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It’s a process of elimination.

You have many different things that can be checked and verified.

As you work through the different checks, some will check out fine and some will have a problem.

When you have multiple issues, you need to find them and fix them.

The vacuum gauge is defective, so that should be replaced.

The flow meter might be inaccurate, so you can replace it or add a second flow meter to see if you get the same readings.

The impeller was “allegedly” “worn” and maybe it was and maybe it wasn’t.

The impeller replacement seems like it did not help much.

It’s usually best to fix the least expensive things first.

In my opinion, the motor sounds off, but that is difficult to tell for sure.

I would think that a Mechanical Contractor or an Electrician could do the necessary measurements in a standard service call.

Note that 99.9% of service people will not know how to check a 3-phase motor correctly.

So, you have to make sure that they know exactly what they are doing and that they give you a written evaluation including the actual measurements and an explanation of why the numbers are correct or not correct.

The low flow can under load the motor, so the current will be low.

Has this pump ever worked properly?

What is the highest recorded flow from the records?
 
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JamesW said:
It’s a process of elimination.

You have many different things that can be checked and verified.

As you work through the different checks, some will check out fine and some will have a problem.

When you have multiple issues, you need to find them and fix them.

The vacuum gauge is defective, so that should be replaced.

The flow meter might be inaccurate, so you can replace it or add a second flow meter to see if you get the same readings.

The impeller was “allegedly” “worn” and maybe it was and maybe it wasn’t.

The impeller replacement seems like it did not help much.

It’s usually best to fix the least expensive things first.

In my opinion, the motor sounds off, but that is difficult to tell for sure.

I would think that a Mechanical Contractor or an Electrician could do the necessary measurements in a standard service call.

Note that 99.9% of service people will not know how to check a 3-phase motor correctly.

So, you have to make sure that they know exactly what they are doing and that they give you a written evaluation including the actual measurements and an explanation of why the numbers are correct or not correct.

The low flow can under load the motor, so the current will be low.

Has this pump ever worked properly?

What is the highest recorded flow from the records?
Click to expand...
First.... thanks for all your help with this.... invaluable and greatly appreciated!

Pictures of the impeller that the pool company sent me this morning are attached. I asked them to return the part, so I have evidence for the Board (in case questions arise). The Service Manger told me the impeller and diffuser were "on their last days and I doubt they would have made it much longer"

I'm not sure if the pump ever worked properly. I have been here 2 years and I understand the pump is about 10 years old. The highest flow rate reading I see from past records going back 2-3 years was 100 gpm. Mostly, the flow rate was never recorded! No one ever made an issue of it, including our current pool company (not the same company that replaced the impeller recently). I'm trying not to use our current pool service provider because I think they are incompetent and am trying to replace them. It isn't until recently that I became aware of the minimum flow rate requirement by reading the regulations and doing the calculations myself. The pool company should have known this and addressed it long ago. (They also allowed CYA in the pool to get to 180 ppm before I arrived here and tested the water..... they should have been fired immediately!)
 

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JPMorgan said:
Pool company quoted repair at $1,800. The engineer we are working with on pool modifications thinks it makes sense to do the repair. Pump is about 10 years old.
Click to expand...
The motor date code has a 12, which is probably 2012, so about 11 years old.

I would not have put $1,800.00 into this old pump.

I would have replaced the pump with a 5 HP WhisperFlo VS pump.

What is the engineer doing for you?

It does not seem like they are giving you much help with anything.

Maybe the pump was never installed correctly?

It looks like the motor can be a 3 hp or a 5 hp motor depending on the power supply.

What is the supply voltage?


1694105288248.png


full
 
It looks like the DMJ3 is a 5 HP, 3 phase pump.

However, it also looks like the motor can be wired as a 3 HP motor.

So, I am not sure exactly what you have.

I would ask Pentair and Leeson (The motor manufacturer) to provide additional information about what you have to be sure and what the measurements should be.

www.pentair.com

Customer Service

Contact Pentair for information regarding our sustainable water products and solutions or for more information on our global company.
www.pentair.com www.pentair.com

www.regalrexnord.com

LEESON® Electric Motors

The LEESON band spans thousands of alternating current (AC) and direct current (DC) motors, gearmotors, washdown and variable-speed control solutions.
www.regalrexnord.com www.regalrexnord.com

10” of mercury is about 11.3 feet of head loss on the suction.

