DC Pump Output... Pump Curve vs. %Speed

[mstgkillr]

After one of my two COR20 return pumps failed, I did a flow comparison with a replacement return pump (Sicce Syncra SDC 7.0) on my Red Sea S-1000. Unfortunately, I do not have flow sensors, so most of the measurements/comparisons are using a 100% open return drain valve. Also, these comparisons are using dual return pumps with one COR20 and one SDC 7.0.

I was interested to note the following:
1. The COR20 did not output any additional flow past 50%
2. The SDC 7.0 continued to incrementally increase flow all of the way to 100%. It appears that it handles the minor/major piping losses better.
3. With the COR20 anywhere between 50% and 100%, and the SDC 7.0 at 50%, the return drain valve needed to be opened 100% and maintained a perfect level in the overflow, which is maxing out the overflow.
4. The COR20 at 50% and the SDC 7.0 at 40%, with the return drain opened 100% maintained a perfect level in the overflow. Again, maxing out the overflow.

I was a little confused seeing the COR20s max output at 50% and not increase even at 100%. I assume it's due to the S-1000 dual 3/4 return piping restriction.

The SDC 7.0 is LOUD... any idea how dual Varios-4 pumps might perform? I'm wondering if the 3/4" piping is choking out the larger pumps and if a smaller pump would perform similar.

 

[benbalter]

Do you have a neptune apex? You ezyly add a flow sender to it. Then you see 5he real flow rate. Yes it can be done for about 15$. You may be mixing up flow rate and head presser

 

[JNalley]

After one of my two COR20 return pumps failed, I did a flow comparison with a replacement return pump (Sicce Syncra SDC 7.0) on my Red Sea S-1000. Unfortunately, I do not have flow sensors, so most of the measurements/comparisons are using a 100% open return drain valve. Also, these comparisons are using dual return pumps with one COR20 and one SDC 7.0.

I was interested to note the following:
1. The COR20 did not output any additional flow past 50%
2. The SDC 7.0 continued to incrementally increase flow all of the way to 100%. It appears that it handles the minor/major piping losses better.
3. With the COR20 anywhere between 50% and 100%, and the SDC 7.0 at 50%, the return drain valve needed to be opened 100% and maintained a perfect level in the overflow, which is maxing out the overflow.
4. The COR20 at 50% and the SDC 7.0 at 40%, with the return drain opened 100% maintained a perfect level in the overflow. Again, maxing out the overflow.

I was a little confused seeing the COR20s max output at 50% and not increase even at 100%. I assume it's due to the S-1000 dual 3/4 return piping restriction.

The SDC 7.0 is LOUD... any idea how dual Varios-4 pumps might perform? I'm wondering if the 3/4" piping is choking out the larger pumps and if a smaller pump would perform similar.

I have an SDC 6.0 and it's dead quiet at 100%... Are you sure something isn't wrong? Don't get me wrong, I got on Sicce about the XStream SDC's being loud when I first got them, so they're capable of making loud pumps in a market where silent is better, but the SDC's eventually got to a state of silent after about 3 months of break in...

 

[benbalter]

I have an SDC 6.0 and it's dead quiet at 100%... Are you sure something isn't wrong? Don't get me wrong, I got on Sicce about the XStream SDC's being loud when I first got them, so they're capable of making loud pumps in a market where silent is better, but the SDC's eventually got to a state of silent after about 3 months of break in...

Well I run jebao pumps my self. Dirt cheap and very quiet. Pumps do have a max flow rate. When they rate pumps they are measured in the best possible conditions. No head pressure no turns and no lift. So then we install them with a flow meter people go "oh the meter is causing a big flow loss ". No we live in the real world lifting water up 2 to 6 feet up and with turns. So i would say get a flow meter and see what's really going on

 

[JNalley]

Well I run jebao pumps my self. Dirt cheap and very quiet. Pumps do have a max flow rate. When they rate pumps they are measured in the best possible conditions. No head pressure no turns and no lift. So then we install them with a flow meter people go "oh the meter is causing a big flow loss ". No we live in the real world lifting water up 2 to 6 feet up and with turns. So i would say get a flow meter and see what's really going on

Huh? I'm not understanding what any of that had to do with my post saying OP may have a faulty pump if they're saying it's loud... It's a DC pump and only 1 size up from mine... It should be dead quiet...

 

[benbalter]

Huh? I'm not understanding what any of that had to do with my post saying OP may have a faulty pump if they're saying it's loud... It's a DC pump and only 1 size up from mine... It should be dead quiet...

