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All of the tests that I've seen show that the aerator pumps are significantly slower than reversibles. The problem is that their flow rate is greatly reduced by any amount of head loss (pumping up against gravity in this case) - you will never reach anything close to their stated numbers like "1200 gph" in any real world application. The impeller pumps do not suffer as badly and will operate much closer to their stated numbers.Quote:
Originally Posted by trayson
Interesting. I had a ballast puppy (640GPH) in my Supra that was hooked to a 370 pound tube sack. I had both the Rule 2000 (1200GPH) and a Attwood Tsunami (1200GPH) as over the side pumps to fill 750's.
From what I remember it took about the same amount of time for the impeller pump to fill a bag to about 350 as the aerators took to fill up the 750 bags. Of the two aerators, the Rule was actually faster than the Tsunami.
The impeller might have finished 350lbs a little before the aerator finished around 700lbs, but it certainly wasn't done in 1/2 the time of the aerator. So my first hand experience was that the aerators were significantly faster. I probably should have timed it to be more scientific, but honestly I just wanted to start surfing instead of documenting results...
I guess I'm in the minority but... while there may be some efficiency loss with the aerator going uphill to the sacs (??), I've timed mine and they take a little over 7 min to fill an 1100 to about 95% capacity. Setup properly for priming with vented loops and check valves I'm going on 3 years without a single issue in my aerator system.Quote:
Originally Posted by gregski
I could see the benefit and ease of reversibles if you have timers on them, but don't timer modules run about $150 a pop?
The most scientific test I've seen documented was over at centurioncrew. I posted the summary here: https://forum.moomba.com/showthread....104#post232104 His motivation was to study the effect of the sprinkler valves (and removing the internal springs) but he also tested with a brass shut off valve which is more relevant since it would add a little more resistance but not much overall and is probably representative of the loss going through the various couplers and connectors in a typical system.
For starters, all of the aerator pumps only perfermed at about 70% of their spec in his unrestricted test (3' of 1.25" hose only). Then, as soon as you add some more resistance in the form of a shut off valve, the aerator performance drops to <40% of the spec number. The impeller pump? It lost about 8%.Quote:
Here are the results for the Johnson Ultra Ballast pump:
Advertised @ 13.7 GPM or 822 GPH
Unrestricted Test: 13.5 GPM or 810 GPH
1” brass 12 vdc valve: 12.5 GPM or 750 GPH
Here are results for the Tsunami 1200 aerator pump:
Advertised @ 20.0 GPM or 1200 GPH --- Actually should be 1100gph or 18.3gph @ 12V for comparison
Unrestricted Test: 13 GPM or 780 GPH
1” brass 12 vdc valve: 7.5 GPM or 450 GPH
The loss isn't due to efficiency, it's just a fact of the pump design that the manufactures tell you about.Quote:
Originally Posted by bergermaister
Here's the spec sheet for the Tsunami: http://www.attwoodmarine.com/userfil...bilge-spec.pdf
Their spec is 1200 gph @ 0' and 900 gph @ 3.3' of head. (0 gph at 11') -> 25% loss in flow (and remember the "real world" performance is probably half of their spec)
And a spec sheet for the Johnson Ultra Ballast: http://www.pumpvendor.com/media/john...690_series.pdf
Their spec is 822 gph @ 0 psi and 810 gph @ 1.4 psi -> 1.5% loss in flow, almost nothing
(note: 1.4 psi = 38.8 inH2O or 3' 2.8" so these are comparing the same thing).
The Johnson pump doesn't lose flow rate but it does increase current draw. The aerator loses flow but uses the same current. Pump design is a trade off.
Combining the data, I would estimate that the real world flow of the Johnson pump would go from about 750 gph to 743 gph as an 1100# sack fills (to 24" high). Likewise, I estimate the Tsunami would go from 450 gph to 383 gph.
I used the 1" brass valve test as a starting point to represent the real world head loss and then calculated 60% of the change of flow due to head loss at 39". Note that this is all based on pumps installed such that they have to pump the output water upwards against gravity. It would be a totally different thing to use one "over the side" where the pump is held above that ballast bag. Flow would probably be close to the "unrestricted test" or better if you actually set up a bit of a siphon.
Overall, my point is there's much more to real world performance than a spec like "1200 gph" but I do believe the available impeller pumps are faster than aerator pumps. They are also more expensive.
