Pentair UV Killing Flow

[Dj City]

I read my last post and realize type does not translate as well as spoken word.
I promise I said it with a much nicer tone than was translated in text.

It's the way the sensor reads the flow, not just the velocity of the water passing through it.
That's why the 1/2 inch sensor can only read up to 250.

 

[Bob Lauson]

It all depends on the type of flow sensor

 

[DCR]

This is just wrong.
The sensor reads what neptune programmed it to read. The 1 inch sensor thinks it's on a 1 inch pipe and will read as such.

Go argue with Terrance of Neptune systems if you don't like the answer.

I doubt that is what BRS or Neptune said. I have done fluid hydraulics for 40 years as an engineer, and I can assure you it is incorrect. The GPH in the pipe circuit of an incompressible fluid such as water is the same everywhere, regardless of whether the pipe diameter changes. The APEX has to be programmed for the right sensor size to give the correct conversion to GPH, but the sensor has no knowledge and does not care what the pipe diameter is after it leaves the sensor. The GPH through the sensor and the downstream pipe has to be the same.

 

[Dj City]

I understand and agree with you.
You can doubt it if you like.

Check my build thread and you will see where I state that I just got off thr phone with them TODAY. This morning in fact.
Or
You can call them yourself.

I don't like anyone calling me a liar directly or indirectly and sir, that is exactly what you have done.

 

[DCR]

I did not call you a liar. I am sorry if you took it that way. I simply think you misunderstood what Neptune told you. You can increase the downstream piping from a flow sensor and it does not invalidate sensor reading.

Otherwise a bucket flow test would be meaningless. ​

There may be some short amount of straight run pipe required downstream of the meter, but I would not think it would be much for their paddle wheels.

 

[CuzzA]

incorrect. if mounting vertically, you want the flow to run from bottom to top

Yes, I already corrected the typo.

 

[Dj City]

@DCR
No problem.

What they explained to me was for my situation (set up)
I have a pump with 3/4 water outlet feeding a manifold. I have 3/4 pipe going to tee's. The tee's are 3/4 both sides to 1/2 down. I have 1/2 inch gate valve then 1/2 inch flow sensor to 1/2 inch barb fitting.
My flow loss through my UV was massive.

I called them about going straight from 3/4 pipe to 3/4 bushing on UV and using a 1 inch sensor with a 3/4 reducer on both ends since Neptune does not make a 3/4 sensor.
They told me putting a 1 inch sensor on the 3/4 pipe would give me inaccurate readings. They said you can't use one of their flow sensors with different size pipe even if you use a reducer or expand the pipe just at the sensor.
They said the 1/2 inch sensor will give good readings UP TO 250gph. It will show numbers higher than that but they will be inaccurate past 250gph.

Believe me or not, I did not misunderstand. I understood perfectly what they explained to me.

You are welcome to contact them yourself.

 

[Dj City]

You can increase the downstream piping from a flow sensor and it does not invalidate sensor reading.

Otherwise a bucket flow test would be meaningless. ​

There may be some short amount of straight run pipe required downstream of the meter, but I would not think it would be much for their paddle wheels.

I agree with this.
Problem is (I think) that their flow sensor is not simply mechanical. They may have some funky algorithm that calculates flow in some weird non traditional non (strictly) mathematical way.
That is a pure guess on my part but the best I can come up with.

 

[DCR]

It is just a paddle wheel meter. The higher the flow, the faster it spins and the speed is correlated to the flow. I can imagine you need some straight run pipe upstream and downstream of it, but it is likely only a few pipe diameters at most. Neptune's response confirms my suspicion that they really do not know much about all of these auxiliary products (pumps, meters, probes etc) that they have third party manufacturers produce for them.

 

[Dj City]

I've taken it apart. I know it's a paddle wheel meter.
I don't understand why it would not read whatever speed the wheel is spinning at to calculate gph.

 

[Dj City]

I used to fork for D.C. Water. (Washing D.C. water company)
I used to do flow analysis, flow tests and pressure tests.

I'm not absolutely clueless on how this is "supposed" to work.

I don't know their algorithms though.
BRS told me they asked Terrance about using 1 inch with 3/4 pipe and he said it will not read accurately. I called Neptune after getting off the phone with BRS because this did not sound right to me but Neptune tech told me the same thing.

 

[ca1ore]

This might sound uneducated but...

The hole on the 1/2 inch barb fitting is way smaller than the opening on the 1/2 inch pipe.
Is that just me and my perseption or is that how it is?

That is why, IMO, barb fittings are best avoided.

 

[ca1ore]

This just is not true. The velocity in the piping will change when you change the piping size, but the volumetric flow rate is the same. GPH is GPH regardless whether the sensor size is the same as the pipe size, upstream or downstream.

I agree with this. I have upsized almost all of my flow meters and I get broadly accurate gph readings (within the error of the sensor). Not sure what the BRS/Neptune referenced ‘conversation‘ was; perhaps they misunderstood.

 

[ca1ore]

I used to fork for D.C. Water. (Washing D.C. water company)
I used to do flow analysis, flow tests and pressure tests.

I'm not absolutely clueless on how this is "supposed" to work.

I don't know their algorithms though.
BRS told me they asked Terrance about using 1 inch with 3/4 pipe and he said it will not read accurately. I called Neptune after getting off the phone with BRS because this did not sound right to me but Neptune tech told me the same thing.

But they don’t make a 3/4” flow sensor and going down to 1/2” would crate the same kind of problem if their logic is correct. Doesn’t really sound right to me either. If it were critical to match the sensor to plumbing size, then they’d have 1 1/2” sensors as well. I’m using the 2” sensor on my 1 1/2” return line and its pretty much spot on.

 

[CuzzA]

Why is everyone hung up on using Neptune's overpriced flow meters? This is not a parameter for a UV sterilizer that needs continous monitoring. There's plenty of flow meters out there. Hell I think Orbit irigation makes one in 3/4" hose. Just check it every now and then to ensure the unit is still clean. UV sterilizers by and large are set it and forget it. I would not waste my money on a module and a sensor when there's option out there for around $15.

 

[Dj City]

Something I'm not sure of is...
Does it matter "where" you measure the flow? Should you measure flow going in or coming out?
Does it make a difference?

 

[ShpwrkReefsS]

Something I'm not sure of is...
Does it matter "where" you measure the flow? Should you measure flow going in or coming out?
Does it make a difference?

Per the instruction manual flow should be measured at the outlet...

 

[ca1ore]

Why is everyone hung up on using Neptune's overpriced flow meters? This is not a parameter for a UV sterilizer that needs continous monitoring. There's plenty of flow meters out there. Hell I think Orbit irigation makes one in 3/4" hose. Just check it every now and then to ensure the unit is still clean. UV sterilizers by and large are set it and forget it. I would not waste my money on a module and a sensor when there's option out there for around $15.

Unless, of course, you want flow alerts integrated to apex. I find that useful.

 

[ca1ore]

Something I'm not sure of is...
Does it matter "where" you measure the flow? Should you measure flow going in or coming out?
Does it make a difference?

Doesn't matter .....same water flow comes out as goes in.

 

[Dj City]

Doesn't matter .....same water flow comes out as goes in.

That's what I thought as long as there are no air pockets in the UV or plumbing after the uv.