Flow sensor

[jasperb]

Hi,

I have purchased an Flowsensor 5000 l/h last week.

Does the flowsensor need to be calibrated?

I'm using a Tunze Silence 1073.05 with the flowsensor, according to Tunze this pump should have a maximum of 3000 l/h, according to the flowsensor the flow is around 1060 l/h. I have tested it with two identical Tunze pumps, both have the same amount of flow on the sensor when running on maximum speed.

The height of the tubing is only 50 cm, so this couldn't be an issue.



Are both the Tunze pumps failing, or is the reading not right?



Regards,
Jasper

[Gunther]

Does the flowsensor need to be calibrated?

You have set it as 5000l/h sensor (6.22 ml/pulse) which is all you need to do.

Are both the Tunze pumps failing, or is the reading not right?

None of both, it´s simply a misunderstanding on your side. In general the Tunze is able to pump 3000l/h, but only as free flow pump without any resistances. In real life there are resistances like pipes, filters, height distances etc. which reduces the flow.

The height of the tubing is only 50 cm, so this couldn't be an issue.

For sure it is. Have a look into the manual for the pump. The diagram "Pumping capacity and height" for the 1073.5 shows the relation between flow (x.axis) and the flow resistance (y-axis). If you have a flow of 1066l/h there are resistances of approx. 2.3m water column (aka 0.23 bar) which seems normal.

[jasperb]

You have set it as 5000l/h sensor (6.22 ml/pulse) which is all you need to do.







None of both, it´s simply a misunderstanding on your side. In general the Tunze is able to pump 3000l/h, but only as free flow pump without any resistances. In real life there are resistances like pipes, filters, height distances etc. which reduces the flow.







For sure it is. Have a look into the manual for the pump. The diagram "Pumping capacity and height" for the 1073.5 shows the relation between flow (x.axis) and the flow resistance (y-axis). If you have a flow of 1066l/h there are resistances of approx. 2.3m water column (aka 0.23 bar) which seems normal.

Hi Gunther,

Thank you for your reply.

I understand that the pump capacity will be lower than 3000l/h. But I'm only pumping 0.5m in height, so I would expect to have Approximately 2500l/h left (according to the Tunze table).

For testing I have created a closed circuit from 1.4m tubing with a height difference of 0.5m (this resulted in the 1060l/h flow reading).

Is it really possible to loose so much capacity on so a short distance?

I use the flow sensor to measure the flow going to the chiller, but if the above is true I'm concerned that my return pumps from the sump are way under the capacity they should be. I use 2x Tunze 1073.05 from the sump the height is 1.4m, according to Tunze this should give a capacity of 1700/1800l/h but if I should believe the flow sensor this is much lower.

How many flow sensors can be connected to the Profilux? I have read two. In the software are four flow sensors shown but only level channel 1 and 2 can be selected.

Regards,
Jasper

[Gunther]

I think, the flow sensor is very accurate - the measurement failure is only 1-3 percent of the measured flow.

However, if you don't believe that, simply measure it. Simply pump from one bucket into another one and count the needed time. With 3000l/h a 10 liter bucket needs twelve seconds, with only 1000l/h it needs 36 seconds

You can connect up to four sensors, but for sensor 3+4 an additional level card is neccessary due level 3+4 are not usable for the flow sensors

[RichardW]

I have 2 x 9000 lph flow sensors on my tank and the reduction in flow boggled me for ages but after months of research the flow rate they provide is accurate within a few %. Multiple factors come into play to reduce flow so don't try and think of approximates as they simply don't work. Any form of restriction, glued fitting, bends, 90 or 45 to even gradual curves restrict the overall flow. I have 2 x vectra L1 (3500gph)and they under preform significantly compared to their illustrated ratings, I spoke to Echotech for weeks but the reality is my GHL was providing the accurate data, and it actually made me reconsider how I could maximise my return pipes to obtain the best flow... What size pipe do you have from the pump and then connected to the sensor as if there is a restriction between these 2 then this will reduce the results. I use mine to monitor my return flow as I fully understand the exact flow I need when using nutrient export function on my mp60. The other is to maintain the correct flow running through my zeovit filter, it only needs to be 500lph but I use a 9000lph flow meter. The reactor is running 25mm pipe (same as the 9000lph sensor) and I can acuralty dial my zeo reactor into its desired flow rates as there is zero restriction.

This may help and worth a read anyway http://www.engineeringtoolbox.com/pv...ngs-d_801.html

[jasperb]

Hello,

I bought a new pump today: Jecod DCS-7000

Q-max: 7200 l/h
H-max: 4.5 m

I connected it to the flow sensor and to a small piece of tubing.

