high pump amperage

[highamp]

My submersible deep well irrigation pump was installed by a person who is now out of business. From the beginning, if I opened up the flow so that the pump ran continuous (without reaching the 60 psi cutoff pressure), the overload protector on the Franklin controller would trip after 5-10 minutes. With a lower flow demand, the pump cycles on and off with the pressure switch and will run fine. I understand now that this is hard on a pump to rapidly cycle, plus I'm not getting the full use out of the pump.
I recently measured the amperage drain and found it to be 15% higher than the Myers published values. However, all the resistence checks recommended in the Myers booklet for line leakage and motor windings check good. The specs are:
Myers 1-1/2 HP 230V 20 GPM (3ST152-20)
18 gal bladder tank @38 psi charge
cutin-cutout: 40-60 psi
-----------------Myers --------------- My
---------------- Values ---------------Readings
supply Volt .........230 ........................240 (4% high but not 15%)
lead amps...Y ......11.5 ......................13.2
................B ......11.0 ......................12.8
................R ......1.3 ........................1.2
I was ready to pull the pump and inspect the wiring and splices but since the resistence readings are good, now I'm not sure. Suggestions?

 

[Bob NH]

Exceeding specs on motor

Pumps require more power as the flow increases.

You have a problem that is common when submersibles are selected for irrigation service where the head requirements may be low. You can get too much flow through the pump. I believe the pump you have is rated at 24 GPM maximum.

Is the pump actually installed in a deep well? Sometimes people put pumps selected for a deep well in a lake and the motor is overloaded. The usual pump sellers will sell well pumps for everything. You usually want a pump with fewer stages if you are not going to run it at high head.

The Franklin manual
http://www.franklin-electric.com/Manual/pdf/fullAIM.pdf (page 16) gives maximum service factor load for 1.5 HP 3-wire pump as Yellow 11.5, Black 11.0, and Red 1.3 Amps. That matches your observations.

Check the current at maximum recommended flow for the pump.

Your tank is very small for that application. You have a situation where a Cycle Stop Valve and/or some kind of flow limit may be the best solution.

 

[Sponsor]

 

[highamp]

The pump is in a 4 inch 135 foot deep well. The high amperage readings are the same at minimum flow. I guess my questions are:
(1) Is there any component(s) in the Franklin Control box that if bad can cause excessive current drain?
(2) Are these currents excessively large (the Myers booklet gives values for "Max amps" of 11 and 11.5 on the run windings)? I'd hate to pull the pump if all I have is a marginally weak overload sensor. Then, again, I don't want to pay for wasted power either.

Another consideration is that there was no safety cable installed with the pump. Its on 1-1/4 sch 40 glued PVC only. If I pull it, I have the stainless cable to put on it after I get it out. Also a torque arrestor which it currently doesn't have.

 

[Bob NH]

The current values from Meyers are the same as the Service Factor current values at the Franklin site.

You may have a damaged capacitor, or a winding that is partially shorted. You could check the resistance readings for the windings at the link in my previous reply. I would check the resistance and capacitors before considering pulling the pump.

It is possible that the pump has a problem such as dragging internally that is causing the higher current. In that case, you will need to replace the pump, and probably the motor.