeister]

And why would you say it doesnt hold true?

 

[manderx]

and why would you say it does hold true?

and what is a 'square inch of neck diameter' anway?

 

[JCTewks]

simple math. radius squared X PI.

so a 4" neck has 12.5668 sq/in of area X 70lph=879.676lph/60=14.6612 lpm.

 

[JCTewks]

The height of the neck to some extent will affect how much air it will handle....well, it really just determines where your water level will be at for good skimate production.
I was able to put 10 LPM into my Octopus DNW110 with a 5"X20" body and 2.5" neck...but the water level was 3" below the top of the body I added an 18" neck extension for a total neck length of about 23" and could still only put about 7lpm into it without having the water level down into the body a lot. I'm currently feeding about 5lpm without the neck extension and the water level is right where the neck comes out of the cone. By hahns figures that 2.5" neck can handle 4.908-5.727 lpm of air...so i think his figures are pretty close.

 

[hahnmeister]

Yes, 1/2 diameter squared x 3.14 = square inches.

Dont get me wrong, you can go above these numbers... there are many skimmers that do... when you go above 100 though, you are more overflow prone... and yes, the height of the neck plays a role as well, but in most cases, the ideal neck size is 60-70lpm/in2. Sure, standard pipe sizes can cause this to vary (usually for a higher number than lower), but they still hold true.

I got these numbers by getting the stats on all major skimmers out there... H&S, Deltec, ER (note: 80, 750, 1000 are over 100, yes, but these models are also overflow prone), BK, ATI, Tunze, Grotech, ASM, Octo, etc. The stat isnt out of thin air. And it only covers the diameter, not the height. The height is a very subjective thing... in general, when in doubt, go taller... since you can always raise the water level above the reducer (it should be anyways), but you cant lower it past that point w/o problems. I will also note that this does not include becketts... they are a different beast all together.

What matters most is the throughput of air per square inch, since the water level can be varied anyways, and as long as you have a proportional height, you should be fine. The transition to the neck also varies the final neck height. Skimmers with 'flatter' transitions (like the ER shape) often need taller necks. Skimmers with the tall cone bodies dont need as much. But like I said, all Im talking about with those figures is the throughput, so cross sectional area/square inches is the primary concern. When you look at the maximum flow through a bulkhead/hole, the length isnt a concern... or the maximum amount of air that a skimmer diameter can take... the height doesnt play a role. Its not like a 6' tall 8" diameter skimmer can take more air per square inch than a 2' tall 8" diameter skimmer just because its taller. The most you want to put through an 8" diameter body is 1800lph.... short or tall. Same goes for necks.

 

[Bax]

Thanks all for the input to this tread.

Once again, I've miss applied some important pieces of information, AGAIN, ( that neck vs body diameter thing) my fault, and spent a lot of time playing with mods that won't work in the long run (mainly of my own misconstrued design) . But, I am learning a bit more about skimmer construction each time. It is threads like this one that really put out a lot of solid information out for those of us who are otherwise skimmer challenged to sift through and mull over.

Thanks again

 

[ostrow]

Experience tells that those numbers are wrong as far as how skimmers work. Look at the Reeflow with its 6" neck for goodness' sake. Look at the bubblekings.

In any case, my skimmer can handle much more air than I am putting in (becuase I can still lower the water level quite a bit). I may see if I can push the Sicce's some more -- but gonna wait a month or two first.

 

[hahnmeister]

There are some exceptions, but the ReefFlo and BK's are close to the numbers as well. The ReefFlo is on the high end, dont get me wrong (120-130) but its also a recirc so it is less sensitive. And, nobody said 6" diameter was ideal for it either. 8" diameter is better for 3600lph. BK's follow the guidelines though. Their skimmers were part of how I came up with the original numbers.

 

[ostrow]

Starting to get a nice foam head on mine. Will post pics again perhaps tomorrow.

 

[pescadero]

<a href=showthread.php?s=&postid=10390420#post10390420 target=_blank>Originally posted</a> by rishma
not sure if the QO start-up issue are is related to the mesh mod. That is a consistent complaint about the QO3000.

i wonder if anyone has weighed their impellers before/after modding them to see if there's a difference in the weight of the native impeller vs. the mesh mod impeller. with any magnetic pump that has no internal moving parts, there is a limit to the available startup torque. if its exceeded, the pump will try to change directions and you can get stuck in an endless loop.

the docs for the QO3k explicitly state that this is not abnormal. has anyone read them? with an unmodded impeller, if the startup torque is exceeded the pump will reverse directions "in an effort to clear itself of an obstruction." eventually the (stock) impeller should start rotating in the right direction, as the motor only provides enough torque to run the impeller in one direction because of its rounded blades.