The flow sensor measures a max flow of 2160 l/h. I would expect that it should go out of the measure range of the sensor (5000 l/h).

I can't believe that the pump would lose approximately 5000 l/h on such a small tubing.

I will buy a second flow sensor so I can compare them. I really think the flow sensor is incorrect.







Regards,
Jasper

[RichardW]

You can see the areas of restricted flow in the second photo, your union connection from pipe to the sensor ( what size pipe comes off the jeabo as the internal pipe dimensions of the Union look smaller (restricted) then you have 2x 90% bends very close together and one right in front of the flow sensor (read instructions there needs to be a decent amount of strait before you add the sensor. Also to add to this the 2x 90% bends reduce head hight by % based on the pipe dimensions( look at my post above there is a url that show restrictions vrs bends vs pipe sizes... Pipe looks like 3/4" so these would reduce the head hight by 9ft - 4.5.ft per 90% around a 2meter drop.. Looking at your results verses what the picture one show then the 2.1k is about right.

[jasperb]

You can see the areas of restricted flow in the second photo, your union connection from pipe to the sensor ( what size pipe comes off the jeabo as the internal pipe dimensions of the Union look smaller (restricted) then you have 2x 90% bends very close together and one right in front of the flow sensor (read instructions there needs to be a decent amount of strait before you add the sensor. Also to add to this the 2x 90% bends reduce head hight by % based on the pipe dimensions( look at my post above there is a url that show restrictions vrs bends vs pipe sizes... Pipe looks like 3/4" so these would reduce the head hight by 9ft - 4.5.ft per 90% around a 2meter drop.. Looking at your results verses what the picture one show then the 2.1k is about right.

Hi Richard,

I had a look at the mentioned website, it's now becoming clear to me. A 90° bend reduces the flow equivalent to 1.3 m head height.

What I still don't understand is that when I would use a bigger pipe size (for example 25mm instead of 20mm) the loss will be 1.6 instead of 1.3. So this wouldn't help, or am I missing something?

I want to completely redesign my tubing with the loss factors in mind, I didn't calculated this when setting up the tank and I wonder if it will help to install 25mm instead of 20mm tubing (or even 32mm)

Thanks,
Jasper

[Gunther]

I want to completely redesign my tubing with the loss factors in mind, I didn't calculated this when setting up the tank and I wonder if it will help to install 25mm instead of 20mm tubing (or even 32mm)

To calculate losses you can use this online calculator: http://www.pressure-drop.com/Online-Calculator/
If you want to minimize losses you should try to have a flow speed of not more than 2.5m/s (better 1.5m/s, shown in result page)
There is a very simple quadratic relation: If you double the pipe diameter, you reduce the losses to a quarter.

[RichardW]

Hi Richard,

What I still don't understand is that when I would use a bigger pipe size (for example 25mm instead of 20mm) the loss will be 1.6 instead of 1.3. So this wouldn't help, or am I missing something?

Thanks,
Jasper

Think of it like this if you have a 3 lane motor way and then it drops to one lane, no mater how much you try efficiency the volume of traffic will have to slow down over this section. Let's say your jeabo has a 32mm connection on its out pipe and you use 20 Mm pipe then your halving its proformance before it's even left the pump ( supper inefficient ) so in theory a 4000lph pump running the 20mm fitting would proformance more effectively in this set up.

Now going back to the motorway scenario, your Motorway needs to go round bends to get to its destination as a simple principle, a 3 lane bend will slow the traffic slightly but not as much as the single lane plus it's additional traffic - the bend has to be there..

There is also a big factor to remember as well with the flow meters from GHL - they also have an internal dimension and you don't want this smaller than your own pipe (irrelevant of flow specifications) as if your restricting the flow going through the meter this will only add to your issues... I use a 9000 to measure my 500 litre requirements at its the same size internal dimensions as my pipe.

I was running 2x 12000 Jeabo and couldn't work out why my flow was restricting even after redesigning my 32mm pipe for max efficiency it was the flow sensor causing all the issues (I wish here GHL would add just one more sensor for bigger tank users with 32mm connection )

I recently had to change my tank to a smaller red sea reefer 525 and I have my flow sensors on my return line, I've used my vectra l1 and it would only show 3.5K at 100%, I knew with pipe restrictions 25mm instead of 32 I would loose head pressure but there was a pre fabricated part the significantly reduced the flow back into the tank casing the issue, so I redesigned this so I can acquire the turnover I wanted within the tank.
Restricted area below - red sea what you thinking look at the 90% reduction wtf
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