Sorry yes sounds like you have a bad pump

 

[DCR]

Noisy pump issues aside, as an engineer familiar with sizing piping, I can tell you that your 3/4" piping is going to severely limit your flow. I would not expect much more than 250-300 gph from any aquarium pump through a 3/4" return line, regardless of the rated flow of the pump (zero head). You could probably get equal performance from a pump rated for 600-800 gph at zero head. The only advantage of an oversized DC pump is that you may be able to run it at a lower speed for noise reduction.

 

[mstgkillr]

Noisy pump issues aside, as an engineer familiar with sizing piping, I can tell you that your 3/4" piping is going to severely limit your flow. I would not expect much more than 250-300 gph from any aquarium pump through a 3/4" return line, regardless of the rated flow of the pump (zero head). You could probably get equal performance from a pump rated for 600-800 gph at zero head. The only advantage of an oversized DC pump is that you may be able to run it at a lower speed for noise reduction.

It has been a while since I calculated major/minor loses in fluids. I appreciate the reply, but how confident are you in that statement? Are you saying that a VariouS-4 (1050 GPH and max head at 14.7 ft) would perform the same as a Syncra 7.0 (1900 GPH and max head at 16.5 ft) with 3/4 piping?

 

[DCR]

It has been a while since I calculated major/minor loses in fluids. I appreciate the reply, but how confident are you in that statement? Are you saying that a VariouS-4 (1050 GPH and max head at 14.7 ft) would perform the same as a Syncra 7.0 (1900 GPH and max head at 16.5 ft) with 3/4 piping?

The Syncra generates 16 ft of head at 300 gph while the Varios 4.0 is only about 8 ft so you will get some additional flow, but it will come at a price in noise and power consumption. The friction losses in 3/4" piping increase significantly as you go over 250-300 gph. I am just saying that you will be wasting a lot of power to try to get much more than 300-gph by increasing the pump size with the 1900 gph pump. If you want more flow than 250-300 gph, it would be far better to increase your pipe size.

 

[mstgkillr]

The Syncra generates 16 ft of head at 300 gph while the Varios 4.0 is only about 8 ft so you will get some additional flow, but it will come at a price in noise and power consumption. The friction losses in 3/4" piping increase significantly as you go over 250-300 gph. I am just saying that you will be wasting a lot of power to try to get much more than 300-gph by increasing the pump size with the 1900 gph pump. If you want more flow than 250-300 gph, it would be far better to increase your pipe size.

I'm currently running dual Syncra SDC 7.0 pumps at 58% with the main drain of my Red Sea S-1000 opened 100%. Just wondering if dual Varios 4 pumps could produce the same flow (maybe even at a higher run percent). It would be much easier if I had real pump curves to review.

 

[NancyFish]

The Syncra generates 16 ft of head at 300 gph while the Varios 4.0 is only about 8 ft so you will get some additional flow, but it will come at a price in noise and power consumption. The friction losses in 3/4" piping increase significantly as you go over 250-300 gph. I am just saying that you will be wasting a lot of power to try to get much more than 300-gph by increasing the pump size with the 1900 gph pump. If you want more flow than 250-300 gph, it would be far better to increase your pipe size.

I’m looking at a 1200 overflow into a max 900 reefmat, the overflow is 3/4” drains .. are you saying if I matched the return line (heard they’re supposed to be same or smaller) it won’t be anywhere near that in return because of the pipe?

 

[DCR]

I’m looking at a 1200 overflow into a max 900 reefmat, the overflow is 3/4” drains .. are you saying if I matched the return line (heard they’re supposed to be same or smaller) it won’t be anywhere near that in return because of the pipe?

Yes, that is what I am saying. I would say you will not get anywhere near 900-1200 gph through a single 3/4" drain or return line. Your set-up should work fine, but I would not expect much more than 250-300 gph through a 3/4" line. I would run a 3/4" return for your return for a 3/4" drain. You definitely do not want a larger return line than your drains, but equal size should be fine.

I do not believe the ratings on these overflows - at least on a practical basis. To put it in perspective, 1200 gph will fill up a 5 gallon bucket in 15 seconds. Try to imagine that much flow coming out of a 3/4" PVC pipe. The turbulence would be incredible and would likely wash over your rim if it was anywhere near the surface, and you would almost certainly be running full siphon on your secondary or emergency overflow.

I think most reefers over-estimate how much return flow they are actually getting because the friction losses are much greater than they think. I see it in threads where they actually put flow meters in the lines and are surprised by the results - and then question their pump performance. It still all works because I don't think you really need the 5-10X per hour return rates that are commonly stated.