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Old 11/09/2017, 05:34 PM   #1
teo241
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vectra L1 head loss

Help me understand something please.

I had the unfortunate luck to come home to a seized vectra L1 (using as a return pump).

I replaced it temporarily with an eheim 1262 pump -- rated at 900 gph. When running the eheim the flow meter on the return gave me a reading of ~560 gph. (a head loss of about 48%).

I just plumbed in my replacement vectra L1 pump rated at 3100 gph. The same flow meter on the same return reads 830 gph. (a head loss of almost 75%).

The vectra is calibrated in return mode and is running at full speed. Its the same return plumbing. Even if the flow meter is inaccurate (which I doubt) this suggests a huge difference in head loss as it would be inaccurate for both pumps. For what its worth, the previous vectra L1 gave me a max reading of ~880 gph.

Any ideas of why the difference is so much greater with the more powerful pump?


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Old 11/09/2017, 06:58 PM   #2
Dross
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The frictional head loss (pressure drop) increases with the square of the flow rate. There is a lot more pressure drop (head loss) at 830 than at 560 GPH. There is also a lot more head loss in our piping return systems than we generally believe. Getting more than 800-900 gph from 1" piping is difficult without a pressure rated pump. The published zero head, end of curve, flow ratings that people quote are meaningless unless you plan on using it as a powerhead.


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Old 11/09/2017, 07:18 PM   #3
teo241
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Thank you, I was incorrect assuming it was a linear relationship.

Damn you physics.


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Old 11/09/2017, 10:47 PM   #4
ca1ore
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Further, the Vectra pumps are designed for flow not pressure, thus they drop off faster than one that prioritizes pressure over flow. For example, my panworld 200 pumps only loses 20% pumping up 12 feet in my system - because that's what it's designed for.


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Old 11/10/2017, 08:56 AM   #5
Dmorty217
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Quote:
Originally Posted by ca1ore View Post
Further, the Vectra pumps are designed for flow not pressure, thus they drop off faster than one that prioritizes pressure over flow. For example, my panworld 200 pumps only loses 20% pumping up 12 feet in my system - because that's what it's designed for.
+1 they are only suited for close loop applications IMO. The seizing of the motor is a problem they are still working to correct, I'm on my third pump from them because of this problem.


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Current Tank Info: 625g, 200g sump, RD3 230w, Vectra L1 on a closed loop, 2 MP60s
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Old 11/10/2017, 03:23 PM   #6
Vinny Kreyling
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DC PUMPS have problems with head pressure.
Abyzz & Red Dragon pumps are the exception.


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Old 11/11/2017, 04:31 PM   #7
teo241
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Quote:
Originally Posted by Dmorty217 View Post
+1 they are only suited for close loop applications IMO. The seizing of the motor is a problem they are still working to correct, I'm on my third pump from them because of this problem.


That explains why they sent me a replacement without any question about mine failing. Itís out of warranty and they didnít even blink an eye.

Itís probably time for a red dragon. Iíll get the flow I need.

Iím just disappointed given how expensive it was. Iíve had eheim and mag drive pumps running on other tanks without any maintenance for years.


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Old 11/14/2017, 07:18 PM   #8
Dmorty217
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Quote:
Originally Posted by teo241 View Post
That explains why they sent me a replacement without any question about mine failing. Itís out of warranty and they didnít even blink an eye.

Itís probably time for a red dragon. Iíll get the flow I need.

Iím just disappointed given how expensive it was. Iíve had eheim and mag drive pumps running on other tanks without any maintenance for years.


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Mine has seized up on me now for the 3rd time... always happens within 9 months of use. Ecotech is sending me yet another one. My last pump from them was so new off the production line, it didn't even have a sticker on it. My last warranty claim was back in February they informed me today.


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Fish are not disposable commodities, but a worthwhile investment that can be maintained and enjoyed for many years, providing one is willing to take the time to understand their requirements and needs

Current Tank Info: 625g, 200g sump, RD3 230w, Vectra L1 on a closed loop, 2 MP60s
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Old 11/14/2017, 09:59 PM   #9
ca1ore
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Quote:
Originally Posted by teo241 View Post
That explains why they sent me a replacement without any question about mine failing. Itís out of warranty and they didnít even blink an eye.

Itís probably time for a red dragon. Iíll get the flow I need.

Iím just disappointed given how expensive it was. Iíve had eheim and mag drive pumps running on other tanks without any maintenance for years.


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So explain to me why you would pay for something like a red dragon pump versus just sticking with an eheim. Even if there are electricity savings, quick math suggests the payback period is measured in decades. I just don't get it.


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Simon

Got back into the hobby ..... planned to keep it simple ..... yeah, right ..... clearly I need a new plan! Pet peeve: anemones host clowns; clowns do not host anemones!

Current Tank Info: 450 Reef; 120 refugium; 60 Frag Tank, 30 Introduction tank; multiple QTs
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