Quote:
Originally Posted by bergermaister
Okay, let's take Berg's real world test then.Quote:
Originally Posted by gregski
His claim: 95% capacity of an 1100 bag in "a little over 7 minutes".
So crunching the numbers 1100 pounds * 95% = 1,045 pounds.
Assume that "a little over 7 minutes" = 7.25 minutes. That means that he's theoretically getting 144 pounds/minute. That converts to 1,036 gallons/hour. If we compare that to your assumption of the real world rate of a Johnson, Berg's pump is over 38% faster than the Johnson.
So, I am pretty confident that Berg can tell time. However, I'm not totally sure that he's spot on with Capacity estimations (You should see the drunk texts he sent me one night after a "few" beers).
So let's tweak his capacity number to be more conservative and look at the range of possibilities:
95% capacity = 1036 GPH
90% capacity = 982 GPH
85% Capacity= 927 GPH
80% capacity = 872 GPH
75% capacity = 818 GPH
70% capacity = 764 GPH
65% capacity = 709 GPH
If we assumed that the Johnson had the your real world estimate of between 750GPH and 743GPH, then the fill time would be as follows:
750GPH to 95% capacity = 10 minutes
743GPH to 95% capacity = 10 minutes 7 seconds
750GPH to 65% capacity = 6 minutes 51 seconds
743GPH to 65% capacity = 6 minutes 55 seconds
So, my takeaway from this is that for the speed of Berg's aerators to be equal to your Johnson real world estimation, that means he'd have to be grossly mistaken and think that a 68% - 69% full bag was 95% full.
Likewise with Berg claiming that an 1100 bag fills to 95% capacity in 7.25 minutes, if we then assumed your estimate of a real world flow rate of 450 to 383gph, then that would mean that Berg is claiming that a bag is 95% full when in fact it's only between 42% and 35% full.
In summary, I think Berg could certainly be over-optimistic in saying that his bags fill to 95% capacity in a bit over 7 minutes. However, for him to be off by the magnitude required to equal your dismal real world estimate of aerator flow rates is almost inconceivable. There's no way that Berg is going to think a bag that's 40% full is 95% full, EVEN IF HE's BEEN DRINKING HEAVILY.
Hmmm.
Berg, I assume your pumps are installed, not used "over-the-side", right?
The real discrepancy is between Bergand Fresh Fish via CenturionCrewQuote:
Originally Posted by bergermaister
I'd rather believe berg but like you said, his measurement is a little casual. Plus, I've got to trust Fresh Fish's 780 gph measurement because he was trying his best to do a controlled experiment. So if we assume 780 gph is the best case scenario, the only way to get berg's observation to fit is to take one of your calculations for something "a bit more than 7 minutes" and "a bit less than 95%". But then yeah, there wouldn't be much more loss due to other components. I don't know anything about the brass valve that was used in the test so maybe that was too restrictive.Quote:
Originally Posted by Fresh Fish via CenturionCrew
Then the conclusion would be that the aerator pumps perform about the same as the impeller pumps but are very sensitive to installation, so be careful.
The 25% loss in flow due to head is real and straight off of the spec sheet. Can those pumps produce much suction, if primed? Maybe it's better to mount them higher? But it seems like priming would be impossible.
Berg has the hard installed Attwood Tsunami T1200 pumps. They have 1" hardware all the way around and utilize vented loops so they would be subject to head pressure to the tops of the gunwales. He basically has as good of aerator system setup as I can imagine... Not really much room for improvement from what I can remember...Quote:
Originally Posted by gregski
I'm sure he'll chime in with respect to his accuracy. But then again, we might have to wait a bit, because it's almost happy hour...
I agree. I'm a CPA/MBA, so I find it interesting to crunch the numbers and do analysis. I made a cool spreadsheet comparing the components needed for aerator vs. impeller. I've also added a tab that compares fill time and GPH (i.e. the figures I've just been posting above). Finally, I have a "cool" use for the Excel that I labor behind all day long!Quote:
Originally Posted by gregski
I think it would also be cool to have real world specs from people with installed impeller systems. I sent out a text to a buddy of mine with Johnsons and I'll see if he's ever timed his and the size of bags in his rear lockers. He has a 23' like I do, so his time would probably be pretty relevant. When I get feedback, I'll of course share.
Heck, if he and I are running the same sized bags, maybe next summer we'll do a shootout! :-)
Not sure I'd trade the reliability of the reversibles to save 3-4 minutes of fill time. Haven't all newer boats moved away from the other pumps ?
This is starting to sound like a tower speaker thread!