24 psi is 55.4 feet of head.

So, that is a total of 66.7 feet of head.

That should put the flow close to about 195 GPM if the pump is 5 HP or about 125 GPM if you have a DMH 3 HP pump.

So, the performance matches the 3 HP pump and not the 5 hp pump.

We need to know the voltage, current, power, power factor and frequency for the power supply.

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That impeller is over $580.00!

Yikes, that is an expensive impeller!

What part number did they use for the impeller?

It looks like the correct part number is C5-247.

Is that what they used?

It says that it is a 5 HP impeller, so it should be a 5 hp pump.

Maybe the way it is wired changes the speed and it runs slower and that makes it a 3 HP pump?

The motor label shows two different speeds.

The speeds are difficult to read in the picture.

Can you post what the label says for RPM?

Maybe the motor is running at the slower speed?

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Pentair Sta-Rite D Series Medium Head Impeller, 5 HP - C5-247 - INYOPools.com

C5-247 - IMPELLER, 5HP (C5-247)
www.inyopools.com www.inyopools.com

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JamesW said:
What is the engineer doing for you?

It does not seem like they are giving you much help with anything.

Maybe the pump was never installed correctly?

It looks like the motor can be a 3 hp or a 5 hp motor depending on the power supply.

What is the supply voltage?
Click to expand...
Engineer is doing the required drawings for pool modifications we are planning for next spring. He thought repairing the pump was a reasonable alternative to purchasing a new $5,000 - $6,000 pump. We are pretty reliant on the advice of professionals in deciding the best course of action for getting our pool "up to speed." I had no reason to question his advice (until you just advised that a new pump was the way to go). We've also had a couple other pool companies look at our system and tell us that "it's a good pump.... just change parts when you need to."

No idea what the supply voltage is. (I'm clueless when it comes to electricity!)
 
JPMorgan said:
what I see on the RPM is 3000/2920. Does that make sense?
Click to expand...
It might be 3,500 and 2020, but I cannot see it clearly.

Maybe put a piece of paper over the label and rub a pencil over the numbers to see it the indented image will transfer over or maybe use chalk to rub on the label to see if that helps highlight the numbers.
 
The power looks like 3.7Kw (5 HP = 3.7 Kw) and 2.24Kw (3 HP = 2.21 Kw).

It looks like the speeds are 3,500 RPM and 2920 RPM.

P1/P2 = N1^3/N2^3

N2^3 = (N1^3)(P2)/P1

N2 = cuberoot((N1^3)(P2)/(P1))

P2 = (P1)(N2^3)/N1^3

Using the affinity law, the second speed comes out to about 2960 RPM, so that seems likely.

P1 = 3,700 watts.

P2 = 2,240 watts

N1 = 3,500 RPM

N2 = cube root((N1^3)(P2)/(P1))

N2 = cube root((3500^3)(2240)/(3700))

N2 = 2960.85

If the flow is 195 at 3,500 RPM, then the flow should be about 163 GPM at 2,920 RPM.

If we use 2920 as the starting RPM, the higher RPM should be about 3,450 RPM, which is typical of a single speed pump.

If the flow is 130 at 2920 RPM, then the flow should be about 156 GPM at 3,500 RPM.

I suspect that the motor is wired for the lower speed and that changes the performance curve to look more like a 3 HP pump.

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The pump can take 50 Hz power or 60 Hz power and that might explain the difference.

The higher frequency will create a higher speed.

If the 60 Hz speed is 3,500 RPM (60 hz = 60 cycles per second and that is 3,600 RPM synchronous speed. The 3,500 RPM is due to "Slip").

3,500 RPM x 50/60 = 2,917 RPM.

So, the difference is the frequency.

The slower speed uses less power.

You need to know the voltage, current, power, power factor and frequency.

Check the current on all three legs.
 
That information is way above my comprehension level!!! :)

I have contacted an electrician that I know and forwarded your comments to him to see if he can help.

Comment from Service Manager at the pool company when I asked about this: The amp draw is simple and only takes a half hour. If the amp draw is ok then there is no need for an electrician to be involved.

Sounds like you feel it's a little more complex than that.
 
The amp draw check takes 5 to 10 minutes on site using a clamp on ammeter.

Clamp the meter onto the power wires and read the values.
 

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