Flow Restrictor

[knox2175]

Have a 3 hp Gould 7GS20 installed. It is set at 641'; static is at 588' with a Franklin #282 302 8310 and a Dole flow restrictor of 7 gpm.

Already replaced the main overload and it has only been in place 3 months.

The previous pump did not have a flow restrictor, and pumped into the top of a 3500 gal storage tank at the rate of approx 10 gpm.

The previous pump quit for various reasons, none of which was related to the flow.

At 7 gpm, in order to keep up with the volume, the pump runs nearly constantly with normal usage. A fan must be run on the Franklin box to keep the main overload from tripping.

Thought about R and R the 7gpm with a 10 gpm. The purpose would be to reduce amp load.

Would this be the proper fix?

 

[JRLAKE]

The proper fix would be to correctly size the pump so that flow restrictors and fans on the overload are not needed. Otherwise you are treating the symptoms of the real problem which is an incorrectly applied pump. When you keep it from overloading, you'll probably then have seal and bearing failures.

 

[Valvecrazy]

Restricting the flow should lower the amperage. Check your amp draw and make sure it is not pulling over the service factor. That 7S20 Goulds is only a 2 HP pump, which should not pull more than 14 amps. If you really have a 3 HP motor on that 2 HP pump, you should not be tripping an overload until over 17 amps. If you are running the 3 HP motor with a 2 HP control box, the overload will trip. Could also be a problem with cooling flow over the motor. A flow inducer would make sure all the water flowed past the motor to keep it cool. Otherwise you need to install the pump above the screen in the well. Sometimes even when installed above the screen, the motor will get hot as the static water pulls down. The motor is not getting the proper flow to stay cool until the static is pulled off and water starts coming from below. Then a flow inducer is very important, even though the pump is set above the screen. If the amp draw is normal and the box is still tripping, you may need a new overload. These type overloads will only trip a few times before they get weak and start tripping to soon.

 

[Tmoose]

There are some Variable speed drives available pretty reasonably these days. Increase the speed until the flow is met, and lock the speed with the password. You could even "read" the flow or pressure to set the rpm continuously. Your motor would have to be inverter rated, but many are.

We've bought a few of these - AC Technology Corporation.Uxbridge, MA.

Our technical folks report they are quite reliable and phone tech support (all that we needed) is excellent.
No affiliation, just a satisfied customer.

Dan Timberlake

 

[Valvecrazy]

That Franklin number you gave us is a 3 HP Deluxe single phase control box. It should not be tripping with that 2 HP pump load. It is a single phase motor and will not work with a Variable Speed Drive. Restricting the pump with the Dole valve should give you almost exactly the same power reduction as slowing the RPM with a drive. I also believe the 641' of wire down hole will cause a problem with a drive. The longer the wire to the motor, the higher the voltage to the motor because of the reflective wave caused by the drive. A 230 volt motor may be seeing 1000 volts at the end of that long wire. The drive will also give you problems with vibration at critical speeds, harmonics fed back into the grid, and stray voltage. The harmonic frequencies of a drive also increase heat to the motor even at reduced amperage.

There should be no problem using the Dole valve to control the output of the pump. Check the amperage. If the amperage is normal and the overloads are tripping, the overload needs replacing. If the amperage is high, you probably have a cooling problem with the motor. There is either something wrong with the motor/pump, or it just needs a flow inducer shroud.

 

[thewellguy]

Valve crazy and I will almost always disagree about VFDs, however the rest of his posts are correct. I would try a new control box befor pulling the pump just because its alot cheaper.

 

[Valvecrazy]

I don't mind disagreeing about VFD's but, I do not believe I am incorrect. My information comes from lots of experience with VFD's. Please let me know what you believe I am incorrect about.

 

[knox2175]

UPDATE...Actually have a 3 hp Gould 7GS30 (not a 7GS20) Installed...sorry for the bad info.

It is a Franklin 3 hp box. Just installed a 10 gpm Dole flow restricter, as well as a new run capacitor. 7 gpm flow restricter did not keep up with flow required and made pump run 12-14 hrs without shut-off.

Water temp runs in the high 80 degree F. range and outside air temp upper 90's F.

Original pump would run approx 3 hrs and shut off because storage tank was full. And it would be off 2-3 hrs before repeating cycle.

Did this for 14 years, until replaced with new Gould unit in Dec 06.

 

[Valvecrazy]

If the run capacitor was bad, that would cause the overload to trip. If the unit trips out again, I would replace the overload. Like I said, they just get weak after tripping a few times. You probably did not need the 10 GPM Dole valve. That pump will not even pump 10 GPM unless your water level is higher than 600'. With a pump setting of 641', the pump restricts itself to 10 GPM when the water level gets lower than 600'.

 

[hydrae]

Some Frankins control boxes need to be calibrated to the actual amperage demand, in this calibration there is both a low amp and high amp cutoffs, the low amp setpoint will save the motor in case of underload due to lack of water.
Hydrae

 

[knox2175]

Removed 10gpm Dole Valve, checked amperage...16.6 @ 10+gpm. Everything seems to be in range with adequate flow. Problem seems to be solved.

Thanks to all.