I have an Apex Fluid flow sensor on the return line. I show flow of 634 GPH with the gate valve full open
When I use the head loss calculator on the home page it comes to 828.
Which is most likely correct. The pump is an Iwaki 100RLTheadloss.png
I have an Apex Fluid flow sensor on the return line. I show flow of 634 GPH with the gate valve full open
When I use the head loss calculator on the home page it comes to 828.
Which is most likely correct. The pump is an Iwaki 100RLTheadloss.png
What size sensor? If you are within the operating range of the sensor, I would go with it over the calculator. I have used that calculator a lot of the years, but hydraulic analysis is based on a lot of assumptions and limitations, which are not provided with that calculator.
And speaking of limitations, I want to point out that 828 gph in a 3/4" line results in a velocity of 10 ft/s, which is very high and possibly outside the bounds of applicability for the equation and coefficients used. Additionally, there is no 3/4" sensor, so if you are running this flow through a 1/2" sensor, then that flow will be wrong too. If you are running this through a 1" sensor, then I would trust the sensor.
I am using the 1" sensor. 3/4" pipe to up to 1" at sensor down to 3/4" after sensor.Originally Posted by clsanchez77
I am going to time how long it takes for the sump level to drop 2" when the pump comes on (allowing a couple seconds to reach max.) and compute a GPH based on that. Will report back tomorrow.
I would trust the apex on that one. You have so many 90s on that I would not expect the flow to act laminar (which the calculator requires) which would add some loss. You may also have incorrectly guessed the loss related to the flow meter itself, which I couldn't verify since neptune hasn't released the minor loss coefficients for it. Add to that additional friction from whatever gunk may be hiding in some of the bends or on the impeller. Also pump head loss curves have some variability between pumps and moreso as loading gets toward the upper limit.
If you want more flow, I would look into ways to reduce the number of 90s.
You might be an engineer if...You have no life and can prove it mathematically.
I think many people underestimate the head created by plumbing. I haven't heard one person add the flow sensors be suprised at how high the flow is
I have not added my flow sensors yet, but I have tested my flow through other measures and got it pretty close. I think the biggest issue is we WAY undersize our piping in this hobby and then are using tools developed for industry to calculate head/pressure loss, but we not in the normal operating conditions. 10 fps through pipe and fittings is not acceptable in my line of work and I don't think equivalent length methods for flow loss accurately project this nor our the loss coefficients calibrated for such high velocities. The Reef Central calculator does perform iterations which tells me it is adjusting the loss factors based on velocity (reynolds number or degree of turbulence), but...This still does not even get into the fact we use small pipe diameters, many DIY fittings are not hydraulically 'ideal', we quickly get buildup in our pipes, etc.
Even when dealing with large pipe sizes, lower velocities, professionally installed equipment and fittings, we can only get the head to about plus/minus 10% and the translation to flow error is dependent on the pump curve...better flow prediction on flat curves and far more error on steep curves...and the pumps in our hobby typically have 'steep' pump curves because they are small. Pump manufacturers just are not going to spend a fortune in R&D on developing a better 'hobby' pump. Thats why I still stick with Iwaki
I measured the time to drop 2" and calculated 564 GPH. 31.85 seconds and 5 gallons volume
So likely the FMM is pretty close to dead on. Given the very high velocity in your pipes, I would look into both reducing the number of elbows and increasing to 1" pipe if possible unless you are okay with that flow rate.
You might be an engineer if...You have no life and can prove it mathematically.
The RC Calc, as cool as it is, is missing a few key things. For one, I just noticed you have 3 exits...which means you have a Tee in the system. However there are no options for Tees in the calculator. So if you have flow going through the branch side of a Tee, treat it like another 90 elbow. Also, the calculator does not account for changes in pipe diameters, so if at any point, your changing pipe diameter from 3/4" to 1" and back for a flow sensor or changing from 3/4" to 1/2" at the exits, there are some additional losses the calculator is missing.
Also, while the flow is quite a bit off, looking the pump curve, the difference in head loss between 828 gph (13.8 gpm) and 564 gph (9.4 gpm) is only 2-ft of water, 5.5% error, actually pretty good! Unfortunately with this particular pump, that translates to a 40% error in flow.
Posting Permissions
Reply With Quote
Bookmarks