Protection for 3 phase pump

[Gecko]

This is not VFD but straight 3 phase from the transformer. Grundfos and Franklin and others sell a box that uses inductive sensing to protect against over and undercurrent, quick cycling, etc. They are quite expensive for what they do. CSV sells one that does a lot of that but not over current (for locked motor or wiring fault).

I've got a motor starter on the circuit with overloads. Would this be sufficient to protect the motor against jamming? Or will it be not sensitive or not quick enough?

Second, if I have a CSV on the pump, the current will drop when the valve is closed. It will be a 25S15-9 pump, FLA is supposed to be 7.3A. The instructions for the Grundfos/Franklin style protector suggest setting the minimum current at a fairly high value, like 75% of running amps. Seems like this will run into trouble with the CSV. How low will the current go when the pump is down to 1 g/m?

Third, the installation as it existed prior to this "clean and press" had an overpressure release on the top of the wellhead. I presume to prevent damaging pressure from reaching the rest of the system in the case of a faulty pressure switch. With the CSV, this can't be there, should it be anywhere? Like after the CSV. Even with the CSV, a faulty pressure switch could in theory run the pressure up too much.

 

[Boycedrilling]

A 3 phase motor uses a magnetic contactor to start and stop the motor. A control circuit with a voltage coil opens and closes the magnetic contactor. A submersible motor needs a class 10 overload circuit, standard starters usually come with a class 20 circuit. Some starters can be adjusted to different classes. This means how fast the overload reacts.

Older style starters have “heaters” for overload protection. A heater is rated for a specific amount of amps. You have to use the specific set of heaters to get the proper overload protection. This amperage is much lower than your breaker or fuse rating.

In the 1990’s panel makers started making electronic overloads that are adjustable. I switched from Eaton panels to what is now Siemens panels because of the ESP100 overload. Now most manufacturers have both electronic overloads along with the old style thermal overloads.

30 years ago a single thermal heater element was $10-15. Now they are $50-100 each. It takes 3 heaters. And usually are not in stock.

You would have a size 0 starter. You can buy a new Eaton, ABB, or Siemans starter with the electronic overloads for $250-350. That’s cheaper than you can buy a retrofit symcom 777.

By the time you buy the heaters, the panel with electronic overloads is less expensive. But then I can buy a WEG size 0 with bimetallic adjustable overloads for $75

 

[Sponsor]

 

[Boycedrilling]

Yes, you need to move the pressure relief valve to downstream of the CSV.

 

[Valveman]

The reason the Cycle Sensor doesn't have phase loss of overload is because the electronic overload like Boyce mentioned should already have overload and phase loss, so having it again in the Cycle Sensor would be redundant. The old "K" series heaters are class 10, but they cannot protect from phase loss or single phase.

With an electronic overload to protect from high amperage and phase loss, the Cycle Senor only has to protect against dry run and rapid cycling, which it does. Most other dry run protection devices will not work with a CSV, as like you said the amps will drop more than 25% just from using the CSV. Grundfos pumps will usually drop 50%-60% or so from using the CSV, and a Cycle Sensor will adjust as much as needed.

 

[Gecko]

Any idea what that 1.5 hp motor will draw when dry? What is the difference in amps, pumping into a closed CSV vs. dry well?

 

[Valveman]

Assuming 230V three phase, max amps would be 6.4. When working with a CSV the amps should drop to about 2.5. Running dry the amps would only drop to about 2.0, so an undercurrent setting of about 2.2 is probably about right.

 

[Gecko]

Grundfos says 7.3A full load so we are in the ball park. How do you go about testing this? Not good to run the pump dry. Run it against the CSV, measure amps, then set just a little lower? Get the pump wet then run it with open intake for a few seconds and measure?

My Square D starter has the wrong heaters in it for this pump, fortunately it looks like they sell a retrofit to solid state sensing, only $100+. Heaters would be about $60, might as well go with the solid state.

Thanks for you guys help on this!

 

[Valveman]

Yes the solid state should have phase loss protection as well, which is better. And yes just set the Cycle Sensor slightly lower than the lowest amps seen when using a CSV. Then pulling the pump out of the water while it it running is a good test.

 

[Gecko]

With the CSV on the well head, is there a preferred location for the pressure switch? Right now it is a few feet from the pressure tank and about 15 or 20 feet from the well head and CSV. I'd prefer to keep it there but don't know if the dynamics of the system will be problematic. I'm intended to put the CSV at the top of the drop pipe, and the pressure release on one of the CSV ports.

 

[Reach4]

The closer the pressure switch is to the pressure tank, the better. If a few feet separation is currently working, then that is probably close enough.

 

[Valveman]

That will all work fine. The CSV can be a long ways prior to the pressure tank/pressure switch. But the pressure switch should stay as close to the pressure tank as possible. If the switch is too far from the tank, it will bounce on/off quickly when the pump tries to start. Relief on the side of the CSV1A works fine also.