when a mesh mod is performed all of this "normal" behavior gets thrown out the window. the mesh provides a very high resistance to water flow (or to the impeller's rotation in the water). if you pack too much mesh in there, you might easily exceed the limit of torque that can be supplied by the motor. perhaps taking out a layer or two of mesh (instead of packing as much mesh as will physically fit into the volute) will help to solve the problem.

at any rate, its seems to be well established that the QO3k doesn't have excessive amounts of startup torque. i wonder if by adding enough mass or by adding sufficient impedance to rotation of the impeller, those who are having startup problems after a mesh mod may have simply exceeded the amount of available startup torque that the motor can provide.

with all of the attention that people seem to be paying WRT watts, VA, and SCFM, its somewhat surprising that nobody has taken any torque measurements. it would be interesting to see if anyone could address the inertia & torque issues WRT startup problems. FWIW, i'm not having any startup problems with any of my QO3k pumps. i have two. they have had their I/O ports modded to improve flow but they both have the original impellers.

 

[JCTewks]

I think the main reason that nobody is measuring torque is we just don't know how. I'm giessing that any sort of gadget that could do that would be quite expensive also...and for $60 I got a kill-a-watt and a dwyer meter and can test RMS watts, VA, and SCFH on anything I have. I think it would be a very valid test, I just don;'t know if it would be simple enough for most of us sideline DIYers to do

 

[hahnmeister]

Torque on AC motors isnt constant anyways... the alternating frequency has 'lulls' in between poles, so its not something you CAN exactly measure with a simple instrument. The easier way would be to crack one open, take some specs, and run it in a simulator.

 

[pescadero]

<a href=showthread.php?s=&postid=11394394#post11394394 target=_blank>Originally posted</a> by hahnmeister
Torque on AC motors isnt constant anyways... the alternating frequency has 'lulls' in between poles, so its not something you CAN exactly measure with a simple instrument. The easier way would be to crack one open, take some specs, and run it in a simulator.

yes, the problem is that on a single phase motor, current lags behind the voltage because of the inductance in the coils. split phase motors are pretty lame in terms of the starting torque that they can produce. that's why single phase motors that require more starting torque will use caps or shaded poles. suffice it to say that the inexpensive motors in our QO3k pumps are probably split phase motors, and their startup torque is only going to be about 100% of their rated running torque. hence the problems people have noticed after modding them.

if anyone wanted to get really g33ky with this stuff, you can calculate torque and motor parameters without motion sensors. you can derive the numbers by sampling the waveforms at the motor terminals and doing some math. although the math for this stuff is a little advanced, i don't think that you'd need a bench full of expensive test gear to pull it off. anything that would perform AD/Da conversion could be used to collect the data. you could probably do it today with the garden variety PC sound card.

 

[hahnmeister]

"...and their startup torque is only going to be about 100% of their rated running torque..."

Typo maybe?

 

[pescadero]

<a href=showthread.php?s=&postid=11397304#post11397304 target=_blank>Originally posted</a> by hahnmeister
"...and their startup torque is only going to be about 100% of their rated running torque..."

Typo maybe?

not really a typo, but more of an incomplete statement. the startup torque range for a typical split phase motor is anywhere from 100% to 175% of the running torque. while being inexpensive to produce, this kind of motor doesn't perform well when faced with high impedance to rotation at startup. if the QO3k pump motors are split phase motors (i suspect that they are based on their size and price point) this could explain why so many people have startup problems after modding them. the window for success WRT torque limits is small and easy to overshoot. the result will be failures to start.

I googled around looking for supporting info. (torque limit split phase motor) I found this at the LEESON motors web site's page on Characteristics & Applications of Split-Phase motors:

The split-phase motor's simple design makes it typically less expensive than other single-phase motor types made for industrial use. However, it also limits performance. Starting torques are low, typically 100% to 175% of rated load. Also, the motor develops high starting currents, approximately 700 to 1,000% of rated. Consequently, prolonged starting times cause the start winding to overheat and fail; so don't use this motor if you need high starting torques.

granted, i'm no motor design engineer, so someone else might have something better to say about this than I do. but if we're dealing with a very inexpensive split-phase motor in our pumps, this could explain why people are having startup problems after modding them, and why the motors are burning out after prolonged/unattended failures to start.

 

[kentrob11]

How loud are these pumps mesh-modded and submersed in the sump? I was considering using one of these but need it to be QUIET! Are they as quiet as the Eheims are? Thanks...

 

[ostrow]

The only noise is from the air being sucked in but if you wish that can be muffled. The pumps themselves are silent -- at least the 5 that I have used all have been